Manufacture Of Micro-sieve Structure In Microfluidic Chips

Micro total analysis system (μTAS) is a kind of system which can make thechemical analysis equipment miniaturization and more integratable. The μTAS systemis gradually developed in the recent20years, it is a new kind of miniaturebiochemical analysis system, also known as lab on a chip (LOC) and microfluidicchips. LOC has been applied in many fields, especially in chemistry and biology, suchas gene analysis, protein analysis, medicinal development, medical examination,environmental monitoring. In micro-optics, micro lens, micro gratings, microwaveguides and micro sensors are generated and used in the LOC. And also, LOC isserved as in situ analysis, for example, in situ surface enhanced Raman spectroscopymonitor. Due to its unique advantages, such as low cost and consumption,environmental friendliness, convenient to carry, LOC will have more extensiveapplications in the future.As the microchip system size decrease continuously, even to the micron level,the traditional methods to generate microchips, such as electron beam etching and wetetching, cannot meet the growing demand. It has been more than50years since theinvention of the first ruby laser, the application of laser has gradually penetrated intoscientific research, industrial manufacturing, medical treatment, national defense.Micro machining technology is the strong support of the microelectronics industry,which is widely used in micro electro mechanical system (MEMS), micro opticalmechanical system (MOMS), microfluidic chips. A spatial resolution of tens ofnanometers can be achieved by femtosecond laser direct writing (FsLDW). Theresolution exceeds the optical diffraction limit, in this reason, FsLDW is the mostimportant part of that strong support we said before. In this essay, we explains theprinciple of the femtosecond laser two-photon absorption, and introduces the way thatwe set up the micro machining system, certain conditions that should be satisfiedduring setting up system are given.There are mainly two parts in this essay. 1. With the help of wet etching method we generate glass chips. HF corrodesSiO2to get a micro-channel, the corrosion rate can be controlled by adjustingcorrosive liquid. We use polystyrene (PS) and tetrabutyl orthotitanate (TBOT) to get amicro sieve in channel by the method of annealing.2. Micro sieve fabricated by FsLDW. We present an idea called “expose twiceand develop once” to get microstructure in SU-8channel. The two exposures includeUV lithography and femtosecond laser fabrication. One time development means nodevelopment after UV lithography but after the laser fabrication. This idea comesfrom a paper on magazine Lab On Chip, and in our work SU-8channel avoids therefractive index changing compared to glass channel.