Design of large-displacement asymmetric piezoelectric microgripper based on flexible mechanisms

The output displacement of the traditional symmetrical microgripper is large,but its micro-components or parts are easily damaged due to the uneven force exerted on the left and right jaws of the gripper.The output force of the traditional asymmetric microgripper is stable.However,its output displacement is small,typically half the output displacement of the symmetric microgripper.To solve these problems,in this study,we designed a large-displacement asymmetric microgripper.First,we calculated the relationship between the theoretical input and output variables based on their geometric relationship.Then,we analyzed the performance of the microgripper using finite element software.Lastly,we used a piezoelectric actuator as the input driver of the microgripper.The errors associated with the theoretical and simulated output displacements were 7.05%and 9.24%,respectively.At 150 V of driving voltage,the maximum output displacement was 224μm,and the actual magnificationwas 11.2 times.Microparts can be gripped in parallel and stably,which confirms the validity of the design.

Design of a flexible piezoelectric microgripper based on combined amplification principles

Aiming to address the problem of the low amplification ratio of traditional microgrippers,a two-stage microgripper based on the principle of combined amplification was designed with a high amplification ratio and large displacement,using a simple and compact structure.The relationship between theoretical input variables and output variables were first calculated by a projection theorem.Secondly,the performance of the microgripper was analyzed by finite element analysis(FEA).Finally,the accuracy of the theoretical calculation and FEA was verified experimentally.The results show that the microgripper has high magnification and can be gripped in parallel,with self-adaptability for many irregular shaped micro objects.The actual magnification was 23.2×,which is greater than similar products.

Integrated Fabrication of a Microgripper

Successful implementation of simple mechanism on silicon chip is a prerequisite for monolithic microrobotic systems. This paper describes the integrated fabrication of polycrystalline silicon microgripper. Link, fixed and active joint, and sliding flange structures with dimensions of micrometers have been fabricated on the substrate of monocrystalline silicon using silicon microfabrication technology.This microgripper, which may be applied to transducers or sensors, can be batch fabricated in IC compatible process. The movable mechanical elements are built on layers that are later removed, so that they are free for translation and rotation. Under external driving, a microgripper cut from substrate would be able to catch tiny filament or small particle with dimension of 10～200 micrometers.

DESIGN AND FABRICATION OF A MICRO THERMAL ACTUATOR FOR CELLULAR GRASPING

The development of a novel polymer-based micro robotic gripper that can be actuated in a fluidic medium is presented in this paper.Our current work is to explore new materials and designs for thermal actuators to achieve micromanipulation of live biological cells.We used parylene C to encapsulate a metal heater,resulting in effectively a tri-layered thermal actuator.Parylene C is a bio-compatible dielectric polymer that can serve as a barrier to various gases and chemicals. Therefore,it is suitable to serve as a thermal/electrical/chemical isolation material for protecting the metal heater from exposing to an aqueous environment.We have demonstrated parylene actuators (2mm×100μm×0.5μm)to operate in an aqueous environment using 10 to 80mW input power.The temperature of these actuators at full deflection was estimated to be～60℃,which is much lower than the typical requirement of>100℃ to actuate other conventional MEMS actuators.Danio rerio follicles in fluidic medium were captured successfully using these actuators.Moreover,these actuators were found to be responsive to moderate rise in environmental temperature,and hence,we could vary the fluidic medium temperature to actuate trimorphs on a chip without any input of electrical energy, i.e.,raising the fluidic temperature from 23℃ to 60℃ could actuate the trimorphs to grasp follicles of ～1mm size in diameter.At 60℃,the embryos inside the follicles were observed to be alive,i.e.,they were still moving in the biological fluid isolated by the follicle membrane.The smallest follicles grasped were～500μm in diameter using 800μm×130μm×0.6μm actuators.The fabrication process,modeling, and optimization of the trimorph actuators are presented.Based on the successful operation of these polymer-based actuators,we are currently developing multifinger thermal microgrippers for cellular grasping and manipulation,which can potentially be hybridly integrated with circuits for computer control.