In recent years, Micro electro-mechanical systems(MEMS) aredominating the field of medical, optical acoustics and automotiveapplications. Based on MEMS technologymicrogrippers is a developing technology plays an important role in microassembly and micromanipulation fields. It provides manipulating signal for nerves, tissues, cells andmicromechanical objects, etc. In orderto manufacture microgrippers, microactuators are essential to control theoperations of microgrippers, Microactuators are developed using different actuation principles suchas shape memory alloys, electrostatic, electro thermal, piezoelectric,pneumatic and electromagnetic approaches.
Static model of the MEMS microgrippers can be developed by utilizing themechanics for the electrostatic actuation system(lateral comb drive) andsensing systems(transverse comb drive) for testing the operation of thedevice. Electrostaically actuatedmicrogrippers with a post-assembly self-locking mechanism is the current trendin MEMS microgrippers. The arms aredriven by rotary comb actuators, enabling the microgripper to grip objects ofany size from 0 to 100µm. It enables themicrogripper arms to grip for long periods without continuously applying the externaldriving signal. It significantly reducesthe effects and damage to the gripped objects caused by the external drivingsignals.
The electrothermal microgripperare also leading technique which is fabricated using the PolyMUMPs surfacemicromachining process which gives high reliability, repeatability andreproducibility of jaws gap. Theelectrothermal force sensor has a small footprint, is quite linear and operates with a highaccuracy. It is fabricated frombiocompatible material(silicon) with sufficiently long gripping arms. These microgripper can be used to manipulateliving cells, tissues and other biologically relevant samples, Hydrogel provide a wide range of actuatableand self-folding microstructures where mechanical motion is derived from thelarge and reversible swelling response of this cross linked hydrogel in varyingthermal or pH environmnets.
Thermo-piezoelectric actuatorbased microgripper presents both a high range and a high positioningresolution. The principle of thesemicrogripper is based on the combination of the thermal actuation (for the coarsepositioning) and the piezoelectric actuation (for the fine positioning). This paper presents an overview of recentdevelopment in microgrippers for the actuators(electrostatic, electrothermaland other actuators) and sensors (optical method, piezoresistive force sensor,capacitive force sensor for different application in biomedical and biologicalapplications involves micro-manufacturing operation.