Research On Self-assembly Technology Of Soft Microchips Based On Surface Tension

Flexible electronic technology is increasingly updated,and related flexible devices have a wide application prospect in information,energy,medical and other fields,because of their variability,easy to carry and multi-functional diversification.Due to the undeformable of the traditional rigid,its performance in flexible equipment is not ideal.The flexible chip is more suitable for the thin and soft electronic sensing system than the rigid chip owing to its unique flexibility,and it also helps to improve the sensitivity of the equipment.Chips in micro devices need to be assembled on a micro scale.Due to micro-scale effects,the effects of mass force and volume force on small objects are far less than electrostatic force,van der Waals force and surface tension.At this time,the operation difficulty is much greater than that at the macro scale.In addition,the traditional robot pick-up and release technology is mainly aimed at the rigid chip.The soft chip made of flexible material has greater adhesion,so the robot pick-up and release technology can not complete accurate release.Therefore,it is necessary to study the methods that can effectively manipulate the soft chip in microscale.In this paper,a micromanipulation method based on surface tension is proposed to realize the controllable operation of the soft chip.The extraction,transportation and release of the soft chip are realized by the cooperation of the capillary force micro-gripper and the micro-assembly experimental platform.The micro-convex structure is fabricated on the silicon wafer and PDMS film,and the droplets needed for the self-assembly of the soft chip are limited to the structure.Under the action of the surface tension of the droplets,the soft chip is aligned with the edge of the convex structure to complete self-assembly.The main research contents and results are as follows:(1)The mechanism of self-assembly based on surface tension and the method of restricting droplets are studied.The corresponding assembly model is established,and the maximum droplet volume limited by the structure is calculated.Based on the principle of energy minimization,Surface Evolver software was used to simulate the surface morphology of the droplet and analyze the change of restoring force of the soft chip.The result show that the greater the amount of misalignment,the greater the surface free energy of the assembly system,and the greater the restoring force on the soft chip.(2)Combing the soft chip self-assembly operation process and experimental requirements,a micro-assembly experimental platform is designed and built,which is composed of a capillary force micro-gripper system and a vision system.In order to avoid the influence of human factors and improve the efficiency of the experiment,the operating program is written in Automationbase software to realize the automatic control of the micro-assembly experiment platform.(3)The boss structure and the soft chip are processed by using a laser marking machine.In order to complete the limitation of the boss structure to the droplet,the laser processing parameters of the boss structure are optimized to improve the effect of the droplet limitation and the success rate.The laser marking machine is used to process the soft chip corresponding to the boss structure,and the processing parameters are optimized to prepare the soft chip with higher quality.(4)The experiment verified the self-assembly mechanism of the soft chip.A large number of experiments were carried out on different substrates by using the micro-assembly experimental platform to study the effect of the amount of droplet required for soft chip assembly,soft chip size and different shapes on the success rate of soft chip assembly and assembly efficiency.The experimental results show that under the droplet volume of 30nL-300nL,the success rate of 1000?mx1000?m square soft chip assembly can reach 100%.The smaller the droplet volume,the faster the assembly speed.It is proved that the feasibility of the assembly method and the reliability of the micro-assembly platform can be satisfied with the assembly of a variety of chip.