Development of a Magnetically Driven Microgripper for PicoNewton Force-Controlled Microscale Manipulation and Characterization

Abstract

This paper presents a piconewton force-controlled magnetic microgripper (MMG) for microscale manipulation and characterization. The MMG consists of a cantilevered wrist force sensor and a magnetically driven double-finger gripper at the end. The manipulating force can be accurately detected by the wrist force sensor using an atomic force microscopy (AFM) optical lever. Moreover, the clamping force can be also precisely controlled by regulating the magnetic torque applied to the gripper fingers via the attached ferromagnetic beads. In addition, an AFM dynamic probing method was used for contact and clamping detection with the frequency shift of the oscillating MMG. The performance tests showed that the MMG has a gripping range of 0–17.4 $\mu$ m; it allows for accurate clamping force loading with a resolution of 38 pN and detecting the grasping force with a resolution of 182 pN. The capability of the MMG was verified by conducting three-dimensional manipulation of the microbeads ( $\O2-\O16$ $\mu$ m) with sub-micrometer accuracy and acting as an AFM colloid probe for fast mapping of the adhesion force. The proposed MMG is the first demonstration of a prototype capable of piconewton force-controlled microclamping, and it has great potential for high-precision microscale manipulation and characterization.