Wood-based self-powered smart home systems
(News from Nanowerk) With the increased use of Internet of Things (IoT) devices and artificial intelligence, the technical development of smart home applications is playing an increasingly important role in improving the quality of life and human health. The key components for setting up and operating smart home systems are sensing devices – for light, temperature, motion, pressure, etc. – which are distributed throughout the home environment and function as the basis of all home control systems.
Traditional sensors face limitations due to their need for power source such as limited lifetime, high cost and environmental pollution when using batteries. Therefore, finding low-cost, long-term stable, and highly sensitive sensing technology is the key to lowering the threshold for smart home popularization.
To address this issue with a possible solution, researchers developed a flexible wood-based triboelectric self-powered sensor for use in smart home systems. As the team reports in ACS Nano (“Flexible wood-based triboelectric self-powered smart home system”), using efficient and simple processing method, the wood-based sensor has many advantages, including light weight, small thickness, high sensitivity, flexibility and stability.
A schematic of the manufacturing process of the flexible wood-based triboelectric self-powered sensor (WTSS) is shown in the figure below:
First, natural balsa wood was converted into flexible wood by a two-step strategy involving chemical boiling in a mixed solution of NaOH and Na.2SO3 followed by hot pressing. Then, the obtained flexible wood with a thickness of 0.1 mm was used to fabricate the triboelectric self-powered sensing device. The researchers point out that chemical processing plays a vital role in the production of WTSS.
The flexible wood sheets were cut into small sizes as a dielectric electrification layer. Then, a copper film layer of the same size was glued on the flexible wood as an electrode layer to make the WTSS. Finally, a copper wire was attached to the copper film for electrical connection.
The detection mechanism of WTSS is based on the coupling effect of contact electrification and electrostatic induction. Load transfer occurs on the contact interface between a commercial PTFE film and the wood film during the approach and pressure process.
The size is a major factor in determining the output voltage as well as the sensitivity of the WTSS. For WTSSs of different sizes (1–5 cm side lengths), their voltage output is positively correlated with the surface area of the object, which is attributed to frictional loads induced by larger contact surface.
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. As shown in Figure 2 above, while touching the cabinet-integrated WTSS, an obvious output signal will be generated. Through signal processing and wireless signal transmission, home appliances can be controlled remotely.
Another application demonstrated by the authors is an intelligent soil monitoring system. Made with wooden materials, WTSS can be easily integrated with the wooden floor to realize independent walking behavior and health monitoring. When people walk on the floor, output voltage signals corresponding to each contact position will be produced and collected through a multi-channel data acquisition method. After signal processing and analysis, various functions including gait characteristic recording, path tracking and safety monitoring can be realized simultaneously.
“With its easy manufacturing process and abundant material source, WTSS can greatly improve the safety, convenience and comfort of a living environment,” the authors conclude in their paper. “This research demonstrates the promising applications of eco-friendly WTSS in building smart homes and smart cities, which will provide a great opportunity in the development of a sustainable society in the future.”