POSTER/ORAL PRESENTATIONS

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2 POSTER/ORAL PRESENTATIONS PowerMEMS Components and Systems T-107 TUNABLE THERMO-TRIBOELETRIC ENERGY HARVESTING USING HUMAN BODY HEAT FOR SELF-POWERED APPLICATIONS D.G. Lee Korea Polytechnic University, KOREA We demonstrate a novel tunable thermo-triboelectric energy harvesting system for the use of human body heat as an energy source of self-powered applications. The proposed approach can convert thermal energy from human body heat into electricity by pairing triboelectric effect and MTG concept. W-108 MAGNETICALLY-DRIVEN TRIBOELECTRIC GENERATOR AS A DIRECT POWER SOURCE FOR WIRESSLESS SENSORS J. Qian, D.-S. Kim, and D.-W. Lee Chonnam National University, KOREA We describe a magnetically-driven rotating triboelectric generator (M-TEG) as a direct power source for wireless sensors. 4 M-TEGs are symmetrically placed on the wheel hub of a vehicle. Permanent magnets mounted on the brake caliper provides a non-contact magnetic force to generate a seesaw-like swing motion of the M-TEG in the tire. The unique advantage of the seesaw structure eliminates the influence of a large centrifugal force at a high rotating speed. M-109 A FOOT-TREDING TYPE ELECTRIC POWER GENERATOR USING MICRO/NANO CHANNELS IN A POROUS GLASS FILTER Y. Tanaka 1,2 and Y. Yalikun 1,2 1 RIKEN, JAPAN and 2 Osaka University, JAPAN We here firstly demonstrated an energy harvesting device using water and glass small channels driven by pressure derived from foot-treading. This device is suitable for slow movement scene like human behavior. MEMS Actuators and PowerMEMS Other Actuators and PowerMEMS T-110 DEVELOPMENT OF A BISTABLE CMOS-MEMS MICROBEAM RESONATOR WITH ELECTROSTATIC ACTUATION J. Barceló, S. Bota, J. Segura, and J. Verd University of the Balearic Islands, SPAIN We report, for the first time, experimental demonstration of bistabilty in simple, straight and non-axially-forced clampled-clamped microbeam resonators in the MHz range. The device was fabricated and monolithically integrated with readout circuitry using a commercial 0.35-µm CMOS technology resulting in a low-cost platform to investigate potential bistability applications like switches, mechanical memories, micro-relays, band-pass filters, chaotic generators or energy harvesters. W-111 UNDERWATER ENERGY HARVESTING TECHNOLOGY UTILIZING AN OPTOTHERMALLY PULSATING MICROBUBBLE D. Jang, J. Lee, H. Song, H. Park, and S.K. Chung Myongji University, KOREA This paper presents a new type of underwater energy harvesting technology where a pulsating microbubble (20 ~ 800 nl) actuated by the optothermal effect induces the periodic vibration of piezocantilevers contacted with the microbubble to generate an electric power. The proposed energy harvesting technology can extract a mechanical power from a light energy by optothermally pulsating microbubbles in an aqueous medium and convert the mechanical power to an electric power for wireless devices. 56

3 MAGNETICALLY-DRIVEN TRIBOELECTRIC GENERATOR AS A DIRECT POWER SOURCE FOR WIRELESS SENSORS Jingui Qian 1, * Dong-Su Kim 1, * and Dong-Weon Lee 1,2 1 MEMS and Nanotechnology Laboratory, School of Mechanical Engineering, Chonnam National University, Gwangju 61186, REPUBLIC OF KOREA 2 Center for Next-generation Sensor Research and Development, Chonnam National University, Gwangju 61186, REPUBLIC OF KOREA * These authors contributed equally to this work ABSTRACT This paper describes a magnetically-driven rotating triboelectric generator (M-TEG) as a direct power source for wireless sensors. Four M-TEGs are symmetrically placed on the wheel hub of a vehicle. Permanent magnets mounted on the brake caliper provide a non-contact magnetic force to generate a seesaw-like swing motion of the M-TEG in the tire. The unique advantage of the seesaw structure eliminates the influence of a large centrifugal force at a high rotating speed. High electrical output has been achieved in the wide ranges of rotation speed. The M-TEG at the rotation speed of 100 rpm can deliver a maximal output voltage of 316 V and power of 22.3 mw under a constant magnetic field strength of 0.2 T. There is no obvious decrease in the output voltage of the M-TEG after continuous working for more than 12 h. The power generated by the TEG is stored in a capacitor and the stored energy is used to drive MEMS pressure sensor. The M-TEG has also demonstrated to power a commercial wireless sensor for sending the real-time temperature information to a receiver and displaying on a monitor. INTRODUCTION The demand for embedding tire pressure monitoring systems (TPMS) on wheels is becoming increasingly important to guarantee safety traffic and air-fuel efficiency in automotive industry [1-2]. Currently, the power supply of a wireless sensor especially for the TPMS still is dependent on a lithium battery, which always emerges several drawbacks such as the difficulty of replacement, limited durability, and environmental pollution [3]. Due to these reasons, the development of miniaturized energy harvesting devices to be employed in TPMS takes great attention in the recent years [4]. Generally, piezoelectric, electromagnetic and electrostatic conversion principles have been essentially considered to harvest the unexploited but abundant mechanical energy from the vehicle wheel. For instance, Chen et al. [5] proposed a piezoelectric energy harvesting device for gathering the vibration energy of cars running on rough ground to substitute the battery in TPMS for an advantage of being maintenance-free. Zheng et al. [6] reported a vibration energy harvesting device for tire pressure monitoring application based on a novel asymmetric air-spaced piezoelectric cantilever. However, these energy harvester performances highly depend on the applied frequency, which has quite a narrow bandwidth around its resonance frequency for efficient power generation. In order to address this problem, Yang et al. [7] proposed a nonlinear two-stage oscillator structured energy harvester with frequency up-conversion feature. The non-contact magnetic repulsive driving mechanism eliminates mechanical collision during operation which improves efficiency and endurance of the M-TEG. However, the ultra-low output power of the aforesaid energy harvesters cannot meet the minimum requirement of the electrical energy for available wireless pressure sensors of TPMS [8]. Recently, a new type of energy harvesting technology named as triboelectric generator (TEG) has emerged to harness ambient mechanical motions from vibrations, rotations waves, and impacts. The mechanism is on the basis of the contact-mode and sliding-mode between two triboelectric materials. In this study, we developed a magnetic-driven rotational triboelectric generator (M-TEG) composed of a flexible seesaw structure and a metallic frame. The generation parts of the designed M-TEG consists of two different triboelectric materials with opposite polarities based on the contact mechanism. High output performance of M-TEG can be achieved among the wide ranges of rotational speed and magnetic force. In addition, a pressure sensor is enabled by M-TEG device to measure barometric values of an ambient environment without the battery supply. The M-TEG also has been demonstrated to power a viable wireless sensor for sending the real-time temperature data to a receiver and displaying on a monitor interface. In consequence, the proposed M-TEG is not only used to power the transmitter of TMPS inside of the tire but also can be used to realize the application of self-powered sensor monitoring network. DESIGN AND FABRICATION OF M-TEG The dimensions of the proposed M-TEG are about 56 mm 38 mm 24 mm (l h w) and are suitable to place inside extra space of the vehicle tires. Further, two NdFeB magnets were placed inside of both wings of the seesaw and sealed with square plates. Four rubber sponges are bonded on the wings surfaces of the seesaw and a 60 µm-thick aluminum film is employed as a triboelectricfriction layer. Inductive electrodes are evenly distributed on each sponge layer. As well, the same sponges are placed on the four oblique plates of the metallic frame. An 80 µm-thick PTFE film is conformably bonded to the rubber sponge and a layer of 100 nm aluminum as the back electrode is deposited by sputtering on the reverse surface of the PTFE film. After installing a rotating shaft, the fabricated seesaw body and metallic frame are assembled together. The design and assembling process of M-TEG device are described in Fig. 1. The contact areas of generation material of M-TEG are about 24 cm 2. As shown in Fig. 1, there is a NdFeB magnet mounted on a fixed brake caliper of the vehicle tire. An /18/$ IEEE 673 MEMS 2018, Belfast, Northern Ireland, UK, January 2018

4 additional supporting brace is assembled on the brake caliper to mount another magnet in opposite position. The multiple M-TEGs are symmetrically placed on the wheel hub that not only generating power supply for the TPMS but also helping to keep the balance of the wheel. The periodic rotation motion of seesaw body falls back on external noncontact permanent magnetic force fastened to an immobile brake caliper. relationship between the rotating speeds, real car driving speed and centrifugal acceleration on the M-TEG is evaluated using the experimental setup. Under a magnetic strength of 0.2 T, four different contact pairs of the fabricated M-TEG show stable output voltage performances (Fig. 2 (b)). The electrical output (voltage and current curves) of the M-TEG at a rotation speed of 100 rpm are shown in Fig. 2 (c) and (d), respectively. Each inset represents an enlarged view of the voltage and current peaks exhibiting continuous AC output and oscillating behavior between zero and the peak value. High electrical output has been achieved among the wide ranges of rotation speed and magnetic force based on the quadrupled efficient contact areas. The maximum output voltage and current are as high as 316 V and 64 µa with a load of 3 MΩ (corresponding to the power of 22.3 mw). (a) Figure 2: (a) Testing setup of M-TEG under a magnetic field strength of 0.2 T. (b) Output voltage from four different contact-pairs units at a rotation speed of 100 rpm. (c, d) Output voltage and current from one unit at a rotation speed of 100 rpm (inset: enlarged view of voltage and current peaks). (b) Figure 1: Magnetically-coupled triboelectric nanogenerator (M-TEG) (a) schematic view of M-TEG for wireless sensor application and (b) operation principle of M-TEG. The reliability is one of the superior features of reported M-TEG, which is predominantly embodied by the device mechanical durability and electrical output stability. On one hand, the metallic frame and component parts of M-TEG device can allow standing physical wear and chemical corrosion. The robustness against the long-term continuous operation has been examined and the experimental results are shown in Fig. 3 (a). It is seen that there is no insignificant fluctuation in output voltage at a rotation speed of 100 rpm for continouse rotation of about 12 hours. The circuit ddiagram of the M-TEG as a direct power source for electronics is illustrated in Fig. 3 (c). A total of 120 commercial LED bulbs are utilized as external loads, which divided into two arrays constituting the letters M T and N L, respectively. Figure 3 (d) exhibits that all the 120 LEDs were energized alternately by the generated current from two diagonally synchronous units of the M-TEG. Besides, such high frequency and large magnitude of electrical output of M-TEG imply a large averaged output power density, which also shows its superiority when combined with energy storage units (e.g., RESULTS AND DISCUSSION Figure 2 (a) shows the experimental setup used to measure output performance of the M-TEG. At first, two M-TEG devices are oppositely-placed on a rotation disk to keep the balance of centripetal force. A rotation disk assembled with M-TEGs is connected to a motor. Two permanent magnets are mounted on a plastic plate, which is to imitate the same position of brake caliper in a real wheel. The aluminum frame provides a supporting platform to connect and fasten each part firmly. The whole system is assembled on a vibration isolation table. A slip ring is used to transfer the output signal from the fast rotating M-TEG to the oscilloscope. To investigate the performance of M-TEG under enormous centrifugal force, various rotating speed is utilized in the experiment. The influence of enormous centrifugal force at high operating speed was largely subdued relying on the seesaw structure of balance feature. In the basic experiments, the 674

5 batteries and capacitors) for long-term operations. As shown in Fig. 3 (e), at a rotation speed of 100 rpm, a 10-µF capacitor a charged by the M-TEG with multiple contact units. A gigantic enhancement on equivalent inductive charges from 36 µc to 144 µc accumulated from one unit increasing to four units. Similarly, with the highest tested rotation rate at 500 rpm, an accumulative inductive charge of 136 µc was also achieved in 350 s using the M-TEG device. Next, a self-discharge process of the capacitor was recorded for about 1000 s, as showed in Fig. 3 (f). Excellent charging behavior of an energy storage unit by the M-TEG largely improves the practicability of the TEG system as a direct power supply in a self-powered network application. in a capacitor by using a rectifier circuit, and then the charged capacitor is connected to a wireless sensor to supply the required power for environmental sensing, signal processing, and data transmission. A receiver was accompanied by a computer to collect the temperature information and to display the measured data on the software interface of a monitor. The actual experimental test platform of M-TEG is shown in Fig. 4 (c). Battery-less RF temperature sensor, 3 mf capacitor and the rectifier unit are electrically connected to a bread board. After that, the M-TEG is applied to the continuous operation for about 112 min at a rotation speed of 500 rpm; the capacitor then played the role as a power source to drive a wireless temperature sensor for about 26 s. It emphasizes that multiple M-TEG devices can be symmetrically installed on a wheel of the vehicle tire to generate several-fold electrical power and significantly reduce energy storage time. The behaviors of the capacitor in charging and discharging state when switch on the wireless sensing unit are depicted in Fig. 4 (b). The capacitor voltage is immediately dropped down to about 2.6 V as the wireless sensor is initialized for operation. When the receiver was associated with a computer, the transmitted data from the temperature sensor is obtained and that information directly displayed on the screen of a monitor, as showed in Fig. 4 (d). It is anticipated that the efficiency of aimed battery-less TMPS and wireless sensor network system can be heightened to the level of real-time monitoring by employing arrays of M-TEGs or integrating innovative conversion circuits. Figure 3: (a) Robustness of the M-TEG with continuous operation at a rotation speed of 100 rpm for 12 hours. (b) Configuration of electrical connection for two rows of LEDs constituting the letters M, T and N, L (c, d) Continuous lighting 120 LEDs using the M-TEG as a power source (e) Charging a 10-µF capacitor using the M-TEG at a rotation speed of 100 rpm. (e) Maximum charges at different rotation speed with one unit. As mentioned above, the TPMS consists of a micro-machined pressure sensor, a micro controller for processing, an RF transmitter, and a central receiving unit; it not only monitors the inner pressure and temperature of a pneumatic tire but also transmits the real-time data information to a display unit. In order to further improve the practical application prospect of M-TEG as a direct power source of TPMS, a wireless temperature monitoring sensor system (ez430-rf2500, Texas Instruments) is employed to test the capability of M-TEG. The wireless temperature sensor comprises of an ultralow power microcontroller integrated with a temperature sensor (MSP430F2274), a 2.4-GHz wireless transceiver (CS2500) and a chip antenna, which possess the same constituent elements comparing with a TPMS transmitter. A current of 11 ma and voltage of ranging from 1.8 V to 3.6 V are required for successful transmitting data. These values are very suitable for most of commercial TPMSs. A schematic diagram of the wireless temperature sensor transceiver systems conjunct with M-TEG device and an energy storage unit is shown in Fig. 4 (a). Generated electrical energy from four units of M-TEG can be stored Figure 4: Demonstration of a self-powered wireless temperature sensor equipped with the M-TEG. (a) A schematic diagram of the wireless temperature sensor transceiver system. (b) Charging and discharging behaviors of a 3 mf capacitor employed as energy shortage unit and direct power source of a sensor. (c) Optical image of experimental setup assembled on a bread board. (d) Transmission of environment temperature information from the wireless sensor operated by M-TEG CONCLUSIONS In summary, we have successfully demonstrated a magnetic-driven rotating triboelectric generator (M-TEG) mounted on the wheel hub of vehicle tire for TPMS application. The M-TEG at the rotation speed of 100 rpm can deliver a maximal output voltage of 316 V and power of 22.3 mw with a load of 3 MΩ under a constant magnetic 675

6 field strength of 0.2 T. Meanwhile, the M-TEG device can effectively generate electrical energy up to alarm temperature of 100 C by means of thermally stable polymer films. The surface charge preservation ability of the insulator PTFE film performed well as a function of time. The durability and reliability of miniaturized M-TEG device are dramatically improved for long-term operation. In addition, a pressure sensor is enabled by M-TEG device to detect the ambient environment barometric pressure without the use of a battery. The M-TEG also have been demonstrated to power a commercial wireless sensor system for real-time temperature monitoring, signal processing and sending the data information to a receiver display. This study may push forward a momentous step toward the concrete applications of TEG for scavenging mechanical energy and performing as a direct power source of the tire pressure monitoring system and the wireless sensor node. CONTACT *D-W. Lee, tel: ; mems@jun.ac.kr ACKNOWLEDGEMENTS This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No.2015R1A4A and 2015R1A2A2A ). REFERENCES [1] S. Roundy, Energy harvesting for tire pressure monitoring systems: design considerations, in PowerMEMS 2008 and microems 2008, Sendai, Nov. 9-12, 2008, pp [2] C.R. Bowen, M.H. Arafa, Energy harvesting technologies for tire pressure monitoring systems, Adv. Energy Mater., vol. 5, pp , [3] A.E. Kubba and K. Jiang, A comprehensive study on technologies of tyre monitoring systems and possible energy solutions, Sensors, vol. 14, pp , [4] P. Constantinou, P. H. Mellor, P. D. Wilcox, A magnetically sprung generator for energy harvesting applications, IEEE /ASME Trans. Mechatronics, vol. 17, pp , [5] Y.Y. Chen, H.W. Pan, A piezoelectric vibration energy harvester for tire pressure monitoring systems, Proceedings of Symposium on Ultrasonic Electronics, Nov. 8-10, 2011, pp [6] Q.L. Zheng, H.G. Tu, A. Agee, Y. Xu, Vibration energy harvesting device based on asymmetric air-spaced cantilevers for tire pressure monitoring system, PowerMEMS, Washington DC, Dec. 1-4, 2009, pp [7] Y.L. Yang, Q. C. Tang, and X. X. Li, Non-contact repulsive-force excitation for highly endurable wide frequency-range energy-harvesting, Transducers 2011, Jun. 2011, Beijing, 2011, pp [8] I.-H. Ho, J.-M. Chung, H.-C. Chen and H.-W. Chiu, "A battery-less tire pressure monitoring system," Vehicular Technology Conference, Barcelona, Apr.26-29, 2009, pp