Tunable Strain Microvalve Via Cracked Silica Rubber Surface And Its Application In Microfluidic Devices

Microvalves are used in most integrated microfluidic devices,and their functions include flow controlling,switching,and screening of micro-nanoparticles.The current manufacturing methods of microvalves need expensive equipment,and are very complicated.The preparation period is long,and the regulation is non-dynamic and the function is single.However,there are few researches on the multifunctional and dynamically adjustable microvalves,which limits the development of multifunctional microfluidics.Aiming at the above problems,we used ultraviolet ozone etching technology to make silica rubber become a composite material of thin film/soft substrate system,and the hard layer cracked under the applied tension.The flexible microfluidics valve with normally closed,dynamically adjustable and reversible microchannel array was packaged and prepared.A simple,cheap and practical method is developed,and it has a very important potential value in the application of disposable microfluidics.The main work contents are as follows:(1)Fabrication of tunnel cracks in thin film/soft substrate system.In order to solve the problems in smart surface,such as complicated process,high cost,etc.In this paper,the quasi-periodic intelligent surface of micro-nanometer cracks are constructed by ultraviolet etching on polymer silica rubber for screening different size of particles.This method has simple experimental steps and greatly reduces the expense compared with traditional precision machining.Through the treatment of ultraviolet ozone,a hard oxide layer appears on the silica rubber surface.Under uniaxial stretching,the silica rubber surface forms an array of tunnel cracking with a width ranging from 0 to 400 ?m.(2)Fabrication of crack microvalve actuated by strain.The silicon film with uniform microarrays and the flat silicon film without treatment are sealed irreversibly,forming the microvalves actuated by tensile strain.After being heated,the device can be recycled several times.The preparation method do not require expensive instruments.And the device fabricated in this way not only has the ability to control the flow direction,also can realize some special functions.To test the performance of our microvalves,we test the effect of the encapsulation and measure the ability to regulate the flow rate.(3)Preparation of functional microfluidic devices.We use CO2 laser engraving machine to carve the desired micro channels and chamber in the smooth polymethyl methacrylate(PMMA),recycling secondary rubbing film to reproduce exactly the same morphology with organic glass of flexible base plate and a smooth surface.The method of crack microvalve actuated by strain is applied to the flexible backplane.In this way,it can filter the particles of different size of functional devices,and successfully separated respectively 2 ?m in diameter and 40 ?m of silica microspheres.As a programmable microfluidic logic device,the crack strain microvalve can make the liquid flow out of different outlets by adjusting the strain.The crack strain microvalve is applied to the wearable drug delivery microfluidic device,which successfully transfers the liquid from the container to the outlet by stretching and bending the finger joint.