Experimental and Finite Element Model-based framework for grasping force analysis with electrostatic microgrippers: a case study using a human hair

Microgrippers (MGs) are MEMS devices designed specifically for microscopic-scale object manipulation, which makes them ideally suited for implementation in biomedical tissue manipulation applications. This work presents a novel method for estimating the grasping force of a MG prototype equipped with electrostatic rotary comb-drives and Conjugate Surface Flexure Hinges using a cross-approach based on both experimental and a finite element analysis. Firstly, the torque exerted by the microactuators, necessary to deform the MG has been evaluated. The rotation of the microactuators is measured in the experimental analysis through an image analysis approach developed by the Authors from videos acquired by a camera mounted on a trinocular optical microscope, while the hinge stiffness has been determined using numerical simulations. This torque provided an initial estimate of the grasping force potential. Subsequently, in order to evaluate the force that the jaws of the MG are capable of applying in grasping operations, experimental tests have been carried out on a human hair with a diameter of (86 ± 3) µm. The results obtained show that the jaws of the device apply a maximum force of (1.42 ± 0.18) µN while grasping the hair.