Fabrication Of PMMA Micro/Nanofluidics Chip Integrated With Microelectrodes For Electrochemical Detection

Electrochemical detection has many advantages, such as high sensitivity, ease of miniaturization, low cost, and low-power requirements, etc. Polymethylmethacrylate (PMMA) has many advantages, such as low cost, unbreakable and ease of fabrication.PMMA micro/nanofluidic chips with integrated microelectrodes for electrochemical detection not only has the advantages of PMMA, but also has the advantages of electrochemical detection. However, there are compatibility problem of integrating micro-nano structures on PMMA plate.First, in this paper, a novel method for fabricating PMMA micro/nanofluidic chips with integrated microelectrodes for electrochemical detection was presented. Due to the fabrication incompatibility, there were few reports about integrating microchannel, nanochannel and microelectrodes on one single chip. We proposed that microchannels and nanochannels were fabricated on the cover plate and the substrate plate separately, which obviates the difficulty of integrating microchannels and nanochannels on a substrate plate. The microchannel was fabricated on the cover plate by hot embossing. A plasma etching method was used to fabricate nanochannels on the substrate plate, and then a method based on photolithography processes was applied to fabricate the microelectrode, which solves the incompatibility of integrating nanochannels and microelectrodes on a single plate. To avoid big deformation of the nanochannel during the chip bonding process, a UV-assisted thermal bonding method was put forward to bond the chip. By all above methods, a PMMA micro/nanofluidic chip with Ag microelectrodes was fabricated. With this chip, biotin was detected, and the limit of detection was1aM.Besides, a method for monolithic integration of three-material microelectrodes on PMMA substrates was also presented. Electrochemical detection mostly performs on a three-electrode system, and these three electrodes (working, reference and counter electrodes) are commonly made of different materials. However, by previously reported methods, it is hard to integrate multiple-material electrodes on one PMMA substrate. Hence, in this paper, different methods were studied for fabricating different materials of microelectrodes, and the fabrication sequence of different materials of microelectrodes was optimized, which solves the compatibility problem of fabricating multiple-material electrodes. By this method, Au-Ag-Pt three-electrode and C-Ag-Pt three-electrode systems were demonstrated. By a reversible bonding method, a PMMA substrate plate with Au-Ag-Pt three-electrode systems was bonded with a polydimethylsiloxane cover plate with detecting chambers to make an electrochemical sensing microchip. The performance of the microchip was evaluated by two kinds of electrochemical probes (Ru(bpy)3Cl2and dopamine). The microchip exhibited excellent reproducibilities and linearities, and showed great potential for a variety of electrochemical analyses.