Pečnik Bambič, Maks; (2025) Driving Self-organization of Mesoscale Active Systems Through an Environment-induced Torque. Doctoral thesis (Ph.D), UCL (University College London).

Text PECNIK_BAMBIC_MAKS_thesis.pdf - Accepted Version Access restricted to UCL open access staff until 1 December 2026. Download (79MB)

Abstract

Assembling structures piece-by-piece, akin to putting together a Lego® set, is a reliable way of fabrication at the macroscale. However, due to space and access constraints, the same method does not carry over to smaller scales. Creating small, functional and reconfigurable structures has a myriad of potential applications from drug delivery to micro-robotics and so alternative methods of fabrication are re- quired. Taking inspiration from nature, one possibility is to rely on individual pieces coming together on their own, in a process known as self-organization. The local environment is an important factor in driving self-organization by mediating inter- action between the pieces. Here, I explore how self-organization of two synthetic systems can be driven using torques naturally present in the surrounding environ- ment. The first system consists of kirigami micro-structures that fold due to thermal fluctuations. The structures are held together through flexible hinges whose motion is coupled with a hydrodynamic torque. By making simple modifications to the structure, the magnitude of this torque is changed and the ability o the structures to organize (fold) quickly and successfully can be significantly improved. My second system concerns active particles moving in a heterogeneous environment made of passive Brownian particles. The active particles interact with the passive environ- ment through a torque which steers them away from regions of high density. By tuning the dynamics of the active particles or the effective strength of the torque, for example through increasing the density of the system, the organization and the dynamics of the resulting structures can be changed. This thesis thus contributes to our understanding of how self-organization can be exploited as a means of creating structures at small scales in complex, inaccessible environments.

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