Flexible Thermoelectric Materials Research Articles

Interfacial engineering of flexible Ag2-xSnxS on carbon fabric for enhanced wearable thermoelectric generator

Smart wearable devices are still powered by batteries requiring constant recharging, which is a key challenge faced in wearable technologies. Fabrication of flexible thermoelectric materials that can utilize body heat for wearable applications are an attractive alternative to batteries. Developing a thermoelectric material that is flexible, affordable, and has good performance remains a considerable challenge owing to the constrained thermoelectric efficiency of conducting polymers and the inherent rigidity of inorganic materials. Here, we have used a solvothermal technique to incorporate Ag2-xSnxS into conductive carbon fabric as a flexible thermoelectric material. To further enhance its thermoelectric performance, various concentrations of Ag2-xSnxS are grown on carbon fabric. The monoclinic phase of Ag2S on carbon fabric was verified by XRD analysis. After analyzing the thermoelectric characteristics of Ag1.84Sn0.16S, a maximum power factor of 110 μW/mK2 was observed for the SSS8 sample. This value is four times higher than the percentage of pristine Ag2S-CF. The W-TEG device fabricated using 3 pair modules produced an output voltage ranging from 0.09 to 1.5 mV across a temperature gradient of 3 to 8 K.

Patternable and flexible thermoelectric generators based on Bi2Te3/silk fibroin composites for temperature sensing and wearable applications

Thermoelectric (TE) materials are functional materials that can directly convert heat energy into electrical energy, and have a positive effect on alleviating the energy crisis. Inorganic semiconductor materials have attracted extensive attention due to their excellent TE properties, among which Bi2Te3 is the best and most widely used inorganic TE material at room temperature. However, inorganic TE materials are still restricted by unfavorable factors such as scarcity of raw material resources, heavy metal pollution, high price, high rigidity, and complex processing technology, which greatly limit their development process. Therefore, it is urgent to develop flexible TE materials with high performance, non-polluting, non-toxic and low price. The combination of silk fibroin and inorganic TE materials not only retains the properties of TE materials, but also improves their flexibility. Here, the Bi2Te3/SF TE films are successfully fabricated by the evaporation-assisted self-assembly method with Seebeck coefficient of 199 μV⋅K−1 (p-type) and −240 μV⋅K−1 (n-type). In order to verify the feasibility of collecting and utilizing ambient heat energy in real life, the Bi2Te3/SF TE films are cut into various patterns (such as, flower, rabbit, tree, etc) to collect wasted ambient heat. Further, the Bi2Te3/SF thermoelectric generator (TEG) reaches a maximum power of 21 nW at a temperature difference of 43.5 K. A series of self-power temperature sensing demonstrations from single TE film, TEG, to TEG array are proposed to demonstrate their potential applications in the field of self-power sensors. Finally, by inserting Bi2Te3/SF TEG array into a bracelet, a self-powered smart bracelet can be successfully constructed, demonstrating the feasibility of the Bi2Te3/SF TE film in the development of self-powered wearable electronics.

A Highly Robust, Multifunctional, and Breathable Bicomponent Fibers Thermoelectric Fabric for Dual-Mode Sensing.

Wearable thermoelectric (TE) materials are seen as excellent candidates for flexible electronics because of their unique self-powered properties, multistimulus sensing and human waste heat conversion. However, currently reported flexible TE materials still face challenges such as poor durability, uncomfortable wearing and sensing signals crosstalking each other. Herein, this study describes a hot-air cross-linking method for the preparation of multifunctional TE fabrics with enhanced durability. Poly(ethylene terephthalate) (PET) fibers with core and sheath structures having different melting points were selected as flexible substrates. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs) were embedded stably on the surface of the sheath layer in the presence of heat treatment. The fiber-welded structure created by thermal cross-linking improves the durability of TE fabrics, including consistent mechanical and electrical properties after a 6 h wash test and 6000 compression cycles. The unique fiber structure of TE fabrics ensures excellent breathability (313.7 mm s-1 at 200 Pa), which meets the breathability requirements for human wear. In addition, the fiber-prepared sensors have excellent compressive strain response (20 ms response time and 30 ms recovery time) and precise temperature discrimination (0.17 K minimum discrimination temperature) for accurate real-time monitoring of the sensed signals. Thus, the TE fabrics can be used for human motion recognition, including pulse monitoring, sign language expression, and motions in joint areas. Moreover, the fabricated wearable TE device is connected to a Bluetooth module for wireless transmission, which can be used for mechanical and temperature sensing of the robot arm without signals crosstalking. This new durable TE fabric paves the way for the next generation of smart wearable technology.

Wearable Device with High Thermoelectric Performance and Long-Lasting Usability Based on Gel-Thermocells for Body Heat Harvesting.

Utilizing the thermogalvanic effect, flexible thermoelectric materials present a compelling avenue for converting heat into electricity, especially in the context of wearable electronics. However, prolonged usage is hampered by the limitation imposed on the thermoelectric device's operational time due to the evaporation of moisture. Deep eutectic solvents (DESs) offer a promising solution for low-moisture gel fabrication. In this study, a bacterial cellulose (BC)/polyacrylic acid (PAA)/guanidinium chloride (GdmCl) gel is synthesized by incorporating BC into the DES. High-performance n-type and p-type thermocells (TECs) are developed by introducing Fe(ClO4)2/3 and K3/4Fe(CN)6, respectively. BC enhances the mechanical properties through the construction of an interpenetrating network structure. The coordination of carboxyl groups on PAA with Fe3+ and the crystallization induced by Gdm+ with [Fe(CN)6]4- remarkably improve the thermoelectric performance, achieving a Seebeck coefficient (S) of 2.4mVK-1 and ion conductivity (σ) of 1.4 Sm-1 for the n-type TEC, and ‒2.8mVK-1 and 1.9 Sm-1 for the p-type TEC. A flexible wearable thermoelectric device is fabricated with a S of 82mVK-1 and it maintains a stable output over one month. This research broadens the application scope of DESs in the thermoelectric field and offers promising strategies for long-lasting wearable energy solutions.

Flexible and air-stable n-type oleylamine/carbon nanotube hybrid yarns for high-performance wearable thermoelectric generators

Wearable thermoelectric generators (TEGs), envisioned to harness the temperature gradient (ΔT) between the human body and the environment into electricity, hold great promise for powering wearable electronics. However, their practical application has been hampered by the scarcity of flexible n-type thermoelectric (TE) materials boasting both high performance and long-term air stability. Here, we introduce a significant advancement by developing an n-type TE material through immersing carbon nanotube yarn (CNTY) into an oleylamine (OAm)/ethanol solution, followed by drying under atmospheric conditions. The resulting OAm/CNTY exhibits a Seebeck coefficient of -80.48 μV K-1, an electrical conductivity of 1353.18 S cm-1 and a power factor of 876.25 μW m-1 K-2, all while exhibiting exceptional mechanical flexibility. Notably, this hybrid yarn maintains stable n-type behavior even after enduring exposure to air for over 370 days, surpassing previous n-type TE materials based on CNT fibers and CNTY. Leveraging this advancement, we construct a prototype wearable TEG by alternately embroidering pristine p-type CNTY and n-type OAm/CNTY into a polyester spacer fabric, electrically connecting them in series using conductive silver paint. The resulting wearable TEG, featuring with 150 p-n couples, yields an output voltage of 705.94 mV and a maximum output power of 44.34 μW at a ΔT of 40 K. This groundbreaking work opens new avenues for the development of high-performance, air-stable, and flexible n-type TE material, ushering in a new era for wearable TEGs.

The Influence of Molecular Weights on Dispersion and Thermoelectric Performance of Alkoxy Side-Chain Polythiophene/Carbon Nanotube Composite Materials.

In the development of wearable electronic devices, the composite modification of conductive polymers and single-walled carbon nanotubes (SWCNTs) has become a burgeoning research area. This study presents the synthesis of a novel polythiophene derivative, poly(3-alkoxythiophene) (P3(TEG)T), with alkoxy side chains. Different molecular weight variants of P3(TEG)T (P1-P4) were prepared and combined with SWCNTs to form composite materials. Density functional theory (DFT) calculations revealed a reduced bandgap for P3(TEG)T. Raman spectroscopy demonstrated π-π interactions between P3(TEG)T and SWCNTs, facilitating the dispersion of single-walled carbon nanotubes and the formation of a continuous conductive network. Among the composite films, P4/SWCNTs-0.9 exhibited the highest thermoelectric performance, with a power factor (PF) value of 449.50 μW m-1 K-2. The fabricated flexible thermoelectric device achieved an output power of 3976.92 nW at 50 K, with a tensile strength of 59.34 MPa for P4/SWCNTs. Our findings highlight the strong interfacial interactions between P3(TEG)T and SWCNTs in the composite material, providing an effective charge transfer pathway. Furthermore, an improvement in the tensile performance was observed with an increase in the molecular weight of the polymer used in the composite, offering a viable platform for the development of high-performance flexible organic thermoelectric materials.

A new strategy to simultaneously optimize Seebeck coefficient and electrical conductivity of PEDOT:PSS polymer via L-ascorbic acid

PEDOT:PSS flexible thermoelectric materials are promising for future wearable continuous power support, but it remains challenging due to low power factor. Herein, we propose a “one-stone-two-birds” strategy using L-ascorbic acid as the reductant in synthesis of tellurium nanorods and separating agent in in-situ removing PSS chains. L-ascorbic acid reduces Te4+ to Te, supplying inorganic thermoelectric materials with high Seebeck coefficient as fillers to significantly increase the Seebeck coefficient value of PEDOT:PSS. Meanwhile, L-ascorbic acid separates PSS chains from PEDOT chains, resulting in the increase of electrical conductivity at room temperature by ∼360 % due to structure transformation from benzoid structure to the quinoid structure in PEDOT. As a result, the power factor of optimal PEDOT:PSS with Te fillers and L-ascorbic acid treatment is improved significantly by ∼100 times as compared to that of pristine PEDOT:PSS. Finally, a prototype wearable thermoelectric generator was assembled by 18 legs of Te/PEDOT:PSS composites, which demonstrates a high power density of 2.3 μW·cm−2 with good mechanical stability, flexibility and durability. The present study offers a new strategy for rational design of high-performance flexible thermoelectric materials from PEDOT:PSS.

Stretchable and Skin-Conformal Thermoelectric Generator with Highly Flexible and Plastically Bendable Silver Selenide Films.

Among inorganic thermoelectric materials, flexible thermoelectric materials have attracted considerable attention. In this study, highly flexible and plastically bendable silver selenide films with excellent thermoelectric performance at room temperature are presented. The flexibility of the freestanding silver selenide films was significantly improved through a simple annealing treatment. The highly flexible silver selenide films with a thickness of 26.0 μm displayed outstanding n-type thermoelectric performance, achieving an in-plane zT value of 0.38 at room temperature. Because silver selenide films are plastically bendable with a bending radius of less than 1 mm, they can be shaped into various forms. To achieve stretchability and skin-conformality in the thermoelectric generator, S-shaped silver selenide strips were used as an n-type thermoelectric element. Effective harvesting of electricity from heat of the human body was successfully demonstrated.

A Strategy for Fabricating Ultra-Flexible Thermoelectric Films Using Ag2Se-Based Ink.

Flexible thermoelectric materials have drawn significant attention from researchers due to their potential applications in wearable electronics and the Internet of Things. Despite many reports on these materials, it remains a significant challenge to develop cost-effective methods for large-scale, patterned fabrication of materials that exhibit both excellent thermoelectric performance and remarkable flexibility. In this study, we have developed an Ag2Se-based ink with excellent printability that can be used to fabricate flexible thermoelectric films by screen printing and low-temperature sintering. The printed films exhibit a Seebeck coefficient of -161 μV/K and a power factor of 3250.9 μW/m·K2 at 400 K. Moreover, the films demonstrate remarkable flexibility, showing minimal changes in resistance after being bent 5000 times at a radius of 5 mm. Overall, this research offers a new opportunity for the large-scale patterned production of flexible thermoelectric films.

Thermoelectric bismuth telluride nanostructures fabricated by electrodeposition within flexible templates

Bismuth telluride, a highly efficient thermoelectric material, stands out for applications around room temperature in wearable devices. By harnessing the thermal gradient established between the human body and ambient temperature, we can generate useable electricity. Notably, bismuth telluride nanostructures exhibit significantly lower thermal conductivities compared to their bulk counterparts. As a result, the thermoelectric efficiency achieved is notably higher. Our research focuses on developing efficient nanostructured materials based on bismuth telluride inside a flexible substrate made of polyester. We employ scalable methods, such as template-assisted electrochemical deposition, to fabricate these nanostructures. In this study, we present an approach to the development of flexible nanostructured thermoelectric materials. Despite using a reduced quantity of active material, our electrochemically deposited nanostructures inside a flexible template demonstrate a remarkable performance. They exhibit 24 % of the Power Factor reported for conventional electrochemically fabricated Bi2Te3 thin films, and notably, they even surpass the Power Factor reported for flexible Bi2Te3-based inks used in the creation of flexible generators. This achievement underscores the potential of our method in the advancement of efficient, flexible thermoelectric devices.

Elevating Thermoelectric Performance by Compositing Dibromo-Substituted Thienoacene with SWCNTs.

Composites of organic small molecules (OSMs) and single-walled carbon nanotubes (SWCNTs) have drawn great attention as flexible thermoelectric (TE) materials in recent years. Here, we synthesized thieno[2',3':4,5]thieno[3,2-b]thieno[2,3-d]thiophene (TTA) and 2,6-dibromothieno[2',3':4,5]thieno[3,2-b]thieno[2,3-d]thiophene (TTA-2Br) and compounded them with SWCNTs, obtaining thermoelectric TTA/SWCNT and TTA-2Br/SWCNT composites. The introduction of the electron-withdrawing Br group was found to decrease the highest molecular orbital energy level and bandgap (Eg) of TTA-2Br. As a result, the Seebeck coefficient (S) and power factor (PF) of the OSM/SWCNT composite films were significantly improved. Moreover, suitable energy barrier between TTA-2Br and SWCNTs facilitates the energy filtering effect, which further enhances thermoelectric properties of the 40 wt % TTA-2Br/SWCNT composite film with optimum thermoelectric properties (PF = 242.59 ± 9.42 μW m-1 K-2 at room temperature), good thermal stability, and mechanical flexibility. In addition, the thermoelectric generator (TEG) prepared using 40 wt % TTA-2Br/SWCNT composite films and n-type SWCNT films can generate an output power of 102.8 ± 7.4 nW at a temperature difference of 20 °C. This work provides new insights into the preparation of OSM/SWCNT composites with significantly enhanced thermoelectric properties.

Thermoelectric generator and temperature sensor based on polyamide doped n-type single-walled nanotubes toward self-powered wearable electronics

Due to its ability to convert body heat into electricity, organic thermoelectric material is considered a promising and smart maintenance-free power source to charge wearable electronics. However, developing flexible n-type organic thermoelectric materials and wearable p/n junction thermoelectric devices remains challenging. In this work, two insulated polyamides (PA6 and PA66) that have been widely used as fiber materials are employed as novel dopants for converting p-type single-walled carbon nanotubes (SWCNTs) to n-type thermoelectric materials. Because of the electron transferability of the amide group, polyamide-doped SWCNTs exhibit excellent thermopower values as large as −56.0 µV K−1 for PA66, and −54.5 µV K−1 for PA6. Thermoelectric devices with five p/n junctions connected in series are fabricated. The testing device produces a thermoelectric voltage of 43.1 mV and generates 1.85 µW thermoelectric power under temperature gradients of approximately 80 K. Furthermore, they display charming capability for temperature recognition and monitoring human activities as sensors. These promising results suggest that the flexible polyamide-doped SWCNT composites herein have high application potential as wearable thermoelectric electronics.

Boosting thermoelectric performance of single-walled carbon nanotubes-based films through rational triple treatments

Single-walled carbon nanotubes (SWCNTs)-based thermoelectric materials, valued for their flexibility, lightweight, and cost-effectiveness, show promise for wearable thermoelectric devices. However, their thermoelectric performance requires significant enhancement for practical applications. To achieve this goal, in this work, we introduce rational “triple treatments” to improve the overall performance of flexible SWCNT-based films, achieving a high power factor of 20.29 µW cm−1 K−2 at room temperature. Ultrasonic dispersion enhances the conductivity, NaBH4 treatment reduces defects and enhances the Seebeck coefficient, and cold pressing significantly densifies the SWCNT films while preserving the high Seebeck coefficient. Also, bending tests confirm structural stability and exceptional flexibility, and a six-legged flexible device demonstrates a maximum power density of 2996 μW cm−2 at a 40 K temperature difference, showing great application potential. This advancement positions SWCNT films as promising flexible thermoelectric materials, providing insights into high-performance carbon-based thermoelectrics.

The Enhanced Thermoelectric and Mechanical Performance of Polythiophene/Single-Walled Carbon Nanotube Composites with Polar Ethylene Glycol Branched-Chain Modifications.

In order to develop flexible thermoelectric materials with thermoelectric and mechanical properties, in this study, we designed and synthesized polythiophene derivatives with branched ethylene glycol polar side-chains named P3MBTEMT, which were used in combination with single-walled carbon nanotubes (SWCNTs) to prepare composite thin films and flexible thermoelectric devices. A comparison was made with a polymer named P3(TEG)T, which has a polar alkoxy linear chain. The UV-vis results indicated that the larger steric hindrances of the branched ethylene glycol side-chain in P3MBTEMT could inhibit its self-aggregation and had a stronger interaction with the SWCNTs compared to that of P3(TEG)T, which was also confirmed using Raman spectroscopy. When the mass ratio of SWCNTs to P3MBTEMT was 9:1 (represented as P3MBTEMT/SWCNTs-0.9), the composite film exhibited the highest thermoelectric properties with a power factor of 446.98 μW m-1 K-2, which was more than two times higher than that of P3(TEG)T/SWCNTs-0.9 (215.08 μW m-1 K-2). The output power of the thermoelectric device with P3MBTEMT/SWCNTs-0.9 was 2483.92 nW at 50 K, which was 1.66 times higher than that of P3(TEG)T/SWCNTs-0.9 (1492.65 nW). Furthermore, the P3MBTEMT/SWCNTs-0.5 showed superior mechanical properties compared to P3(TEG)T/SWCNTs-0.5. These results indicated that the mechanical and thermoelectric performances of polymer/SWCNT composites could be significantly improved by adding polar branched side-chains to conjugated polymers. This study provided a new strategy for creating high-performing novel flexible thermoelectric materials.

Copper-Enriched Nanostructured Conductive Thermoelectric Copper(I) Iodide Films Obtained by Chemical Solution Deposition on Flexible Substrates

The objects of our research are flexible thin-film thermoelectric materials with nanostructured CuI layers 0.5–1.0 μm thick, fabricated by the chemical solution method Successive Ionic Layer Adsorption and Reaction (SILAR) on flexible polyethylene terephthalate and polyimide substrates. These cubic γ-CuI films differ from films obtained by other chemical solution methods, such as spin-coating, sputtering, and inject printing, in their low resistivity due to acceptor impurities of sulfur and oxygen introduced into CuI from aqueous precursor solutions during SILAR deposition. Energy barriers at the boundaries of 18–22 nm CuI nanograins and a large number of charge carriers inside the nanograins determine the transport properties in the temperature interval 295–340 K characterized by transitions from semiconductor to metallic behavior with increasing temperature, which are typical of nanostructured degenerate semiconductors. Due to the resistivity of about 0.8 mΩ· m at 310 K and the Seebeck coefficient 101 μV/K, the thermoelectric power factor of the CuI film 1.0 μm thick on the polyimide substrate is 12.3 μW/(m · K2), which corresponds to modern thin-film p-type thermoelectric materials. It confirms the suitability of CuI films obtained by the SILAR method for the fabrication of promising inexpensive non-toxic flexible thermoelectric materials.

Recent Developments on Flexible Materials for Thermoelectrics

In recent decades, thermoelectric materials have gained a significant attention due to their ability to directly convert waste heat into electricity. While extensive research has been focused on enhancing the thermoelectric properties of inorganic bulk materials, a new frontier has emerged in this area as flexible thermoelectric materials. These flexible thermoelectrics are driven by the limitations posed by the rigidity, less functional and toxicity of conventional inorganic thermoelectric materials. Despite notable achievements in the development of high-performance flexible thermoelectric materials, they still pose inferior figure of merit (zT) in comparison to their inorganic counterparts. This review encompasses various aspects of flexible thermoelectric materials including theoretical foundations which highlight the principles that explain the concepts and parameters of thermoelectricity to enhance the overall performance, serving as a foundation for understanding the subsequent developments. Further it is overviewed in detail the corresponding state of the art in development of conducting thermoelectric polymers, inorganic-polymer composites, carbon-based thermoelectric and inorganic thermoelectrics on flexible substrates to enhance their thermoelectric performances. Finally it includes the overlook to the future of flexible thermoelectric for wearable thermoelectrics.

A Highly‐Flexible and Breathable Photo‐Thermo‐Electric Membrane for Energy Harvesting

AbstractPhoto‐thermo‐electric (PTE) technology is a simple but sustainable method that directly converts solar energy into electricity. However, the manufacturing of flexible and breathable PTE generators for practical applications, such as intelligent wearable and self‐powered sensors, poses significant challenges due to the rigid thermoelectric materials and unbreathable substrates. Here, a highly‐flexible and breathable photo‐thermal‐electric membrane (FB‐PTEM) is developed by magnetron sputtering (MS) on a photo‐thermal nanofiber membrane. A single unit of FB‐PTEM produced an open‐circuit voltage of 0.52 V under 1 sun (100 mW cm−2) and 0.2 V under LED illumination, making it suitable for all‐weather use. The photo‐thermal nanofiber membrane exhibited high photo‐thermal conversion capacity of reaching 70 °C within 50 s under 1 sun irradiation. The FB‐PTEM with a thickness of 0.35 mm achieved a self‐temperature difference of 20.6 °C under 1 sun with the low thermal conductivity of the nanofiber membrane. Furthermore, it has a vapor permeability of 14.6 kg m−2 d−1 due to the inherent high porosity of the nanofiber membranes. The FB‐PTEM demonstrates great potential for the development of highly flexible thermoelectric materials, as it encompasses various advantageous features such as self‐temperature difference, lightweight design, high breathability, and all‐weather suitability.

Synthesis of PEDOT/CNTs Thermoelectric Thin Films with a High Power Factor.

In this study, we have improved the power factor of conductive polymer nanocomposites by combining layer-by-layer assembly with electrochemical deposition to produce flexible thermoelectric materials based on PEDOT/carbon nanotubes (CNTs)-films. To produce films based on CNTs and PEDOT, a dual approach has been employed: (i) the layer-by-layer method has been utilized for constructing the CNTs layer and (ii) electrochemical polymerization has been used in the synthesis of the conducting polymer. Moreover, the thermoelectric properties were optimized by controlling the experimental conditions including the number of deposition cycles and electropolymerizing time. The electrical characterization of the samples was carried out by measuring the Seebeck voltage produced under a small temperature difference and by measuring the electrical conductivity using the four-point probe method. The resulting values of the Seebeck coefficient S and σ were used to determine the power factor. The structural and morphological analyses of CNTs/PEDOT samples were carried out using scanning electron microscopy (SEM) and Raman spectroscopy. The best power factor achieved was 131.1 (μWm-1K-2), a competitive value comparable to some inorganic thermoelectric materials. Since the synthesis of the CNT/PEDOT layers is rather simple and the ingredients used are relatively inexpensive and environmentally friendly, the proposed nanocomposites are a very interesting approach as an application for recycling heat waste.

Synergistic Dual Doping of Sulfur and Copper for Improved Thermoelectric Properties of Silver Selenide Nanomaterials.

Research on flexible thermoelectric (TE) materials has typically focused on conducting polymers and conducting polymer-based composites. However, achieving TE properties comparable in magnitude to those exhibited by their inorganic counterparts remains a formidable challenge. This study focuses on the synthesis of silver selenide (Ag2Se) nanomaterials using solvothermal methods and demonstrates a significant enhancement in their TE properties through the synergistic dual doping of sulfur and copper. Flexible TE thin films demonstrating excellent flexibility are successfully fabricated using vacuum filtration and hot-pressing techniques. The resulting thin films also exhibited outstanding TE performance, with a high Seebeck coefficient (S=-138.5µVK-1) and electrical conductivity (σ=1.19×105Sm-1). The record power factor of 2296.8µWm-1K-2 at room temperature is primarily attributed to enhanced carrier transport and interfacial energy filtration effects in the composite material. Capitalizing on these excellent TE properties, the maximum power output of flexible TE devices reached 1.13µW with a temperature difference of 28.6K. This study demonstrates the potential of Ag2Se-based TE materials for flexible and efficient energy-harvesting applications.

Flexible Ag2Se Thermoelectric Films Enable the Multifunctional Thermal Perception in Electronic Skins.

Skin is critical for shaping our interactions with the environment. The electronic skin (E-skin) has emerged as a promising interface for medical devices to replicate the functions of damaged skin. However, exploration of thermal perception, which is crucial for physiological sensing, has been limited. In this work, a multifunctional E-skin based on flexible thermoelectric Ag2Se films is proposed, which utilizes the Seebeck effect to replicate the sensory functions of natural skin. The E-skin can enable capabilities including temperature perception, tactile perception, contactless perception, and material recognition by analyzing the thermal conduction behaviors of various materials. To further validate the capabilities of constructed E-skins, a wearable device with multiple sensory channels was fabricated and tested for gesture recognition. This work highlights the potential for using flexible thermoelectric materials in advanced biomedical applications including health monitoring and smart prosthetics.