Starch Janus Particles:\nBulk Synthesis, Self-Assembly,\nRheology, and Potential Food Applications

Abstract

Although incredible progress in the field of Janus particles\nover\nthe last three decades has delivered many promising smart-material\nprototypes, from cancer-targeting drug delivery vehicles to self-motile\nnanobots, their real-world applications have been somewhat tempered\nby concerns over scalability and sustainability. In this study, we\nadapt a simple, scalable 3D mask method to synthesize Janus particles\nin bulk using starch as the base material: a natural biopolymer that\nis safe, biocompatible, biodegradable, cheap, widely available, and\nversatile. Using this method, starch granules are first embedded on\na wax droplet such that half of the starch is covered; then, the uncovered\nhalf is treated with octenyl succinic anhydride, after which the wax\ncoating is removed. Janus particles with 49% Janus balance can be\nproduced in this way and were observed to self-assemble into wormlike\nstrings in water due to their hydrophobic/hydrophilic nature. Our\nJanus starch granules outperform the non-Janus controls as thickening\nand gelling agents: they exhibit a fourfold increase in water-holding\ncapacity, a 30% lower critical caking concentration, and a viscosity\ngreater by orders of magnitude. They also form gels that are much\nfirmer and more stable. Starch Janus particles with these functional\nproperties can be used as novel, lower-calorie, highly efficient,\nplant-based super-thickeners in the food industry, potentially reducing\nstarch use in food by 55%.