Laser‐guided thin‐film self‐rolling for asymmetric small‐scale swimmers

Abstract

Abstract Small‐scale robots are promising miniaturized devices in biomedicine. Thin‐film self‐assembly is a commonly used strategy to fabricate tubular small‐scale robots. However, the existing methods have limitations like complex manufacturing processes and limited control of self‐assembly behavior. Herein, we present a recently developed laser‐guided self‐assembly strategy that transforms platinum/gold bilayer thin films into three‐dimensional tubular structures. These structures function as chemically actuated, asymmetrically designed small‐scale swimmers. Micro‐roll structures with customizable geometrical asymmetry are prepared through a precise laser‐guided rolling process, in which the laser settings can digitally control the rolling behavior because of the point‐to‐point laser–material interaction. Furthermore, the as‐fabricated micro‐rolls could be directly peeled off the substrate and transferred to the target container by laser irradiation. The specially designed cone‐like asymmetric platinum/gold micro‐roll can swim forward in the hydrogen peroxide solution by ejecting bubbles from the large open end. The movement of small‐scale swimmers in open water can be precisely controlled by adjusting their asymmetry, which is achieved through carefully designed laser scanning paths. The interactions of the asymmetric small‐scale swimmers with various boundaries (both fixed and untethered) are systematically investigated and summarized. Micro‐roll encapsulation with empty capsules can be integrated into the laser transfer process. The dissolution of capsules and release of small‐scale swimmers in aqueous solutions are demonstrated. This research indicates the potential of the one‐step laser‐guided self‐assembly and forward transfer method in manufacturing and encapsulating miniaturized devices.