Theoretical And Experimental Study On Adhesion And Peeling Of Elastic Structures At Microscale

With the rapid development of micro/nano technology and Micro Electro Mechanical Systems(MEMS),the study on the deformation and adhesion of structures and their members has raised extensive concerns of scientists and engineers.At micro/nano scale,the volume forces of objects decay much faster than the surface forces,and in this case surface effects play an essential role in this process.During this situation,adhesion can happen in these microscaled structures under the action of surface and interface forces.The process deals with large deformation,nonlinearity and multiphysics fields.As a result,it is very difficult to perform theoretical analysis and related experiments on this issue,and it is just an emerging area to be explored.Firstly,we carry out a comprehensive exploration directed towards getting more appropriate laws of a circular plate adhered to solid with large deformation,which may provide some inspirations on the design of MEMS and some other micro/nano-devices.Then,the energy functional of the plate-liquid-substrate system is established,which includes the stretching energy,bending energy and interfacial energy.By means of the principle of least potential energy and functional variation with movable boundary condition,the governing equations of the plate and the corresponding transversality condition are derived.The radial displacement and deflection,and the critical adhesion radius of the plate are calculated,and these parameters have also been compared with several experimental results.It manifests that our theoretical prediction is in excellent agreement with the experiments,demonstrating the necessity to adopt the finite deformation model to acquire more accurate solutions.Next,we present the model formulation on the peeling of a soft beam under a concentrated force,by considering its large deformation and axis extensibility.The governing equation group and the transversality condition are then derived,according to the variation on the energy functional with movable boundary conditions.We find that the key parameters in peeling,such as the adhered segment length,applied force and length increment of the beam,are only correlated with two dimensionless variables,i.e.the non-dimensional maximum displacement of the beam and non-dimensional work of adhesion.The calculated results are in excellent agreement with the experimental data,which are also compared with the infinitesimal deformation model and large deformation model with inextensible axis.This fact further stresses that the adhesion and peeling of elastic structures like beam and plate in microscale.These findings shed light on the design of elementary structures in micro and nano-devices,and better application of micro/nano-printing technique.