Micro-tweezers: Design, fabrication, simulation and testing of a pneumatically actuated micro-gripper for micromanipulation and microtactile sensing

This paper presents a novel micro-gripper design with the dual functions of manipulation and force sensing. The device consists of two parallel plates, each mounted on torsion bars, which can be made to rotate towards or away from each other by use of a pneumatically- or hydraulically-actuated elastic membrane. The plates can be conveniently fabricated using photo-etching and the design allows for a range of ratios between actuation pressure and tip opening displacement and force. The elastic gripping tips can be designed to provide sufficient compliance that their strain can be used to monitor and control the gripping force. An exemplar device has been fabricated and its behaviour characterised by a series of mechanical measurements of force and displacement. These measurements have been rationalised using a simple analytical model, backed up with finite element analysis to emphasise the design variables and scalability. This exemplar device, with a maximum tip opening amplitude of 1 mm and maximum force output of 50 mN, has also been demonstrated to perform pick-and-place operations with 200 μm micro-beads.