Hengyu Guo

A nanogenerator for harvesting airflow energy and light energy

Harvesting airflow energy and light energy from the ambient environment to build a self-powered system is attractive and challenging work. In this article, an airflow-induced triboelectric nanogenerator (ATNG) has been fabricated that converts wind energy to alternating electricity. The mechanism of ATNG has also been illustrated. The performance of ATNGs with different sizes was studied, from which we discovered that the ATNG (size: 1 cm × 3 cm, electrode gap: 1.5 mm) could easily collect energy from a gentle wind (5.3 m s−1). Due to the relatively high alternating electricity frequency (179.5–1220.9 Hz), an approximately stable output power (of up to 1.5 mW) was obtained from the ATNG (size: 1 cm × 3 cm, electrode gap: 0.5 mm) with 8.35 μC of charge transferred per second. Meanwhile, the fabricated wind energy harvesting device was used to drive 46 commercial green light-emitting diodes (LEDs) connected in series and charge a 220 μF capacitor to 2.5 V over 50 s. When combined with a dye-sensitized solar cell (DSC), the device can individually and simultaneously harvest wind and light energy. This shows the potential applications of this ATNG in self-powered systems.

Harvesting heat energy from hot/cold water with a pyroelectric generator

Waste heat has been regarded as one of the most important renewable and green energy sources, and its widespread reclamation could help to reduce the negative impacts of global warming and the energy crisis. In this work, we designed a pyroelectric generator based on a polyvinylidene fluoride film for harvesting the heat energy from hot/cold water, which widely exists in industrial processes. To achieve practical application, the device simply contacts a hot flow and cold flow alternately. The output open-circuit voltage and short-circuit current reached a maximum of 192 V and 12 μA, respectively, under a temperature change of 80 °C. The output power density can reach 14 μW cm, which is a great improvement for thermoelectric devices. The prepared pyroelectric generator can drive 42 green light-emitting diodes or charge a commercial capacitor (100 μF) to 3.3 V in 90 s. This work provides a promising strategy for efficiently harvesting waste heat from water and presents significant progress in thermoelectric conversion technology.

Flexible interdigital-electrodes-based triboelectric generators for harvesting sliding and rotating mechanical energy

Triboelectric generators have attracted considerable attention due to their rapidly improved electromechanical conversion efficiency. It is a great challenge to design a triboelectric generator to enable practical and effective operations. In this paper, we present a flexible interdigital-electrodes-based triboelectric generator (FITG) for harvesting sliding and rotating mechanical energy. When a film of flexible interdigital electrodes is placed on a plane, it can be used for harvesting sliding energy. When the film of the flexible interdigital electrodes is rolled into a cylinder, it can be used for harvesting rotating energy. In sliding mode, the maximum open-circuit voltage, short-circuit current and peak power density reach up to 400 V, 120 μA (10 mA m−2) and 13 W m−2, respectively, under a sliding velocity of 3.95 m s−1, which can be used to light tens of light-emitting diodes (LEDs) and to charge a commercial capacitor to 7.2 V within 35 s. The FITG can harvest the mechanical energy of mouse operation and traditional printing. In rotating mode, the maximum output voltage of the generator reaches as high as 1020 V at a rotating speed of 240 rpm. The FITG with interdigital electrodes on a flexible substrate has the advantages of light weight, resistance to wear, multifunction and high output power.

A Flexible micro-supercapacitor based on a pen ink-carbon fiber thread

A highly flexible solid-state micro-supercapacitor based on a pen ink-carbon-fiber (Ink-CF) thread structure was fabricated with excellent electrochemical performance such as a high capacitance of 4.31 mF cm−2 and an energy density of 3.8 × 10−7 W h cm−2 at a power density of 5.6 × 10−6 W cm−2. This fabricated structure shows excellent characteristics such as lightweight, small volume, flexibility and portability. By integrating it with a triboelectric nanogenarator, the micro-supercapacitors could be charged and power 8 commercial LEDs, demonstrating its feasibility as an efficient storage component for self-powered micro/nanosystems.

Double-induced-mode integrated triboelectric nanogenerator based on spring steel to maximize space utilization

Integrated multilayered triboelectric nanogenerators (TENGs) are an efficient approach to solve the insufficient energy problem caused by a single-layered TENG for achieving high output power density. However, most integrated multilayered TENGs have a relatively large volume. Here, a double-induced-mode integrated triboelectric nanogenerator (DI-TENG) based on spring steel plates is presented as a cost-effective, simple, and high-performance device for ambient vibration energy harvesting. The unique stackable rhombus structure, in which spring steel plates act both as skeletons and as electrodes, can enhance the output performance and maximize space utilization. The DI-TENG with five repeated units in a volume of 12 cm × 5 cm × 0.4 cm can generate a short-circuit current of 51 μA and can transfer charges of 1.25 μC in a half period. The contrast experiment is conducted systematically and the results have proved that the DI-TENG has a great advantage over the single-induced-mode TENG (SI-TENG) with only one side of a friction layer on its electrode. Besides, the DI-TENG can easily power a commercial calculator and can be used as a door switch sensor.

Embedding variable micro-capacitors in polydimethylsiloxane for enhancing output power of triboelectric nanogenerator

Polydimethylsiloxane (PDMS) is an excellent material for investigating the mechanism of triboelectricity as it can easily be used to construct various microstructures. In this study, micro-capacitors (MCs) and variable microcapacitors (VMCs) were embedded in PDMS by filling PDMS with silver nanoparticles (NPs) and constructing an internal cellular structure. The output performance of the triboelectric nanogenerators (TENGs) based on MCs@PDMS and VMCs@PDMS films was systematically investigated, with variation of the filling content of silver NPs and the pore ratio and size. The microstructure, permittivity, dielectric loss, and capacitance of the VMCs@PDMS films were well characterized. The output current of the TENG based on the VMCs@PDMS film was respectively 4.0 and 1.6 times higher than that of the TENGs based on the pure PDMS film and MCs@PDMS film, and the output power density of the former reached 6 W·m–2. This study sheds light on the physical nature of conductive nanoparticle fillings and cellular structures in dielectric triboelectric polymers.

Triboelectric nanogenerator based on magnetically induced retractable spring steel tapes for efficient energy harvesting of large amplitude motion

The triboelectric nanogenerator has attracted global attention since it was proposed in 2012; the exploration of new applications is ongoing with much enthusiasm in this field. In this paper, we present a novel triboelectric nanogenerator based on magnetically induced retractable spring steel tapes (MR-TENG) to develop energy harvesting from large amplitude periodic motion, which is an ingenious design that employs a new material. The tape-like structural design ensures that the contact/separate direction of the friction layers is perpendicular to the direction of the external force, breaking the amplitude limitation of previous nanogenerators with vertical contact/separate motion. Combined with flexible spring steel tapes, this design enables portability thus widening its application. The working mechanism and factors that may affect the output performance are systematically studied. The results show that the maximum short-circuit current, open-circuit voltage and instantaneous power are 21 μA, 342 V, and 1.8 mW, respectively. Moreover, we also demonstrate the great potential of the MR-TENG to serve as a self-powered displacement sensor and portable emergency power supply. This work greatly widens the applications of triboelectric nanogenerators (TENGs) through new material selection and innovative structural design.

WGUs sensor based on integrated wind-induced generating units for 360° wind energy harvesting and self-powered wind velocity sensing

Wind, as a natural power source, can be used to produce electricity using wind generators. However, detecting wind velocity has been challenging because wind always blows in a random direction. In this study, we design a self-powered wind velocity sensor based on integrated wind-induced generating units (WGUs) to harvest wind energy from all directions in a plane and as a self-powered wind velocity sensor (denoted as WGUs sensor). A wind-induced generating unit consists of two parallel plate Cu-electrodes (size 1.5 × 4 cm2, gap 0.5 cm) and a polytetrafluoroethylene (PTFE) thin film between them. The W-TGUs sensor can be effectively used to harvest wind energy from all directions in a plane by integrating the W-TGUs in circular and vertical directions. The output current and voltage of every WGU are 1–3.5 μA, and 13–20 V under a wind speed of 6–27 m s−1. The output rectified current of WGUs, with vertically integrated one to five WGUs, was 1.3–6.8 μA under a wind speed of 8 m s−1. Moreover, the W-TGUs sensor can detect a wind velocity from all directions on a plane with a resolution ratio of 0.13 (m s−1) Hz−1 and a response time of 0.15 s, which is a very important advantage as a self-powered wind velocity sensor. The output power of the WGUs sensor can be greatly enhanced by increasing the number of WGUs. This study provides a novel design for harvesting wind energy and sensing wind velocity from a random direction on a plane.