Reconfigurable engineered motile semiconductor microparticles

Ugonna Ohiri,Orlin D Velev,Nan Jokerst,C Wyatt Shields,Koohee Han,Talmage Tyler

doi:10.1038/s41467-018-04183-y

Ugonna Ohiri, Orlin D Velev + Show 4 more

Open Access

https://doi.org/10.1038/s41467-018-04183-y

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Abstract

Locally energized particles form the basis for emerging classes of active matter. The design of active particles has led to their controlled locomotion and assembly. The next generation of particles should demonstrate robust control over their active assembly, disassembly, and reconfiguration. Here we introduce a class of semiconductor microparticles that can be comprehensively designed (in size, shape, electric polarizability, and patterned coatings) using standard microfabrication tools. These custom silicon particles draw energy from external electric fields to actively propel, while interacting hydrodynamically, and sequentially assemble and disassemble on demand. We show that a number of electrokinetic effects, such as dielectrophoresis, induced charge electrophoresis, and diode propulsion, can selectively power the microparticle motions and interactions. The ability to achieve on-demand locomotion, tractable fluid flows, synchronized motility, and reversible assembly using engineered silicon microparticles may enable advanced applications that include remotely powered microsensors, artificial muscles, reconfigurable neural networks and computational systems.

Highlights

Energized particles form the basis for emerging classes of active matter
This design capability can lead to control over the internal and external charge distributions, polarizabilities, and field rectification of the particles in AC electric fields. These particles can be engineered to draw energy to interact and propel in a variety of controllable fashions. We demonstrate their controllable motion through multiple concurrent mechanisms, including dielectrophoresis (DEP)[39], induced charge electrophoresis (ICEP)[32], and diode-based propulsion by AC field rectification (Fig. 1b)[12,13]
Tracer experiments and polarization flow origins for the remaining types of microparticles (i.e., N-0 and PN-II) are discussed in Supplementary Note 8. These results indicate that the p–n junction, metal contact, and the interface between the two materials contribute to the active propulsion of microparticles via ICEP, with the metal contact being more polarizable, as it drives much larger fluid flows

Summary

Introduction

Energized particles form the basis for emerging classes of active matter. The design of active particles has led to their controlled locomotion and assembly. This nonuniform doping concentration creates a non-uniform charge distribution of counterions in the surrounding fluid[41,42], causing weak-ICEP flows and propulsion of the PN-0 microparticles when exposed to an AC electric field.

Results

Conclusion