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Article

High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting

by
Dong-Yi Lin
and
Chen-Kuei Chung
*
Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan
*
Author to whom correspondence should be addressed.
Micromachines 2024, 15(11), 1299; https://doi.org/10.3390/mi15111299
Submission received: 22 September 2024 / Revised: 10 October 2024 / Accepted: 18 October 2024 / Published: 25 October 2024
(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2024)
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Abstract

The triboelectric nanogenerator (TENG) has demonstrated exceptional efficiency in harvesting diverse forms of mechanical energy and converting it into electrical energy. This technology is particularly valuable for powering low-energy electronic devices and self-powered sensors. Most traditional TENGs use single-sided patterned friction pairs, which restrict their effective contact area and overall performance. Here, we propose a novel TENG that incorporates microwave patterned aluminum (MC-Al) foil and microcone structured polydimethylsiloxane (MC-PDMS). This innovative design utilizes two PMMA molds featuring identical micro-hole arrays ablated by a CO2 laser, making it both cost-effective and easy to fabricate. A novel room imprinting technique has been employed to create the micromorphology of aluminum (Al) foil using the PMMA mold with shallower micro-hole arrays. Compared to TENGs with flat friction layers and single-side-patterned friction layers, the double-side-patterned MW-MC-TENG demonstrates superior output performance due to increased cone deformation and contact area. The open-circuit voltage of the MW-MC-TENG can reach 141 V, while the short-circuit current can attain 71.5 μA, corresponding to a current density of 2.86 µA/cm2. The power density reaches 1.4 mW/cm2 when the resistance is 15 MΩ, and it can charge a 0.1 μF capacitor to 2.01 V in 2.28 s. In addition, the MW-MC-TENG can function as an insole device to harvest walking energy, power 11 LED bulbs, monitor step speed, and power a timer device. Therefore, the MW-MC-TENG has significant application potential in micro-wearable devices.

1. Introduction

With the increasing demand for healthcare wearable devices and self-powered electronic sensors, eco-friendly energy harvesting technology has become a crucial method for converting ambient energy into electricity using various energy conversion principles, such as piezoelectric [1,2], electromagnetic [3,4], thermoelectric [5,6], pyroelectric [7,8], electrostatic [9,10], triboelectric [11,12,13,14], etc. In particular, Wang’s group proposed triboelectric nanogenerators (TENGs) as a means to convert mechanical energy from the environment into electrical energy by coupling contact electrification and electrostatic induction [15,16,17,18]. To date, TENGs have demonstrated superiority and convenience in the fields of human biomechanical energy collection and motion monitoring owing to their significant advantages of high-power density, low frequency, low cost, and ease of fabrication [19,20,21].
In theory, the output of a TENG depends solely on the actual contact area and surface transfer charge density [22]. Controlling the increase in effective contact area through surface engineering is a widely employed strategy to enhance the electrical performance of TENGs [23,24]. In surface morphology control engineering, various micro- and nano-scaled morphological structures have been employed to enhance the electrical performance of TENGs. These structures include nano-pyramids, lines, cubes [25], nanocolumnars [26], micro balloons [27], and microneedles [28]. However, it is common for only one side of the friction pairs to be patterned, which limits the electrical output performance of the TENG. As a result, to further increase the effective contact area, double-sided patterning surface engineering has been proposed in recent years. For example, microcone–microcone [29], microyarn–microyarn [30], nanogrit–nanogrit [31], micropore–nanoparticles [32], nano roughened structure–nanograting [33], or nanopillar–nanopillar [34], as list in Table 1. Nevertheless, the aforementioned nano/microstructures are primarily fabricated using methods, such as lithography [25], etching [25,29], evaporation [29], plasma [33], electrodeposition [34], and chemical functional groups [35]. These methods are high-cost and time-consuming, which limits the further application and development of TENGs.
In this article, we propose a new double-sided patterning approach to enhance the sustainable mechanical-electrical energy conversion, energy storage, and output performance of a novel TENG consisting of aluminum (Al) with microwave (MW) structure arrays and polydimethylsiloxane (PDMS) with microcone (MC) structure arrays. Moreover, they are fabricated using polymethyl methacrylate (PMMA) molds through a green, low-cost, easy-fabrication CO2 laser ablation method [36]. The laser writing technique has proven to be a powerful, precisely programmable process, that has been widely applied in energy storage and wearable electronics [28,37]. Two imprinting methods are employed to pattern the friction layers. The WW-Al is created through room temperature imprinting using a separate mold with a shallow hole array; while the MC-PDMS is produced via a rapid prototyping casting process using a mother mold with a deep hole array. To compare the differences in electrical performance output, four different types of TENGs were invested, as listed in Table 2. The electrical performance of open-circuit voltage (Voc), short-circuit current (Isc), transfer charge [38] (Qsc), and current density (Jsc), of four TENGs, follows: flat-flat-TENG < MW-flat-TENG ≈ flat-MC-TENG < MW-MC-TENG. The Voc, Isc, and Jsc of the MW-MC-TENG are 141 V, 71.5 µA, and 2.86 µA/cm2, respectively. These values represent increases of 54%, 64%, and 64%, compared to the control flat-flat-TENG attributed to the enhanced effective contact surface area. Additionally, the output power of the MW-MC-TENG can reach 34.7 mW, corresponding to a power density of 1.4 mW/cm2, when the external resistance is 15 MΩ. Furthermore, the MW-MC-TENG may charge a 0.1 µF capacitor to 2.01 V in 2.28 s and to a maximum voltage of 2.32 V. The MW-MC-TENG, characterized by its significantly smaller cone height and width achievable under lower laser ablation power, demonstrates superior electrical output performance compared to recently reported double-sided patterned TENG devices, as shown in Table 1. Furthermore, its performance exceeds that of the MN–TEG [28], IWA-SMD-TEG [39], and OL-TENG [40], all of which can be also fabricated using CO2 laser technology. In the application test, the MW-MC-TENG was utilized as a wearable self-powered sensor, capable of detecting human walking motion, power 11 LED bulks embedded in a shoe, and power an electronic timer. Overall, the MW-MC-TENG demonstrates a highly sensitive response to motion status under different walking speeds and provides a reliable power supply for low-power electronic devices. This indicates that the proposed MW-MC-TENG has significant potential applications in micro wearable devices.

2. Materials and Methods

2.1. The Material Selection and Fabrication of Friction Pairs

Preparation of the MW-Al friction and Electrode. The fabrication of the MW-Al electrode is as follows: The PMMA mother mold with micro-pore array was fabricated through CO2 laser ablation at a power of 0.06 W, as shown in Figure 1a. CorelDraw software was utilized for the array design, and a CO2 laser source (VL-200, General Laser System Inc., Scottsdale, AZ, USA) system was employed to control CO2 laser processing parameters. The conductive Al tape with a thickness of 60 µm was affixed to the side of PMMA featuring a microporous array within a 50 mm × 50 mm area. Then, a pre-prepared flat flexible PDMS was sandwiched between a flat PMMA board and the conductive aluminum tape, with pressure applied using a hydraulic press (100 kg/cm2) machine, as shown in Figure 1b. The MW-Al tapping on the PMMA played the role of the top tribo-layer and electrode, as shown in Figure 1c.
Preparation of the MC-PDMS film. The PMMA mother mold with a micro-pore array was also fabricated through CO2 laser ablation at a laser power of 0.33 W, a scanning speed of 11.4 mm/s, and a PPI of 110 µm, as shown in Figure 1a. Secondly, the PDMS and curing agent were mixed evenly in a 10:1 ratio, and, subsequently, placed into the PMMA mold, as depicted in Figure 1d. The mixture was vacuumed in a vacuum pump kettle for 10 min to ensure that all holes were filled. It was then cured in an oven at 85 °C for 1 h. Finally, the PDMS film was peeled off from the PMMA and cut into sizes of 50 mm × 50 mm, as shown in Figure 1e, to remove irregular burrs. The PDMS films, including flat-PDMS and MC-PDMS, were prepared with identical area (50 mm × 50 mm) and thickness.

2.2. The Measurement of MW-MC-TENG

To test the electrical output performance of the MW-MC-TENG, a vertical pneumatic cylinder (FESTO, D: S-PAZ-DW20-100PPV, Esslingen, Germany) test platform was utilized to facilitate vertical repeated contact-separation of the TENGs. The schematic representation of the electrical system of the MW-MC-TENG is depicted in Figure 2a. The two triboelectric layers of MW-MC-TENG, namely MW-Al and MC-PDMS, were adhered to the drive shaft and the stage, respectively. The two electrodes of MW-MC-TENG consist of flat Al on the stage and MW-Al affixed to the PMMA substrate. The testing platform is driven by air pressure (input air pressure of 2 kg/cm2) and operates at a frequency of 3 to 7 Hz, with a force of 30 N, maintaining a distance of 20 mm between the test piece and the MW-Al electrode. The aluminum electrode and the test piece are connected using copper wires to a transient waveform recorder to measure the open-circuit voltage signal during the testing process. When measuring the short-circuit current, it is essential to perform so in parallel with a high-resistance load. Furthermore, to evaluate the various DC performances of MW-MC-TENG, a bridge rectifier was employed to convert the MW-MC-TENG signal, and a capacitor was connected in parallel. Due to its high stability, the platform can maintain stability without degradation during high-cycle impact experiments designed to assess the stability of MW-MC-TENG. The microstructure characterization of MW-MC-TENG was conducted using optical microscopy (OM, Olympus BX 51 M, Tokyo, Japan). The Voc and Isc of MW-MC-TENG were measured using an oscilloscope (HIOKI Memory HiCorder MR8870-20, Nagano, Japan).

3. Results

3.1. The Micromorphology Structure of the MW-Al and MC-PDMS

The micromorphology structure of the MW-Al is illustrated in Figure 3, and the structure of the Al was fabricated using a CO2 laser with parameters for speed, density, and power. To measure the height and width of the cross-sectional morphology, the PDMS solution was poured into the MW-Al, and the resulting film was peeled off after curing in an oven at 85 °C for 1 h. The microstructure of the MW-Al and the corresponding PDMS film were then analyzed using optical microscopy (OM). As shown in Figure 3a,b, the surface of the MW-Al exhibited a grid-like shape with a regular hole array, with an average hole distance of approximately 250 µm. The cross-sectional morphology of the MW-Al, as shown in Figure 3c, reveals a wavy shape, with the height of the microwaves measuring about 18 µm and the wavy width measuring approximately 201.6 μm (see Figure 3d and Table 2).
The micromorphology of the MC structures on PDMS is displayed in Figure 4. The height and width of the microcones were measured using OM. The front-view image of the MC-PDMS reveals an average height of 180 µm, an average width of 146 µm, and a layer thickness of approximately 700 µm.

3.2. The Working Mechanism of the MW-MC-TENG

The working mechanism of the MW-MC-TENG can be explained as the combination of triboelectrification and electrostatic induction, where frictional materials and electrode materials play key roles, as shown in Figure 2a. Initially, when the two frictional materials are in full contact and rub against each other under external pressure, an equal number of transferred charges are generated on the surfaces of both materials, as shown in Figure 2b. According to the difference in the polarity of the triboelectric series, the MW-Al acquires positive charges, while the MC-PDMS gains negative charges. When the external pressure is released, the two charged layers begin to separate from each other. Due to the need for potential difference balance, the electrode flow is driven from the bottom electrode to the upper one, generating a current in the opposite direction, as shown in Figure 2c. When the two friction layers reach the maximum separation distance position, the flow of the electrons disappears for the electrostatic equilibrium, as shown in Figure 2d. If the external force is applied again, the opposite electrode flow is generated in the direction from the upper electrode to the bottom one due to the electrostatic induction, as shown in Figure 2e. When the friction layers re-contact, the induced charges of the opposite electrodes neutralize each other and reach an equal electrostatic equilibrium state. The periodic contact and separation between the MC-PDMS and MW-Al lead to charge transfer and redistribution on the contact surface.

3.3. The Output Performance of the MW-MC-TENG

To compare the effect of the microstructure on the performance of the TENG, we prepared untreated Al (flat-Al) and untreated PDMS (flat-PDMS) to assemble TENGs alongside other test samples. The vertical pneumatic cylinder test platform was utilized to control the contact separation frequency (6 Hz). Figure 5a–c show the Voc, Isc, and Qsc of the TENGs with different friction pairs, demonstrating a trend as follows: flat-flat-TENG (91.5 V, 43.5 μA, 0.23 nF, 1.74 μA cm−2) < flat-MC-TENG (118 V, 54 μA, 0.31 nF, 2.16 μA cm−2) ≈ MW-flat-TENG (114 V, 56.5 μA, 0.29 nF, 2.26 μA cm−2) < MW-MC-TENG (141 V, 71.5 μA, 0.40 nF, 2.86 μA cm−2). The output performance of the flat-MC-TENG and MW-flat-TENG is higher than that of flat-flat-TENG, which can be attributed to the increased surface contact area provided by the roughened Al-flat PDMS combination or the flat Al-roughened PDMS combination. The double-side patterned MW-MC-TENG’s Voc, Isc, and Jsc are approximately 54%, 64%, and 64% higher than those of the flat-flat-TENG without a microstructure. The output performance of the TENGs is significantly affected by the surface morphology of the friction pairs under different microstructure conditions. In total, the output performance of TENGs with roughened Al and PDMS friction layers is superior to that of other ones with more surface contact area. Consequently, the MW-Al and MC-PDMS were selected as the tribo-layers of MW-MC-TENG.
The output performance of the MW-MC-TENG was evaluated at different frequencies (3 Hz–7 Hz) using the testing platform, maintaining a constant distance of 20 mm (Figure 5d,e). The Voc and Isc gradually increase with the increase of contact-separation frequency and reach the peak value of 147 V and 78 μA, respectively, at the highest frequency. As the speed of contact and separation between the two friction layers increases, their contact time decreases, decreasing the number of neutral charges on the two plates. This phenomenon promotes an increase in both Voc and Isc.

3.4. Enhancement Mechanism of the MW-MC-TENG

Figure 6 illustrates the enhancement mechanism of the MW-MC-TENG through 3D modeling, depicting the meshing, deformation, and restoring process of the MCs during the cyclic pressing–releasing operation, as observed using OM. Figure 6a exhibits the initial state of the MC-MW-TENG, where no charging occurs. Figure 6b displays the initial contact state of the two friction pairs. At this state, MW-Al and MC-PDMS are not yet in contact with each other, and the slight deformation is primarily confined to the tip of the MCs. Figure 6c presents the further contact and friction state. In this state, the contact area increases with the increase in the deformation amount of the MC-PDMS, initiating dipole triboelectric charging. Figure 6d depicts the complete contact and deformation state, where the maximum equilibrium of triboelectric distribution is established between the two triboelectric materials. At this point, the contact area and deformation of the MC-PDMSs reached the maximum amount, which resulted in the high performance of the MW-MC-TENG and the peak of the voltage and current. Finally, Figure 6e illustrates the restoring state of the MC-PDMS after the external pressure is released, resulting in an unequal potential that generates a negative current through an external circuit.
It is evident from the OM–observation process that the morphology and surface area of the micropores in the Al film significantly impact the contact area of the two friction layers. In our case, the micropores in the MW-Al exhibit spherical crown shapes (see Figure 3a,c) with their dimensions listed in Table 3 and illustrated in Figure 3d. The average surface area of the micropores is calculated as 41,259.6 μm2, as indicated by Formula (1). Considering that the array density of micropores is 1600 #/cm2, the total number (N) of micropores is determined as 40,000, leading to a contact area of 2874.2 mm2, as derived from Formula (2), where L means the length of the square samples. It is evident that the contact area of the MW-MC pairs is considerably larger than that of flat-flat pairs, which have a contact area of 2500 mm2. Thus, the estimated and measured output electric performance is correspondingly higher. The measured voltages and currents are close to the calculated results.
S = 2πRH,
CS = (L2 − Nπr2) + NS,
The deformation phenomenon shown in Figure 6 suggests the potential influence of the flexoelectric effect on the output performance of the TENG due to strain gradient. To further investigate and analyze the collaborative flexoelectric and triboelectric effects on the TENGs, the output voltage performance of the flat-flat-TENG and MW-MC-TENG was measured using a pushing platform tester. The flat-flat-TENG served as a prototype in which only the triboelectric effect contributed to the output voltage for comparison. The results shown in Figure 7a,b distinctly indicate the enhanced triboelectric charging in the MW-MC-TENG device; specifically, the output voltage of the MW-MC-TENG is greater than that of the flat device. Figure 7c illustrates that the difference in output between the double-side patterned and flat devices increases with applied force. Figure 7d shows that the force sensitivity of the MW-MC-TENG (31.12 V/kgf−1) is almost twice that of the flat-flat-TENG (15.93 V/kgf−1). This phenomenon is attributed to the increased polarization strength resulting from the flexoelectric effect as the MC deformation and strain gradient rise, leading to enhanced piezoelectric output and force sensitivity of the device. These results confirm the significant contribution of concurrent flexoelectricity in MW-MC-TENG.

3.5. Power Generation, Energy Storage, and Durability

To achieve the maximum output power of MW-MC-TENG, it is externally connected to a range of resistors from 1000 Ω to 500 MΩ and tested with an external circuit. As the resistance value increases, the output voltage initially rises slowly and then rapidly (Figure 8a). In contrast, the output current exhibits a decreasing trend, transitioning from slow to fast. When the resistance is 15 MΩ, the voltage and current reach 14.7 V and 48.1 μA, respectively, resulting in a peak power of 34.7 mW (see Figure 8b) for the MW-MC-TENG, which corresponds to a power density of 1.4 mW/cm2.
Figure 8c illustrates the charging voltage of MW-MC-TENG as a function of time for six different capacitors (0.1–10 µF). The charging voltage (Vc) reached 2.01 V at 2.28 s with a maximum value of 2.32 V for 0.1 µF. The 1 µF capacitor registered 1.80 V at 18.5 s, and the 2.2 µF capacitor recorded 1.7 V at 40.88 s. The 3.3 µF capacitor achieved 1.6 V at 57.29 s, and the 4.7 µF capacitor reached 1.4 V at 55.95 s. Furthermore, the charging behavior of the flat-flat-TENG, MW-flat-TENG, flat-MC-TENG, and MW-MC-TENG was tested for energy storage capabilities using the same 1 µF capacitor, as shown in Figure 8d. The MW-MC-TENG exhibited a stable Vc of approximately 2.2 V, whereas the average Vc for MW-flat-TENG and flat-MC-TENG was 1.6 V, and for the flat-flat-TENG, it was 1.2 V. The practice tests of electrical charging demonstrate the potential application of the power supply in electronic devices.
The mechanical durability of the optimal TENG was confirmed, as it consistently generated electric power for 1000 s, corresponding to more than 6000 cycles of contact-separation operation, as shown in Figure 9.

3.6. Demonstration

Since the MW-MC-TENG can generate high output voltage and power, it was tested for energy harvesting from human motion. The device was characterized under real-time human walking motions to evaluate its feasibility for daily life applications, specifically in supplying electricity for electronic devices. During testing, we embedded the MW-MC-TENG device within the insole of a shoe’s heel, as shown in Figure 10a. Figure 10b presents a snapshot of the instantaneous powering of 11 commercial LEDs driven by the proposed harvester prototype under a medium walking speed, demonstrating the potential application of MW-MC-TENG in self-powered luminous shoes for children. Figure 10c displays the output voltages at different walking speeds: 11 V, 20 V, and 55 V, indicating that the self-powered sensor exhibits high-speed sensitivity and can be applied for monitoring walking speed. Additionally, we compared our sensor with other devices, as shown in Table 4. The MW-MC-TENG-based insole sensor demonstrated higher output performance than other TENG sensors under the same walking/stepping speed or even slower.
To investigate the real-time applications of the harvester under practical conditions, we designed an energy management circuit by combining a rectifier bridge and a 10 μF capacitor. When the TENG is affixed to the insole of the shoes, it can continuously store electricity in the capacitor through stepping. As shown in Figure 10d,e, after stepping for nearly 180 s, and then turning on the switch, the electronic timer illuminated and lasted for 0.1 s.

4. Conclusions

In summary, this work presents a double-sided surface patterning method using CO2 laser technology, which is simple and cost-effective, to enhance the electrical output performance of TENGs. The MW-MC-TENG was fabricated by combining a PDMS featuring a microcone structure with an Al foil featuring a microwave structure. Two PMMA molds with the same micro-hole array were prepared through laser marking; the deeper mold was used to demold the PDMS, and the shallower one was used for cold imprinting the Al foil. The Voc, Isc, and Jsc values of the MW-MC-TENG reached 141 V, 71.5 μA, and 2.86 μA/cm2, respectively, at a frequency of 6 Hz and a distance of 20 mm. When the resistance is 15 MΩ, the maximum power density of 1.4 mW/cm2 is achieved. Additionally, MW-MC-TENG can charge a 0.1 μF capacitor to 2.01 V in 2.28 s. Furthermore, the proposed TENG device can be also employed as a wearable insole to efficiently harvest walking energy, monitor step speed, and power a timer device. Based on these results, we believe that the proposed processing technique is essential for realizing an inexpensive triboelectric energy harvester and is advantageous for large-scale fabrication in future portable and wearable device applications.

Author Contributions

D.-Y.L. and C.-K.C. proposed the original idea; D.-Y.L. and C.-K.C. worked together on the conceptualization, organization, discussion and the draft writing; D.-Y.L. prepared the experiments, figure drawing, and information survey. D.-Y.L. and C.-K.C. discussed the concept, methodology, and writing of the electrical performance analyzed, and application. C.-K.C. made the final review, editing, and supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partially sponsored by the National Science and Technology Council (NSTC), Taiwan, under No NSTC113-222-1-E006-099-MY3.

Data Availability Statement

Data are presented in the coauthors’ research results and schematic drawings available on request.

Acknowledgments

We also would like to thank the Core Facility Center in the National Cheng Kung University for analysis instrument support.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Wang, S.; Wang, C.H.; Yuan, H.Z.; Ji, X.P.; Yu, G.X.; Jia, X.D. Size effect of piezoelectric energy harvester for road with high efficiency electrical properties. Appl. Energy 2023, 330, 120379. [Google Scholar] [CrossRef]
  2. Wang, Z.M.; Chen, Y.H.; Jiang, R.J.; Du, Y.; Shi, S.H.; Zhang, S.M.; Yan, Z.M.; Lin, Z.L.; Tan, T. Broadband omnidirectional piezoelectric-electromagnetic hybrid energy harvester for self-charged environmental and biometric sensing from human motion. Nano Energy 2023, 113, 108526. [Google Scholar] [CrossRef]
  3. Bai, S.M.; Cui, J.; Zheng, Y.Q.; Li, G.; Liu, T.S.; Liu, Y.B.; Hao, C.C.; Xue, C.Y. Electromagnetic-triboelectric energy harvester based on vibration-to-rotation conversion for human motion energy exploitation. Appl. Energy 2023, 329, 120292. [Google Scholar] [CrossRef]
  4. Wan, J.; Wang, H.B.; Miao, L.M.; Chen, X.X.; Song, Y.; Guo, H.; Xu, C.; Ren, Z.Y.; Zhang, H.X. A flexible hybridized electromagnetic-triboelectric nanogenerator and its application for 3D trajectory sensing. Nano Energy 2020, 74, 104878. [Google Scholar] [CrossRef]
  5. Tu, S.; Tian, T.; Xiao, T.X.; Yao, X.T.; Shen, S.C.; Wu, Y.S.; Liu, Y.L.; Bing, Z.S.; Huang, K.; Knoll, A.; et al. Humidity Stable Thermoelectric Hybrid Materials Toward a Self-Powered Triple Sensing System. Adv. Funct. Mater. 2024, 34, 2316088. [Google Scholar] [CrossRef]
  6. Feng, Z.; Yang, S.; Jia, S.X.; Zhang, Y.J.; Jiang, S.; Yu, L.; Li, R.; Song, G.W.; Wang, A.B.; Martin, T.; et al. Scalable, washable and lightweight triboelectric-energy-generating fibers by the thermal drawing process for industrial loom weaving. Nano Energy 2020, 74, 104805. [Google Scholar] [CrossRef]
  7. Ryu, H.; Kim, S.W. Emerging Pyroelectric Nanogenerators to Convert Thermal Energy into Electrical Energy. Small 2021, 17, 201903469. [Google Scholar] [CrossRef]
  8. Li, H.Y.; Bowen, C.R.; Yang, Y. Phase transition enhanced pyroelectric nanogenerators for self-powered temperature sensors. Nano Energy 2022, 102, 107657. [Google Scholar] [CrossRef]
  9. Ding, R.; Cao, Z.Y.; Wu, Z.B.; Xing, H.T.; Ye, X.Y. All-in-One High Output Rotary Electrostatic Nanogenerators Based on Charge Pumping and Voltage Multiplying. ACS Nano 2021, 15, 16861–16869. [Google Scholar] [CrossRef]
  10. Rui, P.S.; Zhang, W.; Wang, P.H. Super-Durable and Highly Efficient Electrostatic Induced Nanogenerator Circulation Network Initially Charged by a Triboelectric Nanogenerator for Harvesting Environmental Energy. ACS Nano 2021, 15, 6949–6960. [Google Scholar] [CrossRef]
  11. Wu, Y.X.; Li, Y.S.; Zou, Y.; Rao, W.; Gai, Y.S.; Xue, J.T.; Wu, L.; Qu, X.C.; Liu, Y.; Xu, G.D.; et al. A multi-mode triboelectric nanogenerator for energy harvesting and biomedical monitoring. Nano Energy 2022, 92, 106715. [Google Scholar] [CrossRef]
  12. He, Y.; Tian, J.; Peng, W.B.; Huang, D.Y.; Li, F.P.; He, Y.N. On the contact electrification mechanism in semiconductor–semiconductor case by vertical contact-separation triboelectric nanogenerator. Nanotechnology 2023, 34, 295401. [Google Scholar] [CrossRef]
  13. Yu, Y.; Gao, Q.; Zhang, X.S.; Zhao, D.; Xia, X.; Wang, J.L.; Li, H.Y.; Wang, Z.L.; Cheng, T.H. Contact-sliding-separation mode triboelectric nanogenerator. Energy Environ. Sci. 2023, 16, 3932–3941. [Google Scholar] [CrossRef]
  14. Ren, D.H.; Yang, H.K.; Zhang, X.M.; Li, Q.Y.; Yang, Q.X.; Li, X.C.; Ji, P.Y.; Yu, P.; Xi, Y.; Wang, Z.L. Ultra-High DC and Low Impedance Output for Free-Standing Triboelectric Nanogenerator. Adv. Energy Mater. 2023, 13, 2302877. [Google Scholar] [CrossRef]
  15. Wang, Z.L.; Zhu, G.; Yang, Y.; Wang, S.H.; Pan, C.F. Progress in nanogenerators for portable electronics. Mater. Today 2012, 15, 532–543. [Google Scholar] [CrossRef]
  16. Cao, X.; Jie, Y.; Wang, N.; Wang, Z.L. Triboelectric Nanogenerators Driven Self-Powered Electrochemical Processes for Energy and Environmental Science. Adv. Energy Mater. 2016, 6, 1600665. [Google Scholar] [CrossRef]
  17. Wang, Z.L. Catch wave power in floating nets. Nature 2017, 542, 159–160. [Google Scholar] [CrossRef]
  18. Wang, Z.L.; Chen, J.; Lin, L. Progress in triboelectric nanogenerators as a new energy technology and self-powered sensors. Energy Environ. Sci. 2015, 8, 2250–2282. [Google Scholar] [CrossRef]
  19. Liu, X.R.; Zhao, Z.H.; Gao, Y.K.; Nan, Y.; Hu, Y.X.; Guo, Z.T.; Qiao, W.Y.; Wang, J.; Zhou, L.L.; Wang, Z.L.; et al. Triboelectric nanogenerators exhibiting ultrahigh charge density and energy density. Energy Environ. Sci. 2024, 17, 3819–3831. [Google Scholar] [CrossRef]
  20. Li, Z.J.; Yang, C.; Zhang, Q.; Chen, G.; Xu, J.Y.; Peng, Y.; Guo, H.Y. Standardized Volume Power Density Boost in Frequency-Up Converted Contact-Separation Mode Triboelectric Nanogenerators. Research 2023, 6, 0237. [Google Scholar] [CrossRef] [PubMed]
  21. Guess, M.; Soltis, I.; Rigo, B.; Zavanelli, N.; Kapasi, S.; Kim, H.; Yeo, W.-H. Wireless batteryless soft sensors for ambulatory cardiovascular health monitoring. Soft Sci. 2023, 3, 24. [Google Scholar] [CrossRef]
  22. Lin, L.; Xie, Y.N.; Niu, S.M.; Wang, S.H.; Yang, P.K.; Wang, Z.L. Robust triboelectric nanogenerator based on rolling electrification and electrostatic induction at an instantaneous energy conversion efficiency of ~55%. ACS Nano 2015, 9, 922–930. [Google Scholar] [CrossRef] [PubMed]
  23. Kim, D.; Lee, H.M.; Choi, Y.K. Large-sized sandpaper coated with solution-processed aluminum for a triboelectric nanogenerator with reliable durability. RSC Adv. 2017, 7, 137–144. [Google Scholar] [CrossRef]
  24. Zi, Y.L.; Niu, S.M.; Wang, J.; Wen, Z.; Tang, W.; Wang, Z.L. Standards and figure-of-merits for quantifying the performance of triboelectric nanogenerators. Nat. Commun. 2015, 6, 8376. [Google Scholar] [CrossRef] [PubMed]
  25. Fan, F.R.; Lin, L.; Zhu, G.; Wu, W.Z.; Zhang, R.; Wang, Z.L. Transparent Triboelectric Nanogenerators and Self-Powered Pressure Sensors Based on Micropatterned Plastic Films. Nano Lett. 2012, 12, 3109–3114. [Google Scholar] [CrossRef]
  26. Cheng, G.G.; Jiang, S.Y.; Li, K.; Zhang, Z.Q.; Wang, Y.; Yuan, N.Y.; Ding, J.N.; Zhang, W. Effect of argon plasma treatment on the output performance of triboelectric nanogenerator. Appl. Surf. Sci. 2017, 412, 350–356. [Google Scholar] [CrossRef]
  27. Deng, W.L.; Zhang, B.B.; Jin, L.; Chen, Y.Q.; Chu, W.J.; Zhang, H.T.; Zhu, M.H.; Yang, W.Q. Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator. Nanotechnology 2017, 28, 135401. [Google Scholar] [CrossRef]
  28. Trinh, V.L.; Chung, C.K. A Facile Method and Novel Mechanism Using Microneedle-Structured PDMS for Triboelectric Generator Applications. Small 2017, 13, 1700373. [Google Scholar] [CrossRef]
  29. Yao, G.; Xu, L.; Cheng, X.W.; Li, Y.Y.; Huang, X.; Guo, W.; Liu, S.Y.; Wang, Z.L.; Wu, H. Bioinspired Triboelectric Nanogenerators as Self-Powered Electronic Skin for Robotic Tactile Sensing. Adv. Funct. Mater. 2020, 30, 1907312. [Google Scholar] [CrossRef]
  30. Li, M.Q.; Xu, B.A.; Li, Z.H.; Gao, Y.Y.; Yang, Y.J.; Huang, X.X. Toward 3D double-electrode textile triboelectric nanogenerators for wearable biomechanical energy harvesting and sensing. Chem. Eng. J. 2022, 450, 137491. [Google Scholar] [CrossRef]
  31. Rasel, M.S.; Maharjan, P.; Salauddin, M.; Rahman, M.T.; Cho, H.O.; Kim, J.W.; Park, J.Y. An impedance tunable and highly efficient triboelectric nanogenerator for large-scale, ultra-sensitive pressure sensing applications. Nano Energy 2018, 49, 603–613. [Google Scholar] [CrossRef]
  32. Chun, J.S.; Ye, B.U.; Lee, J.W.; Choi, D.; Kang, C.Y.; Kim, S.W.; Wang, Z.L.; Baik, J.M. Boosted output performance of triboelectric nanogenerator via electric double layer effect. Nat. Commun. 2016, 7, 12985. [Google Scholar] [CrossRef]
  33. Wang, H.S.; Jeong, C.K.; Seo, M.H.; Joe, D.J.; Han, J.H.; Yoon, J.B.; Lee, K.J. Performance-enhanced triboelectric nanogenerator enabled by wafer-scale nanogrates of multistep pattern downscaling. Nano Energy 2017, 35, 415–423. [Google Scholar] [CrossRef]
  34. Choi, H.J.; Lee, J.H.; Jun, J.; Kim, T.Y.; Kim, S.W.; Lee, H. High-performance triboelectric nanogenerators with artificially well-tailored interlocked interfaces. Nano Energy 2016, 27, 595–601. [Google Scholar] [CrossRef]
  35. Cai, X.; Xiao, Y.; Zhang, B.W.; Yang, Y.H.; Wang, J.; Chen, H.M.; Shen, G.Z. Surface Control and Electrical Tuning of MXene Electrode for Flexible Self-Powered Human–Machine Interaction. Adv. Funct. Mater. 2023, 33, 2304456. [Google Scholar] [CrossRef]
  36. Lin, L.; Chung, C.K. PDMS Microfabrication and Design for Microfluidics and Sustainable Energy Application: Review. Micromachines 2021, 12, 1350. [Google Scholar] [CrossRef]
  37. Zhu, S.L.; Xia, Y.F.; Zhu, Y.; Wu, M.; Jia, C.Y.; Wang, X. High-performance triboelectric nanogenerator powered flexible electroluminescence devices based on patterned laser-induced copper electrodes for visualized information interaction. Nano Energy 2022, 96, 107116. [Google Scholar] [CrossRef]
  38. Ke, K.H.; Lin, L.; Chung, C.K. Low-cost micro-graphite doped polydimethylsiloxane composite film for enhancement of mechanical-to-electrical energy conversion with aluminum and its application. J. Taiwan Inst. Chem. Eng. 2022, 135, 104388. [Google Scholar] [CrossRef]
  39. Trinh, V.L.; Chung, C.K. Harvesting mechanical energy, storage, and lighting using a novel PDMS based triboelectric generator with inclined wall arrays and micro-topping structure. Appl. Energ. 2018, 213, 353–365. [Google Scholar] [CrossRef]
  40. Chung, C.K.; Ke, K.H. High contact surface area enhanced Al/PDMS triboelectric nanogenerator using novel overlapped microneedle arrays and its application to lighting and self-powered devices. Appl. Surf. Sci. 2020, 508, 145310. [Google Scholar] [CrossRef]
  41. Song, J.; Gao, L.B.; Tao, X.M.; Li, L.X. Ultra-Flexible and Large-Area Textile-Based Triboelectric Nanogenerators with a Sandpaper-Induced Surface Microstructure. Materials 2018, 11, 2120. [Google Scholar] [CrossRef] [PubMed]
  42. Xiao, Y.; Lv, X.; Yang, L.P.; Niu, M.Y.; Liu, J.C. A High-Performance Flexible Triboelectric Nanogenerator Based on Double-Sided Patterned TiN/PDMS Composite Film for Human Energy Harvesting. Energy Technol. 2021, 9, 2100665. [Google Scholar] [CrossRef]
  43. Prasad, G.; Graham, S.A.; Yu, J.S.; Kim, H.D.; Lee, D.W. Investigated a PLL surface-modified Nylon 11 electrospun as a highly tribo-positive frictional layer to enhance output performance of triboelectric nanogenerators and self-powered wearable sensors. Nano Energy 2023, 108, 108178. [Google Scholar] [CrossRef]
  44. Gajula, P.; Muhammad, F.M.; Reza, M.S.; Jaisankar, S.N.; Kim, K.J.; Kim, H.D. Fabrication of a silicon elastomer-based self-powered flexible triboelectric sensor for wearable energy harvesting and biomedical applications. ACS Appl. Electron. Mater. 2023, 5, 1750–1760. [Google Scholar] [CrossRef]
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Figure 1. The process of preparing the frictional appearance of MW-MC-TENG. (a) Micro-hole arrays were ablated on PMMA molds with a CO2 laser machine. (b) The Al foil was imprinted into a PMMA mold through a PMMA flat plate and a soft flat PDMS medium under external pressure (the red arrow). (c) After removing the PMMA board and PDMS, the positive friction layer adhered to the PMMA mold was formed. (d) PDMS was poured into another PMMA mold. (e) After baking and demolding, the negative fiction layer was formed.
Figure 1. The process of preparing the frictional appearance of MW-MC-TENG. (a) Micro-hole arrays were ablated on PMMA molds with a CO2 laser machine. (b) The Al foil was imprinted into a PMMA mold through a PMMA flat plate and a soft flat PDMS medium under external pressure (the red arrow). (c) After removing the PMMA board and PDMS, the positive friction layer adhered to the PMMA mold was formed. (d) PDMS was poured into another PMMA mold. (e) After baking and demolding, the negative fiction layer was formed.
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Figure 2. The measurement and working principle of MW-MC-TENG. (a) The electrical system of MW-MC-TENG includes the MW-Al friction and conductive layer, the PDMS friction layer, and the Al conductive layer, under the initial state. (b) The triboelectric effect with maximum charge transferred, under complete contact. (c) The restoring of two contact surfaces induced electronic flow via an external circuit from the bottom electrode to the top electrode when the force is released. (d) A new electrical equilibrium at complete separation. (e) The electronic flow from the top electrode to the bottom electrode was induced when the pressing again of two contact surfaces.
Figure 2. The measurement and working principle of MW-MC-TENG. (a) The electrical system of MW-MC-TENG includes the MW-Al friction and conductive layer, the PDMS friction layer, and the Al conductive layer, under the initial state. (b) The triboelectric effect with maximum charge transferred, under complete contact. (c) The restoring of two contact surfaces induced electronic flow via an external circuit from the bottom electrode to the top electrode when the force is released. (d) A new electrical equilibrium at complete separation. (e) The electronic flow from the top electrode to the bottom electrode was induced when the pressing again of two contact surfaces.
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Figure 3. (a) Front view OM diagram of the MW-Al foil; (b) CCD camera image of MW-Al foil morphology at a distance of 5 cm; (c) Side view of the OM diagram of 18 μm microwave structure on Al foil; (d) The basic dimension schematics of the MWs.
Figure 3. (a) Front view OM diagram of the MW-Al foil; (b) CCD camera image of MW-Al foil morphology at a distance of 5 cm; (c) Side view of the OM diagram of 18 μm microwave structure on Al foil; (d) The basic dimension schematics of the MWs.
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Figure 4. OM image of the microcone structure on PDMS.
Figure 4. OM image of the microcone structure on PDMS.
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Figure 5. The electrical characteristic generated by the MW-MC-TENGs. (a–c) The open–circuit voltage, short–circuit current, and calculated transfer charge of the TENGs constructed by flat Al, flat PDMS, MW-Al, and MC-PDMS, respectively. (d,e) show the open-circuit voltage and the short-circuit current of the MW-MC-TENG under different contact-separation frequencies.
Figure 5. The electrical characteristic generated by the MW-MC-TENGs. (a–c) The open–circuit voltage, short–circuit current, and calculated transfer charge of the TENGs constructed by flat Al, flat PDMS, MW-Al, and MC-PDMS, respectively. (d,e) show the open-circuit voltage and the short-circuit current of the MW-MC-TENG under different contact-separation frequencies.
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Figure 6. The enhancement process of the contact area and friction of the MCs in the meshing and deformation process. (a) The initial state of the MC-MW-TENG; (b) The starting contact point; (c) The contact area and friction increase with further meshing and deformation; (d) The multi-contact area and multi-friction between the MW-Al and MC-PDMS substrate at the maximum deformation state; (e) The releasing state.
Figure 6. The enhancement process of the contact area and friction of the MCs in the meshing and deformation process. (a) The initial state of the MC-MW-TENG; (b) The starting contact point; (c) The contact area and friction increase with further meshing and deformation; (d) The multi-contact area and multi-friction between the MW-Al and MC-PDMS substrate at the maximum deformation state; (e) The releasing state.
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Figure 7. Output voltage details for (a) flat-flat-TENG, and (b) MW-MC-TENG under different forces. (c) The comparison of the two TENGs output voltage as a function of force. (d) The comparison of the two TENGs force sensitivity.
Figure 7. Output voltage details for (a) flat-flat-TENG, and (b) MW-MC-TENG under different forces. (c) The comparison of the two TENGs output voltage as a function of force. (d) The comparison of the two TENGs force sensitivity.
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Figure 8. Output (a) voltage, current, and (b) power of the MW-MC-TENG under different external resistances. (c) Charging voltage of the MW-MC-TENG from 0.1 to 10 μF capacitor. (d) The charging voltage curve on a 1 μF capacitor of flat-flat-TENG, MW-flat-TENG, flat-MC-TENG, and MW-MC-TENG.
Figure 8. Output (a) voltage, current, and (b) power of the MW-MC-TENG under different external resistances. (c) Charging voltage of the MW-MC-TENG from 0.1 to 10 μF capacitor. (d) The charging voltage curve on a 1 μF capacitor of flat-flat-TENG, MW-flat-TENG, flat-MC-TENG, and MW-MC-TENG.
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Figure 9. The electrical performance of MW-MC-TENG is stable after 6000 cycles of beating test.
Figure 9. The electrical performance of MW-MC-TENG is stable after 6000 cycles of beating test.
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Figure 10. Application of the proposed TENG harvester. (a) Photographic image of the TENG device fixed into a shoe’s sole for harvesting the walking energy. (b) Eleven LEDs embedded in the shoe can be lit under medium walking speed. (c) The output voltage under different walking speeds. (d) The direct drive of the electronic timer by MW-MC-TENG through a 10 μF energy management circuit. (e,f) Shows the charging and driving process.
Figure 10. Application of the proposed TENG harvester. (a) Photographic image of the TENG device fixed into a shoe’s sole for harvesting the walking energy. (b) Eleven LEDs embedded in the shoe can be lit under medium walking speed. (c) The output voltage under different walking speeds. (d) The direct drive of the electronic timer by MW-MC-TENG through a 10 μF energy management circuit. (e,f) Shows the charging and driving process.
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Table 1. Comparison of surface morphology, materials, fabrication methods, operation conditions, and electrical characteristics.
Table 1. Comparison of surface morphology, materials, fabrication methods, operation conditions, and electrical characteristics.
MorphologyMaterialFabrication MethodOperation ConditionElectrical CharacteristicsRef.
Voc (V)Isc (µA)Power Density (mW/cm2)
Microcone–microconePDMS@AgNWs-PDMS@ PTFE tiny burrsReplication and molding,
spray coating,
evaporation and reactive ion etching		25 kPa,
0.6 Hz		3.140.0263-[29]
Yarn–yarnTPU-PDMSCoating150 N,
6 Hz		763~0.02[30]
Nanogrit–nanogritPDMS@CNT-PDMSSpin casting,
dispersion and magnetic stirring		450 kPa,
1 Hz		92550.007[31]
Micropore–nanoparticlesAl/porous PDMS-Al@Au NPsSpin coating and curing50 N
10 Hz		~120~0.125-[32]
Nano roughened structure–nanogratingPET-AuMagnetron sputtering, inductively coupled plasma (ICP)10 Hz~125~31.2~0.32[33]
Nanopillar–NanopillarNi-PDMSSpin coating,
electrodeposition		10 kgf,
3 Hz		~100~23-[34]
MW-Al and MC-PDMSAl/PDMS/AlCO2 laser ablation, cold imprinting30 N
6 Hz		14171.51.4ours
Table 2. Detail of Types of TENG Devices for Each Combination.
Table 2. Detail of Types of TENG Devices for Each Combination.
CombinationPatterning TypeStructure of AlStructure of PDMSElectrical Characteristics
Voc (V)Isc (µA)J (µA/cm2)
flat-flatNonpatternedFlatFlat91.543.51.74
flat-MCSingle-SidedFlatMicrocone118542.16
MW-flatSingle-SidedMicrowaveFlat11456.52.26
MW-MCDouble-SidedMicrowaveMicrocone14171.52.86
Table 3. The dimensions and area of the two types of Al friction layers.
Table 3. The dimensions and area of the two types of Al friction layers.
ItemsSymbolMW-AlFlat-Al
Size (cm2) 5 × 55 × 5
The square sample length (mm)L5050
Average MW center depth (μm)H18-
Average MW bottom diameter (μm)d201.6-
Average MW bottom radius (μm)r100.8-
Average MW spherical radius (μm)R365-
Average MW estimated surface area (μm2)S41,259.6-
Number of MWsN40,000-
Grain density (number of MWs/cm2) 1600-
Estimated surface area (Contact area) (mm2)CS2874.22500
Estimated voltage (V) 128.985.0
Estimated current (μA) 65.857.2
Measured voltage (V) 14191.5
Measured current (μA) 71.543.5
Table 4. Comparison of the MW-MC-TENG device with other TENGs in output performance when used as an insole in stepping/walking motion monitoring application.
Table 4. Comparison of the MW-MC-TENG device with other TENGs in output performance when used as an insole in stepping/walking motion monitoring application.
DevicePatterning TypeArea (mm2)Frequency (Hz)Voltage (V)Ref.
P3000-T-TENGSingle-side50 × 60~4~4[41]
DSP-TiN/PDMS-based TENGSingle-side40 × 40~56[42]
EC10S+PNy 11 TENGDouble-side20 × 2022[43]
SF-TESDouble-side20 × 20~1.54[44]
3D-FTENGDouble-side28 × 301.540[30]
MW-MC-TENGDouble-side50 × 501.555Ours
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Lin, D.-Y.; Chung, C.-K. High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting. Micromachines 2024, 15, 1299. https://doi.org/10.3390/mi15111299

AMA Style

Lin D-Y, Chung C-K. High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting. Micromachines. 2024; 15(11):1299. https://doi.org/10.3390/mi15111299

Chicago/Turabian Style

Lin, Dong-Yi, and Chen-Kuei Chung. 2024. "High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting" Micromachines 15, no. 11: 1299. https://doi.org/10.3390/mi15111299

APA Style

Lin, D.-Y., & Chung, C.-K. (2024). High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting. Micromachines, 15(11), 1299. https://doi.org/10.3390/mi15111299

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