Soft Robots in Medical Device Design—Integrated Design, Manufacturing and Operation of Microscale Printed Compliant Mechanisms Using Topology Optimization

The promise of microrobots capable of navigation and manipulation <i>in vivo</i> could transform disease detection and treatment. To these ends, we have developed a hybrid material approach for microrobot assembly comprised of an optical path, an environmentally responsive actuator, and a printed compliant mechanism. The compliant exoskeletal gripper head can be autonomously actuated by stimuli-responsive materials (e.g., hydrogels, elastomers) that respond to light, pH, and temperature. Toward the development of clinically relevant designs, we aimed to improve robot performance under physiological conditions, such as small changes in pH that may indicate disease. For this we employ a topology optimization approach—applied to the exoskeletal geometry—to maximize the mechanical output to environmental cues. This design-manufacture-operate optimization schema accounts for printed material properties, printer parameters, and hydrogel-environment interactions. Bringing manufacturing and operation conditions into the analytical design process facilitates robot design for specific tasks (e.g., retrieval/deployment of low to high-modulus payloads). We demonstrate that we can achieve marked improvements in design objective functions when parameters from design, fabrication, and operation are included. We also see in testing printed designs that we have good agreement between analytical and experimental results, tested in vitro. Though realizing topology-optimized forms has been well suited to additive manufacturing for static mechanics, we show that substantial increases in dynamic performance at micro/nano length scales is achieved by integrating the complementary processes of design, manufacturing and operation which, in turn, enables new robot designs optimized for specific operations such as grippers, sensors, displays, and active surfaces.