Performance comparison between single-joint and multi-joint microgrippers equipped with conjugated-surface flexure hinges

The rise of microscale technology has empowered research on the development of micromanipulators. This paper presents a comparative analysis of three microgrippers fabricated on Silicon-On-Insulator (SOI) substrates, utilizing photolithography and Deep Reactive Ion Etching (DRIE) for device layer patterning, and wet etching for the release of moving parts. Each gripper uses electrostatic rotary comb-drive actuators, chosen for their ease of design, high precision, and quick response times. The motion of these grippers is eased by curved beams acting flexure hinges, which replace traditional rotary joints at the microscale. The first microgripper, identified as S1, features a simple rotational motion of the tips, while the second and third, S2 and S3, incorporate complex mirrored 4-bar linkages with eight hinges each, allowing for more dexterous of motion. Experimental trials assessed the tip motion and rotation of the comb structures when voltage is applied. This study underscores the feasibility and functionality of these micromanipulators, highlighting their potential for precise, reliable, and energy-efficient operation in microscopic interventions.