Although there has been extensive development and exploration of small-scale robots, the technological challenges associated with their complicated and high-cost fabrication processes remain unresolved. Here, we report a one-step, bi-material, high-resolution three-dimensional (3D) printing method for the fabrication of multi-stimuli-responsive microactuators. This method exploits a two-phase femtoliter ink meniscus formed on a double-barreled theta micropipette to continuously print a freestanding bilayer microstructure, which undergoes an asymmetric volume change upon the adsorption or desorption of water. We show that the 3D-printed bilayer microstructures exhibit reversible, reproducible actuation in ambient humidity or under illumination with infrared light. Our 3D printing approach can assemble bilayer segments for programming microscale actuation, as demonstrated by proof-of-concept experiments. We expect that this method will serve as the basis for flexible, programmable, one-step routes for the assembly of small-scale intelligent actuators.

Continuous-flow microreactors enable ultrafast chemistry; however, their small capacity restricts industrial-level productivity of pharmaceutical compounds. In this work, scale-up subsecond synthesis of drug scaffolds was achieved via a 16 numbered-up printed metal microreactor (16N-PMR) assembly to render high productivity up to 20 g for 10 min operation. Initially, ultrafast synthetic chemistry of unstable lithiated intermediates in the halogen–lithium exchange reactions of three aryl halides and subsequent reactions with diverse electrophiles were carried out using a single microreactor (SMR). Larger production of the ultrafast synthesis was achieved by devising a monolithic module of 4 numbered-up 3D-printed metal microreactor (4N-PMR) that was integrated by laminating four SMRs and four bifurcation flow distributors in a compact manner. Eventually, the 16N-PMR system for the scalable subsecond synthesis of three drug scaffolds was assembled by stacking four monolithic modules of 4N-PMRs.