Autoperforation of Two-Dimensional Materials to Generate Colloidal State Machines Capable of Locomotion
A central ambition of the robotics field has been to increasingly miniaturize such systems, with perhaps the ultimate achievement being the synthetic microbe or cell sized machine. To this end we have introduced and demonstrated prototypes of what we call Colloidal State Machines (CSMs) as particulate devices capable of integrating sensing, memory, energy harvesting as well as other functions onto a single particle. One technique that we have introduced for creating CSMs based on 2D materials such as graphene or monolayer MoS2 is autoperforation, where the nanometer scale film is fractured around a designed strain field to produce structured particles upon liftoff. While CSMs have been demonstrated with functions such as memory, sensing, and energy harvesting, the property of locomotion has not yet been demonstrated. In this work, we introduce an inversion molding technique compatible with autoperforation that allows for the patterning of an external catalytic surface to be introduced to enable locomotion in an accompanying fuel bath. Optimal processing conditions are elucidated for adding a catalytic Pt layer to one side of an autoperforated CSM. The resulting propulsion is studied, including the average velocity, as a function of fluid surface tension and H2O2 concentration in the bath. Lastly, since machines have to encode for a specific task, this work summarizes efforts to create a microfluidic testbed that allows for CSM designs to be evaluated for the ultimate purpose of navigation through complex fluidic networks, such as the human circulatory system. We introduce a CSM design that mimic aspects of human immunity to solve search and recruitment tasks in such environments. These results advance CSM design concepts closer to promising applications in medicine and other areas.
- This article is part of the themed collection: Chemistry of 2-dimensional materials: beyond graphene