Research On One-way Sensitive Microfluidic Inertial Time Delay Switch

Micro inertial switch,integrating sensing judgment and execution,can detect acceleration signals and perform switch closing operations,which is widely used in weapon fuze safety insurance system.This paper combines microfluidics technology to design micro inertia switch which can be used in low-load weapon fuze such as rocket missile.This paper uses a combination of theoretical analysis,finite element numerical simulation and experimental testing.The developed switch can realize the functions of identifying acceleration threshold,controllable delay response and reliable latching.According to the background of the project,the material selection of the microfluidic chip is analyzed,and a switch design scheme using silicon as a substrate and mercury droplets as the working fluid is determined.Based on single-phase flow simulation,four typical flow channel structures with good flow and heat transfer characteristics are analyzed.The influence of the characteristic parameters of different structures on the flow pressure drop is obtained,and the selection of the structural parameters of the flow channel unit is guided.Based on the numerical simulation of multiphase flow,the influence of the single characteristic parameter of U-shaped microchannel on the characteristics of delay microchannel is analyzed.By simulating a large number of samples,the design criteria of the delayed microchannel based on the BP neural network model is determined.The delay time of the U-shaped microchannel can be predicted by entering the width,radius,length,and acceleration load of it.The structure of a unidirectional sensitive microfluidic inertial delay switch is designed.The switch si sensitive to the positive acceleration load of the X axis.The capillary force at the capillary valve is analyzed to obtain the theoretical formula for calculating the switching acceleration threshold.The error between the delay time of the simulation and predicted by the neural network model does not exceed 9%.The prototype switch was fabricated by wet etching and magnetron sputtering metal technology.The unidirectional sensitivity of the switch is verified by the Machite drop weight experiment.The centrifugal experimental platform is used to test the threshold of the switch.When the throat widths of the capillary valve are 80μm,120μm,and 160μm,the thresholds of the switch are 75.1 g,46.6 g,and 36.5 g,and the switch is latching reliably.The delay response function of the switch was verified through the delay test experiment,and the actual delay time of the switch under different load is determined.