Design And Experimental Study Of 3D 3-Fingered Electrothermal Microgripper With Multiple Degrees Of Freedom

Micro-manipulation is a hot field of current research.Though various micro tools for micro-manipulation have been developed,these tools,in general,can only perform very simple translational manipulation,i.e.,picking up and placing down of micro objects.Further rotations of micro objects require extensive manual work and skills.However,the micropipettes,optical tweezers,and various microgrippers have been proven to be capable of producing limited three-dimensional(3D)mobilities,but not to be good enough to conduct dexterous manipulation of micro objects in 3D space.Among them,micropipettes and optical tweezers only provide single degree of freedom(DOF)and are only suitable for manipulating certain objects with limited flexibility.In contrast,the microgripper possessing larger room for designs and can be used for 3D manipulation of micro objects.At present,almost all the microgrippers are based on the planar two-jaw design,producing only one DOF and have limitations.With the increasing demand for manipulation of micro objects,the research on multi-finger and multi-DOF 3D microgripper has important practical application value.In this paper,aiming at the problems faced by micro-manipulation,we take the 3D electrothermal microgripper as the research object,and focus on structure design of 3D electrothermal microgripper,the statics model of actuator,simulation analysis and micromanipulation experiments.The main research content of the thesis is as follows:First of all,the 3D U-shaped electrothermal actuator is designed,and on this basis,two kinds of three finger 3D electrothermal microgripper with multi DOFs composed of3 D U-,bidirectional Z-shaped electrothermal actuator and 3D U-and V-shaped electrothermal actuator are designed.The two kinds of 3D microgripper are composed of three identical fingers respectively,which are independent and evenly distributed.Each finger is composed of a bidirectional Z-or V-shaped electrothermal actuator and a Ushaped electrothermal actuator.Each finger can provide multi DOFs in the X,Y,and Z directions,with the cooperation of these three fingers,the microgripper can picking up,gripping,rotating and releasing micro objects in 3D space.In addition,the simulation analysis of the static model of the electrothermal actuator is carried out to verify the feasibility and rationality of the electrothermal actuator and the 3D microgripper;Secondly,the static model of the 3D U-shaped electrothermal actuator is deduced by the deflection formula of the beam and the superposition principle,and the relationship between the temperature loads and the output displacements is obtained.The accuracy of the results of the static model is verified by simulation analysis.The results show that the theoretical results and the simulation result of the 3D U-shaped actuator is less than 1%,which verifies the accuracy of the theoretical model of the actuator;Thirdly,the material selection,processing method,driving method and the measurement method of the output displacement of the 3D microgripper are introduced.On this basis,the static and dynamic output displacements of the 3D U-,V-and bidirectional Z-shaped electrothermal actuators were measured experimentally.In addition,the temperature load measured on the electrothermal actuator is substituted into the theoretical model and simulation analysis model of the 3D U-shaped actuator,and the obtained results are compared with the actual measurement results.The results show that the error between the experimental and theoretical results of the output displacement of the actuator is about 11%,which verifies the experimental feasibility of the static model;Finally,the picking,rotating,and releasing of the micro objects are accomplished with two kinds of the 3D microgripper.We use micro balls with a diameter of 2mm and zebrafish embryos with a diameter of around 600-800μm to illustrate the feasibility of the3 D microgripper to operate micro objects.The experiments show that the novel 3-fingered 3D microgripper with multi DOFs can meet the requirements of micromanipulation with micro objects,and improve the flexibility of the 3D microgripper in micro-manipulation experiments.