A Stiff-Soft Composite Fabrication Strategy for Fiber Optic Tethered Microtools

The ability to capture, manipulate, and release microscale objects using autonomous systems can enable widespread applications-from microsurgery and selective cell extraction to the assembly of complex microdevices. With continuing development of smart and environmentally responsive materials compatible with 3D printing, microgrippers with environmental adaptability can give rise to biocompatible devices. In this paper, the design, fabrication, and testing of hybrid stiff-soft microgrippers using compliant synthetic polymers and hydrogels to achieve autonomous actuation while avoiding an overly complex mechanical gripping system are described. Building microgrippers using 2-photon polymerization additive manufacturing based on nonplanar, bioinspired architectures on the end of an optical fiber is investigated. To control actuation, current regulated growth of hydrogels within the printed architecture is demonstrated. Forces are generated by expansive gels actuated by changes in pH, temperature, and application of light via optical fiber. The resulting multimaterial actuators incorporate inert skeletal components with active hydrogels on the tip of a 200 mu m diameter core fiber. The response time, accuracy, and cyclic durability of hybrid grippers are evaluated. This work provides a foundation to integrate stimuli-responsive mechanical functions with microscale optical devices to expand the suite of tools available for minimally invasive surgical procedures.