Buckling Of Suspended Stiff Film And Mechanical Design Of Electromagnetic Assisted Transfer-printing Stamp

In recent years,flexible and stretchable electronics have received widespread attentions.The main reason is that the mechanical properties of flexible electronics are better than that of traditional electronics.The flexible electronics can be adapted to a variety of stretching,curling,folding,twisting and flexible electronics can be applied to a variety of complex surface.However,due to the short development time of flexible electronics,the related basic theories,design methods and control technologies have not yet been fully developed.In particular,theoretical studies on improving stretchability of flexible electronics and transfer-printing are in urgent need of further exploration.Of course,improving the stretchability of flexible electronics and transfer technology are two of the most important studies in flexible electronics.Therefore,this article will proceed from these two aspects,and further study of the flexible electron.According to the structure-induced stretchability,this paper introduces a new type of buckling structure-the electronic film is suspended on a soft tripod substrate to improve the stretchability of flexible electronics.The mechanical behavior of buckling and post-buckling of electronic film suspended on a soft tripod substrate was analyzed by energy method,minimum potential principle and finite element simulation.At the same time,because transfer-printing is an important part of flexible electronics manufacturing,this paper presents a new transfer-printing method-Electromagnetic assisted transfer-printing.The relationship between the electromagnetism driving force and the parameters of stamping structure was obtained and this result is theoretical guidance for future experiments.The main contents and conclusions of this paper are as follows:1.The buckling and post-buckling behavior of the stiff film suspended on a soft substrate with tripod surface relief structure were investigated.The total energy of the film-substrate system and the principle of minimizing the potential energy were used to establish the relationship between the amplitude of buckling and post-buckling and the maximum value of film strain on pre-strain and applied strain.The results show that the amplitude of the buckling film and the maximum film strain increase with the increase of the tip spacing and pre-strain of the substrate.During post-buckling,the amplitude of post-buckling film increases with the initial adjacent tripod tip spacing and pre-strain,and decreases with increasing applied strain.At the same time,through the theoretical analysis and finite element simulation,in comparison to trench surface relief structure,the tripod surface relief structure on the soft substrate provides even higher stress reduction.2.A new transfer-printing method-electromagnetic assisted transfer-printing was introduced.By changing the pressure in the cavity of the stamp structure,the adhesion between the electronic components and the stamp can be controlled.The mechanical model of the magnetic-responsive stamp with the cylindrical cavity and the four-ridged cavity was analyzed.The relationship between the maximum displacement of the bottom PDMS film and the electromagnetic driving pressure of the upper film at the cavity was obtained by the energy method and the principle of minimum potential energy.The results show that during the process of inking and printing,the pressure at the bottom open cavity and the maximum deformation of the bottom PDMS film are proportional to the electromagnetic driving pressure.However,it is inversely proportional to the PDMS elastic modulus,film thickness,film radius / side length ratio.In the printing process,the cavity pressure is proportional to the electromagnetic driving pressure.By comparing the aspect ratio or the radius ratio,it can be found that the stamp with a side length ratio or a radius ratio of less than one is most effective in the transfer-printing process.The results provide theoretical guidance for the design and optimization of the results of the new stamping.