Multifunctional 3D-Printed Pollen Grain-Inspired Hydrogel Microrobots for On-Demand Anchoring and Cargo Delivery.

While a majority of wireless microrobots have shown multi-responsiveness to implement complex biomedical functions, their functional executions are strongly dependent on the range of stimulus inputs, which curtails their functional diversity. Furthermore, their responsive functions are coupled to each other, which results in the overlap of the task operations. Here, a 3D-printed multifunctional microrobot inspired by pollen grains with three hydrogel components is demonstrated: iron platinum (FePt) nanoparticle-embedded pentaerythritol triacrylate (PETA), poly N-isopropylacrylamide (pNIPAM), and poly N-isopropylacrylamide acrylic acid (pNIPAM-AAc) structures. Each of these structures exhibits their respective targeted functions: responding to magnetic fields for torque-driven surface rolling and steering, exhibiting temperature responsiveness for on-demand surface attachment (anchoring), and pH-responsive cargo release. The versatile multifunctional pollen grain-inspired robots conceptualized here pave the way for various future medical microrobots to improve their projected performance and functional diversity.