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Flexible electronics on low-temperature substrates like paper are very appealing for their use in disposable and biocompatible electronic applications and areas like healthcare, wearables, and consumer electronics. Plasma-jet printing uses a dielectric barrier discharge plasma to focus aerosolized nanoparticles onto a target substrate. The same plasma can be used to change the properties of the printed material and even sinter in situ . In this work, we demonstrate one-step deposition of gold structures onto flexible and low-temperature substrates without the need for thermal or photonic post-processing. We also explore the plasma effect on the deposition of the gold nanoparticle ink. The plasma voltage is optimized for the sintering of the gold nanoparticles, and a simple procedure for manufacturing traces with increased adhesion and conductivity is presented, with a peak conductivity of 6.2 x10 5 S/m. PJP-printed gold LED interconnects and microheaters on flexible substrates are developed to demonstrate the potential of this single-step sintered deposition of conductive traces on low-temperature substrates.more » « less
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Additive manufacturing has become a promising method for the fabrication of inexpensive, green, flexible electronics. Printed electronics on low-temperature substrates like paper are very appealing for the flexible hybrid electronics market for their use in disposable and biocompatible electronic applications and in areas like packaging, wearables, and consumer electronics. Plasma-jet printing uses a dielectric barrier discharge plasma to focus aerosolized nanoparticles onto a target substrate. The same plasma can be used to change the properties of the printed material and even sinter in situ. The technology can also be utilized in space and microgravity environments since the plasma-assisted deposition is independent of gravity. In this work, we show plasma voltage effect on deposition of gold nanoparticles and direct printing of flexible, conductive gold structures onto low-temperature paper substrates without the need for thermal or photonic post-processing. The effects of plasma parameters on the conductivity and flexible reliability of the printed films are studied, and a paper-based LED electrode is demonstrated.more » « less
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Thermoelectric generators (TEGs) convert temperature differences into electrical power and are attractive among energy harvesting devices due to their autonomous and silent operation. While thermoelectric materials have undergone substantial improvements in material properties, a reliable and cost-effective fabrication method suitable for microgravity and space applications remains a challenge, particularly as commercial space flight and extended crewed space missions increase in frequency. This paper demonstrates the use of plasma-jet printing (PJP), a gravity-independent, electromagnetic field-assisted printing technology, to deposit colloidal thermoelectric nanoflakes with engineered nanopores onto flexible substrates at room temperature. We observe substantial improvements in material adhesion and flexibility with less than 2% and 11% variation in performance after 10 000 bending cycles over 25 mm and 8 mm radii of curvature, respectively, as compared to previously reported TE films. Our printed films demonstrate electrical conductivity of 2.5 × 10 3 S m −1 and a power factor of 70 μW m −1 K −2 at room temperature. To our knowledge, these are the first reported values of plasma-jet printed thermoelectric nanomaterial films. This advancement in plasma jet printing significantly promotes the development of nanoengineered 2D and layered materials not only for energy harvesting but also for the development of large-scale flexible electronics and sensors for both space and commercial applications.more » « less
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Thermoelectric generators are being used as a successful power sources for space applications since 1960's in radioisotope-thermoelectric generators (RTGs) to supply power to space systems in deep space. RTG’s are capable of directly converting heat energy to uninterrupted electric power with no moving parts involved. The ability of thermoelectric materials to convert heat energy to electrical energy is defined by a dimensionless value known as the thermoelectric figure of merit (ZT) 1. This value quantifies the maximum thermoelectric efficiency of a thermoelectric generator (TEG) and is calculated by ZT= S2σT/κ, where S, σ, T, and κ represent Seebeck coefficient, electrical conductivity, temperature, and thermal conductivity, respectively. Among all of the thermoelectric materials, Bi2Te3 and its alloys have been reported to have high ZT values for low temperature energy harvesting and are highly suitable for powering wearables and self-powering sensors2, 3.more » « less
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Abstract Printing is a versatile method to transform semiconducting nanoparticle inks into functional and flexible devices. In particular, thermoelectric nanoparticles are attractive building blocks to fabricate flexible devices for energy harvesting and cooling applications. However, the performance of printed devices are plagued by poor interfacial connections between nanoparticles and resulting low carrier mobility. While many rigid bulk materials have shown a thermoelectric figure of merit
ZT greater than unity, it is an exacting challenge to develop flexible materials withZT near unity. Here, a scalable screen‐printing method to fabricate high‐performance and flexible thermoelectric devices is reported. A tellurium‐based nanosolder approach is employed to bridge the interfaces between the BiSbTe particles during the postprinting sintering process. The printed BiSbTe flexible films demonstrate an ultrahigh room‐temperature power factor of 3 mW m−1K−2andZT about 1, significantly higher than the best reported values for flexible films. A fully printed thermoelectric generator produces a high power density of 18.8 mW cm−2achievable with a small temperature gradient of 80 °C. This screen‐printing method, which directly transforms thermoelectric nanoparticles into high‐performance and flexible devices, presents a significant leap to make thermoelectrics a commercially viable technology for a broad range of energy harvesting and cooling applications. -
Abstract Thermoelectric generators are an environmentally friendly and reliable solid‐state energy conversion technology. Flexible and low‐cost thermoelectric generators are especially suited to power flexible electronics and sensors using body heat or other ambient heat sources. Bismuth telluride (Bi2Te3) based thermoelectric materials exhibit their best performance near room temperature making them an ideal candidate to power wearable electronics and sensors using body heat. In this report, Bi2Te3thin films are deposited on a flexible polyimide substrate using low‐cost and scalable manufacturing methods. The synthesized Bi2Te3nanocrystals have a thickness of 35 ± 15 nm and a lateral dimension of 692 ± 186 nm. Thin films fabricated from these nanocrystals exhibit a peak power factor of 0.35 mW m−1·K−2at 433 K, which is among the highest reported values for flexible thermoelectric films. In order to evaluate the flexibility of the thin films, static and dynamic bending tests are performed while monitoring the change in electrical resistivity. After 1000 bending cycles over a 50 mm radius of curvature, the change in electrical resistance of the film is 23%. Using Bi2Te3solutions, the ability to print thermoelectric thin films with an aerosol jet printer is demonstrated, highlighting the potential of additive manufacturing techniques for fabricating flexible thermoelectric generators.