02307nas a2200265   4500008004100000022001400041245010600055210006900161260000800230300001600238490000700254520141800261653001801679653002001697653002301717653001601740653001901756100001801775700002201793700002101815700002401836700002201860700002701882856013201909       2017                        eng d  a1936-085100aLinking catalyst-coated isotropic colloids into ``active'' flexible chains enhances their diffusivity0 aLinking catalystcoated isotropic colloids into active flexible c  cOCT  a10025-100310 v113 aActive colloids are not constrained by equilibrium: ballistic propulsion, superdiffusive behavior, or enhanced diffusivities have been reported for active Janus particles. At high concentrations, interactions between active colloids give rise to complex emergent behavior. Their collective dynamics result in the formation of several hundred particle-strong flocks or swarms. Here, we demonstrate significant diffusivity enhancement for colloidal objects that neither have a Janus architecture nor are at high concentrations. We employ uniformly catalyst-coated, viz. chemo-mechanically, isotropic colloids and link them into a chain to enforce proximity. Activity arises from hydrodynamic interactions between enchained colloidal beads due to reaction-induced phoretic flows catalyzed by platinum nanoparticles on the colloid surface. This results in diffusivity enhancements of up to 60% for individual chains in dilute solution. Chains with increasing flexibility exhibit higher diffusivities. Simulations accounting for hydrodynamic interactions between enchained colloids due to active phoretic flows accurately capture the experimental diffusivity. These simulations reveal that the enhancement in diffusivity can be attributed to the interplay between chain conformational fluctuations and activity. Our results show that activity can be used to systematically modulate the mobility of soft slender bodies.10aactive matter10aBrownian motion10acolloidal assembly10adiffusivity10aice templating1 aBiswas, Bipul1 aManna, Raj, Kumar1 aLaskar, Abhrajit1 aKumar, P., B. Sunil1 aAdhikari, Ronojoy1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/linking-catalyst-coated-isotropic-colloids-active-flexible-chains-enhances-their-diffusivity02650nas a2200217   4500008004100000022001400041245012400055210006900179260000900248300001100257490000700268520187900275653001202154653003002166653001902196653002602215653001202241100002102253700002702274856013102301       2019                        eng d  a0022-372700aEffect of electrostatic interactions on structure and mechanical properties of ice templated colloid-polymer composites0 aEffect of electrostatic interactions on structure and mechanical  cMAY   a2140020 v523 a<p>When an aqueous dispersion of negatively charged colloids, cationic polymer and crosslinker is frozen and the polymer is allowed to crosslink in the frozen state, we obtain a self-standing macroporous composite foam. This material is soft, despite the high concentration of colloids and yet is remarkably elastic to large compressive strains. In these macroporous composites, the pore walls comprise colloidal particles held within a crosslinked polymer network. Here, we investigate the effect of varying colloid- polymer interactions in pre-fabricated macroporous composites on their microstructure and mechanical properties. During preparation of the composite, cationic polymer adsorbs on the negatively charged colloids. We tune the surface charge of particles embedded in a macroscopic monolith by immersing the composites in water maintained at different pH. In this way, we tune polymer-particle interactions in the composite. We observe a sudden increase in interparticle distance and swelling of composite when pH is decreased below the particle's isoelectric point. Correspondingly, we observe reduction in Young's and shear moduli, compression strength and macroscopic energy dissipation. We did not observe any pH dependent changes in pure polymer sponges (prepared by ice templating and crosslinking a polymer solution that does not contain colloidal particles). Therefore, the pH dependent structural and mechanical property changes arise from the composite structure rather than purely from the crosslinked polymer. We believe that the reduction in mechanical stiffness when the polymer-particle interaction becomes repulsive is because of the reduction in interfacial contacts between particle and polymer. Therefore, the mechanical stiffness of ice templated composite is strongly influenced by interactions between the polymer and particle surface.</p>10acolloid10aelectrostatic interaction10aice templating10amechanical properties10aPolymer1 aSuresh, Karthika1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/effect-electrostatic-interactions-structure-and-mechanical-properties-ice-templated-colloid02445nas a2200241   4500008004100000022001400041245013500055210006900190260000900259300001600268490000700284520158700291653002901878653002201907653001901929653001801948100001501966700002101981700001702002700002702019700003102046856012602077       2021                        eng d  a0272-884200aHighly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property0 aHighly compressible ceramicpolymer aerogelbased piezoelectric na  cJUN   a15750-157580 v473 a<p>Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 ?W/cm2 (49.79 ?W/cm3) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.</p>10aCeramic polymer aerogels10aenergy harvesting10aice templating10apiezoelectric1 aRam, Farsa1 aSuresh, Karthika1 aTorris, Arun1 aKumaraswamy, Guruswamy1 aShanmuganathan, Kadhiravan  uhttps://library.ncl.res.in/content/highly-compressible-ceramicpolymer-aerogel-based-piezoelectric-nanogenerators-enhanced