Reconfigurable and Actuating Microbowls with Variable Steps

Polymeric microdevices with bioinspired multifunctional features like defined geometrical actuation or spatially segregated surface properties are attractive with potential applications in sensors, microfluidic systems, on-demand carriers, and biomedical devices. In this regard, here, we aim at enhancing the programability of multi-shape memory micro-objects using atomic force microscopy (AFM) to achieve a sequential shape reconfiguration or actuation at different geometrical levels on demand. Temperature-memory polymer-based microcuboids were designed and fabricated as a model system. The first step in the programing of the microcuboids was achieved by compression between glass slides with external force at selected programing temperatures T_p. Then, microbowls were generated by AFM nanoindentation using a spherical tip on the surface of the microcuboids to create temporary nanocavities at different T_p,inds. The geometry and surface structure of the microcuboids was analyzed by AFM height images. By varying T_p/T_p,inds and the sequence of the procedure, multiple nanocavities can be generated on the same microbowl to achieve sequential full recovery and actuations of 2-6%. In addition, a demonstration of microbowl trapping and sequential elevating submicron particles was performed to prove the concept of the on-demand carrier and release system. The technology presented in this work can inspire future design of multifunctional micro-objects in order to fulfill complex tasks with shape reconfiguration or actuation functions on micro-/nanolevel.