Research Projects

Among various self-assembly processes, colloidal self-assembly draws great deal of attention from scientific community owing to its potential applicability as model systems for fundamental explorations and practical applications. Patchy colloidal particles interacting via anisotropic potentials are interesting candidates for applications in biology, sensing, soft robotics etc. Patchy colloidal particles are those with their surfaces embellished with attractive or repulsive patches, thereby making them sticky along preferred directions (anisotropic interaction). The Patches can be either ‘enthalpic’ in nature wherein the selective stickiness along preferred directions are created by surface modification of the host particle, or ‘entropic’ in nature where the sticky patches are designed as a pair of physical protrusions and depressions leading to their effective attraction. Literature pertaining to patchy colloids is mainly focused on fabrication and self-assembly of HARD patchy colloids. Studies on their SOFT counterparts are surprisingly scarce. In this proposal we aim (i) To investigate the depletion mediated self-assembly of soft patchy particles fabricated via stop flow lithography process, (ii) to customize and fabricate soft patchy colloidal units, leading to the formation of 'predictable aggregates' through their self-assembly. Such customization will be done by taking cues from the depletion mediated self-assembly experiments performed during the execution of the project, and theoretical and computational insights from the honorary investigator, and (iii) to investigate the viscoelastic properties of the soft patchy particle laden air-water interface of a Langmuir Blodgett trough. The fabrication technique detailed in this proposal can simultaneously address various aspects pertaining to the fabrication of soft patchy particles, thereby creating particles with good control over their geometry, softness, and the number and placement of sticky patches. Following the successful fabrication of soft patchy colloids, their depletion mediated self-assembly will be investigated. In order to bring in depletion attraction between the shape complementary entropic patches, a non adsorbing polymer (such as polyethylene glycol) will be introduced to the colloidal system. Colloids are expected to form lock-and-key like bonds between shape compatible patches. The effect of depletant concentration (the strength of depletion interaction) on the assembly of fabricated particles will be investigated through in-situ optical microscopy observations. Further, the effect of particle softness on their assembly will also be investigated. Achieving the research objectives will lead to potential collaborations with researchers working on protein assembly, where our versatile soft patchy colloids will be applicable as model systems. Successful completion of the project is therefore, guaranteed to improve our understanding of complex assembly processes in nature, and improve the application prospects of patchy colloids.