Biodegradable sensor measures pesticides in three minutes

Scientists at the University of São Paulo have developed biodegradable wearable sensors to detect pesticides in plants and food quickly, non-destructively, and on-site. The device uses carbon ink printed by screen printing on flexible cellulose acetate films. The platform identifies diquat, carbendazim and diphenylamine in three minutes and twenty-eight seconds.

The sensor can adhere to irregular, wavy, and curved plant surfaces. Application occurs directly on leaves, stems, peels, apples, and peppers. The wearable design allows for decentralized analysis, eliminating the need to take samples to a laboratory. The system delivers real-time results via a portable wireless potentiostat connected via Bluetooth to a cell phone, computer, or tablet.

Two units

Each device comprises two sensor units. One uses square wave voltammetry to measure diquat. The other uses differential pulse voltammetry to detect carbendazim and diphenylamine. The study reports the use of a single sample drop and sequential operation on the same chip. Diquat reading occurs within the first fifty-two seconds. Simultaneous measurement of carbendazim and diphenylamine takes an additional one hundred and ninety-seven seconds.

The device costs less than $0,077 per unit. The low cost matters because the sensors are for single use. According to Paulo Augusto Raymundo-Pereira, a professor at the São Carlos Institute of Physics at USP (University of São Paulo), the proposal combines speed, low environmental impact, and field analysis.

Sensor base

The sensor base uses cellulose acetate. This material is of plant origin and can come from agricultural waste. The study also evaluated plasticizers. The best results were obtained with cellulose acetate plasticized with 5,4 millimoles of glycerol. This formulation showed better dynamic range, linearity, and sensitivity compared to films plasticized with triethyl citrate.

In the tests, the sensors detected diquat in the range of 0,1 to 1,0 micromolar. For carbendazim, the range was between 0,2 and 2,0 micromolar. For diphenylamine, the range was between 2,5 and 25 micromolar. The detection limits reached 3,2 nanomolar for diquat, 180 nanomolar for carbendazim, and 1,34 micromolar for diphenylamine.

Field use

The team simulated a field use condition. Pesticide solutions were sprayed onto the peel of apples and bell peppers at a concentration of 1.000 micromolar. The products were allowed to dry for five hours. Then, the sensor was attached to the surface. The reading was taken using a 500 microliter drop of phosphate buffer solution to allow for electrical conduction and a chemical response from the electrode.

The study also tested human saliva and tap water with added pesticides. In these samples, the system detected all three targets in the same 150-microliter droplet. The results indicated potential use in food, water, and biological samples, as well as agricultural monitoring.

The platform demonstrated selectivity in the face of potential interfering substances. Tests included nitrate, sulfate, glucose, urea, fenitrothion, thiabendazole, dopamine, linuron, methyl parathion, ascorbic acid, and proline. The sensor also withstood vertical, horizontal, and diagonal bending cycles with little alteration in voltammetric responses.

Biodegradation of devices

The study evaluated the biodegradation of the devices over 240 days. Sensors made with cellulose acetate plasticized with glycerol degraded completely within this period. Devices made only with cellulose acetate remained intact. The image on page eleven of the article shows a visual comparison between the two formulations throughout the degradation period.

The team also calculated green analytical chemistry metrics. The method scored 0,77 on the AGREE approach and 81 on the Analytical Eco-Scale. The Blue Applicability Grade Index reached 77,5, a value cited by the researchers as indicative of analytical applicability.

The study was conducted by Samiris Côcco Teixeira, Nathalia O. Gomes, Sergio AS Machado, Taíla Veloso de Oliveira, Nilda FF Soares, and Paulo A. Raymundo-Pereira.

Further information is available at doi: 10.1016/j.biosx.2026.100758