Soft Matter Photonics

An alternating electric fi eld is employed to induce a tunable dipolar contribution in soft-ionic microgel colloids, where eff ective volume fractions far above close packing can be reached. Novel fi eld-induced structural transitions are discovered, both at intermediate as well as at very high eff ective volume fractions.

arXiv (Cornell University), 2018

Development of artificial materials exhibiting unusual optical properties is one of the major strands of current photonics research [1]. Of particular interest are soft-matter systems reconfigurable by external stimuli that play an important role in research fields ranging from physics to chemistry and life sciences [2-7]. Here, we prepare and study unconventional self-assembled colloidal optical waveguides (CWs) created from wavelength-size dielectric particles held together by long-range optical forces [8]. We demonstrate robust non-linear optical properties of these CWs that lead to optical transformation characteristics remarkably similar to those of gradient refractive index materials and enable reversible all-optical tuning of light propagation through the CW. Moreover, we characterize strong optomechanical interactions responsible for the CW self-assembly; in particular, we report self-sustained oscillations of the whole CW structure tuned so that the wavelength of the laser beams forming the CW is not allowed to propagate through. The observed significant coupling between the mechanical motion of the CW and the intensity of light transmitted through the CW can form a base for designing novel mesoscopic-scale photonic devices that are reconfigurable by light.

We use monodisperse poly(N-isopropylacrylamide) (PNIPAM) microgels as a model system for soft repulsive colloids and study their density dependent structural ordering and phase behaviour using confocal laser scanning microscopy (CLSM). The experiments are carried out at low temperatures, where the particles are in the swollen state and interact via a Hertzian potential, evidenced through a quantitative comparison of the pair correlation functions g(r) obtained with CLSM and computer simulations. We worked over a broad range of effective volume fractions f eff below and above close packing (f cp ). CLSM allows us to identify a fluid-glass and a fluid-crystal transition by looking at the structure and dynamics of the suspensions. The density dependent g(r) values exhibit clearly visible anomalies at high f eff > f cp which we interpret as a structural signature of the glass transition related to the particle softness. These results are discussed in light of the previously studied phase behaviour of colloidal systems interacting with hard and soft repulsive interaction potentials.

Nature communications, 2014

Refraction at a dielectric interface can take an anomalous character in anisotropic crystals, when light is negatively refracted with incident and refracted beams emerging on the same side of the interface normal. In soft matter subject to reorientation, such as nematic liquid crystals, the nonlinear interaction with light allows tuning of the optical properties. We demonstrate that in such material a beam of light can experience either positive or negative refraction depending on input power, as it can alter the spatial distribution of the optic axis and, in turn, the direction of the energy flow when traveling across an interface. Moreover, the nonlinear optical response yields beam self-focusing and spatial localization into a self-confined solitary wave through the formation of a graded-index waveguide, linking the refractive transition to power-driven readdressing of copolarized guided-wave signals, with a number of output ports not limited by diffraction.

2007

Preface. List of Contributors. Part I: Experimental Advances. Microemulsion Templating W.F.C. Sager. Nanofabrication of Block Copolymer Bulk and Thin Films: Microdomain Structures as Templates Takeji Hashimoto and Kenji Fukunaga. Characterization of Surfactant Water Systems by X-Ray Scattering and 2H NMR Michael C. Holmes. Polyelectrolyte Diblock Copolymer Micelles: Small Angle Scattering Estimates of the Charge Ordering in the Coronal Layer Johan R.C. van der Maarel. Structure and Shear-Induced Order in Blends of a Diblock Copolymer with the Corresponding Homopolymers I.W. Hamley, V. Castelletto and Z. Yang. Electric Field Alignment of Diblock Copolymer Thin Films T. Xu, J. Wang and T.P. Russell. Control of Block Copolymer Microdomain Orientation from Solution Using Electric Fields: Governing Parameters and Mechanisms Alexander Boker. Structure and Dynamics of Cylinder Forming Block Copolymers in Thin Films Larissa Tsarkova. Part II: Mathematical and Theoretical Approaches. Mathema...

2015

Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. Accepted Manuscript

2008

Journal of Nanoscience and Nanotechnology, 2006

We review the forces that rule interactions between phospholipid membranes and other soft nanomaterials such as polymers and colloids. Contrary to traditional nanostructures, soft materials display a high susceptibility to the fluctuations of the thermal environment, leading to new forces of an essentially entropic nature.

Testing showed the device capable of measuring nanoparticles in the range of 200 to 900 nm. [45] Further exploration of this topic would not only broaden the knowledge of Soft Mattonics, but also encourage multidisciplinary research from specialists across different disciplines and promote diverse soft and smart photonic applications. [44] This research is therefore an important step towards the understanding and efficient use of colloidal mixtures and block copolymers which helps the design of soft matter systems with desired properties. [43] NUS physicists have discovered a theoretical behavior known as the "critical skin effect" influencing how changes between different phases of matter occur.