Crop Disease Spore Flow Dynamic Detection Method Based on Airborne Microfluidic Chip

Crop disease monitoring has always been a research hotspot in the field of agricultural engineering because of its serious damage to the world ' s food. In recent years, the use of microfluidic chip microbial sensors for crop disease detection has received attention from scholars. However, most of current microfluidic chips have the defect of low reuse rate. In response to this problem, a parallel double sheath flow focusing microfluidic chip was proposed,which was composed of an injection channel,a double sheath flow channel, a partial pressure channel, a detection channel and a circular chamber. Fungal spores entered the chip from the sampling channel with the airflow,and then were arranged in the center of the chip by the action of the double sheath airflow. Air pressure was controlled by the partial pressure channel to ensure that the fungal spores entered the detection area of the chip at the speed required by the test. Subsequently, fungal spores followed the airflow into the circular enrichment area. Experimental data showed that the spore velocity was decreased with the increase of the chamber diameter. Circular chamber diameter of 2 500 jxm had the best enrichment effect, and the particle enrichment rate can reach 96. 7% . An air pump was connected to the outlet of the chip to extract fungal spores, which can improve the reuse rate of the chip. Rice spores used were from the China National Rice Research Institute,and polystyrene microsphere samples were purchased from Tianjin Daye Technology Co.,Ltd. . The experimental platform was built by aerosol generator, semiconductor laser, microfluidic chip, circuit board, focusing optical path device and other equipment. In order to realize the focused arrangement of fungal spores,the sample inlet flow rate and sheath flow rate needed to be optimized. Optimization results showed that, when the sampling flow rate and sheath flow rate of the chip were 2. 5 mL/min and 12 mL/min,respectively, the particle focus width was 8 jxm, which can realize the particle focus arrangement and flow through the detection area in a row. The entire detection system was also composed of a focusing optical path device and a signal acquisition circuit. The focusing optical path device was composed of a filter, a half lens with a focal length of 14 mm and an aperture surface of 10 |xm,which can focus the light source to about 10 jxm. The laser would excite spores passing through the detection area to produce forward and side scattered light,and then these two scattered lights would be collected by the signal collection circuit and transmitted to the upper computer. The forward scattered light signal contained the size information of the particles. Based on the experimental results, a detection model for the particle size and light intensity was established,with coefficient of determination of 0.966 6,which had a good linearity. The side-scattered light signal contained the complexity of the particles. The forward and side-scattered light intensity information was fused to achieve effective classification of rice spore spores and polystyrene microspheres,with an average detection error of 7. 04%,and the chip reuse rate was increased by about 9 times. The research result can provide a basis for the research and development of crop disease monitoring sensors. © 2022 Chinese Society of Agricultural Machinery. All rights reserved.