Highly Stretchable, Biodegradable, and Recyclable Green Electronic Substrates.

As a steady stream of electronic devices being discarded, a vast amount of electronic substrate waste of petroleum-based nondegradable polymers is generated, raising endless concerns about resource depletion and environmental pollution. With coupled reagent (CR)-grafted artificial marble waste (AMW@CR) as functional fillers, polylactic acid (PLA)-based highly stretchable biodegradable green composite (AMW@CR-SBGC) is prepared, with elongation at break up to more than 250%. The degradation mechanism of AMW@CR-SBGC is deeply revealed. AMW@CR not only contributed to the photodegradation of AMW@CR-SBGC but also significantly promoted the water degradation of AMW@CR-SBGC. More importantly, AMW@CR-SBGC showed great potential as sustainable green electronic substrates and AMW@CR-SBGC-based electronic skin can simulate the perception of human skin to strain signals. The outstanding programmable degradability, recyclability, and reusability of AMW@CR-SBGC enabled its application in transient electronics. As the first demonstration of artificial marble waste in electronic substrates, AMW@CR-SBGC killed three birds with one stone in terms of waste resourcing, e-waste reduction, and saving nonrenewable petroleum resources, opening up vast new opportunities for green electronics applications in areas such as health monitoring, artificial intelligence, and security.

Synthesis and Characterization of Superhydrophobic Epoxy Resin Coating with SiO2@CuO/HDTMS for Enhanced Self-Cleaning, Photocatalytic, and Corrosion-Resistant Properties.

The exceptional corrosion resistance and combined physical and chemical self-cleaning capabilities of superhydrophobic photocatalytic coatings have sparked significant interest among researchers. In this paper, we propose an economical and eco-friendly superhydrophobic epoxy resin coating that incorporates SiO2@CuO/HDTMS nanoparticles modified with Hexadecyltrimethoxysilane (HDTMS). The application of superhydrophobic coatings effectively reduces the contact area between the metal surface and corrosive media, leading to a decreased corrosion rate. Additionally, the incorporation of nanomaterials, exemplified by SiO2@CuO core-shell nanoparticles, improves the adhesion and durability of the coatings on aluminum alloy substrates. Experimental data from Tafel curve analysis and electrochemical impedance spectroscopy (EIS) confirm the superior corrosion resistance of the superhydrophobic modified aluminum alloy surface compared to untreated surfaces. Estimations indicate a significant reduction in corrosion rate after superhydrophobic treatment. Furthermore, an optical absorption spectra analysis of the core-shell nanoparticles demonstrates their suitability for photocatalytic applications, showcasing their potential contribution to enhancing the overall performance of the coated surfaces. This research underscores the promising approach of combining superhydrophobic properties with photocatalytic capabilities to develop advanced surface modification techniques for enhanced corrosion resistance and functional properties in diverse industrial settings.

Wearable Thermoelectric Cooler Based on a Two-Layer Hydrogel/Nickel Foam Heatsink with Two-Axis Flexibility.

A wearable thermoelectric cooler (w-TEC) shows promising prospects in personal thermal management due to its zero emission, high efficiency, lightweight, and long-term stability. The flexible heatsinks are able to promote the cooling effect of coolers, but the cooling capacity of current coolers still has much room for improvement because of the relatively large thermal resistance between the cooler and heatsink. In this work, the two-layer heatsink units composed of hydrogel and nickel foam are fabricated and attached to a thermoelectric cooler via the thermal silica gel. Thanks to the high thermal conductivity of nickel foam and a tight bond between the hydrogel and nickel foam, effective heat conduction from the cooler to the body of the heatsink was achieved. In addition, the discrete heatsink units endow the w-TEC with excellent flexibility. The bending radius of this w-TEC is as small as 7.5 mm, and a long-term temperature reduction of ∼10 °C can be realized at an input current of 0.3 A for a flat or bent w-TEC. In the on-body testing, a stable temperature reduction of 7 °C can be obtained using an AA battery with an input voltage of 1.5 V.

Simultaneous Realization of Flexibility and Ultrahigh Normalized Power Density in a Heatsink-Free Thermoelectric Generator via Fine Thermal Regulation.

Wearable thermoelectric generators (w-TEGs) can incessantly convert body heat into electricity to power electronics. However, the low efficiency of thermoelectric materials, tiny terminal temperature difference, rigidity, and negligence of lateral heat transfer preclude broad utilization of w-TEGs. In this work, we employ finite element simulation to find the key factors for simultaneous realization of flexibility and ultrahigh normalized power density. Using melamine foam with an ultralow thermal conductivity (0.03 W/m K) as the encapsulation material, a novel lightweight π-type w-TEG with no heatsink and excellent stretchability, comfortability, processability, and cost efficiency has been fabricated. At an ambient temperature of 24 °C, the maximum power density of the w-TEG reached 7 µW/cm2 (sitting) and 29 µW/cm2 (walking). Under suitable heat exchange conditions (heatsink with 1 m/s air velocity), 32 pairs of w-TEGs can generate 66 mV voltage and 60 µW/cm2 power density. The output performance of our TEG is remarkably superior to that of previously reported w-TEGs. Besides, the practicality of our w-TEG was showcased by successfully driving a quartz watch at room temperature.

Enhanced Performance of Monolithic Chalcogenide Thermoelectric Modules for Energy Harvesting via Co-optimization of Experiment and Simulation.

With the development of application of wireless sensor nodes (WSNs), the need for energy harvesting is rapidly increasing. In this study, we designed and fabricated a robust monolithic thermoelectric generator (TEG) using a simple, low-energy, and low-cost device fabrication process. Our monolithic device consists of Ag2S0.2Se0.8 and Bi0.5Sb1.5Te3 as n-type and p-type legs, respectively, while the empty space between the legs was filled with highly dense, flexible, and thin Ag2S that serves as both an insulating spacer and a shock absorber, which potentially augments the robustness of preventing from damage from an external mechanical force. From the optimization of the device structure via finite element method (FEM) simulations, a three-pair device with dimensions of 12 mm × 10 mm × 10 mm was found to have a theoretical maximum power density of 8.2 mW cm-2 at a ΔT of 50 K. For considering this inevitable contact resistance, experimental measurement and FEM simulation were combined for quantifying the junction resistance; a power density of 2.1 mW cm-2 was established with the consideration of the contact resistance at the p-n junctions. Using these optimized structural parameters, a device was fabricated and was found to have a maximum power density of 2.02 mW cm-2 at a ΔT of 50 K, which is in good agreement with our simulations. The results from our monolithic TEG show that despite the simple, low-energy, and low-cost device fabrication process, the power generation is still comparable to other reported TEGs. It is worth mentioning that our design could be extended to other chalcogenide materials of appropriate temperature regions and/or better zT. Besides, the quantification of contact resistance also exhibited reference value for the enhancement of thermoelectric conversion application. These results provide a convenient, economic, and efficient strategy for waste energy harvesting close to room temperature, which can broaden the applications of waste heat harvesting.

Thermoelectric Flexible Silver Selenide Films: Compositional and Length Optimization.

Silver selenide is considered as a promising room temperature thermoelectric material due to its excellent performance and high abundance. However, the silver selenide-based flexible film is still behind in thermoelectric performance compared with its bulk counterpart. In this work, the composition of paper-supported silver selenide film was successfully modulated through changing reactant ratio and annealing treatment. In consequence, the power factor value of 2450.9 ± 364.4 µW/(mK2) at 303 K, which is close to that of state-of-the-art bulk Ag2Se has been achieved. Moreover, a thermoelectric device was fabricated after optimizing the length of annealed silver selenide film via numerical simulation. At temperature difference of 25 K, the maximum power density of this device reaches 5.80 W/m2, which is superior to that of previous film thermoelectric devices. Theoretically and experimentally, this work provides an effective way to achieve silver-selenide-based flexible thermoelectric film and device with high performance.