Join the Conference

under the aegis of MICROFLUSA project

ABOUT THE CONFERENCE

We are glad to bring to your attention the International Conference on “Colloidal Science and Metamaterials” which is organized in the frame of the EU-funded project MICROFLUSA. The goal of the event is to foster research aiming at the elaboration of metamaterials using approaches developed in the field of colloidal science. Topics that will be covered include:

  • Applications in the domains of photonics, acoustics, hyper frequencies, microwaves,etc;
  • Technological approches (self-assembly, microfludics, 3D printing, etc);
  • Functionalities (photonic band gaps, etc);
  • Hyperuniformity, correlated disorder, etc.

The Conference attendance will be provided free-of-charge to all people that have registered.

KEYNOTE SPEAKERS

‌‌‌‌‌‌Eli Yablonovitch
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‌‌‌‌‌‌Eli Yablonovitch

University of California, Berkeley

‌‌‌‌Wiebke Drenckhan
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‌‌‌‌Wiebke Drenckhan

Institut Charles Sadron

‌‌‌David J. Pine
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‌‌‌David J. Pine

New York University

‌‌‌Salvatore Torquato
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‌‌‌Salvatore Torquato

Princeton University

‌‌Frank Scheffold
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‌‌Frank Scheffold

University of Fribourg

‌Silvia Vignolini
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‌Silvia Vignolini

University of Cambridge

Paul Chaikin
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Paul Chaikin

New York University

INVITED SPEAKERS

Arnaud Tourin
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Arnaud Tourin

Institut Langevin

Ludovic Berthier
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Ludovic Berthier

University of Montpellier

Marian Florescu
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Marian Florescu

University of Surrey

Peter Schall
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Peter Schall

Institute of Physics in Amsterdam

Philippe Barois
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Philippe Barois

Centre de Recherche Paul Pascal

Romain Pierrat
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Romain Pierrat

ESPCI

Valeria Garbin
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Valeria Garbin

Imperial College

PROGRAM

The agenda of the Conference has been finalized and can be found below.

WELCOME COFFEE

30min

Patrick Tabeling – CSM2019 Committee

Welcoming Speech

10min

‌Patrick Tabeling

Dr. Patrick Tabeling is leader of the group MMN (Microfluidics MEMS and Nanostructures), a prominent team in the field of microfluidics. He is the cofounder of the startup MicroFactory. He occupied various positions at the University: visiting researcher in Chicago University (1984‐1985), Chargé/Directeur de Recherches CNRS in the Department of Physics in ENS (1985‐2001), visiting […]

https://www.mmnlab.com/

Eli Yablonovitch – The Electromagnetic Spectra of Ordinary Objects

There is an aspect of Electromagnetics that has been somewhat overlooked. Common everyday objects can act as electromagnetic resonators. Indeed ordinary objects have a series of resonant frequencies extending from radio waves up to optical frequencies. These resonant modes can be modeled as LC circuits. Thus every object that we encounter is an LC resonator. Since LC circuits support ac currents, and since ac currents imply electron acceleration, they inherently radiate into the far-field. Therefore ordinary objects that we come across, in our daily lives, can act as electromagnetic antennas. This means that ordinary object have a Q-factor and a radiation Q-factor for each resonant mode. The lowest frequency resonance is the most characteristic of the object geometry, but there is an entire spectrum of higher frequencies to work with, different and characteristic for every object. Many of the properties that have been attributed to plasmonic resonances are actually universal, and they arise already in ordinary electromagnetics. In communications technology, the antenna application is the most important. The antennas in cellphones, carried by almost everyone on the planet, are examples of multi-frequency resonant objects, enabling wireless connectivity.

45min

‌‌‌‌‌‌Eli Yablonovitch

Eli Yablonovitch is the Director of the NSF Center for Energy Efficient Electronics Science (E3S), a multi-University Center headquartered at Berkeley. He received his Ph.D. degree in Applied Physics from Harvard University in 1972. He worked for two years at Bell Telephone Laboratories, and then became a professor of Applied Physics at Harvard. In 1979 […]

https://www2.eecs.berkeley.edu/Faculty/Homepages/yablonovitch.html

Arnaud Tourin – Acoustic bubbly metamaterials: subwavelength focusing, negative refraction and super-absorption

I will show that air bubbles trapped in a soft solid are excellent candidates for creating acoustic metamaterials. They indeed exhibit a strong low-frequency monopolar resonance, which can lead to interesting effective acoustic properties at wavelengths that can be hundreds of times larger than their radius. First, I will show the possibility of focusing inside a bubbly metamaterial with a subwavelength resolution. The demonstration will be based on numerical results obtained with a Multiple Scattering Theory (MST) code that fully incorporates multiple-scattering effects. Then, I will explain how to create a 3D disordered double negative metamaterial composed solely of monopolar resonators. Finally, I will demonstrate that acoustic superabsorption can be achieved over a broad frequency range by tuning the parameters of a single layer of bubbles, referred to as a metascreen, which is confirmed by both finite element simulations and experiments.

30min

Arnaud Tourin

Arnaud Tourin is the Director of Institut Langevin from 2014 in Paris, France. His main areas of focus are the multiple ultrasound diffusion; Wave control in disordered media; Applications of time reversal techniques to telecommunications and geophysics; Phononic crystals and acoustic metamaterials. He has published many articles in prestigious journals and he has deposited 6 […]

https://www.institut-langevin.espci.fr/arnaud_tourin

COFFEE BREAK

30min

Frank Scheffold – Band gap formation and Anderson localization in hyperuniform disordered photonic materials

In this presentation I will discuss the properties, the fabrication and the characterization of three-dimensional disordered hyperuniform silicon networks, a new type of metamaterials displaying photonic features for electromagnetic vector waves. I will first present our results on the fabrication of polymer templates of the network structures using direct laser writing (DLW) lithography. Next, by infiltration and double-inversion, we converted the mesoscopic polymer networks into silicon structures with a refractive index near n=3.6. The resulting metamaterials display a pronounced photonic gap in the optical transmittance at λ=2.5µm. To obtain a deeper understanding about the physical parameters dictating the properties of amorphous photonic materials we have performed extensive numerical simulations of the density of states and optical transport properties. To this end we study the band gap formation and Anderson localization in hyperuniform structures in two and three dimensions. We identify the evanescent decay of the transmitted power in the gap and diffusive transport far from the gap. Near the gap we find that transport sets off diffusive but, with increasing slab thickness, crosses over gradually to a faster decay, signalling localization. We show that the transition to localization at the mobility edge can be described by the self-consistent theory of localization based on the concept of a position dependent diffusion coefficient.

45min

‌‌Frank Scheffold

Frank Scheffold is the head of the Soft Matter and Photonics Group in the physics department at the University of Fribourg, Switzerland. He studied at the University of Konstanz in Germany, as well as the Weizmann Institute of Science (Israel, with Prof. J. Klein). He obtained his doctorate summa cum laude at the University of […]

http://physics.unifr.ch/en/page/54/

Konstantin Morozov – Photonics of template-mediated lattices of colloidal clusters

The recent progress in microfluidic microfabrication enables mass production of “colloidal molecules” with preprogrammed geometry (e.g., dumbbells, tetrahedrons, etc.). Such colloids can be used as elementary building blocks in fabrication of colloidal crystal with unique optical properties. Anisotropic clusters, however, cannot be readily assembled into regular lattices. In this paper we study photonic properties of compact cubic templates of microdrops encapsulating complex “colloidal molecules”. Since monodisperse droplets can be easily packed into dense cubic lattices and encapsulation techniques (e.g., using microfluidics) are well developed, such material is experimentally feasible. The rationale behind such methodology is that for particular alignment of the encapsulated “colloidal molecules” (e.g., by applying an external magnetic or electric field) the resulting structures resemble a diamond lattice, which is known to exhibit a wide complete photonic band gap. The photonic properties of two cubic templates encapsulating dumbbells (symmetric and asymmetric) and tetrahedrons are investigated numerically. In particular, we show the emergence of the complete 3D bandgap (~8% wide for the dielectric contrast = 12.25) for symmetric dumbbells embedded within fcc template and oriented along the space diagonal of the elementary cubic cell. Keywords: colloidal photonic crystal, microfluidic assembly, photonic bandgap, colloidal molecules

30min

Ilham Maimouni & Maria Russo – Microfluidic fabricated foams for photonic applications

In past decades, polymeric foams have gained interest in a myriad of applications such as the food industry, biomedical engineering and photo-catalysis due to their interesting structural properties (lightweight porous structure and large specific surface area). Recently, 2D foams have been investigated to be self-assembled materials exhibiting interesting photonic properties. In the present study, we aim at exploring the 3D foams case. In this perspective, microfluidic technologies are used to develop 3D, solid, highly monodisperse polymeric foams by packing air bubbles in aqueous solution containing a polymer. The bubbles are produced in a PDMS (Polydimethylsiloxane) microfluidic chip and directly assembled in a microfluidic channel giving birth to highly tunable 3D foam. Indeed, by varying fluid pressures, the foam composition and the polymerization process, we manage to sharply control bubbles production and thereby govern the structural properties of the obtained material: porosity, pores size, connectivity and polydispersity. Electromagnetic simulations are then performed to study wave propagation in such materials, looking up for the existence of a photonic band-gap.

20min

Ilham Maimouni

Dr. Ilham Maimouni is a research engineer with a PhD (2017) in fluid dynamics obtained at Ecole Nationale des Ponts et Chaussées, France. During her PhD, Ilham worked for Schlumberger, at Schlumberger Riboud Product Center (SRPC), on the stability of two-phase yield-stress fluid flows, mainly cement slurries muds ones, in oil wells. Today, Dr. Maimouni […]

https://www.espci.fr/
Maria Russo

Dr. Maria Russo is a Biomedical Engineer with a PhD in Industrial product and process Engineering achieved in 2017 at University of Naples “Federico II”, Italy. Her PhD thesis was about the designing of a microfluidic platform to produce crosslinked hydrogel nanoparticles for enhanced Magnetic Resonance Imaging. At the same time, she was a Research […]

https://www.espci.fr/

LUNCH

1h30min

Wiebke Drenckhan – Hard packing problems with soft objects: towards an explicit control of bubble or drop assemblies

Liquid foams or emulsions are excellent templates for macro-cellular metamaterials whose structural units (bubbles or drops) « self-order » into purpose-designed architectures. Since thermal fluctuations are negligible at the bubble (drop) scale, the obtained architectures are shaped by an intricate interplay between the strongly non-local bubble (drop) interactions and the packing protocol. Ordinary bubbles (drops) are soft, frictionless objects whose interactions are dominated by interfacial tension, giving rise to well-defined architectures with a narrow range of geometrical/topological features. In order to obtain an explicit handle on these architectures, we need to establish an explicit handle on bubble (drop) interactions and develop associated packing protocols which drive the bubble (drop) assemblies towards the desired architectures. The obtained assemblies can then be solidified to obtain a solid, cellular material. I will discuss different strategies in the liquid state or during solidification which can be used to obtain solid foams or emulsions with (novel) architectures of potential interest for metamaterials.

45min

‌‌‌‌Wiebke Drenckhan

Wiebke Drenckhan is CNRS researcher at the Institut Charles Sadron in Strasbourg, France. Her main research interests are dedicated to understanding the physical properties of dispersed systems – such as foams and emulsions – in the liquid or solid state. This concerns in particular their generation, their stability and their structure/property relations.

http://www.ics-cnrs.unistra.fr/drenckhan/main/

Raj Kumar – Soft foam as acoustic gradient index metasurfaces

Metasurfaces are rationally engineered 2D objects of thickness t that strongly interact with wave of characteristic wavelength λ >> t. The General action of metasurface is to shape a given phase front to self – bending beams, twisted wavefronts, beam focusing, artificial Mie resonances etc. These objects with such unusual functionalities may be used to realize focusing devices, beam deflectors, filters, superlenses, mirrors etc. Most of the realized devices were obtained using mechanical approaches to build up Helmholtz resonators, membranes and coiling-up space structures for the control of air-borne acoustic waves. Here we present a new class of subwavelength (t~= λ/5) acoustic gradient–index (GRIN) metasurfaces; engineered from soft graded- porous silicone rubber with high acoustic index for broadband ultrasonic three-dimensional wavefront shaping in water. We use the dependence of the refractive index n of soft porous polymer materials with their porosity φ(n = c0/cL) where c0 and cL are the longitudinal sound speed in a reference medium and in a given material respectively) that we showed in previous works. Here, we achieve a spatial gradient of porosity in the materials using soft–matter technology to fulfil required refractive index profile. The obtained GRIN samples were fabricated by UV polymerizing successive layer of emulsion exhibiting different and fully controlled volume fractions. The final wet samples were dried using supercritical CO2, without collapse and deformation of the pore structures. The ultrasonic experiment characterization of these soft flat lenses demonstrates unprecedented functionalities such as beam steering, beam focusing and vortex beam generation in free space. Our GRIN metasurfaces permit portable, low-cost and efficient applications such as biomedical imaging, industrial non-destructive testing and contactless particle manipulation.

15min

Claas Willem Visser – In-air microfluidics enables rapid fabrication of emulsions

Microfluidic chips enable reproducible generation of complex droplets and particles, but have a low throughput that blocks their industrial use. Furthermore, the resulting particles cannot be readily used as building blocks for solid (meta)materials, as they are contained by a liquid phase. Here we address these limitations by ejecting a train of droplets into the air and manipulating their properties by impact of a second liquid jet. The surface tension of the jet was reduced, so that it encapsulates the droplet by Marangoni spreading. Subsequent on-the-fly manipulations, including solidification and controlled deformation, enable fabrication of monodisperse emulsions, particles, and fibers with diameters of 20 to 300 μm at rates that are 10 to 100 times higher than chip-based droplet microfluidics. Deposition of the partly-solidified droplets onto a solid substrate enables one-step manufacture of three-dimensional (3D) multiscale materials. For example, we demonstrate an artificial pancreatic tissue in which each solidified droplet forms a controlled micro-environment in which MIN6-cells maintain their viability and capacity to produce insulin. In-air microfluidics, as we name this approach, enables fabrication of controlled particles and capsules at industrially relevant rates of up to 6 ml/minute/nozzle. I will present recent results including the fabrication of composite (magnetically and chemically active) hydrogel Janus particles for enzymatic cascade reactions, and sketch how In-air microfluidics may contribute to one-step fabrication of multi-scale materials with controlled mechanical, biological, optical, or thermal properties. Keywords: Functional Materials, Fluid Mechanics, Microparticles, Microfluidics, Soft Metamaterials

15min

Gaël Ginot – Many-body interactions in loose packing of soft deformable objects

The self-assembly of micron-scale colloidal structures is commonly driven by the interplay between pairwise colloidal interactions and thermal fluctuations. By fine- tuning and complexifying the interactions parameters (bond orientation, complementary sticky patch), one can target specific structural configuration for the ensemble in equilibrium. Many metamaterials (mechanics, acoustics, infra-red, electromagnetics...) require characteristic object sizes well above a few micrometers which are insensitive to thermal fluctuations. It is therefore necessary to develop a systematic approach to the assembly of objects driven by mechanical interactions, rather than thermal equilibrium. Particularly interesting model systems are liquid foams or emulsions, which are tight packings of highly deformable bubbles or drops within a liquid carrier phase. Liquid foams and emulsions are already routinely used as templates for the generation of porous materials. Yet we lack a sufficiently fine understanding and control of the bubble interactions in order to explicitly tune the assembly process and hence the final foam structure. Using a model system of equal-volume millimetric air bubbles in water, we combine experiments, simulations and theory to show that bubble/bubble interactions cannot be captured by pairwise interaction potentials. We propose an analytical model, based on previous work by Morse and Witten, which captures well the structural and rheological properties of foams close to the jamming transition. Adding more complex bubble interactions, such as adhesion, friction or surface elasticity, will provide additional handles on the assembly process and potentially promising routes towards a purely mechanical assembly of meta-materials.

15min

Jacopo Vialetto – Direct adsorption and organization of colloidal particles at the air/water interface: structural and dynamic properties

Fine tuning of colloidal particles assemblies at liquid interfaces is of great interest for fundamental studies and practical applications. Rendering these systems stimulus responsive is thus a desired challenge both for investigating dynamic phenomena and realizing reconfigurable materials. In this communication we describe a novel method to precisely control the from-bulk adsorption and subsequent collective organization of colloidal particles at the air/water interface. We show that micromolar amount of conventional cationic surfactants can be used to induce the adsorption of highly charged particles at the air/water interface, promoting the formation of disordered assemblies or polycrystalline patches in a particle and surfactant concentration-dependent manner. Long-range two-dimensional ordered assemblies of micro and nano-sized particles are obtained in a reliable and well-controlled fashion, resulting in bright structural colours. Taking a step further, we describe the first reversible photocontrol of two-dimensional colloidal crystallization at the air/water interface, where millimeter-sized assemblies of microparticles can be actuated through the out-of-equilibrium behaviour of a photosensitive surfactant added to the suspension. The light-dependent adsorption/desorption properties of the photosensitive surfactant at/from the air/water interface allows us to dynamically switch the particle organization between a highly crystalline (under light) and a disordered (in dark) phase, with a very fast response time (crystallization in ~10 s, disassembly in ~1 min). These results evidence a new kind of dissipative system since the crystalline state can be maintained only upon energy supply.

15min

FLASH TALK (SESSION I)

20min

Stefan Aeby – 3D Disordered Photonic Metamaterials by Direct Laser writing

Structured dielectric materials in three dimensions can exhibit photonic properties that allow control of the propagation of light. For crystalline structures, a complete or incomplete photonic band gap emerges and the propagation of light is hindered or even completely suppressed over a certain range of wavelengths. Full photonic band gaps open up for structured dielectric materials with a sufficiently high refractive index contrast. Interestingly, photonic band gap formation does not only appear in crystalline dielectric metamaterials but is also present in designer disordered photonics structures such as hyperuniform networks. Here we present the fabrication and characterization of such three-dimensional disordered metamaterials showing photonic features in the near infrared. We discuss the fabrication of the structures by means of direct laser writing (DLW) and self-assembly of colloids. Eventually, these polymer templates are converted into titania or silicon by infiltration using atomic layer or chemical vapor deposition. We show that hyperuniform network exhibits a photonic pseudo band gap, presented as dips in the optical transmission spectra at λ=2μm. Furthermore, we study experimentally and numerically the influence of random and correlated defects in periodic woodpile structures and the light scattering properties of jammed dielectric spheres and their inverse structure.

5min

Noa Burshtein – Inertioelastic flow instability at a stagnation point

High molecular weight polymers are often used in industrial applications in small amounts to suppress inertial flow instabilities and in order to reduce drag in turbulent flows. Yet the exact process of how a polymer acts on inertial instabilities and on turbulent flow is difficult to study. Using micro particle imaging velocimetry, in a novel configuration of a cross-slot geometry, we exploit a flow instability to create and study a single steady streamwise vortex, which can be considered as a single element of turbulent flow. Our experiments, supported by numerical simulations, show the dramatic effect that the addition of dilute polymer solution, has on both the onset conditions of a flow instability and the subsequent intensification of streamwise vorticity. By changing the parameter space of elasticity and Reynolds number we can map the different regimes in our flow configurations and by doing so we can define a regime where the flow will remain stable and when inertial or elastic instabilities will occur. Our findings fill an important gap in the literature by linking inertial and elastic instabilities that arise in confined flows around stagnation points.

5min

Jean Cappello – Controlling particle trajectories in confined flows via particle shape

Transport properties in confined geometries show very specific characteristics, as for example lateral drift for fibers inclined with respect to the flow direction. Due to viscous friction with top and bottom walls transported particles act like moving obstacles and induce strong flow perturbations. These perturbations are at the origin of the observed lateral drift, oscillatory movement between lateral walls or the deformation of flexible fibers. When fiber shape is perturbed by adding for example an additional arm, an L shaped fiber is formed, and fiber symmetry is broken. This induces fiber rotation until a stable equilibrium orientation is reached. Lateral drift is then observed until interaction with side walls becomes important. Tuning the fiber asymmetry allows for a precise control of particle trajectories, including the approach of side walls, robust even against small perturbations. Our investigation combines precise microfluidic experiments as well as numerical simulations based on modified Brinckman equations. The knowledge gained here can be used for targeted delivery or particles capture inside microchannels. keywords : transport, fibers, confinement, symmetries

5min

Lucie Ducloué – Secondary flows of viscoelastic fluids in curved microchannels

The flow of viscoelastic fluids is well-known to develop purely elastic instabilities in curved geometries at low Reynolds numbers [1,2]. Below the critical shear rate at which the instability is triggered, a steady, secondary flow develops in the cross-section of the channel. The relative strength of this secondary flow increases with the magnitude of the elastic contribution to the flow. For channels of constant curvature with a square cross-section, the secondary flows had so far only been observed numerically [3]: in the absence of inertia, they take the shape of two counter-rotating vorticeslocated in the plane of the channel cross-section. We present the first experimental visualization evidence and characterization of these steady secondary flows. Using a dilute solution of polyethylene oxide, we first capture the nature of the flow by performing confocal imaging of the stream-dyed fluid in the channel cross-section. We show that the observed dye transport is in good qualitative agreement with the flow lines computed numerically. We then use micro-PIV techniques to measure the components of the flow velocity in the plane of the microchannel, half-way between the top and bottom boundaries. We show that the measured streamlines and the relative velocity magnitude of the secondary flows are again in good agreement with the numerical results. This first step in visualizing and quantifying the secondary flows opens up perspectives for the control of efficient mixing at low Reynolds numbers, as well as useful insights for particle focusing and biostreaming. Keywords: viscoelastic fluids, microfluidics, confocal microscopy, PIV

5min

COFFEE BREAK

25min

Salvatore Torquato – Generation of Disordered Hyperuniform Materials with Novel Physical Properties

Disordered hyperuniform many-particle systems can be regarded to be new states of disordered matter in that they behave more like crystals or quasicrystals in the manner in which they suppress large-scale density fluctuations, and yet are also like liquids and glasses because they are statistically isotropic structures with no Bragg peaks. It has been established by a variety of groups that disordered hyperuniform materials possess desirable photonic and electronic band properties. More recently, we have shown that they possess nearly optimal transport and elastic properties. I will describe these developments. It has been a numerical and experimental challenge is to create very large samples that are hyperuniform with high fidelity. I will discuss recent progress that we have made in this direction and its implications for novel physical properties.

45min

‌‌‌Salvatore Torquato

Salvatore Torquato is an American theoretical scientist born in Falerna, Italy. His research work has impacted a variety of fields, including physics, chemistry, applied and pure mathematics, materials science, engineering, and biological physics. He is the Director of the Complex Materials Theory Group, based at Princeton University in the Department of Chemistry, the Princeton Institute […]

http://chemlabs.princeton.edu/torquato/

WELCOME COCKTAIL

1h

WELCOME COFFEE

30min

Paul Chaikin – Quantifying Hidden Order

Abstract will be available soon

45min

Paul Chaikin

Paul Chaikin is a Silver Professor of Physics at NYU and co-founder of the Center for Soft Matter Research. He is a condensed matter experimentalist with interests in both soft and hard matter systems. Current research includes: artificial systems that self –replicate and evolve, self-assembly and self-organization, active matter and driven systems, nanolithography with diblock […]

Marian Florescu – Hyperuniformity and Local Self-Uniformity in Photonic Networks

The fundamental connection between geometrical and topological characteristics of structured photonic materials and advanced photonic functionalities is central to the design of novel photonic materials. Here, we introduce new metrics, hyperuniformity and local self-uniformity as measures of the structural order of photonic network structures. The hyperuniformity concept is built upon the properties of the structure in the reciprocal space, whereas local self-uniformity characterises the intimate connection between uniformity on local and global length scales. Hyperuniformity is associated with a constrained randomness such that density fluctuations on large scales behave more like those of ordered solids, crystals or quasicrystals, rather than those of conventional amorphous materials. On the other hand, local self-uniformity is a measure of a random network’s internal structural similarity and can be used to rank networks on a continuous scale from crystalline, through glassy intermediate states, to chaotic configurations. Despite their distinct characteristics, both metrics provide novel design strategies for achieving advanced photonic functionalities in non-periodic materials. We then explore the connection between the hyperuniformity and local self- uniformity and the photonic band gap formation and introduce novel photonic- network architectures, the local self-uniform amorphous diamond network and the amorphous gyroid network or triamond. We demonstrate that all architectures displaying large photonic band gaps, be they periodic or disordered, are characterized by large values of the newly introduced disordered metrics. A comparison between their predicted properties and recent experimental results will also be provided.

30min

Marian Florescu

Marian Florescu joined the University of Surrey in 2011. He graduated from the University of Bucharest with a BSc in Physics and then obtained his PhD in Theoretical Quantum Optics at the University of Toronto. Prior to joining the Physics Department at Surrey he was a Research Scholar and Lecturer at Princeton University and a […]

COFFEE BREAK

30min

Romain Pierrat – Wave propagation in disordered hyperuniform structures: from transparency to strong absorption

In this talk, we will discuss some surprising wave properties of disordered hyperuniform structures, a new class of disordered and correlated materials where the structure factor S(q) vanishes for small q. In particular we will focus on the stealth hyperuniformity, a subclass where the structure factor is strictly nul on a finite size domain around q = 0. We will show that such a structure can be transparent while a fully disordered material with the same size and density is opaque. This theoretical and numerical result will be illustrated in photonics by the possibility to fabricate such materials using self-assembly techniques. Moreover we will discuss the potential of correlated disorder to strongly enhance wave absorption. By deriving an upper bound for the power absorbed, we will show that stealth hyperuniform structures can be very good candidates for blackbody like absorption (strong absorption with wide angular acceptance and frequency bandwidth). All these results pave the way to design innovative disordered materials with predefined wave properties.

30min

Romain Pierrat

Romain Pierrat works in Langevin institute (ESPCI) as a Chargé de Recherche for the French National Center for Scientific Research (CNRS, Paris, France). His main areas of focus are the diffusion in atomic systems, the spontaneous emission in disordered media and speckle and diffusion in correlated media.

Luis Froufe-Pérez – Light Transport Properties in Stealthy Hyperuniform 2D Materials

In our numerical work we aim at unraveling the relation between structural correlations and photon transport in 2D dielectric metamaterials. Photonic hyperuniform (SHU) disordered materials are dielectric structures defined though their structural properties in reciprocal space. Their distinctive characteristic is the lack of density fluctuations asymptotically or abruptly, above a certain threshold length scale. SHU materials, despite being disordered, share many characteristics with photonic crystals: at low frequencies they present transparency while, depending on the exact geometric properties and materials, at higher frequencies they show a full isotropic photonic bandgap. We find that in between frequency intervals of transparency and band gap other transport regimes are present that are controlled by photon diffusion, Anderson localization and tunneling. To summarize our results, we propose a light transport schematic phase diagram in two-dimensional SHU systems. We demonstrate, through extensive statistical electromagnetic simulations, the transport characteristics of the different regimes in the correlation-frequency plane. Finally, we present experimental results on such stealthy hyperuniform 2D materials in the microwave domain.

15min

Mayte Gomez Castano – Tunable index metamaterials made by bottom-up approaches

Despite the exciting electromagnetic properties that metamaterials exhibit, their implementation in nowadays technology is limited by the traditionally used top-down techniques, which involve costly and low-throughput processes. As alternative, we present an inexpensive and up scalable route to fabricate double fishnet metamaterials over centimeter-sized areas (Figure left) that relies on the combination of colloidal lithography and metallic electrodeposition. Our design is based on a hexagonally ordered monolayer of polystyrene beads used as template for the infiltration of two symmetric gold layers separated by an air gap (Figure right). The obtained structures were characterized by vis-NIR microspectroscopy, exhibiting extinction resonances in the near-infrared range. The good agreement between the optical measurements and the finite-difference time-domain (FDTD) simulations attests the success of our fabrication process. The effective optical properties, retrieved from the calculations by the homogenization method, demonstrate that we are experimentally able to tailor the refractive index from positive to negative and zero values by the proper choice of the particles diameter and the gap width between metallic layers. In particular, negative metamaterials exhibiting a refractive index of -1 in the near-infrared and working over a 100 nm wide spectral band have been successfully fabricated. Our results open the door to a new approach for the low-cost fabrication of negative index metamaterials.

15min

Ville Liljeström – Electrostatic self-assembly protein cages, viruses, and synthetic nanoparticles into periodic superstructures

Electrostatic interaction is one of the most important factors that determine the colloidal stability and aggregation behavior of water-soluble colloidal particles. Electrostatic repulsion increases the colloidal stability whereas electrostatic attraction between oppositely charged particles easily leads to aggregation of particles, such that distinct periodic structures self-assemble. However, the ionic strength of the solvent modulates the electrostatic interaction. We have studied the effect of particle geometry (shape, patchiness) and surface charge properties on the ionic strength dependent electrostatic self-assembly of structures with specific physical and chemical properties. The nanoparticles used in the study are on one hand biological particles (protein cages, viruses) and on the other hand uniform or close to uniform synthetic nanoparticles (gold nanoparticles, polymer dendrimers). The self-assembly of various combinations of oppositely charged nanoparticles occurs in a range of ionic strengths. We have characterized the assembly conditions and the structure of the self-assemblies using both (light and X-ray) scattering and (light and electron) microscopy methods. Our results confirm that uniform nanoparticles often self-assemble into well-defined periodic superstructures. The lattice parameters can be directly related to the dimensions of the building units. The conditions where assembly occurs can mostly be related to the surface charge properties, whereas the macroscopic habit of the nanoparticle superstructures can be related to the shape and assembly mechanism of the building units.

15min

Round Table

Band Gap, Hyperuniformity, Self-assembly…

30min

LUNCH

1h30min

Philippe Barois – The bottom-up approach to metamaterials operating in visible light

The field of metamaterials emerged in years 2000 with the prospect of creating novel artificial materials displaying unprecedented or rarely observed optical properties. Major successes have indeed been obtained in the top-down approach whereby sub-wavelength elements are imprinted or carved on a substrate. In visible light though, the powerful techniques of lithography reach their limits when elements of nanometer size are required. On the other hand, the bottom-up approach based on the large-scale synthesis of nano-sized optical resonators has proved its ability to produce optical nanostructures exhibiting some of the most popular meta-properties such as extreme refractive indices, hyperbolic dispersion or optical magnetism. We review in this presentation some of the meta-structures realized within the bottom-up approach combining chemical synthesis and colloidal physical-chemistry. We focus in particular on the generation of artificial optical magnetism and we show how a bulk material presenting a non-natural isotropic magnetic permeability was designed and characterized. Recent advances aiming at increasing the magnetic response open the way to the fabrication of bulk magnetic metamaterials of large or zero permeability, and of Huyghens metasurfaces based on optical resonators of equal electric and magnetic response over a broad frequency range.

30min

Philippe Barois

Philippe Barois is a research director (Directeur de Recherche) at the CNRS (French National Center for Scientific Research), in Bordeaux (Centre de Recherche Paul Pascal). He is part of the team «Matériaux Fonctionnels par Ingénierie Colloïdale».

Valeria Garbin – Dynamic capillary assembly of colloids at interfaces with 10,000g accelerations

High-rate deformation of soft matter is an emerging area central to our understanding of far-from-equilibrium phenomena during shock, fracture, and phase change. Monolayers of colloidal particles are a convenient two-dimensional model system to visualise emergent behaviours in soft matter, but previous studies have been limited to slow deformations. We have developed an experimental method to probe and visualise the evolution of a monolayer of colloids confined at a bubble surface during high-rate deformation driven by ultrasound. We observed the emergence of a transient network of strings, and used discrete particle simulations to show that it is caused by a delicate interplay of dynamic capillarity and hydrodynamic interactions between particles oscillating at high frequency. Remarkably for a colloidal system, we found evidence of inertial effects, caused by accelerations approaching 10,000g. These results also suggest that extreme deformation of soft matter offers new opportunities for pattern formation and dynamic self-assembly.

30min

Valeria Garbin

Valeria Garbin is a senior Lecturer at the Department of Chemical Engineering, Imperial College London. Her group is interested into the study of microscale transport phenomena of structured fluids and interfaces. Examples include emulsification and foaming, processing flows for advanced materials, biomedical flows and drug delivery. Their research combines multiple experimental techniques to provide precise, direct, dynamic measurements […]

Andreea Pasc – Responsive surfactants and solid lipid particles templating for nanostructured silica materials

Responsiveness to external stimuli (temperature, pH, light, magnetic field...) is suited for many applications, including advanced colloids and material science design. Herein we will present the preparation and potential application of meso or meso;macroporous silica materials template with magnetoresponsive surfactants and solid lipid nanoparticles. Tuning magnetic properties is a challenge in advanced materials research, for various applications including high storage capacity media, diagnostics, imaging, hyperthermia probes or targeted delivery. Most of magnetic systems consist of either molecular nanomagnets (n < 0 atoms) or magnetic nanoparticles (n= 00;1000). Very recently, colloidal systems (i.e. micelles, micro;emulsions and emulsions), based on magneto;responsive surfactants were reported as being able to bridge this gap, allowing thus fine control upon the cluster size n, whilst combining magnetic ordering with low;density and electrical insulation. Herein will be presented novel contributions on magnetic surfactants that are able to form micelles, vesicles or solid lipid nanoparticles. Straightforward applications of these systems might be found in magneto;responsive drug delivery or catalysis. Moreover, hexagonally ordered meso; and meso;macroporous materials with magnetic properties could be achieved by using magnetic surfactants as structure directing agents of silica. Finally, it will be shown that magnetic properties of the self;assembled surfactants and of the resulting materials are highly dependent on the molecular organization system and on confinement of the metallic centres, respectively.  

15min

Vincent Poulichet – Dynamic photocontrol of particle deposition in a moving meniscus

Controlling the organisation of particles on surfaces is essential for exploiting their emerging collective properties and for their integration into devices. A popular technique for organising particles on surfaces consists in using a moving meniscus that traps particles between a liquid layer and a solid surface at the three-phase contact line. Particle deposition from a moving meniscus is defined by the surface properties and hence does not offer the possibility for reconfiguring and dynamically controlling the deposition. For its spatio-temporal resolution, tunability, and contactless nature, light appears as an ideal stimulus to remotely control the particle deposition in a dynamic way. Our group has shown in the past various ways to optically control the particle deposition process using photosensitive surfactants to exploit either optical Marangoni flows or light-dependent particle-interface interactions. However, this was done in sessile drops with a modest pattern resolution and on a limited deposition area. I will present how we implemented these light-induced effects in the case of particle depositions assembled by a moving meniscus. A microparticle suspension was spread at a controlled speed onto substrates of different wettabilities and topologies. Different concentrations of photosensitive surfactants were added to the suspension and light was shined following different spatio-temporal patterns on the moving meniscus. I will show how light affects the deposition in both capillary and evaporative regimes, and emphasise how light-dependent particle interactions or optical interfacial flows in the meniscus can change the deposition process. Notably, we identified conditions where the particle deposition was dynamically switched on and off using light. These first results illustrate interesting coupling effects between particle interactions, interfacial flows and capillary forces, as well as open perspectives for arbitrary, reconfigurable particle deposition protocols in a user-defined manner.

15min

Rajam Elancheliyan – Optical resonators with large magnetic responses

When submitted to an electromagnetic field, most sub-micron nanoparticles exhibit a strong electric response but a weak magnetic one. It was however shown that, when arranged in a controlled manner, clusters of plasmonic nanoparticles (PNPs) may possess a strong magnetic response to electromagnetic field. Such clusters, also called “meta atoms”, strongly interact with light and, when realizing the Kerker condition, do scatter waves mostly forward with a fully controllable phase delay (Huyghens scatterers). The synthesis and 2D deposition of such meta-atoms thus give access to “meta-surfaces” with novel electromagnetic properties (such as total transmission, reflection, focusing effects etc). Recently a new design of NPs assembly was proposed by Dezert et al., which consists in spherical clusters of PNPs of controlled size. Simulations show that these clusters give rise to magnetic and electric resonances of same and high amplitude and same spectral position, thus optimizing their response. We recently obtained some suspensions of these clusters of plasmonic NPs using an emulsion-based fabrication approach. The synthesis involved the emulsification of an aqueous gold NPs suspension into an oil phase followed by the controlled ripening of the water droplets at low pressure. The structure of these clusters was characterized using UV spectroscopy and transmission electron microscopy, which show that dense assembly of NPs can be obtained. Static light scattering4 measurements also show that the clusters exhibit an up to now unattained ratio of 0.6 for the magnetic/electric responses in excellent agreement with simulations. These results pave the way for the realization of metasurfaces permitting the design of any types of phase fronts.

15min

FLASH TALK (SESSION II)

15min

Nicolas Pannacci – Wettability effect on CO2-foam flow in porous medium

Foam flow in a porous medium and questions related to wettability effects and foam destabilization with oil are the subject of numerous studies (1-3). Understanding the phenomena involved in the flowing under confinement of such complex system (containing gas, water, surfactants and oil) is important for a lot of applications. For example, Enhanced Oil Recovery or CO2 Carbon Utilization and Storage (CCUS) are processes where foam-injection can help to increase gas mobility control. The purpose of this study is to provide initial answers by focusing on the influence of wettability and oil saturation on the behavior of CO2-foam flows. Experiments were performed on rocks (sandstones with 16 % porosity and 600 mD permeability) injecting supercritical CO2 (P = 160 bar, T = 60°C). Water-wet (WW) rock samples and partially-wetting (PW) rocks are used to explore wettability effects. Consequences of oil content was also considered. Anionic surfactant formulations and gas were co-injected with a gas fraction of 0.7. Foam rheology was assessed by measuring foam apparent viscosity through flow rate variation. Preliminary results are also shown on the perspective of the use of solid particles to stabilize foams thanks to injection tests in micromodels. Results show formation of strong foams with shear-thinning rheological behavior (see figure). The foam apparent viscosity drops off by 30 % in altered wettability cases. Oil presence mainly induces a delay in foam formation. These results underline the importance of the wettability and oil content parameters and may provide some guidance for future foam studies. Keywords: foam, porous medium, shear-thinning, pressure

5min

Mohamad Danial Shafiq – Evaporation of drops: The role of long-range colloidal interactions

The drying of a colloidal droplet has attracted considerable attention because of its inherent complexity as well as its significance in applications such as coating, printing, and layering processes. There has been great interest in controlling the well-known 'coffee-ring' effect, in which the contact line of an evaporating drop ispinned to the substrate so that dispersed particles are deposited onto the three-phase contact line. Large microscale convection-driven flows typically determine the structure of the deposited film. Interparticle forces which operate on nm-separations, at least in aqueous systems, are relatively unimportant. Our aim is to explore if much longer-range colloidal forces, comparable to hydrodynamic flows, could be used to control particle drying. We generate controllable micrometer range electrostatic interactions in a suspension by using a charge control additive (the surfactant, dioctyl sodium sulfosuccinate [AOT]), and an organic salt, tetradodecylammonium tetrakis (3,5-bis (trifluoromethyl)phenyl)borate (TDAT) in a nonpolar solvent. The drying of drops containing monodisperse, fluorescent poly-(methyl methacrylate) (PMMA) particles was studied by confocal light scanning microscopy (CLSM). Image analysis was used to quantify the spatial deposition of the particles onto a hydrophobically-coated glasssubstrate. The existence and extent of a ‘coffee-ring’ deposit was characterized. We find that the drying patterns are controlled by a competition between the evaporation rate of the solvent and the strength and range of the electrostatic interactions. In highly-volatile solvents, such as hexane, hydrodynamic flows dominate particle deposition. With weak electrostatic interactions a well-defined 'coffee-ring' is produced. Increasing the strength of repulsions, the intensity of the ‘ring’ is observed to first reduce and then in highly-charged systems to be totally suppressed. In less volatile solvents, such as dodecane where evaporation is diffusion-controlled, the role of colloidal forces is more complex with evidence for modification of both particle-particle and particle-substrate interactions. Finally, high salt concentrations induce particles attraction and the formation of clusters in bulk solution which inhibit the formation of a ring-like deposit. Keywords: Evaporation, charge, electrostatic

5min

Inese Silkina – Microgravity Experiments in Colloid Science

Gravity may strongly influence the nucleation and dynamics of growth and thus the morphology of resulting colloidal structures. Previously, the SODI-COLLOID instrument was used to follow early stages of aggregation induced by Casimir forces in a fluid at the critical point with near field scattering. The results that feature growth kinetics in microgravity were published by the Science Team. Currently, a new instrument for COLLOIDAL SOLIDS project is being developed and is planned to be launched on the ISS in 2021. The project plans to use diverse and innovative light scattering diagnostics, including, small-angle light scattering (SALS) in transmission, depolarized dynamic light scattering (DLS) and photon correlation imaging (PCI) at three different angles. With the novel instrument, the international Science Team is looking forward to study long intermittent dynamics in colloidal glasses, restructuring and aging of colloidal gels, self-assembly of patchy colloidal particles and optothermal manipulation of colloidal solids. In addition, experiments on nucleation of protein solutions will be performed.

5min

Coffee Break

30min

Reinhard Höhler – Tuning attractive bubble interactions in monodisperse foams yields new equilibrium structures

In a foam with small liquid content and repulsive bubble interactions, the soap films separating bubbles meet by three at “Plateau borders” and these borders meet by 4 at tetrahedral vertices. Due to this structure governed by Plateau’s rules which solid foams inherit from their liquid precursors, the macroscopic deformation of a solid foam is mostly due to the bending of the Plateau borders. Such bending dominated networks are light but also very soft. Surface Evolver simulations show that beyond a critical strength of attraction between bubble interfaces, monodisperse foams can form a simple cubic equilibrium structure that violates Plateau’s rules. Solid foams derived from such liquid foams would form anisotropic stretch dominated networks of Plateau borders, much stiffer than conventional solid foams. This behavior is similar to that of stretch dominated mechanical metamaterials to be produced by additive manufacturing processes, origami like sheet folding and bonding methods. We also discuss how attractive bubble interactions can be integrated in analytical models of bubble interactions, derived from first principles and based on Morse-Witten theory. Experimentally, attractive interactions of the required order of magnitude can for instance be induced by nanoparticles adsorbed by the interfaces.

15min

Sophie Ramananarivo – Boosted annealing of colloidal monolayers driven by active dopants

Molecular motors have an important role in biological processes, assisting and boosting self-assembly or intracellular transport. Another remarkable example is the case of plant gravisensors, for which active fluctuations generated in cells play a key role in the detection of minute inclinations. Self-propelled colloids that consume energy to move hold similar potential to accelerate otherwise long thermal processes and for the man-made assembly of microparticles. Pure suspension of such microswimmers have shown collective behavior or broken microscopic reversibility. Yet, their use to tune the internal activity and control the assembly of passive colloids remains largely unexplored, although numerical work suggested remarkable departure from equilibrium. Here we show a massive acceleration of the annealing of a monolayer of passive beads by adding a moderate amount of self-propelled microparticles. A dense layer of colloids is formed through sedimentation and quenched into a polycrystalline state with domains of mismatching orientations. We study the effect of active dopants on the coarsening process of this monolayer and its evolution towards an ordered state. We rationalize our observations with a model of collisions that drive active fluctuations and activate the annealing. The experiment is compared with Brownian dynamic simulations that further highlight the non-equilibrium nature of the process and its sensitivity to the dynamics of the active particles. Our findings uncover the role of active dopants to boost the relaxation of a system and show their potential to control the properties of matter microscopically and in real time. Key words: Active matter, active fluctuation, self-assembly, colloids

15min

Mao Fukuyama – Control of the molecular transfer between microdroplets and nanodroplets in microfluidics

Backgrounds. Recently, Micrometer-sized droplets (microdroplets) have been used as small chemical containers and applied for bioassays such as single-cell assay. The detection of microdroplet contents is still one of bottlenecks for the application to bioassays due to small amount of samples in the droplets. Recently, we found that the microdroplet contents can be selectively enriched in the microdroplet using spontaneous nanodroplet formation induced by a nonionic surfactant, Span 80 [1]. When microdroplets of aqueous sample solution are formed in an organic phase containing Span 80, nanodroplets generate at the interface and the microdroplets shrink. The microdroplets’ contents stay in the microdroplet or partition into nanodroplets depending on their properties. Purpose. The purposes are to establish the control method of the selectivity and the application to bioassays. Methodology. In a polydimethylsiloxane microfluidic device, 200 µm-sized microwells were prepared on the ceiling of a 2 mm-wide straight channel. By introducing an aqueous phase and the hexadecane solution of Span 80, a microdroplet is formed in each microwell. Results and Discussion. From the observation of the behavior of droplets containing Rhodamine 123 or NaCl during the nanodroplet formation, we found that (1) the apparent partition coefficient of the solute in the microdroplet to nanodroplets and (2) the concentration magnification can be controlled by changing the water activity of the micelles. Conclusion. We established the control method for the selectivity and concentration magnification. In the presentation, we will report some application to the biochemical analysis.

15min

Dinner for Invited Speakers

WELCOME COFFEE

30min

David J. Pine – Self-assembly of Janus colloids into colloidal fibers, bilayers, and rings (catalyzed by planar surfaces)

We have developed a new scalable method for fabricating Janus colloids, where one part of the colloidal surface is purely repulsive and the other part is coated with DNA, which results in an attractive interaction whose strength can be precisely tuned by changing the temperature by a few degrees.  We observe the growth and formation of small compact colloidal assemblies, fibers of varying internal structure, and bilayers depending on the Janus balance, which can be precisely controlled from 0.01 to 0.81.  We also find that adding a non- specific depletion interaction leads to substrate-catalyzed ring formation. Because the colloidal particles are visible under an optical microscope, we can follow the formation of the various self-assembled structures.  The formation of fibers is particularly interesting as it proceeds by different cooperative polymerization processes that are often used to describe the formation of protein fibers, such as amyloids.

45min

‌‌‌David J. Pine

David J. Pine is an American physicist who has made contributions in the field of soft matter physics, including studies on colloids, polymers, surfactant systems, and granular materials. He is Professor of Physics in the NYU College of Arts and Science and Chair of the Department of Chemical and Biomolecular Engineering at the NYU Tandon School of Engineering. Pine received his B.S. […]

http://www.physics.nyu.edu/pine/

Ludovic Berthier – The large scale structure of jammed particle packings

I will discuss the behaviour of large scale structural fluctuations observed in jammed particle packings, discussing in particular the relevance of hyperuniformity to describe packings constructed by experimentally realizable methods. I will explain the relevant thermodynamic framework to understand these materials, and I will present the results of large scale numerical simulations to illustrate the discussion.

30min

Ludovic Berthier

Ludovic Berthier is a researcher (Directeur de Recherche) in the French National Center for Scientific Research (CNRS, médaille de Bronze). He works at the University of Montpellier. His areas of research cover physics, condensed matter, soft matter, disordered systems and materials science.

COFFEE BREAK

30min

Damien Baigl – Reconfigurable self‐assembly: from self‐foldable DNA nanomachines to photoswitchable dissipative colloidal crystals

Self-assembly is a both a formidable method to organize molecular or colloidal entities into functional superstructures and a playground for the scientific endeavor on how matter organizes itself. Self-assembly is also a key-feature of how life builds its components. However, compared to their living counterparts, synthetic materials made by self-assembly usually lack some of the characteristic properties of living systems such as reconfigurability, adaptability or evolution. In this presentation, I will describe two systems where such properties can emerge from self-assembled synthetic materials. First, I will show that elaborate DNA nanostructures with a user-defined shape can be obtained with conventional methodologies (DNA origamis, SST) but in an isothermal manner at room temperature rather than following the usual thermal treatments believed to be necessary to reach the target shape.1-3 This new self-assembly method processes through a variety of folding pathways, opening perspectives for systems capable of autonomously finding the most stable state in a pool of DNA components, with applications ranging from self-adaptive materials to nanostructure optimization by evolution. I will then describe the first reversible photocontrol of two- dimensional colloidal crystallization at the air/water interface, where millimeter-sized assemblies of microparticles are actuated through the out-of-equilibrium behavior of a photosensitive surfactant added to the suspension.4-6 This allows us to photoreversibly switch the particle organization between a highly crystalline (under light) and a disordered (in dark) in a fast manner, evidencing a new kind of dissipative system where the crystalline state can be maintained only upon energy supply. Key-words: DNA nanotechnology, dissipative self-assembly, colloidal crystal, photocontrol

30min

Tommaso Pietro Fraccia – Liquid crystal self-assembly of nucleotides triphosphate in backbone-free nucleic acids exhibiting Watson-Crick selectivity

Nucleic acid (NA) oligomers as short as 4 base pairs can form lyotropic columnar liquid crystal (LC) phases trough the self-assembly steps of sequences hybridization, end-to-end aggregation of duplexes and condensation of linear aggregates [1]. The LC matrix provides an ordered but fluid environment which strongly promotes the chemical ligation of the oligomeric constituents into longer polymers[2, 3]. Since elongated molecules enhance the LC stability, this system is characterized by a positive feedback loop which can provide an autocatalytic pathway for the prebiotic appearance and selection of the first genetic polymers. Here we report about our recent demonstration that aqueous solutions of NA mononucleotide triphosphates (dNTPs and rNTPs), at sufficiently high concentration and low temperature, can exhibit a phase transition in which chromonic columnar LC ordering spontaneously appears [4]. Remarkably, this polymer-free state exhibits, in a self-assembly of NA monomers, the key structural elements of biological nucleic acids, including: long-ranged duplex stacking of base pairs, complementarity-dependent partitioning of molecules and Watson– Crick selectivity. We observed for the first time LC order in aqueous solution of dATP/dTTP, dGTP/dCTP and mixtures of all 4 dNTPs (Fig. 1). LCs were not observed in mixtures containing only individual triphosphates or non-complementary nucleobases, with except for dGTP quartets formation. These findings set the basis for the exploration of the abiotic polymerization of potentially reactive NA monomers, templated by their LC self-assembly, having relevance for the investigation on the origin of life. Key words: DNA self-assembly, Liquid Crystals, Origin of Life

15min

Mauricio Pilo-Pais – DNA-Mediated Self-Assembly of Plasmonic Antennas with a Single Quantum Dot in the Hot-Spot

DNA can be used as a tool to rationally assemble metallic nanoparticles (NPs) with a defined arrangement, nanometer spacing and tunable plasmon resonance. These structures can be tailored to have unique optical properties such as custom-tuned hot spots for surface enhanced Raman and fluorescence spectroscopies. More recently, we have shown the feasibility of using DNA origami to fabricate plasmonic cavities with small mode volumes, able to promote strong-coupling between plasmons and molecular excitons. In this talk, I will discuss our assembly strategies to modify the optical properties of single colloidal quantum dots (QDs). Specifically, using DNA complementarity along stoichiometry and spatial-exclusion, we position an individual QD at exactly the center of two metallic NPs. Gold NPs and QDs are conjugated with complementary DNA strands, and mixed at stoichiometric ratios of 5:1 Au:QD. The large molar excess of the larger species and their disproportionate size difference prevents more than two NPs to be attached to an individual QD. The resulting structures display high emission enhancement compared to individual QDs. The flexibility of using DNA as an assembly methodology is an ideal approach to study plasmon-single emitters coupling and to integrate nanocomponents for optical applications. Keywords: fluorescence, nanoantennas, DNA self-assembly, quantum dots, plasmonic enhancement

15min

Itzhak Fouxon – Hydrodynamic interactions and formation of droplet clusters in Poiseuille flow

It was found in recent experiments that transport of droplets by Poiseuille flow can result in the formation of regular clusters of particles. This opens opportunity for creation of new materials using transport by fluids. The cluster formation is due to a combination of hydrodynamic interactions and adhesive forces. This talk concentrates on the role of hydrodynamic interactions. We provide the theory of long-range interactions that allows to explain previous empirical observations of particle swapping in the three-body problem. We demonstrate, again in accord with observations, that dilute solutions of many particles have tendency for breaking in separated doublets and singlets of particles. Then we consider the theory of interactions at arbitrary distance which includes close interactions that occur in clusters. This study is confined to two particles. We demonstrate that presence of walls at a distance, similar to that in the experiments, can profoundly change the result of the interaction. We derive new equation of motion for the interparticle distance that includes the effects of the boundary. Numerical simulations of this equation demonstrate that the boundary can lead to opening of closed trajectories and thus destruction of bound states. It also changes of the topology of open trajectories, the fact that was previously observed in experiments. We discuss the implications for the cluster formation. Keywords: hydrodynamic interactions, bound states, fluid transport

15min

Anthony Ge – Flow-assisted droplet assembly in a 3D microfluidic channel

Self-assembly of soft matter, such as droplets or colloids, has become a promising scheme to engineer novel materials, model living matter, and explore non-equilibrium statistical mechanics. In this talk, we present detailed numerical simulations of few non-Brownian droplets in various flow conditions, specifically, focusing on their self-assembly within a short distance in a three-dimensional (3D) microfluidic channel. Contrary to quasi two-dimensional (q2D) systems, where dipolar interaction is the key mechanism for droplet rearrangement, droplets in 3D confinement produce much less disturbance to the underlying flow, thus experiencing weaker dipolar interactions. Using confined simple shear and Poiseuille flows as reference flows, we show that the droplet dynamics is mostly affected by the shear-induced cross-stream migration, which favors chain structures if the droplets are under an attractive depletion force. For more compact clusters, such as three droplets in a triangular shape, our results suggest that a non-uniform cross-sectional inflow profile is further required. Overall, the accelerated self-assembly of a small-size droplet cluster results from the combined effects of strong depletion forces, shear alignments, and fine-tuned inflow conditions. The deterministic nature of the flow-assisted elf-assembly implies the possibility of large throughputs, though calibration of all different effects at play is likely difficult.

15min

Amir Gat – The Effect of Connections Between Fluid-Filled Cavities on the Dynamics of Solid-Liquid Composite Beams

The study of elastic structures embedded with fluid-filled cavities received considerable attention in fields such as smart materials, sensors, actuators and soft-robotics. This work studies an elastic beam embedded with a set of fluid-filled bladders, similar to a honeycomb structure, which are interconnected via an array of slender tubes (see figure below). The configuration of the connecting tubes is arbitrary, and each tube may connect any two bladders. Beam deformation both creates, and is induced by, the internal viscous flow- and pressure-fields which deform the bladders and thus the surrounding solid. Applying concepts from poroelasticity, and leveraging Cosserat beam large-deformation models, we obtain a set of three coupled equations relating the fluidic pressure within the bladders to the large transverse and longitudinal displacements of the beam. We show that by changing the viscous resistance of the connecting tubes we are able to modify the amplitude of oscillatory deformation modes created due to external excitations on the structure. In addition, rearranging tube configuration in a given bladder system is shown to add an additional degree of control, and generate varying mode shapes for the same external excitation. The presented modified Cosserat model is applied to analyze a previously suggested energy harvester configuration and estimate the efficiency of such a device. The results of this work are validated by a transient three- dimensional numerical study of the full fluid-structure-interaction problem. The presented model allows for the analysis and design of soft smart-metamaterials with unique mechanical properties.

15min

LUNCH

1h30min

Blaise Delmotte – Hydrodynamic Genesis of Colloidal Creatures

When colloidal particles are rotating adjacent to a nearby floor, strong advective flows are generated around them, even quite far away. When a group of these microrollers is driven by an external field, the strong hydrodynamic coupling between particles leads to formation of new structures. Our experimental observation show that a suspension of microrollers undergoes a cascade of instabilities: an initially uniform front of microrollers evolves first into a shock-like structure, which then quickly becomes unstable, emitting fingers of a well-defined wavelength; then the fingertips pinch off to form compact motile structures translating at high speed. These colloidal creatures are self-sustained and form a stable state of the system. They are the result of spontaneous self-assembly driven by hydrodynamics. Combining experiments, large scale numerical simulations and continuum models, we will detail the mechanisms involved at each step and demonstrate that the whole process is primarily controlled by a geometric parameter: the height of the particles above the floor. Hydrodynamic interactions are predominant in the development of these colloidal creatures. Thanks to these hydrodynamic collective effects, microrollers offer a promising platform for particle transport, mixing and flow generation in confined environments. Key words: Colloids; Self-assembly, Hydrodynamics

15min

Peter Schall – Colloidal architectures: assembly and mechanical properties

Recent breakthroughs in the synthesis and design of colloidal building blocks allow the assembly of complex colloidal structures with unprecedented control over the assembled architecture. In particular, patchy particles that exhibit highly directional bonding have recently enabled the assembly of “colloidal molecules”, analogues of molecular compounds at the colloidal scale. Such assembly control promises fascinating applications in the design of new functional materials at micrometer and nanometer length scales. In this talk, I will present a new combination of patchy particles and solvent- mediated “critical Casimir” interactions that enables directional bonding with precise control of the patch-patch interaction strength. Using tetramer particles, we assemble colloidal analogs of well-known carbon compounds such as C-rings (C 5 and C 6 ), Butane and Butene, and investigate their thermally excited vibrations. We also investigate the mechanical response of these colloidal metamaterials to external forces. We find that already a simple assembled chain under compression exhibits an intriguing buckling instability that is accompanied by diverging fluctuations upon approaching the buckling transition. These results demonstrate the new exciting physics encountered in the structure formation and mechanics of these novel colloidal architectures, whose assembly has just become available.

30min

Peter Schall

Peter Schall  is Professor in Physics at the Institute of Physics in Amsterdam, The Netherlands. Previously he was a Humboldt fellow in the Department of Engineering and Applied Sciences at Harvard University (Cambrigde, U.S.A), after he obtained his PhD in physics at the RWTH Aachen (Germany) in 2002. His work in experimental soft matter physics aims […]

Silvia Vignolini – Colour Engineering: from nature to applications

The most brilliant colours in nature are obtained by structuring transparent materials on the scale of the wavelength of visible light. By controlling/designing the dimensions of such nanostructures, it is possible to achieve extremely intense colourations over the entire visible spectrum without using pigments or colorants. Colour obtained through structure, namely structural colour, is widespread in the animal and plant kingdom. Such natural photonic nanostructures are generally synthesised in ambient conditions using a limited range of biopolymers. Given these limitations, an amazing range of optical structures exists: from very ordered photonic structures, to partially disordered, to completely random ones. In this seminar, I will introduce some striking example of natural photonic structures and review our recent advances to fabricate bio-mimetic photonic structures using the same material as nature. Biomimetic with cellulose-based architectures enables us to fabricate novel photonic structures using low cost materials in ambient conditions. Importantly, it also allows us to understand the biological processes at work during the growth of these structures in plants.

45min

‌Silvia Vignolini

Dr. Silvia Vignolini studied Physics at the University of Florence, Italy. In 2009, she was awarded a PhD in Solid State Physics at the European Laboratory for non-Linear Spectroscopy and the Physics Department at the University of Florence. In 2010, she moved to Cambridge as a post-doctoral research associate working in the Cavendish Laboratory and […]

https://www.ch.cam.ac.uk/person/sv319

CONCLUDING REMARKS

10min

Talk Sessions breakdown

 45 min 40 min talk &  5 min questions

 30 min 25 min talk &  5 min questions

 20min 18 min talk &  2 min questions

 15min 13 min talk &  2 min questions

 5min (Flash Talks) | No question time will be allocated but discussion is welcome during the following coffee breaks

Download the Agenda

You can click here to download the agenda in PDF form

HOW TO PARTICIPATE IF YOU ARE NOT PRESENTING

Abstract submission is now closed.

However, if you want to attend the conference without presenting your work, please register on the following link.

 

 

The Conference attendance is FREE-of-charge but places are limited, therefore Registration is mandatory.

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To ease the submission process and the subsequent follow up process please consider the following guidelines, information, tips and terms mentioned.

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  • The international scientific committee will review your abstract and acceptance or rejection notifications will be sent to you by January 18ᵗʰ, 2019.
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Important Dates

  • Abstract Submission Deadline: January 15ᵗʰ, 2019
  • Acceptance or rejection notifications: January 18ᵗʰ, 2019

Further details for the registration procedure will come soon.

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VENUE

IPGG - Institut Pierre-Gilles de Gennes

6 Rue Jean Calvin, 75005 Paris, France
+33 (0) 1 40 79 59 00

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OUTSTANDING SPEAKERS

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‌Patrick Tabeling

ESPCI

Ilham Maimouni
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Ilham Maimouni

ESPCI

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Maria Russo

ESPCI

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