Research On Underwater Adhesive Flexible Sensor For In Situ Monitoring Of Organic Acids Secreted By Plant Roots

The organic acids in plant root exudates can reduce the toxicity of heavy metals to plants through metal chelation,complexation,and other effects,and improve the tolerance of plants to heavy metals.Previous studies have shown that the nature and relative abundance of components of the organic acids secreted by plant species under heavy metal stress is quite different.Therefore,the secretion of organic acids could provide a basis for rapid screening for the selection of heavy metals tolerant corps.However,continuous real-time monitoring of the organic acids in plant exudates remains challenging using the traditional methods,such as IC,HPLC,and GC-MS,due to their complex sample pretreatments.Therefore,in this study,a flexible and stretchable p H sensor with underwater adhesion was developed by combining the micro-nano processing technology of flexible electronics and hydrogel materials,which can be used to adhere to the root of plants and realize in situ and real-time monitoring of the organic acids secreted by plant roots.The main research contents and results of this paper are as follows:1.A flexible and stretchable p H sensor was fabricated by using micro-nano processing technology and electrochemical deposition technology.The obtained flexible p H sensor is 75μm thick and its sensitivity is-71.63 m V/p H.It also exhibits good H~+selectivity and temperature tolerance.The flexible p H sensor can normally function for more than 12 hours under water,with a potential fluctuation<5 m V.2.A tannic acid/PEGDA hydrogel with underwater adhesion ability was prepared.The adhesion strength of hydrogel can reach 42.5 k Pa,and it can adhere underwater for more than 24 hours.The hydrogel exhibits a low swelling rate(～35%)and self-healing ability.This adhesive hydrogel effectively solved the problem of fixing the flexible p H sensor on the plant root.3.A simulation experiment of malic acid secretion was carried out,which preliminarily verified the feasibility of the sensor for underwater real-time monitoring of organic acid secretion of plant roots;The feasibility of the sensor to monitor the organic acid secretion behavior of plant roots was verified by monitoring the p H changes in the rhizosphere of watermelon seedlings under cadmium stress.