With the increased use of Internet of Things (IoT) devices and artificial intelligence, the technical development of smart home applications plays an increasingly important role in improving people's quality of life and health. The key component for setting up and running smart home systems are sensing devices – for light, temperature, motion, pressure, etc. – which are distributed across the home environment and function as the basis for all home control systems. But these systems can have power issues. Issues that might be solved with wood-based sensors.

According to a report on the NanoWerk website, researchers from the Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, have developed such sensors. The report, based on a research paper, Flexible Wood-Based Triboelectric Self-Powered Smart Home System (WTSS), available through the American Chemical Society, researchers have developed a flexible wood-based triboelectric self-powered sensor to be used in smart home systems. The new sensors overcome the limitations of traditional sensors such as limited lifetime, high cost, and environmental pollution when using batteries. The fabricated wood-based sensor has numerous advantages, including lightweight, low thickness, high sensitivity, flexibility, and stability.

According to the report, balsa wood was converted into flexible wood by a two-step strategy involving chemical boiling in a mixed solution of NaOH and Na2SO3 followed by hotpressing. The flexible wood, with a thickness of 0.1 mm, was used for fabricating the triboelectric self-powered sensing device. The researchers point out that chemical treatment plays a vital role in the production of the WTSS.

The flexible wood sheets were cut into small sizes as the dielectric electrification layer. Then, a layer of copper film of the same size was pasted on the flexible wood as the electrode layer to fabricate the WTSS. Finally, a copper wire was attached to the copper film for an electric connection.

The sensing mechanism of the WTSS is based on the coupling effect of contact electrification and electrostatic induction. The charge transfer occurs on the contact interface between a commercial PTFE film and the wood film during the process of approaching and pressure.

Size is a major factor to determine the output voltage as well as the sensitivity of the WTSS. For WTSSs with different sizes (side lengths from 1 to 5 cm), their output voltage is positively correlated with the object area, which is attributed to the friction charges induced by a larger contact area.

The team developed a self-powered smart appliance control system by integrating their WTSS with home furniture, a simple signal control circuit, and some household appliances. While touching the WTSS integrated with the furniture, an obvious output signal will be generated. Through signal processing and wireless signal transmission, the household appliances can be remotely controlled.

Another application demonstrated by the authors is a smart floor monitoring system. Fabricating with wood materials, the WTSSs can be easily integrated with the wooden floor for realizing self-powered walking behavior and health monitoring. When people walk on the floor, output voltage signals corresponding to each touching position will be produced and collected via a multichannel data acquisition method. After signal processing and analysis, various functions, including gait characteristics recording, path tracking, and safety monitoring can be simultaneously realized.