Elastomeric microsystems with stimuli-responsive actuation : co-doping fabrication and biomimetic applications

Abstract

Elastomeric microsystems are soft devices that employ elastomers as the basic material and integrate various functional micro and nano components, such as mechanical, optical, and fluidic components. With decades of development, elastomeric microsystems have been well applied in the biochemical analysis as microfluidics, health monitoring as soft electronics, and human-machine interaction as soft robotics, respectively. With the demand for precise controllability and environmental responsiveness, stimuli-responsive actuation, referring to mechanical deformation in response to external stimuli such as light, temperature, and humidity, is introduced into elastomeric microsystems. However, disparities in the properties and fabrication methods of stimuli-responsive materials and conventional elastomers lead to the coordinated integration of microstructures, responsive materials, and other functional components into a microsystem remaining a challenge. In addition to developing new micro-processing techniques for responsive materials, modification and functionalization of existing elastomeric microsystems is a compromise between satisfying the well-established micro-processing methods and developing new functions of stimuli-responsiveness. However, endowing an inherently inert elastomer with responsiveness inevitably requires multiple processing steps, raising the threshold of technology and cost. Therefore, a concise and effective method for preparing and functionalizing the stimuli-responsive elastomeric microsystems is urgently required in order to reduce technical barriers and save costs. In addition, although stimuli-responsive microsystems have already proved their practicality in individual fields, many areas with potential translational value are still unexplored. In particular, biomimetic designs inspired by the stimuli-responsive shapes or color variations of natural organisms are promising great applications in biomedicine, optics, and energy. In this thesis, we propose a co-doping fabrication method to facilitate the integration of stimuli-responsive actuators into elastomeric microsystems. In addition, through biomimetic design, we have developed responsive elastomeric microsystems into novel soft robots, color-changing systems, and microfluidic devices, respectively. In particular, in Chapter 3, we propose the co-doping fabrication method to optimize the preparation and functionalization of the hydrogel-elastomer actuator. Based on this actuator, a series of bio-inspired soft micro-bots are designed, demonstrating their biomimetic motions, such as grabbing, crawling, and jumping. In Chapter 4, we take inspiration from the bi-color of a butterfly’s wing and propose a pixelation method towards solvent-responsive structural coloration via concavity array. Upon solvent stimulation, the prepared array composed of photonic crystal elastomer actuators can form a concavity and thus change color to form letters and patterns, which could be used in dynamic display and camouflage. In Chapter 5, we propose a concept of transformable origami microfluidics inspired by the nastic movement of plants. The designed microfluidic device can change its shape in response to the changes in the environment and can thus be applied to environmentally adaptive photosynthesis. In summary, the main focus of this thesis is to develop techniques to integrate stimuli-responsive actuation into elastomeric microsystems. The designed stimuli-responsive actuator microsystems are applied in biomimetic applications, such as soft micro-robots, programmable color-changing systems, and transformable origami microfluidics. We believe that the above studies could deepen our understanding of stimuli-responsive microsystems and inspire novel applications in biomedical, optical, and energy engineering.