Fabrication And Application Of Tunable Microfluidic Devices Based On Ph-responsive Hydrogel

Filtering and trapping of microparticle/cell are the basis of single-cell analysis and biomedical research,and these manipulation methods based on microfluidic chips have attracted wide attention,due to their low reagent consumption,fast sample processing,high integration and low cost.The cell trapping is mainly achieved by external force fields such as optic,magnetic,acoustic,electric,or achieved by the interaction of the channel geometry and fluid.However,these methods have their own disadvantages like complex external apparatuses are needed or the trapped cell will easily escape,respectively.In this paper,femtosecond laser processing technology is used to integrate the pH-responsive hydrogel microstructure into the microfluidic chip,which can achieve stable particle/cell trapping without the needed of external apparatuses.In this paper,the spatial light modulator is used to modulate the femtosecond laser into Bessel light,turning the spot from a point into a ring with an adjustable diameter.The effects of different topological charge numbers and axicon radius on the distribution of Bessel light field generated by modulation are studied,and the microstructures are fabricated to test the actual fabrication by Bessel beam with different parameters.In this paper,a pH-responsive hydrogel material is used,arid the microstructures fabricated by this material can swell when pH>9 and shrink when pH<9.It is found that the degree of polymerization of the hydrogel microstructures can be precisely controlled by the laser processing dosages,thereby the deformation range of the microstructures can be well controlled.In addition,through quantitative analysis,it is found that the hydrogel microstructure fabricated by holographic fabrication technology has a greater deformability and a better surface quality than these fabricated by laser direct writing.Finally,the pH-responsive hydrogel microstructure array whose deformation can be accurately controlled is integrated into the microfluidic chip to make a tunable microfluidic chip,which can control the gap of array by adjusting the pH value in the channel.The gap and deformation of the microstructures can be precisely controlled by changing the fabrication position and laser processing dosages according to the needs.Using this tunable microfluidic chip,the filtering of multi-particles,the complete trapping of single particle/multi-particles and the complete trapping of multi-cells are also realized without the needed of external apparatuses.