Research And Application Of Low Cost Digital Microfluidic Chip Based On Dielectric Wetting

As a new droplet manipulation technology,digital microfluidic technology based on dielectric wetting is widely used in biomedicine and analytical chemistry because of its advantages of small amount of experimental reagent,rapid operation response and automatic parallel processing of multiple droplets.But generally speaking,due to its harsh experimental conditions and expensive experimental cost,digital microfluidic technology mainly exists in the laboratory research stage.In order to improve the reliability and universality of digital microfluidic experiment,this subject designs and builds a digital microfluidic system,prepares two low-cost digital microfluidic chips with different electrode materials,analyzes the stress in the process of droplet movement,tests and optimizes the performance of the prepared chip,and finally carries out the application of NO₂^—concentration detection.The main research contents of this paper are as follows:Firstly,the digital microfluidic system is designed and built.The digital microfluidic system is composed of three parts:power supply device,circuit control device and digital microfluidic chip.The power supply device selects function signal generator and high-voltage amplifier.The circuit control device uses single chip microcomputer and relay,and the relay is connected with the electrode on the digital microfluidic chip.The single chip microcomputer controls the on-off of the electrical signal transmitted from the power supply device to the relay,and then directionally controls the movement of droplets on the digital microfluidic chip connected with the relay.Secondly,two low-cost digital microfluidic chips with different electrode materials were prepared.A digital microfluidic chip with indium tin oxide（ITO）electrode was fabricated by laser etching based on polyethylene terephthalate（PET）;A digital microfluidic chip with carbon ink electrode was fabricated based on polyester film and non-woven fabric by screen printing technology.The two chips realize the directional movement and combination of droplets,and analyze the force of moving droplets.The performance of the two chips was tested,and the relationship between the contact angle and the external voltage was measured;The effects of droplet volume and electrode opening and closing time on the threshold voltage of driving droplets were investigated;Detect the overflow current density of the two chips.In addition,the factors affecting the threshold voltage of droplet driving:electrode shape,electrode spacing,waveform and frequency of AC are studied,and the arrangement of chip electrodes is optimized to realize the"steering"movement of droplets.Finally,based on Griess color reaction,the concentration of NO₂^—was detected by digital microfluidic system.The system controls the sodium nitrite solution,acid sulfonamide solution and n-1-naphthyl ethylenediamine solution to move and fuse successively to make them have color reaction.The greater the concentration of NO₂^—is,the darker the color of the product is.The color of the product is converted into gray value,and the gray value concentration standard curve is drawn,which can be used to detect the concentration of nitrite ions in river water and food.