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Abstract Thermoelectric materials are highly promising for waste heat harvesting. Although thermoelectric materials research has expanded over the years, bismuth telluride‐based alloys are still the best for near‐room‐temperature applications. In this work, a ≈38% enhancement of the average ZT (300−473 K) to 1.21 is achieved by mixing Bi0.4Sb1.6Te3 with an emerging thermoelectric material Sb2Si2Te6, which is significantly higher than that of most BiySb2−yTe3‐based composites. This enhancement is facilitated by the unique interface region between the Bi0.4Sb1.6Te3 matrix and Sb2Si2Te6‐based precipitates with an orderly atomic arrangement, which promotes the transport of charge carriers with minimal scattering, overcoming a common factor that is limiting ZT enhancement in such composites. At the same time, high‐density dislocations in the same region can effectively scatter the phonons, decoupling the electron‐phonon transport. This results in a ≈56% enhancement of the thermoelectric quality factor at 373 K, from 0.41 for the pristine sample to 0.64 for the composite sample. A single‐leg device is fabricated with a high efficiency of 5.4% at ΔT = 164 K further demonstrating the efficacy of the Sb2Si2Te6 compositing strategy and the importance of the precipitate‐matrix interface microstructure in improving the performance of materials for relatively low‐temperature applications.

Despite best efforts in air purification, airborne infectious diseases will continue to spread due to the continuous emission of bioaerosols by the host/infected person. Hence, a shift in focus from air purification to bioaerosol inactivation is urgently needed. To explore the potential of the cold plasma technology for preventing rapid spread of airborne infectious diseases, we studied a cold plasma ionizer (CPI) device and an electrostatic precipitator (ESP)-coupled CPI (CPI-ESP) device for the inactivation and cleaning of surface-spread microorganisms and bioaerosols, using porcine respiratory coronavirus (PRCV), Escherichia coli (E. coli), and aerosolized E. coli as representatives. We firstly demonstrated that CPI coupled with ESP is an effective technology for inactivating virus and bacteria spread on surfaces in an in-house test chamber. We then demonstrated the efficacy of CPI-coupled ESP for the inactivation of aerosolized E. coli in the same chamber. Furthermore, we have demonstrated the efficiency of a CPI-ESP coupled device for the inactivation of naturally occurring airborne microbials in a few indoor settings (i.e., a living room, a discussion room, a schoolroom, and an office) to determine the treatment duration- and human activity-dependent efficacy. To understand the disinfection mechanism, we conducted a fluorescence microscopy study to reveal different degrees of E. coli bacteria cell membrane damage under CPI treatment.

Decades of studies on thermoelectric materials have enabled the design of high‐performance materials based on basic materials properties, such as bandgap engineering. In general, bandgap energies correspond to the temperature at which the peak thermoelectric performance occurs. For instance, CuGaTe2 with a relatively wide bandgap of 1.2 eV has its peak zT > 1 at > 900 K. On the other hand, the zT is usually very low (

Abstract Due to global aging problems, the rising number of patients suffering from chronic or hard‐to‐heal acute wounds imposes a significant burden on healthcare systems. Wound healing is a complicated and dynamic physiological process with distinct molecular and cellular levels at each phase. Despite numerous strategies and advanced wound dressings being developed, successful wound management through smart dressing materials that can adapt to changing wound microenvironments and address the needs of wounds at different stages remains a big challenge. Over the last decade, hydrogel‐based dressings have emerged as one of the most potent biomaterials for wound treatment with favorable biological characteristics and a high potential for active intervention during the wound‐curing process. In the current contribution, we present the most recent progress in smart hydrogel dressings that can regulate the release of therapeutics in response to external stimuli (such as light) as well as endogenous changes in wound environments (e.g., temperature, pH, glucose, and reactive oxygen species) to facilitate wound healing. We also introduce the cutting‐edge technologies of intelligent “sense‐and‐treat” dressings through a combination of built‐in sensors or sensing molecules with responsive hydrogels, which enable real‐time monitoring of wound conditions and prompt on‐demand therapy.

Lillianite materials usually have low thermoelectric efficiency due to the inherently inferior electrical properties. Here, the authors evaluate thermoelectric performances in Pb7Bi4Se13 based lillianites enabled by convergence of nested conduction bands.

Abstract The recent advancements in thermoelectric materials are largely credited to two factors, namely established physical theories and advanced materials engineering methods. The developments in the physical theories have come a long way from the “phonon glass electron crystal” paradigm to the more recent band convergence and nanostructuring, which consequently results in drastic improvement in the thermoelectric figure of merit value. On the other hand, the progresses in materials fabrication methods and processing technologies have enabled the discovery of new physical mechanisms, hence further facilitating the emergence of high-performance thermoelectric materials. In recent years, many comprehensive review articles are focused on various aspects of thermoelectrics ranging from thermoelectric materials, physical mechanisms and materials process techniques in particular with emphasis on solid state reactions. While bottom-up approaches to obtain thermoelectric materials have widely been employed in thermoelectrics, comprehensive reviews on summarizing such methods are still rare. In this review, we will outline a variety of bottom-up strategies for preparing high-performance thermoelectric materials. In addition, state-of-art, challenges and future opportunities in this domain will be commented.

Abstract Transition metal dichalcogenides (TMDs) possess intrinsic spin–orbit interaction (SOI) with high potential to be exploited for various quantum phenomena. SOI allows the manipulation of spin degree of freedom by controlling the carrier's orbital motion via mechanical strain. Here, strain modulated spin dynamics in bilayer MoS2 field‐effect transistors (FETs) fabricated on crested substrates are demonstrated. Weak antilocalization (WAL) is observed at moderate carrier concentrations, indicating additional spin relaxation path caused by strain fields arising from substrate crests. The spin lifetime is found to be inversely proportional to the momentum relaxation time, which follows the Dyakonov–Perel spin relaxation mechanism. Moreover, the spin–orbit splitting is obtained as 37.5 ± 1.4 meV, an order of magnitude larger than the theoretical prediction for monolayer MoS2, suggesting the strain enhanced spin‐lattice coupling. The work demonstrates strain engineering as a promising approach to manipulate spin degree of freedom toward new functional quantum devices.

Phase Change Materials (PCM) are efficient materials for thermal management and energy storage due to its high latent heat and recyclability. Many strategies have been employed to form stabilize PCMs through their phase transition; however these materials are almost invariably rigid. Herein a novel flexible form-stable PCM composite was successfully prepared by physical mixing and low temperature curing. They were well characterized in terms of various techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), mechanical and leakage test, etc. A leakage test showed that the composite with 50% octadecane loading was form-stable with only 2.44% leakage. From the differential scanning calorimetry (DSC) results, the octadecane/silicone (Oct/Si) composite was found to possess a latent heat of 103.8 J/g, and an upshift in phase transition temperature was also observed from octadecane's melting point of 30.3 °C to between 34.4 and 37.8 °C, probably due to thermal insulation or microencapsulation by the silicone matrix. Thermogravimetric analysis (TGA) data supported its good thermal stability within this temperature range and mechanical testing of the composites further confirmed its flexibility and durability as evidenced by the Young's Modulus at 388.92 kPa and elongation at 341.42%, making Oct/Si composites useful for application in areas of temperature regulation, cooling, energy harvesting and wearable devices.

Abstract Transparent and flexible thermoelectrics has been highly sought after for future wearable devices. However, the main stumbling block to prevent its widespread adoption is the lack of p-type transparent thermoelectrics and the stringent criteria of electrical and thermal properties matching appropriately between p-legs and n-legs. This work demonstrates the fabrication of p-type PEDOT:PSS films whose optical properties, electrical conductivity, thermal conductivity, and Seebeck coefficient were engineered to perfectly match the n-type indium tin oxide (ITO) counterparts. The dense p-type PEDOT:PSS and n-type ITO thin films show a thermoelectric figure of merit of zT = 0.30 and 0.29 at 450 K, and a thermal conductivity of 0.22 and 0.32 W m−1 K−1, respectively. A flexible thermoelectric generator (TEG) module with a high transmittance of >81% in the visible wavelength range of 400–800 nm is fabricated using 10 pairs of p-type PEDOT:PSS and n-type ITO thin film legs. An ultra-high power density of 22.2 W m−2 at a temperature gradient of 80 K was observed, which is the highest power density reported for organic/hybrid-based flexible TEGs so far. Our transparent flexible thin-film p–n junction thermoelectric module with exceptionally high power generation may take a tremendous step forward towards multi-functional wearable devices.

SARS-CoV-2 presence in wastewater has been reported in several studies and has received widespread attention among the Wastewater-based epidemiology (WBE) community. Such studies can potentially be used as a proxy for early warning of potential COVID-19 outbreak, or as a mitigation measure for potential virus transmission via contaminated water. In this review, we summarized the latest understanding on the detection, concentration, and evaluation of SARS-CoV-2 in wastewater. Importantly, we discuss factors affecting the quality of wastewater surveillance ranging from temperature, pH, starting concentration, as well as the presence of chemical pollutants. These factors greatly affect the reliability and comparability of studies reported by various communities across the world. Overall, this review provides a broadly encompassing guidance for epidemiological study using wastewater surveillance.

The key to designing a half-Heusler begins from the understanding of atomic interactions within the compound. However, this pool of knowledge in half-Heusler compounds is briefly segregated in many papers for specific explanations. The nature of the chemical bonding has been systematically explored for the large transition-metal branch of the half-Heusler family using density-of-states, charge-density, charge transfer, electron-localization-function, and crystal-orbital-Hamilton-population plots. This review aims to simplify the study of a conventional 18-electron configuration half-Heusler by applying rules proposed by renowned scientists to explain concepts such as Zintl-Klemm, hybridization, and valence electron content (VEC). Atomic and molecular orbital diagrams illustrate the electron orbital transitions and provide clarity to the semiconducting behavior (VEC = 18) of half-Heusler. Eighteen-electron half-Heusler usually exhibits good thermoelectric properties owing to favorable electronic structures such as narrow bandgap (

Thermoelectrics convert heat to electricity and vice versa. They are of technological importance in cooling and energy harvesting. Their performances are defined by figure of merit, zT. Decades of studies have largely focused on the development of novel and advanced materials reaching higher performance in devices. To date, the lack of sufficiently high-performance thermoelectrics, especially among Earth-abundant and lightweight materials, is one of the reasons why there is no broad commercial application of thermoelectric devices yet. This challenge is due to the complex correlations of parameters that make up the zT. Theoretical estimation can reveal the optimal charge carrier concentration, which can provide a good idea of doping compositions. Depending on the material characteristics, decoupling these intercorrelated parameters could be viable. Broadly speaking, increasing carrier mobility, inducing a large fluctuation in density of states (DOS) at the Fermi level, and lowering the lattice thermal conductivity lead to better thermoelectric performance. In this mini review, we provide a broad picture of electronic property optimization for thermoelectric materials. This work will be a useful guide to quickly take readers to the forefront of thermoelectric research.

Scanning of a high-power laser beam on the surface of martensitic stainless steel (SS420) has been studied, addressing the effect of scanning rate V on integrity modifications in the near-surface regions. Structural, compositional, and crystallographic characterizations revealed the presence of ablations, surface melting/resolidification, surface oxidations, and austenite ( γ -phase) precipitations when V ≤ 20 mm s ^−1 . Melt pool (MP), heat affected zone (HAZ), and base material have been clearly distinguished at the cross-section of the slow-scanned samples. Adjacent MPs partially overlapped when V = 5 mm s ^−1 . The γ -phase precipitations solely occurred in the MPs, i.e., of ∼ 400 μ m deep for V = 5 mm s ^−1 , while oxidations dominantly occurred in the surface regions of shallower than ∼30 μ m within the MPs. Compositional analysis revealed increased Cr-, Mn-, and Si-to-Fe ratios at the laser-scanned surface but without variations along the surface normal direction. The enhanced surface hardness has been achieved up to 805 HV, and the hardness monotonically decreased when moving deeper (i.e., ∼1000 μ m) into the base material. These observations shed new light on surface engineering of metallic alloys via laser-based direct energy treatments.

Biomaterials is an interdisciplinary field of research to achieve desired biological responses from new materials, regardless of material type. There have been many exciting innovations in this discipline, but commercialization suffers from a lengthy discovery to product pipeline, with many failures along the way. Success can be greatly accelerated by harnessing machine learning techniques to comb through large amounts of data. There are many potential benefits of moving from an unstructured empirical approach to a development strategy that is entrenched in data. Here, we discuss the recent work on the use of machine learning in the discovery and design of biomaterials, including new polymeric, metallic, ceramics, and nanomaterials, and how machine learning can interface with emerging use cases of 3D printing. We discuss the steps for closer integration of machine learning to make this exciting possibility a reality.

Small-sized droplets/aerosol transmission is one of the factors responsible for the spread of COVID-19, in addition to large droplets and surface contamination (fomites). While large droplets and surface contamination can be relatively easier to deal with (i.e., using mask and proper hygiene measures), aerosol presents a different challenge due to their ability to remain airborne for a long time. This calls for mitigation solutions that can rapidly eliminate the airborne aerosol. Pre-COVID-19, air ionizers have been touted as effective tools to eliminate small particulates. In this work, we sought to evaluate the efficacy of a novel plant-based ionizer in eliminating aerosol. It was found that factors such as the ion concentration, humidity, and ventilation can drastically affect the efficacy of aerosol removal. The aerosol removal rate was quantified in terms of ACH (air changes per hour) and CADR- (clean air delivery rate-) equivalent unit, with ACH as high as 12 and CADR as high as 141 ft3/minute being achieved by a plant-based ionizer in a small isolated room. This work provides an important and timely guidance on the effective deployment of ionizers in minimizing the risk of COVID-19 spread via airborne aerosol, especially in a poorly-ventilated environment.

Thermoelectrics can convert waste heat to electricity and vice versa. The energy conversion efficiency depends on materials figure of merit, zT, and Carnot efficiency. Due to the higher Carnot efficiency at a higher temperature gradient, high-temperature thermoelectrics are attractive for waste heat recycling. Among high-temperature thermoelectrics, silicon-based compounds are attractive due to the confluence of light weight, high abundance, and low cost. Adding to their attractiveness is the generally defect-tolerant nature of thermoelectrics. This makes them a suitable target application for recycled silicon waste from electronic (e-waste) and solar cell waste. In this review, we summarize the usage of high-temperature thermoelectric generators (TEGs) in applications such as commercial aviation and space voyages. Special emphasis is placed on silicon-based compounds, which include some recent works on recycled silicon and their thermoelectric properties. Besides materials design, device designing considerations to further maximize the energy conversion efficiencies are also discussed. The insights derived from this review can be used to guide sustainable recycling of e-waste into thermoelectrics for power harvesting.

Auxetic-like strain states were generated in self-assembled nanocomposite thin films of (Ba0.6Sr0.4TiO3)1−x − (Sm2O3)x(BSTO − SmO). A switch from auxetic-like to elastic-like strain behavior was observed for x > 0.50, when the SmO switched from being nanopillars in the BSTO matrix to being the matrix with BSTO nanopillars embedded in it. A simple model was adopted to explain how in-plane strain varies with x. At high x (0.75), strongly enhanced ferroelectric properties were obtained compared to pure BSTO films. The nanocomposite method represents a powerful new way to tune the properties of a wide range of strongly correlated metal oxides whose properties are very sensitive to strain.