Ultraminiaturized Microfluidic Electrochemical Surface-Enhanced Raman Scattering Chip for Analysis of Neurotransmitters Fabricated by Ship-in-a-Bottle Integration

Abstract

Electrochemical surface-enhanced Raman scattering (EC-SERS) is a promising technique for the diagnosis of trace amounts of neurotransmitters, because it can elucidate neurotransmitters’ behavior on electrodes to deduce their functions in the human body. However, the current EC-SERS devices need several tens of milliliters of analyte solution to collect enough signal for analysis. Miniaturization of EC-SERS devices is crucial for the early diagnosis of disease and point-of-care testing. Herein, a new type of EC-SERS sensor based on 3D microfluidic chips for the analysis of neurotransmitters in ultrasmall volumes is proposed. The microfluidic EC-SERS chip is fabricated by a ship-in-a-bottle technique based on hybrid laser processing. The working electrode is modified using silver/zinc oxide materials, enabling the formation of a unique “candy apple” structure. To assess the fabricated microfluidic EC-SERS chips, ascorbic acid is analyzed using the ingenious microfluidic EC-SERS chips to elucidate its redox reaction by EC-SERS spectroscopy. Significantly, a sub-10 μL volume of analyte solution is sufficient for EC-SERS analysis, which is several orders smaller in volume than the requirements of current EC-SERS devices. The unprecedented microfluidic EC-SERS chips fabricated by the ship-in-a-bottle integration technique can be used in portable and smart analyzers for next-generation biomedicines and catalysts.