Calorimetry reaches an atomic junction: Electrical and thermal conductivity in metals are linked at the macroscopic length scale because electrons carry both heat and current. Cui et al. found that this relationship, the Wiedemann-Franz law, holds down to the atomic scale in gold and platinum (see the Perspective by Segal). They made thermal and electrical conductance measurements through a point contact only one atom thick. In gold, the thermal and electrical conductance was quantized, owing to the electronic band structure of the metal. The experiments pave the way for high-resolution calorimetry and other thermal measurements at the nanoscale. Science , this issue p. 1192 ; see also p. 1125

As demands for portable electronic devices grow, wireless energy transfer (WET) has started to become readily available. Until now, studies on WET have been mainly based on the electromagnetic (EM) induction method using EM waves. However, it is still challenging to utilize current EM wave mediated WET in those areas where it is most needed: underwater, body-implant, and EM-shielded cases (liquid/metals). Acoustic energy transfer (AET) can be an alternative to EM-wave based WET. Here, we present a simple but powerful triboelectric AET module by tuning the work function of the triboelectric layer via the large polarization of the embedded relaxor single crystal. Additionally, uniform displacement, a quasi-mode oscillation, across the flexible electrode surface in response to the square wave has improved energy transfer efficiency. A systematic investigation was conducted for energy transferring conditions of receiving angle and ferroelectric polarization. We successfully demonstrated the transmission of 8 mW electric power at a distance of 6 cm underwater, which is sufficient to use in most demanding but inaccessible areas. In addition, AET is demonstrated and discussed in both liquids (underwater and in-body), and solids (metal, wood, and plastic). We anticipate that our approach will enable current next-level AET technology to be utilized in the actual field.

Wireless energy transfer (WET) based on ultrasound‐driven generators with enormous beneficial functions, is technologically in progress by the valuation of ultrasonic metamaterials (UMMs) in science and engineering domains. Indeed, novel metamaterial structures can develop the efficiency of mechanical and physical features of ultrasound energy receivers (US‐ETs), including ultrasound‐driven piezoelectric and triboelectric nanogenerators (US‐PENGs and US‐TENGs) for advantageous applications. This review article first summarizes the fundamentals, classification, and design engineering of UMMs after introducing ultrasound energy for WET technology. In addition to addressing using UMMs, the topical progress of innovative UMMs in US‐ETs is conceptually presented. Moreover, the advanced approaches of metamaterials are reported in the categorized applications of US‐PENGs and US‐TENGs. Finally, some current perspectives and encounters of UMMs in US‐ETs are offered. With this objective in mind, this review explores the potential revolution of reliable integrated energy transfer systems through the transformation of metamaterials into ultrasound‐driven active mediums for generators.

Calorimetry has been widely used in metabolic studies, but direct measurements from individual small biological model organisms such as C. elegans or isolated single cells have been limited by poor sensitivity of existing techniques and difficulties in resolving very small heat outputs. Here, by careful thermal engineering, we developed a robust, highly sensitive and bio-compatible calorimetric platform that features a resolution of ~270 pW—more than a 500-fold improvement over the most sensitive calorimeter previously used for measuring the metabolic heat output of C. elegans. Using this calorimeter, we demonstrate time-resolved metabolic measurements of single C. elegans worms from larval to adult stages. Further, we show that the metabolic output is significantly lower in long-lived C. elegans daf-2 mutants. These demonstrations clearly highlight the broad potential of this tool for studying the role of metabolism in disease, development and aging of small model organisms and single cells.

Piezoelectric materials are a class of materials that can generate an electric charge when subjected to mechanical stress, or vice versa. These materials have a wide range of applications, from sensors and actuators to energy-harvesting devices and medical implants. Recently, there has been growing interest in using 3D printing to fabricate piezoelectric materials with complex geometries and tailored properties. Three-dimensional printing allows for the precise control of the material’s composition, microstructure, and shape, which can significantly enhance piezoelectric materials’ performance. Three-dimensional printing has emerged as a promising technique for fabricating piezoelectric materials with tailored properties and complex geometries. The development of high-performance piezoelectric materials using 3D printing could have significant implications for various applications, including sensors, energy harvesting, and medical devices. In this review paper, 3D printing methods for piezoelectric materials, their advantages and disadvantages, representative piezoelectric ceramics, and examples of 3D printing are presented. Furthermore, the applications utilizing these materials are summarized.