Self‐Powered Active Sensing Based on Triboelectric Generators

Abstract

for above concepts. These technological tools require a large number of different types of sensors for real-time monitoring of the parameters of interest, with the aim of increasing efficiency or productivity, enabling predictive actions (e.g., maintenance, monitoring potential hotspots for spread of diseases) and optimizing supply chain and asset traceability while developing a safer and more secure environment. Accordingly, numerous physical, chemical, and biosensors based on different working mechanisms and transducer materials have been reported. [3][4][5][6] Most of these sensors require continuous operation, for which reliable power source is critical.The widely used power source is the batteries that are often bulky, have a limited lifetime, and are difficult to recycle because of toxic chemicals. [7] As a result, they compromise the sensors portability and, in certain cases, also require a complex and costly process to replace after they run out. Coin cells are other alternatives that are now heavily commoditized and usually present a low-cost solution for powering standalone, lightweight, portable, and miniaturized sensors. However, they still require replacement at regular intervals. A self-reliant and sustainable way of powering the sensors to acquire data and send them wirelessly to a data hub, would be ideal. One solution is to combine a small, long-life, energy-storage devices (e.g., a supercapacitor or a rechargeable solid-state battery) with an energy harvester or wireless powering device. [8] There are many ways of harvesting energy from the environment, from solar energy using photovoltaic panels, or heat using thermal electric generators and vibration with piezoelectric and triboelectric generators (TEGs). [9] Herein, we use the term triboelectric generator (TEG), which also covers the triboelectric nanogenerators (TENGs). If the energy budget is balanced correctly, these two components, i.e., energy storage device and the energy harvester, do not need to be large to work for a long time. The availability of ultralow-power electronics and the constantly improving efficiency of energy harvesting devices (e.g., high-efficiency indoor solar cells can provide at least 20 mW cm −2 and the TEGs can provide up to 50 mW cm −2 ) also support such solutions. [9a,10] Further, the sensors and power management integrated components are becoming increasingly less power hungry. [7b] However, this approach The demand for portable and wearable chemical or biosensors and their expeditious development in recent years has created a scientific challenge in terms of their continuous powering. As a result, mechanical energy harvesters such as piezoelectric and triboelectric generators (TEGs) have been explored recently either as sensors or harvesters to store charge in small, but long-life, energy-storage devices to power the sensors. The use of energy harvesters as sensors is particularly interesting, as with such multifunctional operations it is possible to reduce the number devices needed in a system, which a...

Triboelectric Nanogenerators as Power Sources for Chemical Sensors and Biosensors

“…Compared to other energy harvesters such as piezoelectric nanogenerators (PENGs), TENGs produce high output, and they are comparatively easy to design. Further, they do not have a huge material restriction, offer design flexibility, and can be easily shaped in flexible and wearable form factors. ,− Further, triboelectrification can also occur in solid–liquid contacts along with solid–solid interactions . A TENG can be considered as a capacitor with varying capacitance, as illustrated in the center of Figure , which displays the four working modes of TENG, viz., vertical contact-separation (C-S) mode, single-electrode (SE) mode, lateral sliding (LS) mode, and freestanding triboelectric layer (FT) mode.…”

“…The electrode connected to the ground serves as the reference for electric potential. In this mode, the contact separation or sliding of the movable layer creates a potential difference for the flow of electrons. , …”

“…Currently, batteries are most widely employed as the power source for these sensors. Batteries are difficult to recycle, offer a limited lifetime or require frequent charging, and involve toxic contents. , As a result, different energy harvesting methods and self-powered sensors have been attracting attention. , …”

“…TENGs generally produce an alternating current (AC) output signal which needs to be processed using a power management unit (PMU), comprising a rectifier and energy storage device, as shown in Figure a. Apart from being a power source, TENGs can also act as active sensors where a chemical or biological analyte induces direct variation in the TENG output. , …”

“…35,36 As a result, different energy harvesting methods and self-powered sensors have been attracting attention. 37,38 The mechanical energy harvesters based on piezoelectric and triboelectric effects offer a versatile solution as an alternative portable source of power. 39−45 Among them, the triboelectric nanogenerator (TENG) presents unique advantages such as a wide choice of materials, distinct device working modes, light weight, high-power density, cost-effectiveness, and ease of fabrication.…”