Prof. Yunlong Zi Profile

Prof. Yunlong Zi

at Hong Kong Univ Sci Tech - Guangzhou

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Publications (4)

Proceedings Article | 18 April 2022 Presentation

Tribo-photonics: an emerging field toward fully-self-powered wireless sensing

Yunlong Zi

Proceedings Volume PC12043, (2022) https://doi.org/10.1117/12.2615158

KEYWORDS: Sensor networks, Photonics, Optical sensing, Liquids, Liquid lenses, Internet, Electromagnetic radiation, Electroluminescence

Proceedings Article | 22 March 2021 Poster + Presentation

Tribo-induced solutions for smart lighting and wireless sensing applications

Yunlong Zi, Jiaqi Wang

Proceedings Volume 11588, 115881R (2021) https://doi.org/10.1117/12.2589752

KEYWORDS: Solid state lighting, Light sources and illumination, Signal processing, Photography, Titanium dioxide, Televisions, Sensors, Liquids, Liquid lenses, Lamps

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Proceedings Article | 24 April 2020 Presentation

Self-powered electrowetting optical switch driven by a triboelectric nanogenerator for wireless sensing (Conference Presentation)

Jiaqi Wang, Haoyu Wang, Xiaoyi Li, Yunlong Zi

Proceedings Volume 11376, 113761J (2020) https://doi.org/10.1117/12.2566093

KEYWORDS: Optical switching, Sensors, Mechanical sensors, Internet, Energy harvesting, Human-machine interfaces, Signal detection, Liquid crystals, Liquids, Optical sensing

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Internet of things (IoTs) enables a cloud of physical devices to be network-connected, providing real-time information of the physical environment for decision-making [1,2]. The recently advocated 5th-generation (5G) communication with nearly zero time-delay has greatly contributed the development of IoTs. It is estimated that 20.4 billion connected items will be in use by 2020, forecasted by Gartner, Inc [3]. An IoT system usually consists of sensors, actuators, controlling and communication circuits. Each sensor serves as a node in the network, and there are usually more than ten thousand sensor nodes in an IoT system. It is a challenging issue to supply electrical power to a cluster of sensor nodes. The employment of battery in a sensor will greatly affect the device reliability and durability where the battery replacement is usually difficult, and the chemical substances in batteries are normally harmful to environments [4,5]. To solve this issue, self-powered electronic devices have emerged as an alternative approach to operate without external electrical power supply, where the electrical power can be harvested from the ambient environment energy including solar, thermal and mechanical energies

6], [7], [8], [9

. Among various paradigms for energy harvesting, the recently proposed triboelectric nanogenerator (TENG) has capacity to harvest the mechanical energy from the ambient environment by coupling the triboelectrification and electrostatic induction effects, where the extremely high voltage can be attained and the thickness of the device can be shrank down to be an extremely small size

10], [11], [12

. A TENG is intrinsically a self-powered mechanical sensor with a high signal to noise ratio owing to its high-voltage output. In this case, a variety of self-powered TENG stress sensors have been proposed including seawater pressure sensor, human-machine interface, smart keyboard, etc

13], [14], [15

. However, even though TENG can achieve extremely high voltage owing to the nature of the low capacitance, the transferred charge between electrodes is very small where the short-circuit current is usually lower than 100 μA. This causes the design of signal processing circuits to be difficult, where extremely high sensitivity is needed. Furthermore, cable connection is usually needed to transfer the mechanical signal detected by a TENG to the control panel, however, for several specific applications including infrastructure health monitoring in severe environments, turbulence detection in the deep sea, wireless smart keyboard, and so forth, cables for electrical connection are not allowed. Thus, cable-free self-powered TENG based mechanical sensing is desirable. Free-space optical communication (FSOC) is an effective approach for the wireless sensing, where information can be carried through the light [16,17]. Optical switch is a key component for the FSOC, where the signal can be loaded by switching on and off

18], [19], [20

Optical switching have been achieved by various physical mechanisms including twisted nematic (TN) cells, surface-stabilized ferroelectric liquid crystals (SSFLCs), polymer-dispersed liquid crystals (PDLCs), electrowetting actuation, etc

20], [21], [22], [23], [24], [25

. Among these approaches, electrowetting optical switch (EOS) presents several advantages such as low manufacturing cost, high reliability as well as long lifetime

25], [26], [27

. The majority of raw materials including conducting fluids, insulating oils for EOS are all available from daily life, which are inexpensive and non-toxic. The fabrication of the EOS is simple, where chemical reactions and micro-fabrications are not needed. In order to actuate the liquid by varying the interfacial tension between the conducting droplet and the dielectric substrate or oil, high-voltage outputs are required. Conventional high-voltage sources are usually bulky, bringing difficulties in system integrations, and dangerous in several specific situations. Circuit design for connecting the high-voltage source and the mechanical sensor is extremely complicated. TENGs, in contrast, can achieve high voltages and mechanical sensing at the same time, of which the structure can be very compact. In this study, it is the first time ever that a TENG-driven electrowetting optical switch was developed by a combination of a freestanding sliding mode triboelectric nanogenerator (FS-TENG) and an electrically tunable liquid lens (ETULL). The ETULL was fabricated by a conducting fluid, an insulating oil, an acrylic cylindrical spacer as well as two indium tin oxide (ITO) electrodes. Upon applying a voltage on the ETULL, the interface between two liquids was curved due to the electrowetting effect, forming an insulating oil based concave lens. The light propagation through the ETULL could be switched between the on state, which means no light diverging at the flat interface, and the off state, where the light was diverged by the concave lens. The switch was controlled by the voltage generated by the FS-TENG. To verify the effectiveness of the proposed self-powered EOS, a wireless sensing system was performed and the mechanical motions were remotely detected. Such a mechanical-electrical-optical signal conversion enabled the wireless sensing, which can be applied for various fields such as human-machine interfaces, remote monitoring of the infrastructure health, security detections, wireless smart keyboard, etc. Reference [1] J Gubbi, R Buyya, S Marusic, M Palaniswami. Internet of Things (IoT): A vision, architectural elements, and future directions, Future Generation Comput.Syst. 29 (2013) 1645-1660. [2] L Tan, N Wang, Future internet: The internet of things, 5 (2010) V5-376-V5-380. [3] https://www.gartner.com/en [4] D Aurbach, I Weissman, A Zaban, P Dan. On the role of water contamination in rechargeable Li batteries, Electrochim.Acta. 45 (1999) 1135-1140. [5] P Onianwa, SO Fakayode. Lead contamination of topsoil and vegetation in the vicinity of a battery factory in Nigeria, Environ.Geochem.Health. 22 (2000) 211-218. [6] A Das, Y Gao, TT Kim. A 220-mV power-on-reset based self-starter with 2-nW quiescent power for thermoelectric energy harvesting systems, IEEE Transactions on Circuits and Systems I: Regular Papers. 64 (2017) 217-226. [7] P Gardonio, M Zilletti. Vibration energy harvesting from an array of flexible stalks exposed to airflow: a theoretical study, Smart Mater.Struct. 25 (2016) 035014. [8] P Glynne-Jones, NM White. Self-powered systems: a review of energy sources, Sens Rev. 21 (2001) 91-98. [9] FK Shaikh, S Zeadally. Energy harvesting in wireless sensor networks: A comprehensive review, Renewable and Sustainable Energy Reviews. 55 (2016) 1041-1054. [10] Y Chen, Y Zhang, T Zhan, Z Lin, SL Zhang, H Zou, et al. An Elastic Triboelectric Nanogenerator for Harvesting Random Mechanical Energy with Multiple Working Modes, Advanced Materials Technologies. (2019) 1900075. [11] F Fan, Z Tian, ZL Wang. Flexible triboelectric generator, Nano energy. 1 (2012) 328-334. [12] G Zhu, J Chen, T Zhang, Q Jing, ZL Wang. Radial-arrayed rotary electrification for high performance triboelectric generator, Nature communications. 5 (2014) 3426 [13] P Bai, G Zhu, Q Jing, J Yang, J Chen, Y Su, et al. Membrane‐based self‐powered triboelectric sensors for pressure change detection and its uses in security surveillance and healthcare monitoring, Advanced Functional Materials. 24 (2014) 5807-5813. [14] J Luo, FR Fan, T Zhou, W Tang, F Xue, ZL Wang. Ultrasensitive self-powered pressure sensing system, Extreme Mechanics Letters. 2 (2015) 28-36. [15] M Xu, S Wang, SL Zhang, W Ding, PT Kien, C Wang, et al. A highly-sensitive wave sensor based on liquid-solid interfacing triboelectric nanogenerator for smart marine equipment, Nano Energy. 57 (2019) 574-580. [16] VW Chan. Free-space optical communications, J.Lightwave Technol. 24 (2006) 4750-4762. [17] K Kiasaleh. Performance of APD-based, PPM free-space optical communication systems in atmospheric turbulence, IEEE Trans.Commun. 53 (2005) 1455-1461. [18] A Boucouvalas, P Chatzimisios, Z Ghassemlooy, M Uysal, K Yiannopoulos. Standards for indoor optical wireless communications, IEEE Communications Magazine. 53 (2015) 24-31. [19] BR Moss, JS Orcutt, VM Stojanovic. Devices and techniques for integrated optical data communication. (2018). [20] Y Silberberg, P Perlmutter, J Baran. Digital optical switch, Appl.Phys.Lett. 51 (1987) 1230-1232. [21] W Lee, C Wang, Y Shih. Effects of carbon nanosolids on the electro-optical properties of a twisted nematic liquid-crystal host, Appl.Phys.Lett. 85 (2004) 513-515. [22] C Zhang, H Wang, S Guan, Z Guo, X Zheng, Y Fan, et al. Self‐Powered Optical Switch Based on Triboelectrification‐Triggered Liquid Crystal Alignment for Wireless Sensing, Advanced Functional Materials. (2019) 1808633. [23] S Shoarinejad, A Sadeghisahebzad. Threshold properties of nanodoped surface stabilized ferroelectric liquid crystals under electric and magnetic fields, Journal of Molecular Liquids. 220 (2016) 1033-1041. [24] R Sutherland, V Tondiglia, L Natarajan, T Bunning, W Adams. Electrically switchable volume gratings in polymer‐dispersed liquid crystals, Appl.Phys.Lett. 64 (1994) 1074-1076. [25] L Li, C Liu, Q Wang. Optical switch based on tunable aperture, Opt.Lett. 37 (2012) 3306-3308. [26] C Murade, J Oh, D Van den Ende, F Mugele. Electrowetting driven optical switch and tunable aperture, Optics express. 19 (2011) 15525-15531. [27] J Wu, Y Du, J Xia, W Lei, T Zhang, B Wang. Optofluidic system based on electrowetting technology for dynamically tunable spectrum absorber, Optics express. 27 (2019) 2521-2529.

Proceedings Article | 22 April 2020 Presentation

Standardized evaluation of the triboelectric nanogenerator for mechanical energy harvesting (Conference Presentation)

Yunlong Zi

Proceedings Volume 11376, 113761E (2020) https://doi.org/10.1117/12.2548668

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