The Experts below are selected from a list of 771 Experts worldwide ranked by ideXlab platform
Dong-weon Lee - One of the best experts on this subject based on the ideXlab platform.
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Galinstan-based flexible microfluidic device for wireless human-sensor applications
Sensors and Actuators A: Physical, 2020Co-Authors: Karthikeyan Munirathinam, Jongsung Park, Yun-jin Jeong, Dong-weon LeeAbstract:Abstract Liquid-metal-based wearable technologies are one of the promising ways to realize soft-skin flexible electronics. Here, we report a flexible microfluidic device that injects Galinstan liquid-metal alloy through the microchannels of a polydimethylsiloxane (PDMS) substrate, targeting an inductor-capacitor (LC) resonant circuit for wireless power transmission and sensing. The surface inside PDMS microchannels is chemically modified using sulfuric acid (H2SO4) solution, making it easier for the liquid metal to flow through the microfluidic channel. Electromechanical characteristics of the capacitive pressure sensors were evaluated by loading and unloading the external pressure continuously in the range of 0–200 mmHg for 300 cycles. After that, the characterization of Galinstan-based flexible microfluidic sensors consisting of the LC circuit conducted in a strain range of up to 30 %. Finally, monitoring of various human motion (e.g., wrist flexion and finger motion) was demonstrated using a wireless sensing platform with an external antenna. Electrical and mechanical performances confirm that the Galinstan-based sensors are reliable, reproducible, repeatable, and flexible with a sensitivity of 5 kHz/mmHg. The proposed flexible microfluidic device has the potential to become an exceptionally reliable candidate for wireless human-machine applications.
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An oxidized liquid metal-based microfluidic platform for tunable electronic device applications
Lab on a chip, 2015Co-Authors: Mitesh Parmar, Dong-weon LeeAbstract:Easy movement of oxidized Galinstan in microfluidic channels is a promising way for the wide application of the non-toxic liquid metal. In this paper, two different surface modification techniques (physical and chemical) are reported, which dramatically improve the non-wetting characteristics of oxidized Galinstan in the microfluidic channel. In the physical technique, normal paper textures are transferred to the inner wall of polydimethylsiloxane (PDMS) channels and four types of nanoparticles are then coated on the surface of the wall for further improvement of the non-wetting characteristics. Highest advancing angle of 167° and receding angle of 151° are achieved on the paper-textured PDMS with titanium oxide (TiO2) nanoparticles. In the chemical technique, three types of inorganic acids are employed to generate dual-scale structures on the PDMS surface. The inner wall surface treated with sulfuric acid (H2SO4) shows the highest contact angle of 167° and a low hysteresis of ~14° in the dynamic measurement. Creating, transporting, separating and merging of oxidized Galinstan droplets are successfully demonstrated in the fabricated PDMS microfluidic channels. After optimization of these modification techniques, the potential application of tunable capacitors and electronic filters is realized by using liquid metal-based microfluidic devices.
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A novel liquid metal-based inkjet nozzle for flexible electronics
2015 Transducers - 2015 18th International Conference on Solid-State Sensors Actuators and Microsystems (TRANSDUCERS), 2015Co-Authors: Dong-weon LeeAbstract:In this paper, we proposed a non-toxic liquid metal inkjet device using the unique characteristics of HCl-treated Galinstan in a microfluidic channel. Galinstan in PDMS microfluidic channels can maintains a true liquid phase when it is surrounded by another coplanar channels filled with 37% HCl solution. This is due to excellent permeability of PDMS material toward HCL solution with high concentration. HCl vapor diffused from surrounded coplanar channels helps the reduction process of oxidized Galinstan. After fabrication of the inkjet nozzle device with PDMS, the behavior of reduced Galinstan in microfluidic channels has been characterized. Meanwhile, the generation of Galinstan droplets (< 1 pL droplet) and metallic lines (< 50 µm in width) on various flexible substrates were conducted using the proposed inkjet nozzle device. A LED-integrated circuit was also fabricated to verify the utility of Galinstan wiring. The inkjet printed circuit board exhibits excellent electrical and mechanical performance after bending, twisting and stretching. We believe that the liquid metal-based inkjet nozzle device can provide a stronger vitality and superiority for flexible electronic applications in future.
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Hydrochloric acid-impregnated paper for gallium-based liquid metal microfluidics
Sensors and Actuators B: Chemical, 2015Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Yunho Lee, Koangki Yoo, Jeong-bong LeeAbstract:We report a simple hydrochloric acid (HCl) impregnation method to substantially improve the lyophobicity of a paper against gallium-based liquid metal. Based on the HCl-impregnated paper, we also propose an extremely simple fabrication method of microfluidic channel for gallium-based liquid metal, Galinstan®. Due to its low cost, easy fabrication, and flexibility, recently paper has drawn attention as microfluidic platforms for various applications. We have treated two different types of paper (paper towel and printing paper) with various treatment methods such as laser printer flattening, fluorocarbon polymer coating, HCl-impregnation, and combination of these methods. We then studied their lyophobicity characteristics by measuring static and dynamic contact angles as well as bouncing experiment. We found that HCl-impregnation is a simple yet powerful method to engineer certain types of papers to make them super-lyophobic substrates against gallium-based liquid metals and effective for more than 30-days after impregnation. To show the feasibility, we demonstrated manipulation of a Galinstan® droplet along microfluidic channels formed on the HCl-impregnated paper.
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PDMS based coplanar microfluidic channels for the surface reduction of oxidized Galinstan
Lab on a chip, 2013Co-Authors: Mitesh Parmar, Daeyoung Kim, Jeong-bong Lee, Dong-weon LeeAbstract:Galinstan has the potential to replace mercury – one of the most popular liquid metals. However, the easy oxidation of Galinstan restricts wide applicability of the material. In this paper, we report an effective reduction method for the oxidized Galinstan using gas permeable PDMS (polydimethlysiloxane)-based microfluidic channel. The complete study is divided into two parts – reduction of Galinstan oxide and behavior of reduced Galinstan oxide in a microfluidic channel. The reduction of Galinstan oxide is discussed on the basis of static as well as dynamic angles. The contact angle analyses help to find the extent of reduction by wetting characteristics of the oxide, to optimize PDMS thickness and to select suitable hydrochloric acid (HCl) concentration. The highest advancing angle of 155° and receding angle of 136° is achieved with 200 μm thick PDMS film and 37 wt% (weight percent) HCl solution. The behavior of reduced Galinstan oxide is analyzed in PDMS-based coplanar microfluidic channels fabricated using a simple micromolding technique. Galinstan in the microfluidic channel is surrounded by another coplanar channel filled with HCl solution. Due to the excellent permeability of PDMS, HCl permeates through the PDMS wall between the two channels (interchannel PDMS wall) and achieves a continuous chemical reaction with oxidized Galinstan. A Lab VIEW controlled syringe pump is used for observing the behavior of HCl treated Galinstan in the microfluidic channel. Further optimization of the microfluidic device has been conducted to minimize the reoxidation of reduced Galinstan oxide in the microfluidic channel.
Jeong-bong Lee - One of the best experts on this subject based on the ideXlab platform.
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Cost-effective surface modification for Galinstan® lyophobicity.
Journal of colloid and interface science, 2016Co-Authors: Shantanu Shrikant Kadlaskar, Jeong-bong Lee, Jun Hyeon Yoo, Abhijeet, Wonjae ChoiAbstract:In this paper we investigate the feasibility of using a cost-effective fabrication method based on sandblasting, chemical etching and spray coating processes, to render common surfaces to be non-wettable by Galinstan®. Although Galinstan® is a non-toxic liquid metal alternative to mercury, the viscoelastic and extremely wetting characteristics of Galinstan® have been the major bottleneck limiting the wide applicability of the gallium-based liquid metal. This paper tries to accomplish non-wettability to Galinstan® by combining surface texture and chemistry with the unique property of Galinstan®, that is, its high surface tension and yield strength that prevent the penetration of the liquid metal into surface asperities. Fabricated surfaces resemble traditional superhydrophobic (water-repellent) surfaces, and exhibit a superior non-wettability to Galinstan® as quantified by high static and dynamic contact angles, small hysteresis, as well as impact resistance. Reported fabrication method based on sandblasting, etching and spray coating is easily applicable to various surfaces ranging from metals, ceramics, to plastics and is scalable to large surfaces.
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Hydrochloric acid-impregnated paper for gallium-based liquid metal microfluidics
Sensors and Actuators B: Chemical, 2015Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Yunho Lee, Koangki Yoo, Jeong-bong LeeAbstract:We report a simple hydrochloric acid (HCl) impregnation method to substantially improve the lyophobicity of a paper against gallium-based liquid metal. Based on the HCl-impregnated paper, we also propose an extremely simple fabrication method of microfluidic channel for gallium-based liquid metal, Galinstan®. Due to its low cost, easy fabrication, and flexibility, recently paper has drawn attention as microfluidic platforms for various applications. We have treated two different types of paper (paper towel and printing paper) with various treatment methods such as laser printer flattening, fluorocarbon polymer coating, HCl-impregnation, and combination of these methods. We then studied their lyophobicity characteristics by measuring static and dynamic contact angles as well as bouncing experiment. We found that HCl-impregnation is a simple yet powerful method to engineer certain types of papers to make them super-lyophobic substrates against gallium-based liquid metals and effective for more than 30-days after impregnation. To show the feasibility, we demonstrated manipulation of a Galinstan® droplet along microfluidic channels formed on the HCl-impregnated paper.
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PDMS based coplanar microfluidic channels for the surface reduction of oxidized Galinstan
Lab on a chip, 2013Co-Authors: Mitesh Parmar, Daeyoung Kim, Jeong-bong Lee, Dong-weon LeeAbstract:Galinstan has the potential to replace mercury – one of the most popular liquid metals. However, the easy oxidation of Galinstan restricts wide applicability of the material. In this paper, we report an effective reduction method for the oxidized Galinstan using gas permeable PDMS (polydimethlysiloxane)-based microfluidic channel. The complete study is divided into two parts – reduction of Galinstan oxide and behavior of reduced Galinstan oxide in a microfluidic channel. The reduction of Galinstan oxide is discussed on the basis of static as well as dynamic angles. The contact angle analyses help to find the extent of reduction by wetting characteristics of the oxide, to optimize PDMS thickness and to select suitable hydrochloric acid (HCl) concentration. The highest advancing angle of 155° and receding angle of 136° is achieved with 200 μm thick PDMS film and 37 wt% (weight percent) HCl solution. The behavior of reduced Galinstan oxide is analyzed in PDMS-based coplanar microfluidic channels fabricated using a simple micromolding technique. Galinstan in the microfluidic channel is surrounded by another coplanar channel filled with HCl solution. Due to the excellent permeability of PDMS, HCl permeates through the PDMS wall between the two channels (interchannel PDMS wall) and achieves a continuous chemical reaction with oxidized Galinstan. A Lab VIEW controlled syringe pump is used for observing the behavior of HCl treated Galinstan in the microfluidic channel. Further optimization of the microfluidic device has been conducted to minimize the reoxidation of reduced Galinstan oxide in the microfluidic channel.
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A Super-Lyophobic 3-D PDMS Channel as a Novel Microfluidic Platform to Manipulate Oxidized Galinstan
Journal of Microelectromechanical Systems, 2013Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Jeong-bong LeeAbstract:We report a 3-D super-lyophobic polydimethylsiloxane (PDMS) microfluidic channel patterned with an array of multi-scale surface texture as a novel microfluidic platform to mobilize naturally oxidized Galinstan. Galinstan is a liquid metal that has multiple advantages over mercury such as non-toxicity, higher thermal conductivity, and lower electrical resistivity. However, Galinstan gets easily oxidized in an air environment and it becomes a viscoelastic liquid that wets almost any solid surface. We studied the feasibility of developing super-lyophobic surfaces against Galinstan, using various flat and textured surfaces including PDMS micropillar and microridge arrays by measuring static and dynamic contact angles. The highest advancing angle of 175 ° and receding angle of 163 ° were achieved on a surface patterned with micropillars, each of which was textured with additional roughness. Pitch distance between pillars was 175 μm. An extremely simple PDMS-PDMS bonding technique was used to fabricate a 3-D super-lyophobic channel structure as a microfluidic platform for oxidized Galinstan droplets. The driving force to actuate a ~ 3-μL Galinstan droplet in the 3-D super-lyophobic channel was 3.11±0.23 mN.
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A super-lyophobic PDMS micro-tunnel as a novel microfluidic platform for oxidized Galinstan®
2012 IEEE 25th International Conference on Micro Electro Mechanical Systems (MEMS), 2012Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Jeong-bong LeeAbstract:We report a micro pillar array-based super-lyophobic poly(dimethyl siloxane) (PDMS) micro-tunnel as a novel microfluidic platform for oxidized Galinstan®. Liquid-metal alloy, Galinstan® was expected to be widely utilized in many MEMS applications due to its favorable properties. However, the fact that Galinstan® gets easily oxidized and wets on almost nearly any surface is the difficult challenge for utilization of Galinstan®. We studied various pitch distance micro pillar arrays and evaluated lyophobicity of Galinstan® using static contact angle and sliding angle. A unique approach to fabricate 3-dimensional (3-D) lyophobic micro-tunnel structure was designed using flexible PDMS, which can overcome the limitation of current lithography techniques. It was demonstrated the movement of oxidized Galinstan® without wetting.
Wonjae Choi - One of the best experts on this subject based on the ideXlab platform.
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Cost-effective surface modification for Galinstan® lyophobicity.
Journal of colloid and interface science, 2016Co-Authors: Shantanu Shrikant Kadlaskar, Jeong-bong Lee, Jun Hyeon Yoo, Abhijeet, Wonjae ChoiAbstract:In this paper we investigate the feasibility of using a cost-effective fabrication method based on sandblasting, chemical etching and spray coating processes, to render common surfaces to be non-wettable by Galinstan®. Although Galinstan® is a non-toxic liquid metal alternative to mercury, the viscoelastic and extremely wetting characteristics of Galinstan® have been the major bottleneck limiting the wide applicability of the gallium-based liquid metal. This paper tries to accomplish non-wettability to Galinstan® by combining surface texture and chemistry with the unique property of Galinstan®, that is, its high surface tension and yield strength that prevent the penetration of the liquid metal into surface asperities. Fabricated surfaces resemble traditional superhydrophobic (water-repellent) surfaces, and exhibit a superior non-wettability to Galinstan® as quantified by high static and dynamic contact angles, small hysteresis, as well as impact resistance. Reported fabrication method based on sandblasting, etching and spray coating is easily applicable to various surfaces ranging from metals, ceramics, to plastics and is scalable to large surfaces.
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Hydrochloric acid-impregnated paper for gallium-based liquid metal microfluidics
Sensors and Actuators B: Chemical, 2015Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Yunho Lee, Koangki Yoo, Jeong-bong LeeAbstract:We report a simple hydrochloric acid (HCl) impregnation method to substantially improve the lyophobicity of a paper against gallium-based liquid metal. Based on the HCl-impregnated paper, we also propose an extremely simple fabrication method of microfluidic channel for gallium-based liquid metal, Galinstan®. Due to its low cost, easy fabrication, and flexibility, recently paper has drawn attention as microfluidic platforms for various applications. We have treated two different types of paper (paper towel and printing paper) with various treatment methods such as laser printer flattening, fluorocarbon polymer coating, HCl-impregnation, and combination of these methods. We then studied their lyophobicity characteristics by measuring static and dynamic contact angles as well as bouncing experiment. We found that HCl-impregnation is a simple yet powerful method to engineer certain types of papers to make them super-lyophobic substrates against gallium-based liquid metals and effective for more than 30-days after impregnation. To show the feasibility, we demonstrated manipulation of a Galinstan® droplet along microfluidic channels formed on the HCl-impregnated paper.
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Hydrochloric acid-impregnated paper for liquid metal microfluidics
2013 Transducers & Eurosensors XXVII: The 17th International Conference on Solid-State Sensors Actuators and Microsystems (TRANSDUCERS & EUROSENSORS X, 2013Co-Authors: Wonjae ChoiAbstract:We report a method of substantially improving lyophobicity of a paper against gallium-based liquid, using hydrochloric acid (HCl) impregnation. We also report an extremely simple fabrication of microfluidic channels on a HCl-impregnated paper for gallium-based liquid metal, Galinstan®. Paper has many favorable properties in microfluidic applications, such as low cost, abundant supply, easy fabrication, and flexibility. We evaluated lyophobicity of several papers by measuring static and dynamic contact angles with a goal of finding optimal super-lyophobic paper-based substrate for microfluidics applications. We found HCl-impregnated laser printer flattened paper towel shows appropriate super-lyophobicity. We performed a bouncing experiment of a Galinstan® droplet on the HCl-impregnated flattened paper substrate and demonstrated movement of a liquid metal droplet in microfluidic channels formed on the HCl-impregnated paper.
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recovery of nonwetting characteristics by surface modification of gallium based liquid metal droplets using hydrochloric acid vapor
ACS Applied Materials & Interfaces, 2013Co-Authors: Peter Thissen, Wonjae Choi, Gloria Viner, Yves J ChabalAbstract:The applicability of gallium-based liquid metal alloy has been limited by the oxidation problem. In this paper, we report a simple method to remove the oxide layer on the surface of such alloy to recover its nonwetting characteristics, using hydrochloric acid (HCl) vapor. Through the HCl vapor treatment, we successfully restored the nonwetting characteristics of the alloy and suppressed its viscoelasticity. We analyzed the change of surface chemistry before and after the HCl vapor treatment using X-ray photoelectron spectroscopy (XPS) and low-energy ion-scattering spectroscopy (LEIS). Results showed that the oxidized surface of the commercial gallium-based alloy Galinstan (Ga2O3 and Ga2O) was replaced with InCl3 and GaCl3 after the treatment. Surface tension and static contact angle on a Teflon-coated glass of the HCl-vapor-treated Galinstan were measured to be 523.8 mN/m and 152.5°. A droplet bouncing test was successfully carried out to demonstrate the nonwetting characteristics of the HCl-vapor-treated...
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A Super-Lyophobic 3-D PDMS Channel as a Novel Microfluidic Platform to Manipulate Oxidized Galinstan
Journal of Microelectromechanical Systems, 2013Co-Authors: Daeyoung Kim, Dong-weon Lee, Wonjae Choi, Jeong-bong LeeAbstract:We report a 3-D super-lyophobic polydimethylsiloxane (PDMS) microfluidic channel patterned with an array of multi-scale surface texture as a novel microfluidic platform to mobilize naturally oxidized Galinstan. Galinstan is a liquid metal that has multiple advantages over mercury such as non-toxicity, higher thermal conductivity, and lower electrical resistivity. However, Galinstan gets easily oxidized in an air environment and it becomes a viscoelastic liquid that wets almost any solid surface. We studied the feasibility of developing super-lyophobic surfaces against Galinstan, using various flat and textured surfaces including PDMS micropillar and microridge arrays by measuring static and dynamic contact angles. The highest advancing angle of 175 ° and receding angle of 163 ° were achieved on a surface patterned with micropillars, each of which was textured with additional roughness. Pitch distance between pillars was 175 μm. An extremely simple PDMS-PDMS bonding technique was used to fabricate a 3-D super-lyophobic channel structure as a microfluidic platform for oxidized Galinstan droplets. The driving force to actuate a ~ 3-μL Galinstan droplet in the 3-D super-lyophobic channel was 3.11±0.23 mN.
Iain M. Kierzewski - One of the best experts on this subject based on the ideXlab platform.
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Ultrafine Pitch Stencil Printing of Liquid Metal Alloys
ACS applied materials & interfaces, 2017Co-Authors: Nathan Lazarus, Sarah S. Bedair, Iain M. KierzewskiAbstract:With high conductivity and stretchable for large cross-sections, liquid metals such as Galinstan are promising for creating stretchable devices and interconnects. Creating high resolution features in parallel is challenging, with most techniques limited to a hundred micrometers or more. In this work, multilevel electroplated stencils are investigated for printing liquid metals, with Galinstan features as small as ten micrometers printed on soft elastomers, a factor of 10 reduction over past liquid metal stencil printing. Capacitors and resistive strain sensors are also demonstrated, showing the potential for creating stretchable conductors and devices.
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Ultrafine Pitch Stencil Printing of Liquid Metal Alloys
2017Co-Authors: Nathan Lazarus, Sarah S. Bedair, Iain M. KierzewskiAbstract:With high conductivity and stretchable for large cross-sections, liquid metals such as Galinstan are promising for creating stretchable devices and interconnects. Creating high resolution features in parallel is challenging, with most techniques limited to a hundred micrometers or more. In this work, multilevel electroplated stencils are investigated for printing liquid metals, with Galinstan features as small as ten micrometers printed on soft elastomers, a factor of 10 reduction over past liquid metal stencil printing. Capacitors and resistive strain sensors are also demonstrated, showing the potential for creating stretchable conductors and devices
Xinkai Xie - One of the best experts on this subject based on the ideXlab platform.
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liquid metal based super stretchable and structure designable triboelectric nanogenerator for wearable electronics
ACS Nano, 2018Co-Authors: Yanqin Yang, Zhen Wen, Ping Cheng, Na Sun, Hechuang Zheng, Huiyun Shao, Yujian Xia, Chen Chen, Huiwen Lan, Xinkai XieAbstract:The rapid advancement of intelligent wearable electronics imposes the emergent requirement for power sources that are deformable, compliant, and stretchable. Power sources with these characteristics are difficult and challenging to achieve. The use of liquid metals as electrodes may provide a viable strategy to produce such power sources. In this work, we propose a liquid-metal-based triboelectric nanogenerator (LM-TENG) by employing Galinstan as the electrode and silicone rubber as the triboelectric and encapsulation layer. The small Young’s modulus of the liquid metal ensures the electrode remains continuously conductive under deformations, stretching to a strain as large as ∼300%. The surface oxide layer of Galinstan effectively prevents the liquid Galinstan electrode from further oxidization and permeation into silicone rubber, yielding outstanding device stability. Operating in the single-electrode mode at 3 Hz, the LM-TENG with an area of 6 × 3 cm2 produces an open-circuit voltage of 354.5 V, transf...
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Liquid-Metal-Based Super-Stretchable and Structure-Designable Triboelectric Nanogenerator for Wearable Electronics
2018Co-Authors: Yanqin Yang, Zhen Wen, Ping Cheng, Na Sun, Hechuang Zheng, Huiyun Shao, Yujian Xia, Chen Chen, Huiwen Lan, Xinkai XieAbstract:The rapid advancement of intelligent wearable electronics imposes the emergent requirement for power sources that are deformable, compliant, and stretchable. Power sources with these characteristics are difficult and challenging to achieve. The use of liquid metals as electrodes may provide a viable strategy to produce such power sources. In this work, we propose a liquid-metal-based triboelectric nanogenerator (LM-TENG) by employing Galinstan as the electrode and silicone rubber as the triboelectric and encapsulation layer. The small Young’s modulus of the liquid metal ensures the electrode remains continuously conductive under deformations, stretching to a strain as large as ∼300%. The surface oxide layer of Galinstan effectively prevents the liquid Galinstan electrode from further oxidization and permeation into silicone rubber, yielding outstanding device stability. Operating in the single-electrode mode at 3 Hz, the LM-TENG with an area of 6 × 3 cm2 produces an open-circuit voltage of 354.5 V, transferred short-circuit charge of 123.2 nC, short-circuit current of 15.6 μA, and average power density of 8.43 mW/m2, which represent outstanding performance values for TENGs. Further, the LM-TENG maintains stable performance under various deformations, such as stretching, folding, and twisting. LM-TENGs in different forms, such as bulk-shaped, bracelet-like, and textile-like, are all able to harvest mechanical energy from human walking, arm shaking, or hand patting to sustainably drive wearable electronic devices
