Thermoelectric Research Articles

Electrode-dependent thermoelectric effect in ionic hydrogel fiber for self-powered sensing and low-grade heat harvesting

Ionic thermoelectric materials show great significance for wearable energy devices, owing to the capability of the conversion between thermal and electrical energy. The two-dimensional massive structure which is difficult to integrate with fabrics of ionic thermoelectric materials, however, prevent them from realizing their full potential when employed in wearable electronics. In this work, ionic thermoelectric 1D PAM/LiTFSI4 hydrogel fibers with high aspect ratio, inherent flexibility, conductivity, anti-freezing, self-adhesion and self-healing properties are constructed by free radical polymerization technology based on a template strategy, which contains a PAM polymer matrix and an LiTFSI conductive material. Based on thermal diffusion, owing to the ion size difference, the covalent cross-linked polymer network and the electrode-dependent effect promote rapid transport of the cations and boost ion concentration difference, resulting in a huge ionic Seebeck coefficient of 19.02 mV K−1. Meanwhile, embedding hydrogel fibers into the woven textile demonstrates a promising thermoelectric wristband with desirable human heat collection and electrical output capabilities. What’s more, thanks to the introduction of LiTFSI, the microstructure and molecular network system of hydrogel fibers are reshaped, which significantly improved the ionic conductivity of hydrogel fiber, and endowed them with anti-freezing, self-adhesion and self-healing properties. The PAM/LiTFSI4 hydrogel fiber also has excellent strain and temperature sensing properties, which enable a variety of human signal monitoring. Besides, the hydrogel fiber-based sensor can realize self-powered sensing by generating a thermovoltage. Thus, combining the merits of one-dimensional structure, superior thermoelectric performances, sensing at low temperature, excellent adhesion, self-healing and anti-freezing properties together, believing that the PAM/LiTFSI4 hydrogel fiber will render new numerous in human signal monitoring and low-grade heat harvesting applications like wearable electronics and wearable energy supply devices.

A first-principles investigation of Ba2CaTeO6 and Ba2CaWO6 compounds for thermoelectric and optoelectronic applications

Herein, structural, optoelectronic, and thermoelectric characteristics of Ba2CaTeO6 and Ba2CaWO6 oxides double perovskite have been evaluated by first-principles calculations. Enthalpy of formation and tolerance factor are computed to ensure the respective structural and thermodynamical stability. Ba2CaTeO6 and Ba2CaWO6 have mBJ computed bandgaps of 5.87 eV and 4.20 eV, respectively. Furthermore, the optical parameters like dielectric constants (ԑ1(ω) & ԑ2(ω)) and other related parameters are computed. The thermoelectric (TE) parameters were examined using the BoltzTraP package. The ZT values of Ba2Ca(Te/W)O6 at 450 K are 0.76/0.79, respectively. The outcomes of the Ba2CaTeO6 and Ba2CaWO6 double perovskite show that these materials are potential contenders for UVbased optical and various TE gadgets.

Experimental analysis on the thermoelectric effect of various solid-state devices used for direct conversion of thermal energy into electrical energy

In this present investigation, the performance of thermoelectric generators (TEGs) was determined for the TEGs made of lead telluride (PbTe3), bismuth telluride (Bi2Te3), silicon germanium (SiGe), and aluminum oxide (Al2O3). In response to variations in the heat input rate and water flow rate, the electric power generated by the TEG was recorded and studied for the aforementioned TEG materials. During the investigation, the water flow rate to the TEG's cold side was chosen to be 0.5 lpm to 2 lpm in the step of 0.5 lpm, and the thermal energy input rate to the hot side was set at 30 W–120 W in the step of 30 W. Among all the TEGs Bi2Te3 was superior in terms of power generation potential in comparison to other TEGs in all the test conditions. The investigation also reveals that all TEGs appear to have a high-power generation when the cooling water flow rate was 2 lpm and the heat input rate was 120 W. At a water flow rate of 2 lpm for the case of Bi2Te3, the power generation potential was elevated by about 20.3 %, 14.4 %, and 6.5 % in comparison to Al2O3, PbTe3, and SiGe respectively.

Exceptional thermoelectric and mechanical performance in (Bi, Sb)2Te3 matrix facilitated by AgInSe2 alloying

The emerging fields of the Internet of Things, intelligent robotics, and smart biomedical devices have sparked an increasing demand for high-performance thermoelectric (TE) devices due to their efficient conversion of thermal energy into electrical power, and vice versa. The environmentally friendly (Bi, Sb)2Te3 (BST) system, which displays superior performance near room temperature, offers a promising solution for optimizing thermoelectrics to meet the needs of commercial applications. Here, we utilized AgInSe2 alloying to enhance the TE and mechanical properties of BST, aiming to optimize electron and phonon transport and elucidate the underlying mechanisms. The synergistic optimization resulted in a peak zT of ∼ 1.3 at 353 K and an average zTave of ∼ 1.11 from 303 K to 503 K in BST-0.1 %AgInSe2, as well as a high Vickers hardness of ∼ 105 Hv. Through rational optimization of the TE device, we achieved a maximum conversion efficiency of ∼ 6 % at a temperature difference of 210 K. Leveraging the robust TE output of the device, we further evaluated its potential as a self-powered information interaction wristband device based on ASCII codes. We envisage this versatile TE device being extensively applied in power generation and human–machine interaction, with promising potential in wearable electronics, telecommunications, and healthcare monitoring.

Electrodeposition Processes for Controlling Surface Morphology of Thick Cu2Se Films As Thermoelectric Conversion Materials

Copper selenides (Cu2Se) are a class of chalcogenides found in various applications owing to their semiconductor material properties. Cu2Se has shown great potential for thermoelectric (TE) device applications, and it has also demonstrated significant room for improvement at high temperatures owing to its phonon glass electron crystal (PGEC), an intrinsic property in potential thermoelectric materials1. Compact morphology and smooth surface are essential parameters in reducing the contact resistance between a thermoleg and the metal electrode2,3. Other studies have focused on further lowering thermal conductivity by increasing phonon drag through nano-structuring and introducing nano-inclusion4,5,6.Among synthesis approaches, the electrodeposition of TE materials appears promising. Morphology control in electrochemical deposition has been demonstrated and has shown outstanding results7. In a Bi2Se3 growth study, the films showed a simultaneous change in morphology, smooth to rough films, and phase, rhombohedral to orthorhombic, with film thickness. These phases exhibit different crystallite sizes and Seebeck coefficients8. It has been demonstrated that film growth and thickness by electrodeposition mainly depend on electrolyte composition and the applied potential to control morphology and stoichiometry. Most studies have focused on tuning these parameters,resulting in films with well-defined stoichiometry but with porous, mossy, or low compactness 9,10,11. There is, therefore, room for improvement, and a better understanding of the deposition processes is key to controlling the growth modes, morphology, and composition.In this work, we study the early stages of Cu2Se electrodeposition for TE application. Our goal is to optimize the electrodeposition conditions to obtain compact, well-crystallized films with Cu2Se stoichiometry. The films were obtained by potentiostatic deposition on a gold electrode from an acidic electrolyte, H2SO4 (pH 0.9 to 1.9), containing 10 mM CuSO4, (1 to 10 mM) H2SeO3, and the bath temperature varied from 25oC to 55oC. All potentials were measured and referred to Ag/Agl/sat, with a platinum mesh serving as the counter electrode. Results showed that at elevated temperature (55oC), pH 1.5, and a precursor concentration ratio [Cu(II) 10mM]/[Se(IV) 5mM] are suitable for Cu2Se film deposition. For films deposited in the potential range -500 mV ≤ V ≤ -50 mV, EDS analysis indicated that atomic composition is relatively constant and close to the desired Cu2Se stoichiometry (66.7 % Cu, 33.3 % Se). XRD spectra present sharp peaks corresponding to Cu2Se, indicating films are well crystallized, with an average crystallite size of 18 nm. SEM showed relatively smooth and compact films with, however, a high density of bulges. For films obtained at potentials more positive than -50 mV and more negative than -500 mV, notable changes in composition to Cu 60.8%, morphology, and the appearance of Cu3Se2 XRD peaks were observed, denoting the existence of mixed phases of Cu3Se2 and Cu2Se. Progress in the investigation of the growth mechanism/processes of Cu2Se films at the early deposition stages will also be presented.References T. Wei, Y.Qin, T. Deng, Q. Song, B. Jiang, R. Liu, P.Qiu, X. Shi, L. Chen,Sci. Chi. Mat. 62, 1, 8–24 (2019) P. Nieroda, A. Kusior, J. Leszczynski, P. Rutkowski, A. Kolezynski, Materials, 14, 3650 (2021)N. Su, S. Guo, F. Li, B. Li. Nanomaterials, 10, 431 (2020)S. Li, X. Lou, X. Li, J. Zhang, D. Li, H. Deng, J. Liu, G. Tang. Chemistry of Materials, 32 (22), 9761-9770, (2020)H. Zhang, D V. Talapin. Angew. Chem Int, 53, 9126-9127 (2014) N. K. Singh, S. Bathula, B. Gahtori, K Tyagi., D. Haranath, A. Dhar. Journal of Alloys and Compounds, 668, 152-158 (2016) K. Cicvaric, L. Meng, D. W. Newbrook, R. Huang, S. Ye, W. Zhang, A. L. Hector, G. Reid, P. N. Bartlett, C. H. K. Groot. ACS Omega , 5, 24, 14679–14688 (2020)R. Ahmed, M. G. Rosul, Y. Xu, M. Zebarjadi, G. Zangari. Electrochimica Acta, 368, 137554, (2021)A. Moysiadou, R. Koutsikou, M. Bouroushian. Materials Letters, 139, 112–115 (2015)D. Lippkow, H. H. Strehblow. Electrochimica Acta, 43, 14-15, 2131-2140, (1998)S. Thanikaikarasan, D. Dhanasekaran, K. Sankaranarayanan. Chinese Journal of Physics, 63, 138-148 (2020)

(Digital Presentation) Synergistic Enhancement of Thermoelectric Performance through One-Dimensional Hybrid Nanocomposites: Wrapped Nickel Oxide-Decorated Multi-Walled Carbon Nanotubes with Polypyrrole

Given the drawbacks of organic materials’ thermoelectric (TE) conversion efficiency, an approach has been made in this study to synthesize a hybrid organic-inorganic material based on polypyrrole (PPy), multi-walled carbon nanotubes (MWCNTs) and nickel oxide nanoparticles (NiO). The nanocomposite is formed through three steps: MWCNTs functionalization via diazonium salt grafting of 5-amino-1,2,3-benzene tricarboxylic acid; in situ generation on their surfaces of NiO nanoparticles with a homogenous distribution; the chemical polymerization of pyrrole using methyl orange as templating and dopant to wrap the MWCNTs-(COOH)3-NiO. To explore the structural and physical properties of the fillers and the nanocomposites, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectrometer, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used. Thereby investigating the electrical conductivity (𝜎), Seebeck coefficient (S) and thermal conductivity (κ) at room temperature, a promising improvement was observed in PPy-MWCNTs-(COOH)3-NiO compared to pure PPy. The observed enhancements in TE properties (ZTPPy-MWCNTs-(COOH)3-NiO = 1.51×10-2) are attributed to the presence of NiO, which acts as a dopant and improves the charge carrier density in the nanocomposite; this result could be increased at higher temperatures. Overall, these results demonstrate the potential of our approach for developing high-performance TE materials with applications in energy harvesting and waste heat recovery. Furthermore, this approach offers the potential for scalability and reproducibility, making it a promising method for large-scale fabrication of high-performance composites. Figure 1

Stacking faults stabilize oxygen vacancies at high temperatures to improve the thermoelectric performance of ZnO

Stabilizing the oxygen vacancies (Ovs) in ZnO at high temperatures is crucial for maintaining the high thermoelectric (TE) performance caused by Ovs. In this study, based on the complex interaction between different kinds of lattice defects, high-density stacking faults (SFs) were fabricated in ZnO with Ovs to effectively stabilize Ovs. The Ovs combined with SFs to significantly improve the electrical conductivity (σ) to 4649 S m−1 at room temperature, leading to an increased power factor (PF) of 280.4 μW m−1·K−2 at 500 °C. Meanwhile, the thermal conductivity was reduced to 3.12 W m−1·K−1 at 500 °C. Notably, the σ and PF were not weakened after five consecutive cycle tests up to 500 °C, suggesting the stabilization of Ovs by SFs at high temperatures. Consequently, the optimized ZT value reached 0.07 at 500 °C, an 18-fold enhancement over the initial sample. The study provides an effective strategy to achieve a simultaneous enhancement in TE performance and stability by modulating different kinds of microstructures.

(Invited) Electron Transport in Nanocarbon Networks for Energy Conversion and Storage Applications

Carbon nanostructures have attracted great attention in recent years as novel electrode materials in batteries with increased capacity and conductivity as well as enhanced material stability. In these nanostructures, nanocarbons such as carbon nanotubes and graphene nanoplatelets are interconnected to construct their three-dimensional networks around the host materials for Li deposition. This work focuses on the study of electron transport phenomena in these nanocarbon networks with two model material systems: (1) single-walled carbon nanotube (SWCNT) networks co-embedded with silica microparticles (Fig. (a)), and (2) free-standing three-dimensional graphene (3DG) structures with polymeric surface modifications (Fig. (b)). We characterize the materials for electrical conductivity and thermopower with varying material contents in the composites to reveal several key factors determining their energy-dependent carrier transport characteristics. It is found that in these three-dimensional nanocarbon networks, carrier tunneling at the junctions between nanocarbons along with the network morphology predominantly determines the transport properties. Simultaneous increase in electrical conductivity and thermopower is achieved for SWCNT networks co-embedded with silica microparticles by increasing silica content up to 40 w.t.% at a fixed CNT content. The enhanced electron transport is attributed to the reduced junction distances due to the intimate network formation on the surface of silica particles with a polymer binder. Our transport theory based on the Landauer formalism for junction tunneling reveals that the junction modification with polymer can alter the potential barrier heights for both electrons and holes at the junction to significantly change the transport properties of the composite. Doping of nanocarbons is also investigated for their impacts on the junction transport and the geometric factor of the networks. Finally, we also investigate the use of these carbon nanostructures in solid-state thermoelectric (TE) energy harvesters and ionic TE capacitors to harvest thermal energy from temperature gradients and fluctuations. Figure 1

Reduced thermal conductivity and enhanced TE performance in CrSb2 via Fe-Bi co-substitution

The efficiency of thermoelectric (TE) technology relies on the performance of TE materials. Substitution with heavy elements is an effective strategy in TE for enhancing phonon scattering without much affecting electrical transport properties. However, selecting suitable dopants to achieve a high TE figure-of-merit (ZT) poses a significant challenge. Thus, in this study, the efficacy of combined (Fe and Bi) co-substitution in CrSb2 is investigated as a promising strategy to enhance ZT by lowering thermal conductivity. A series of co-substituted Cr1−x Fe x BiySb2−y (x = 0, 0.25, 0.50, 0.75, 1 and y = 0.10, 0.15, 0.20,0.25) samples were synthesized via furnace reaction followed by spark plasma sintering technique. Phase analysis and temperature dependence TE transport properties were systematically studied on synthesized samples. Furthermore, to analyze the impact of disorder induced by Bi/Fe substitution, electronic structure calculation was performed using the projector augmented-wave method. Notably, Cr0.75Fe0.25Bi0.15Sb1.85 exhibited a low thermal conductivity of ∼2.5 W m−1 K−1 at 300 K, which reduced to half compared to that of pristine CrSb2 (∼5 W m−1 K−1). This reduction is attributed to the introduction of significant mass fluctuations and point defects along with the presence of Bi at grain boundaries by co-substitution. Consequently, a remarkable 90% enhancement in ZT (∼0.021) at 350 K was achieved for Cr0.75Fe0.25Bi0.15Sb1.85 compared to that of pristine CrSb2 (ZT ∼ 0.012). This study can provide valuable insights into the rational design of effective dopants in other TE materials also.

A novel characteristic curve for thermoelectric cooler application in realistic thermal circumstances: Theory and experiment

On the materials level, the performance of thermoelectric (TE) devices can be defined by the thermoelectric figure of merit (zT). This, however, does not provide a complete picture due to the complex interplay between electronic and thermal transport properties and the uncertain thermal impedance matching between external and internal thermal resistances in different realistic thermal circumstances. Appropriate design of individual material properties and geometry parameters considering the realistic thermal circumstance can greatly enhance the device-level performance of TE devices. In this work, we develop a framework to clarify such interactions in thermoelectric coolers (TEC) with a newly proposed q-h characteristic curve, which can be used to identify how a TEC design is of effectiveness for a specific realistic thermal circumstance. The effects of zT, the individual TE material properties (i.e., thermal conductivity k, electrical conductivity σ and Seebeck coefficient S) as well as the geometry parameters (i.e., pillar height and filling factor) on the q-h characteristic curve are theoretically and experimentally investigated, respectively. TEC modules with higher zT, short pillars and high filling factor show stronger capability to handle high heat flux load, especially for the cases with high heat dissipation coefficient at hot side. The thermal property (k) and electrical properties (σ and S) are responsible for the low heat flux load (e.g., wearable TEC) and high heat flux load (e.g., on-chip TEC cooling), respectively. For wearable TEC, increasing the internal thermal resistance can prevent the back flow heat, which can be achieved with tall pillars, low filling factor and optimizing zT towards lowering thermal conductivity k. For on-chip TEC cooling, reducing the Joule heating and increasing the thermoelectric effect become dominant factors in lowering the code-side temperature of TEC modules. This can be achieved with short pillars, high filling factor and optimizing zT towards increasing the power factor S2σ. This work provides significant insights into the complex interplay between material-level properties, device-level parameters and the external thermal circumstance in determining the performance of TEC devices. The results enable researchers to design optimal TEC devices for realistic applications with different boundary conditions.

Triaxial strain enhanced thermoelectric performance and conversion efficiency in Tl3TaSe4

Thermoelectric (TE) materials have garnered significant attention due to their potential in converting waste heat into useful electrical energy. Strain engineering has emerged as a promising strategy for tailoring the properties of materials, offering opportunities to optimize TE performance. In this study, we employ first-principles calculations to investigate the electronic and thermal transport properties of cubic Tl3TaSe4 under triaxial strain. Our results demonstrate that tensile strain can reduce the effective mass of carriers and contribute to high carrier mobility. The phonon calculation and AIMD simulation reveal excellent dynamic stability and thermal stability of Tl3TaSe4 both with and without strain. The red shift phenomenon of phonon vibration modes and the higher portion of phonon DOS in the low frequency region indicate that tensile strain enhances the anharmonicity of Tl3TaSe4. In addition, triaxial tensile strain can effectively reduce the heat capacity, group velocity, and phonon lifetime, while enhancing the anharmonicity of Tl3TaSe4, which contributes to the lower κl. Compared to the condition without strain, the room temperature κl of Tl3TaSe4 under 1 % and 2 % tensile strain is reduced by about 43 % and 79 %, respectively. Furthermore, the tensile strain exhibits a positive enhancement effect on the ZT value of Tl3TaSe4. At 700 K, the optimal ZT values of p-type and n-type Tl3TaSe4 under 2 % tensile strain are 1.31 and 0.94, respectively, which are three times higher than that of 0.4 and 0.33 without strain. Finally, the TE conversion efficiency of Tl3TaSe4 under 2 % tensile strain is 6.8 %, which is higher than BiCuSeO and α-Cu2+xSe, and comparable to SnSe. Our results demonstrate the effectiveness of triaxial tensile strain in enhancing the phonon scattering, reducing the κl, and improving the TE properties of Tl3TaSe4.

Carbon nanotube fibers as efficient p- and n-type thermoelements within geopolymers: A route for large-scale thermal energy harvesting from building structures

This study reports for the first time, the thermoelectric (TE) performance of continuous p- and n-type carbon nanotube fiber (CNTF) filaments integrated within a sustainable, fine-grained geopolymer (GP) based concrete matrix for the complete replacement of cement with supplementary cementitious materials towards CO2 emissions reduction policy. Moreover, CNTF as CO2 negative, conductive, durable and lightweight material could multidimensionally contribute on the achievement of sustainability goals. Herein, pristine CNTF filaments were molecularly modified with p- and n-type aqueous-based dopants in order to stably tune their intrinsic semi-conducting properties via a facile and scalable dip-coating process. The achieved Seebeck coefficient values of the optimized p- and n-type CNTF were +45.2 μV/K and −38.4 μV/K, respectively. Thereafter, the p- and n-type CNTF filaments were employed as pillar-like thermoelectric elements incorporated within a GP mixture for the assembly of a structural thermoelectric generator (TEG) device. The obtained TEG-enabled GP-based concrete demonstrator comprising of 8 p-n serially interconnected junctions is capable of generating a power output of 0.3 μW at an applied through-thickness temperature gradient (ΔT) of 50 Κ. Subsequently, the experimental work was validated using coupled field of TE simulations. Self-powered infrastructures are forecasted to efficiently benefit from available ΔT on large-scale upon their operational lifetime, further promoting future net-zero energy consumption concepts.

Electron tunneling induced thermoelectric effects

Electron tunneling induced thermoelectric effects

Efficient low-grade heat harvesting with flexible paper-based thermoelectric generators fabricated by facile process

The study presents the fabrication and characterization of paper-based thermoelectric generators (PTGs) using p-type Bi0.5Sb1.5Te3 (BST) and n-type Bi2Te2.7Se0.3 (BTS) thermoelectric (TE) materials, deposited via a novel cotton swab powder deposition technique. This method eliminates the need for complex equipment or high-temperature processes, reducing fabrication complexity and enabling large-scale production. The key advancements of this method are its simplicity, cost-effectiveness, and practical applicability, ensuring uniform coating and good material adherence to the paper substrate. The PTGs, consisting of five p-n pairs interconnected with various materials, were laminated for enhanced stability and humidity protection. Experimental measurements under temperature gradients(ΔTs) of 5–30 °C revealed an optimal configuration achieving an open-circuit voltage(Voc) of 42.60 mV, internal resistance(Rint) of 42.50kΩ, short-circuit current(Isc) of 1.00µA, and maximum power output(Pmax) of 10.65nW for the carbon paste/copper sheet interconnected PTG at ΔT of 30 °C. The obtained normalized power density is 5.68nWcm-2K-1pair-1, which is one of the best among the reported Bi2Te3-based PTGs. A preliminary demonstration on an arm showed the PTG generating an 11.95 mV output voltage in hot weather conditions (ΔT ≈ 8 °C), effectively harnessing body heat for wearable electronics. This work highlights a simple, cost-effective, and scalable method for fabricating PTGs for sustainable energy harvesting in low-power wearable applications. Future efforts will focus on optimizing materials, fabrication techniques, and novel designs to enhance efficiency and scalability.

Enhancement of thermoelectric properties of p-type bismuth telluride bulk composites with Ag-TiO2 nano particles via spray coating and hot deformation process

We aimed to enhance p-type Bi0.4Sb1.6Te3.4 (BST) composite's thermoelectric (TE) properties by minimizing thermal conductivity through hierarchical phonon scattering via nano Ag-coated TiO2 (Ag/TiO2). Hot deformation (HD) was employed to induce multi-scale microstructures in these high-performance p-type TE materials, affecting electrical and thermal transport properties through improved textures and donor-like effects. Our optimization strategy included creating grain boundaries, multiple phonons scattering centers, and introducing high-density lattice defects, significantly reducing lattice thermal conductivity. The combined effects led to a noticeable improvement in the figure of merit (zT) across the temperature range, with all TE parameters measured along the in-plane direction. In the case of the hot-deformed Bi0.4Sb1.6Te3.4 alloy, the maximum zT reached 1.31 at 350 K, while the average zT (zTavg) was 1.17 in the range of 300–400 K, suggesting promising potential for near room temperature TE power generation and solid-state cooling.

Field-Effect Thermoelectric Hotspot in Monolayer Graphene Transistor.

Graphene is a promising candidate for the thermal management of downscaled microelectronic devices owing to its exceptional electrical and thermal properties. Nevertheless, a comprehensive understanding of the intricate electrical and thermal interconversions at a nanoscale, particularly in field-effect transistors with prevalent gate operations, remains elusive. In this study, nanothermometric imaging is used to examine a current-carrying monolayer graphene channel sandwiched between hexagonal boron nitride dielectrics. It is revealed for the first time that beyond the expected Joule heating, the thermoelectric Peltier effect actively plays a significant role in generating hotspots beneath the gated region. With gate-controlled charge redistribution and a shift in the Dirac point position, an unprecedented systematic evolution of thermoelectric hotspots, underscoring their remarkable tenability is demonstrated. This study reveals the field-effect Peltier contribution in a single graphene-material channel of transistors, offering valuable insights into field-effect thermoelectrics and future on-chip energy management.

Citric Acid and Polyvinyl Alcohol Induced PEDOT: PSS with Enhanced Electrical Conductivity and Stretchability for Eco-Friendly, Self-Healable, Wearable Organic Thermoelectrics.

Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is a promising material for organic thermoelectric (TE) applications. However, it is challenging to achieve PEDOT: PSS composites with stretchable, self-healable, and high TE performance. Furthermore, some existing self-healing TE materials employ toxic reagents, posing risks to human health and the environment. In this study, a novel intrinsically self-healable and wearable composite is developed by incorporating environmentally friendly, highly biocompatible, and biodegradable materials of polyvinyl alcohol (PVA) and citric acid (CA) into PEDOT: PSS. This results in the formation of double hydrogen bonding networks among CA, PVA, and PEDOT: PSS, inducing microstructure alignment and leading to simultaneous enhancements in both TE performance and stretchability. The resulting composites exhibit a high electrical conductivity and power factor of 259.3 ± 11.7 S·cm-1, 6.9 ± 0.4 µW·m-1·K-2, along with a tensile strain up to 68%. Furthermore, the composites display impressive self-healing ability, with 84% recovery in electrical conductivity and an 85% recovery in tensile strain. Additionally, the temperature and strain sensors based on the PEDOT: PSS/PVA/CA are prepared, which exhibit high resolution suitable for human-machine interaction and wearable devices. This work provides a reliable and robust solution for the development of environmentally friendly, self-healing and wearable TE thermoelectrics.

Strain-Temperature Dual Sensor Based on Deep Learning Strategy for Human-Computer Interaction Systems.

Thermoelectric (TE) hydrogels, mimicking human skin, possessing temperature and strain sensing capabilities, are well-suited for human-machine interaction interfaces and wearable devices. In this study, a TE hydrogel with high toughness and temperature responsiveness was created using the Hofmeister effect and TE current effect, achieved through the cross-linking of PVA/PAA/carboxymethyl cellulose triple networks. The Hofmeister effect, facilitated by Na+ and SO42- ions coordination, notably increased the hydrogel's tensile strength (800 kPa). Introduction of Fe2+/Fe3+ as redox pairs conferred a high Seebeck coefficient (2.3 mV K-1), thereby enhancing temperature responsiveness. Using this dual-responsive sensor, successful demonstration of a feedback mechanism combining deep learning with a robotic hand was accomplished (with a recognition accuracy of 95.30%), alongside temperature warnings at various levels. It is expected to replace manual work through the control of the manipulator in some high-temperature and high-risk scenarios, thereby improving the safety factor, underscoring the vast potential of TE hydrogel sensors in motion monitoring and human-machine interaction applications.

Oxygen-defect bismuth oxychloride nanosheets for ultrasonic cavitation effect enhanced sonodynamic and second near-infrared photo-induced therapy of breast cancer

Sonodynamic therapy (SDT) relies heavily on the presence of oxygen to induce cell death. Its effectiveness is thus diminished in the hypoxic regions of tumor tissue. To address this issue, the exploration of ultrasound-based synergistic treatment modalities has become a significant research focus. Here, we report an ultrasonic cavitation effect enhanced sonodynamic and 1208 nm photo-induced cancer treatment strategy based on thermoelectric/piezoelectric oxygen-defect bismuth oxychloride nanosheets (BNs) to realize the high-performance eradication of tumors. Upon ultrasonic irradiation, the local high temperature and high pressure generated by the ultrasonic cavitation effect combined with the thermoelectric and piezoelectric effects of BNs create a built-in electric field. This facilitates the separation of carriers, increasing their mobility and extending their lifetimes, thereby greatly improving the effectiveness of SDT and NIR-Ⅱ phototherapy on hypoxia. The Tween-20 modified BNs (TBNs) demonstrate ∼88.6 % elimination rate against deep-seated tumor cells under hypoxic conditions. In vivo experiments confirm the excellent antitumor efficacy of TBNs, achieving complete tumor elimination within 10 days with no recurrences. Furthermore, due to the high X-ray attenuation of Bi and excellent NIR-Ⅱ absorption, TBNs enable precise cancer diagnosis through photoacoustic (PA) imaging and computed tomography (CT).

Enhancing thermoelectric effect with BaTiO3-doped ZrO2 tapes and ferromagnetic nanostructures

The Anomalous Nernst Effect (ANE) emerges as a promising candidate for converting heat into electricity through magnetic nanostructures. However, the substrate plays a central role in optimizing this phenomenon for future technological applications. Tapes of ZrO2 and BaTiO3-doped ZrO2, manufactured by tape casting, possess characteristic flexibility in the green state, which makes them suitable for use as coverings on virtually any curved surface. Moreover, BaTiO3 ceramic materials present piezoelectric properties, which, when combined with thermoelectric properties, can generate interesting heterostructures with simultaneous thermal and vibrational power conversion capabilities. This study explores the combination of tape casting and magnetron sputtering to improve the functionalization of ceramic tapes with ferromagnetic nanostructures. Specifically, it investigates the quasi-static and thermoelectric properties of heterostructures created by depositing NiFe thin films onto sintered ZrO2 and BaTiO3-doped ZrO2 tapes using magnetron sputtering. The results indicate a 71 % increase in the effective thermoelectric coefficient as the amount of BaTiO3 in the ceramic substrate increases. These findings suggest a new approach to integrating these techniques for the production of multifunctional materials for thermoelectric energy conversion.