The excessive pesticide residues in cereals, fruit and vegetables is a big threat to human health, and it is necessary to develop a portable, low-cost and high-precision pesticide residue detection scheme to replace the large-scale laboratory testing equipment for rapid detection of pesticide residues. In this study, a colorimetric device for rapid detection of organophosphorus pesticide residues with high precision based on a microfluidic mixer chip was proposed. The microchannel structure with high mixing efficiency was determined by fluid dynamics simulation, while the corresponding microfluidic mixer chip was designed. The microfluidic mixer chip was prepared by a self-developed liquid crystal display (LCD) mask photo-curing machine. The influence of printing parameters on the accuracy of the prepared chip was investigated. The light source with the optimal wavelength of the device was determined by absorption spectrum measurement, and the relationship between the liquid reservoir depth and detection limit was studied by experiments. The correspondence between pesticide concentration and induced voltage was derived. The minimum detection concentration of the device could reach 0.045 mg·L−1 and the average detection time was reduced to 60 s. The results provide a theoretical and experimental basis for portable and high-precision detection of pesticide residues.

This research proposed a flexible piezoresistive tactile sensor (FPTS) device with imprinted microsphere array to realize the accurate and stable acquisition of human motion data. The thickness of conductive membrane on the sensitivity of the sensor were investigated by FEM simulation, the copper microsphere array mold was prepared by multipoint imprinting process and the electromechanical response curves of piezoresistive tactile sensor consisting of Hydroxylated Multiwalled Carbon Nanotubes/Polyimide (carboxylated MWCNT/PI) composite membrane and Polydimethylsiloxane/Hydroxylated Multiwalled Carbon Nanotubes/Polyimide (PDMS/carboxylated MWCNT/PI) composite membrane with double‐sided microsphere were tested. The result shows that reduce the chord height can improve the sensitivity of the sensor. The composite structure with PDMS/carboxylated MWCNT/PI composite membrane reduces the overall stiffness of the microsphere structure, which is conducive to improve the sensitivity and minimum the detection limit of the FPTS. Multipoint imprinting technology is an efficient processing method to obtain high consistency microsphere array. The electromechanical response curves of piezoresistive tactile sensor consisting of PDMS/carboxylated MWCNT/PI composite membrane with double‐sided microsphere shows that the detection limits can reach 0.0289 kPa, and the sensitivity is 1.139 kPa−1. The sensor has high stability, especially when the wearing radius of curvature is more than 30 mm.

This paper proposed a rapid fabrication process for PMMA microfluidic mixer chip by non-isothermal method based on resistance heating principle, and the prepared microfluidic mixer chip was successfully applied to the portable pesticide residue detection device. Firstly, the creep test of PMMA was carried out and the 6 units Maxwell constitutive model was fitted by Prony series. Secondly, the resistance heating device was designed, the influence of current on heating temperature and heating time was investigated, the effect of current on energy consumption was analyzed. Thirdly, the non-isothermal molding simulation and experiment of PMMA were carried out, the quality of PMMA microfluidic mixer chip fabricated by non-isothermal molding was investigated. Finally, the microfluidic mixer chip was adopted to the designed pesticide residue detection device, and the detection sensitivity of the device is 0.0375mol-1. The research results provide a reference for the efficient preparation of microchannels and the development of portable detection equipment.