Flexible thermoelectric generators for body heat harvesting – Enhanced device performance using high thermal conductivity elastomer encapsulation on liquid metal interconnects

Sargolzaeiaval, Yasaman; Ramesh, V.; Neumann, Taylor V.; Misra, Veena; Vashaee, Daryoosh; Dickey, Michael D.; Öztürk, Mehmet C.

doi:10.1016/j.apenergy.2019.114370

Cited by 131 publications

(89 citation statements)

References 63 publications

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“…The legs are connected in series via EGaIn liquid metal interconnects, which provide excellent stretchability as well as negligibly small interconnect resistance. The EGaIn interconnects are encapsulated by a high thermal conductivity elastomer, previously reported by this laboratory 40,42 . The elastomer not only enhances the mechanical integrity of the device without compromising the device performance by adding a large parasitic thermal resistance but it also acts as a heat spreader between the EGaIn interconnects.…”

Section: Aerogel-silicone Compositementioning

confidence: 99%

“…This final encapsulation layer improves the mechanical integrity of the device and the device performance by acting as a heat spreader on both sides of the device. The details of this elastomer and its application to flexible TEG fabrication can be found in recent publications by this laboratory 40,42 . After curing the encapsulation, the device was flipped and the EGaIn interconnects were formed on the opposite side ( Fig.…”

Section: Aerogel-silicone Composite Preparationmentioning

confidence: 99%

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Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

et al. 2021

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Harvesting body heat using thermoelectricity provides a promising path to realizing self-powered, wearable electronics that can achieve continuous, long-term, uninterrupted health monitoring. This paper reports a flexible thermoelectric generator (TEG) that provides efficient conversion of body heat to electrical energy. The device relies on a low thermal conductivity aerogel–silicone composite that secures and thermally isolates the individual semiconductor elements that are connected in series using stretchable eutectic gallium-indium (EGaIn) liquid metal interconnects. The composite consists of aerogel particulates mixed into polydimethylsiloxane (PDMS) providing as much as 50% reduction in the thermal conductivity of the silicone elastomer. Worn on the wrist, the flexible TEGs present output power density figures approaching 35 μWcm−2 at an air velocity of 1.2 ms−1, equivalent to walking speed. The results suggest that these flexible TEGs can serve as the main energy source for low-power wearable electronics.

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Section: Aerogel-silicone Compositementioning

confidence: 99%

Section: Aerogel-silicone Composite Preparationmentioning

confidence: 99%

Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

et al. 2021

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“…Besides challenges and with the advancement in the processing units and the demand for high-end wearables relying on heavy computations, the currently available battery power resources might not be enough for the extended device operation. Therefore, it is predicted that energy harvesting will be an essential part of the high power future wearables [188]. Many researchers already work on various opportunities to enable this feature, including microkinetic energy harvesting systems utilizing frequencies occurring in human motion to harvest energy [189], powering wearables with solar energy harvesting [190], self-powering smart fabric [191] and wireless power transfer for implantables [192], [193].…”

Section: Challenges and Future Research Directionsmentioning

confidence: 99%

Towards Energy Efficiency in the Internet of Wearable Things: A Systematic Review

et al. 2020

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Personal mobile devices such as smartwatches, smart jewelry, and smart clothes have launched a new trend in the Internet of Things (IoT) era, namely the Internet of Wearable Things (IoWT). These wearables are small IoT devices capable of sensing, storing, processing, and exchanging data to assist users by improving their everyday life tasks through various applications. However, the IoWT has also brought new challenges for the research community to address such as increasing demand for enhanced computational power, better communication capabilities, improved security and privacy features, reduced form factor, minimal weight, and better comfort. Most wearables are battery-powered devices that need to be recharged-therefore, the limited battery life remains the bottleneck leading to the need to enhance the energy efficiency of wearables, thus, becoming an active research area. This paper presents a survey of energy-efficient solutions proposed for diverse IoWT applications by following the systematic literature review method. The available techniques published from 2010 to 2020 are scrutinized, and the taxonomy of the available solutions is presented based on the targeted application area. Moreover, a comprehensive qualitative analysis compares the proposed studies in each application area in terms of their advantages, disadvantages, and main contributions. Furthermore, a list of the most significant performance parameters is provided. A more in-depth discussion of the main techniques to enhance wearables' energy efficiency is presented by highlighting the trade-offs involved. Finally, some potential future research directions are highlighted.

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“…Since not all the metal passes through the stencil, there is some waste, yet most of the metal blocked by the stencil can be recovered. This technique has been used successfully to fabricate soft electrodes [ 51 , 52 , 53 ], sensors [ 54 , 55 ], energy harvesters [ 56 , 57 , 58 ] and antennas [ 59 ] Motivated by these applications, this study examines how it forms robust electrical contacts, especially in comparison to inkjet processing. We also use the spray coating process to pattern thin encapsulating layers of silicone, which are important to ensure the liquid metal does not smear during handling after deposition.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics

et al. 2021

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We report a spray deposition technique for patterning liquid metal alloys to form stretchable conductors, which can then be encapsulated in silicone elastomers via the same spraying procedure. While spraying has been used previously to deposit many materials, including liquid metals, this work focuses on quantifying the spraying process and combining it with silicones. Spraying generates liquid metal microparticles (~5 μm diameter) that pass through openings in a stencil to produce traces with high resolution (~300 µm resolution using stencils from a craft cutter) on a substrate. The spraying produces sufficient kinetic energy (~14 m/s) to distort the particles on impact, which allows them to merge together. This merging process depends on both particle size and velocity. Particles of similar size do not merge when cast as a film. Likewise, smaller particles (<1 µm) moving at the same speed do not rupture on impact either, though calculations suggest that such particles could rupture at higher velocities. The liquid metal features can be encased by spraying uncured silicone elastomer from a volatile solvent to form a conformal coating that does not disrupt the liquid metal features during spraying. Alternating layers of liquid metal and elastomer may be patterned sequentially to build multilayer devices, such as soft and stretchable sensors.

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Flexible thermoelectric generators for body heat harvesting – Enhanced device performance using high thermal conductivity elastomer encapsulation on liquid metal interconnects

Cited by 131 publications

References 63 publications

Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

Towards Energy Efficiency in the Internet of Wearable Things: A Systematic Review

Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics

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