A Forest-Based Triboelectric Energy Harvester

Abstract

Triboelectric nanogenerators (TENGs) are a new class of energy harvesting devices that have the potential to become a dominating technology for producing renewable energy. The versatility of their designs allows TENGs to harvest mechanical energy from sources like wind and water. Currently used renewable energy technologies have a restricted number of materials from which they can be constructed, such as metals, plastics, semiconductors, and rare-earth metals. These materials are all non-renewable in themselves as they require mining/drilling and are difficult to recycle at end of life. TENGs on the other hand can be built from a large repertoire of materials, including materials from bio-based sources. Here, a TENG constructed fully from wood-derived materials like lignin, cellulose, paper, and cardboard, thus making it 100% green, recyclable, and even biodegradable, is demonstrated. The device can produce a maximum voltage, current, and power of 232 V, 17 mA m^-2, and 1.6 W m^-2, respectively, which is enough to power electronic systems and charge 6.5 µF capacitors. Finally, the device is used in a smart package application as a self-powered impact sensor. The work shows the feasibility of producing renewable energy technologies that are sustainable both with respect to their energy sources and their material composition.

Keywords: cellulose; energy harvesting; green electronics; lignin; triboelectric nanogenerators.

Figure 1

a) Schematic of the device structure and charge accumulation during operation. b) Molecular structures of cellulose and NC. c) Schematic illustration of a triboelectric series. d) Schematic of the electrospinning and graphitization process. e) Photograph of lignin fiber mat stabilized at 100 °C. f) Photograph of NC fiber mat. g) Photograph of lignin (Lig100) fibers attaching to cotton fabric after contact. h) Photograph of lignin fiber mat stabilized at 250 °C.

Figure 2

SEM images of lignin films stabilized at 100, 200, or 250 °C (Lig100, Lig200, and Lig250 respectively), as well as carbonized lignin fibers (carbon). a–c) Lig100 sample with scale bar being10, 2, and 1 µm, respectively. d,e) Lig200 sample with scale bars of 10 and 2 µm, respectively. f,g) Lig250 sample with scale bars of 2 and 1 µm, respectively. h,i) Graphitized lignin sample with scale bars of 30 and 1 µm, respectively.

Figure 3

SEM images of pristine NC films (NC prist) and NC films treated with acetone vapor for 30 min (NC 30 m) or 60 min (NC 60 m). a–c) NC prist sample with scale bars of 20, 1, and 100 nm, respectively. d–f) NC 30 m sample with scale bars of 20, 1, and 200 nm, respectively. g–i) NC 60 m sample with scale bars of 20, 1, and 100 nm, respectively.

Figure 4

a–e) Surface charge measured on fiber samples with different post treatments after contacting with different reference materials. f) Charge buildup over repeated contact cycles measured on lignin and NC separately. Each mean value and error bars in panels (a)–(e) were calculated from ten individual measurements (n = 10), while the data point in panel (f) represents single measured values.

Figure 5

Triboelectric response from F‐TENG in an automated actuator setup. a–c) Voltage response for F‐TENG using Lig250 and NC with different acetone treatments (no treatment, 30 min, or 60 min). d) Voltage, current, and power of F‐TENG from Figure 3b using different load resistor values. e,f) Maximum achieved voltage and power for the F‐TENGs in Figure 3a–c. (n = 5 for Mean value and SD calculations in panels (d)–(f)).

Figure 6

F‐TENG driving electronic devices and charging a supercapacitor. a) Photographs of an electrochromic display on cardboard being powered by an F‐TENG. b) Voltage of a 7.5 µF supercapacitor while being charged by an F‐TENG to a total charge of 13 µA s.

Figure 7

F‐TENG device in a smart package application. a) Schematic of the smart package concept, b) photographs of the F‐TENG triboelectric layers and electrodes, c) photograph of an F‐TENG device, d) photograph of the smart package, e) voltage output of the F‐TENG with a 51 MΩ load resistor, f) F‐TENG voltage versus piezovoltage (n = 5 for mean value and SD calculations), g) photograph of the smart package and a tablet displaying the App. h) Schematic of the smart package electronics, i) screenshots from the app window during operation.