Encryption/decryption and microtarget capturing by pH-driven Janus microstructures fabricated by the same femtosecond laser printing parameters

Several natural organism can change shape under external stimuli. These natural phenomena have inspired a vast amount of research on exploration and implementation of reconfigurable shape transformation. The Janus structure is a promising approach to achieve shape transformation based on its heterogeneous chemical or physical properties on opposite sides. However, the heterogeneity is generally realized by multi-step processing, different materials, and/or different processing parameters. Here, we present a simple and flexible method of producing pH-sensitive Janus microactuators from a single material, using the same laser printing parameters. These microactuators exhibit reversible structural deformations with large bending angles of ~31° and fast response (~0.2 s) by changing the pH value of the aqueous environment. Benefited from the high flexibility of the laser printing technique and the spatial arrangements, pillar heights, and bending directions of microactuators are readily controlled, enabling a variety of switchable ordered patterns and complex petal-like structures on flat surfaces and inside microchannels. Finally, we explore the potential applications of this method in information encryption/decryption and microtarget capturing.