Ultra-low Resistance Research Articles

Novel Pb-Free Superconducting Joint Between NbTi and Nb3Sn Wires Using High-Temperature-Tolerable Superconducting Nb–3Hf Intermedia

There was no other method but to use Pb-alloy solder intermedia to establish superconducting joints between NbTi and Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires beyond 0.5 T. However, Pb is environmentally hazardous. In this context, new alternative joint methods without using these substances were strongly desired in applications such as high-field NMR systems. Recently, we have developed a novel superconducting joint method using high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia that enable us to establish the superconducting joint between NbTi and Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires by a combination of chemical and mechanical bonding processes. In this work, the joint was surely confirmed to have ultra-low resistance by current decay measurements. The yield rate of successful superconducting joint between Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn and HTT Nb-alloy was almost 100% and the scattering of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> value was small. Meanwhile, the joint between NbTi and HTT Nb-alloy showed large scattering of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . We observed NbTi filament cracks in mechanically-pressed joints between NbTi and HTT Nb-alloy, using a high resolution X-ray CT device with micro X-ray source. The filament cracking could account for the large scattering of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> in the joints.

Evaporation of Leidenfrost droplet on thin soluble liquid bath with thermal non-equilibrium effect

Leidenfrost droplet evaporation on a liquid bath exhibits unique features such as ultra-low resistance to sample transition and low-temperature operation; however, the physical mechanisms responsible for these phenomena are incompletely understood. Droplet size and temperature are two key parameters influencing Leidenfrost droplet evaporation. We report herein the thermal non-equilibrium process of an FC-72 droplet over a thin oil layer. We show that the Leidenfrost droplet radius follows the power law R(t) ∼ (1 − t/τ)n, where τ is the characteristic droplet lifetime and n ranges from 0.63 to 0.91. Based on experimental results and theoretical predictions, the remarkable nonmonotonic variation of droplet temperature departs from the saturation-temperature assumption. For lower oil superheating, a cold (subcooled) droplet can sustain evaporation until it disappears. For higher oil superheating, the droplet goes through both subcooled and superheating stages. This phenomenon is well described by sensible heat absorption and release throughout droplet evaporation. These results are helpful for applications such as drug delivery, wherein a cold droplet can float on a liquid bath, thereby extending the lifetime of the biological sample in a high-temperature environment via a localized, low-temperature system.

Efficient Charge Transfers in Highly Conductive Copper Selenide Quantum Dot-Confined Catalysts for Robust Oxygen Evolution Reaction.

Defective quantum dots (QDs) are the emerging materials for catalysis by virtue of their atomic-scale size, high monodispersity, and ultra-high specific surface area. However, the dispersed nature of QDs fundamentally prohibits the efficient charge transfer in various catalytic processes. Here, we report efficient and robust electrocatalytic oxygen evolution based on defective and highly conductive copper selenide (CuSe) QDs confined in an amorphous carbon matrix with good uniformity (average diameter 4.25 nm) and a high areal density (1.8 × 1012 cm-2). The CuSe QD-confined catalysts with abundant selenide vacancies were prepared by using a pulsed laser deposition system benefitted by high substrate temperature and ultrahigh vacuum growth conditions, as evidenced by electron paramagnetic resonance characterizations. An ultra-low charge transfer resistance (about 7 Ω) determined by electrochemical impedance spectroscopy measurement indicates the efficient charge transfer of CuSe quantum-confined catalysts, which is guaranteed by its high conductivity (with a low resistivity of 2.33 μΩ·m), as revealed by electrical transport measurements. Our work provides a universal design scheme of the dispersed QD-based composite catalysts and demonstrates the CuSe QD-confined catalysts as an efficient and robust electrocatalyst for oxygen evolution reaction.

Improved thermal stability and ultralow resistance drift of pseudo-binary Sb2Se3–Bi2S3 material

Pseudo-binary material Sb2Se3–Bi2S3 is constructed using Sb2Se3 (high thermal stability but high resistance drift) and Bi2S3 (low resistance drift but low thermal stability). Sb2Se3–Bi2S3 possesses the advantages of the two binary compounds and shows good thermal stability and ultralow resistance drift, which are related to the presence of amorphous Sb–Se phases and precipitation of Bi2S3 nanoparticles, respectively. The (Sb2Se3)43.2(Bi2S3)56.8 material has high crystallization temperature (220 °C) and low resistance drift (0.0022). Therefore, Sb2Se3–Bi2S3 could be one of the most promising materials for phase change memory.

Thermoelectric Clothing for Body Heat Harvesting and Personal Cooling: Design and Fabrication of a Textile‐Integrated Flexible and Vertical Device

Textiles offer the ideal platform to develop thermoelectric (TE) clothing for body heat harvesting and personal thermoregulation. Herein, textiles used in everyday clothing are adapted to fabricate a flexible and vertical TE device architecture. Selective laser patterning is used to create cavities for embedding bulk inorganic Bi2Te3legs into a knitted polyester fabric used in next‐to‐skin sportswear. The device thermal design is optimized using fabric layering to accommodate longer legs up to 0.8 mm, and a flexible 3D‐printed heat sink is integrated to maximize heat dissipation to the ambient. Using flexible copper foil to connect the legs with a low‐temperature soldering paste, a stable and ultralow device electrical resistance (&lt;1 Ω) is achieved, which is unprecedented for wearable textile‐based TE devices. The developed prototype demonstrates power generation of up to 3.8 μW using body heat, and it provides a cooling effect of 1 °C for personal thermoregulation. Furthermore, the prototype withstands a tensile strain up to 20%, over 1000 bend cycles (at a 23 mm radius comparable with the curvature of the human wrist), and ten wash cycles, thereby demonstrating viability for TE clothing. Strategies for optimization are also presented to enable further performance enhancements using all textile‐compatible processes.

Electrostatic Polydopamine-Interface-Mediated (e-PIM) filters with tuned surface topography and electrical properties for efficient particle capture and ozone removal

Ambient particulate matter (PM) poses severe environmental health risks to the public globally, and efficient filtration technologies are urgently needed for air ventilation. In this contribution, to overcome the efficiency-resistance trade-off for fibrous filtration, we introduced an electrostatic polydopamine-interface-mediated (e-PIM) filter utilizing a combined effect of particle pre-charging and filter polarizing. After delineating the PM-fiber interactions in electrostatic filtration, we designed a composite fiber structure and fabricated the filters by a two-step dip-coating. The surface topography and electrical potential of the polyester (PET) coarse substrates were regulated by successively coating polydopamine (PDA) layers and manganese oxide clusters. By this means, an 8-mm-thick Mn-P @ P-100 filter possessed improved efficiency of 96.05%, 97.60%, and 99.14% for 0.3–0.5 µm, 0.5–1 µm, and 1–3 µm particles, the ultralow air resistance of 10.4 Pa at a filtration velocity of 0.5 m/s, and steady ozone removal property. Compared with the pristine PET substrates, the efficiency for 0.3–0.5 µm particles expanded 12 times. Compared with the pristine PET substrates, the efficiency for 0.3–0.5 µm particles expanded 12 times. We expect e-PIM filters and the filtration prototype will be potential candidates as effective and low-cost air cleaning devices for a sustainable and healthy environment.

Anomalous bond softening mediated by strain-induced Friedel-like oscillations in a BC2N superlattice

The crystal structure of ${\mathrm{BC}}_{2}\mathrm{N}$ and the origin of its superhardness remain under constant debate, hindering its development. Herein, by evaluating the x-ray diffraction pattern, the thermodynamic stability at normal and high pressures of a series of ${\mathrm{BC}}_{2}\mathrm{N}$ candidates, the (111) $\mathrm{B}{\mathrm{C}}_{2}{\mathrm{N}}_{2\ifmmode\times\else\texttimes\fi{}2}$ superlattice (labeled $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$) is identified as the realistic crystal structure of the experimentally synthesized ${\mathrm{BC}}_{2}\mathrm{N}$. We further reveal that the strain-induced Friedel-like oscillations dominates the preferable slip systems of $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ by drastically weakening the heterogenous bonds across the slip plane and thus leads to its ultralow dislocation slip resistance, which originates from the metallization triggered by the reduction in energy separation between bonding and antibonding interactions of the softened bonds. Our results rule out $\mathrm{R}2u\ensuremath{-}\mathrm{B}{\mathrm{C}}_{2}\mathrm{N}$ as the intrinsic superhard material surpassing $c\text{\ensuremath{-}}\mathrm{BN}$, whereas the experimentally determined extreme hardness can be attributed to the nanocrystalline grains glued by interfacial amorphous carbon which provides a strong barrier for plastic deformation. These findings provide a view of the longstanding issue of the possible structure of experimentally observed ${\mathrm{BC}}_{2}\mathrm{N}$, and establish a mechanism underlying the strain-driven electronic instability of superlattice structures, providing guidance towards rational design of superhard materials.

Scalable-Manufactured Metamaterials for Simultaneous Visible Transmission, Infrared Reflection, and Microwave Absorption.

Scalable manufacturing of metamaterials with multispectral manipulation capabilities remains highly challenging, which was generally circumvented by integrating several single-spectral metamaterials, potentially leading to complex processes, large thicknesses, and limited fabrication size. We experimentally demonstrate a standalone and scalable-manufactured multispectral metamaterial featuring simultaneous visible transmission, infrared reflection, and microwave absorption. The prepared multispectral metamaterial with an area of 255 cm2 exhibits a visible transmittance of 74.5% at wavelengths of 400-700 nm (the highest 80.2% at 510 nm), a thermal emissivity of 0.08 at the infrared (IR) wavelengths of 2.5-20 μm (the lowest 0.03 at 19.5 μm), and a microwave absorptance of 63.4% at frequencies of 8.2-12.4 GHz (the near-perfect 97.4% at 11.5 GHz) on average with a deep-subwavelength thickness of λ/47. The deep-subwavelength multispectral metamaterial consists of a submillimeter-thick polyethylene terephthalate dielectric spacer sandwiched by a patterned ultrathin metal and a metal mesh back-reflector with ultralow sheet resistances. Unlike the conventional optically transparent microwave absorbers made from indium tin oxides, the surface plasmonic modes can be excited within the submillimeter-thick multispectral metamaterial, bringing about the gap plasmon polaritons-induced microwave attenuation, together with the excellent visible transparency and high IR reflection/low IR emissivity. This work may inspire the designs and practical production of standalone multispectral metamaterials and benefit the protection against ubiquitous IR and microwave reconnaissance without impeding visual observation.

High-Tc Superconducting Microwave and Millimeter Devices and Circuits—An Overview

High temperature (high-Tc) superconductors (HTS) have found many applications in the last two decades. To microwave researchers and engineers, the ultra-low surface resistance of the thin-film HTS materials at microwave and millimeter frequencies and the highly non-linear Josephson junctions are of particular interest. The former can be exploited in the design and fabrication of passive microwave components and circuits with superior performance, and the latter can be exploited to create many novel active HTS devices. This paper provides an overview of the state-of-art development of HTS devices and circuits for microwave and mm-wave communication front-end receiver systems. The paper is particularly focused on the latest advancement of HTS Josephson junction based active devices, monolithic microwave integrated circuits (MMIC), and whole receiver systems integrated with cryocoolers.

Experimental study of ultralow flow resistance fractal microchannel heat sinks for electronics cooling

Silicon-based fractal tree-shaped microchannel heat sinks with different bifurcation angles were designed and manufactured. The heat transfer and pressure drop characteristics of the fractal microchannel network were experimentally studied under an inlet Reynolds number of Re0 = 500–1700. The results showed that compared with the traditional linear microchannel heat sink, the fractal microchannel heat sinks could achieve considerable flow drag reduction and heat transfer enhancement. Maintaining the chip temperature below 85 °C, the pressure drop can be reduced by up to 92%, and the heat transfer coefficient can be enhanced by 1.5 times of the fractal microchannel network at the same flow rate. The optimized bifurcation angle of the fractal network was recommended to be 30°. The COP of fractal microchannel heat sinks with a bifurcation angle of 30° can reach 12–13 times that of the linear microchannel.

Cellular scaffolds based on multiwalled carbon nanotubes interpenetrating conductive metal-organic frameworks as efficient eelectrocatalysts in microbial fuel cells

Sluggish kinetics of the cathodic oxygen reduction reaction (ORR) is one of the major challenges hindering the development of microbial fuel cells (MFCs). In this work, a three-dimensional (3D) cellular scaffolds structure is fabricated by in-situ growth of conductive Ni/Co-catecholate bimetal metal-organic frameworks (MOFs) on multiwalled carbon nanotubes (NiCo-CAT/MWCNTs). Such specific structure successfully achieves favorable electronic channels and fast charge-transfer capacity and displays an ultra-low ohmic internal resistance of 7.27 Ω. Meanwhile, NiCo-CAT/MWCNTs exhibit a superior ORR half-wave potential (−0.442V vs. Hg/HgCl2), onset potential (−0.064V vs. Hg/HgCl2) and high limiting current density (8.25 mA cm−2), which exceed that of commercial Pt/C. In the MFC with the NiCo-CAT/MWCNTs cathode, the maximum power density is 130% higher than Pt/C cathode. The outstanding performance of MFC is mainly due to the optimized electronic structure and fully exposure of the Ni, Co synergistic catalytic active sites. In addition, oxygen permeability is greatly improved by electrospun polyvinylidene fluoride (PVDF) air diffusion layer replacing the traditional carbon cloth cathode. This study provides a new perspective for MFCs performance improvement by ORR conductive MOFs catalysts.

Explosive boiling induced fast transportation of Leidenfrost droplet to target location

Leidenfrost droplet possesses ultra-low flow resistance, but it is challenging to obtain large thrust force for fast transportation and regulate the direction of droplet motion. Here, for the first time, we demonstrate a novel mechanism for the control of droplet dynamics by explosive boiling. Our system consists of two surfaces that have different functions: a smooth surface running in the Leidenfrost state for droplet levitation and a skirt ring edge surface (SRES) as an explosive boiling trigger. For droplet-wall collision with SRES, micro/nanoscale roughness not only enhances energy harvesting from the skirt ring to the droplet due to increased radiation heat transfer but also provides nucleation sites to trigger explosive boiling. The symmetry breaking of explosive boiling creates a thrust force that is sufficient to propel the droplet. The suppression of the thrust force relative to the inertia force regulates the droplet trajectory as it passes through a target location. We show orbit lines passing through a focusing spot that is ∼1% of the Leidenfrost surface area around its center with a maximum traveling speed of ∼85 cm/s, which is ∼2 times of that reported in the literature. The scale law analysis explains the droplet size effect on the self-propelling droplet dynamics. Our work is attractive for applications under the conditions of the required traveling speed and direction of the droplet.

Practically Accessible All‐Solid‐State Batteries Enabled by Organosulfide Cathodes and Sulfide Electrolytes

AbstractThe combination of organic electrode materials and sulfide electrolytes is expected to enable the development of all‐solid‐state organic batteries featuring high energy density, safety, and sustainability. Here, thiuram hexasulfide is first reported as a low‐cost and high‐capacity cathode material for solid‐state organic batteries based on sulfide electrolytes. Notably, a capacity of ≈600 mA h g−1 is delivered and the capacity retention is 80.8% after 500 cycles. An electrochemically reversible change of the cathode interface is revealed upon cycling. The full cell displays an oscillating stress change of up to 0.6 MPa during cycling, predominated by the anode side. The energy density is 1140 Wh kg−1 at the material level and 376 Wh kg−1 at the electrode level, which are among the best‐reported organic cathodes to date. A high areal capacity of 10.4 mA h cm−2 is reached with a high mass loading cathode. A dry‐film approach is further explored to manufacture sheet‐type cells. The free‐standing Li6PS5Cl film with a thickness of only 48 µm demonstrates an ultralow areal resistance of 3.9 Ω cm2, which significantly boosts the cell‐level energy density and reduces the cell internal resistance.

Reducing Contact Resistance and Boosting Device Performance of Monolayer MoS2 by In Situ Fe Doping.

2D semiconductors are emerging as plausible candidates for next-generation "More-than-Moore" nanoelectronics to tackle the scaling challenge of transistors. Wafer-scale 2D semiconductors, such as MoS2 and WS2 , have been successfully synthesized recently; nevertheless, the absence of effective doping technology fundamentally results in energy barriers and high contact resistances at the metal-semiconductor interfaces, and thus restrict their practical applications. Herein, a controllable doping strategy in centimeter-sized monolayer MoS2 films is developed to address this critical issue and boost the device performance. The ultralow contact resistance and perfect Ohmic contact with metal electrodes are uncovered in monolayer Fe-doped MoS2 , which deliver excellent device performance featured with ultrahigh electron mobility and outstanding on/off current ratio. Impurity scattering is suppressed significantly thanks to the ultralow electron effective mass and appropriate doping site. Particularly, unidirectionally aligned monolayer Fe-doped MoS2 domains are prepared on 2 in. commercial c-plane sapphire, suggesting the feasibility of synthesizing wafer-scale 2D single-crystal semiconductors with outstanding device performance. This work presents the potential of high-performance monolayer transistors and enables further device downscaling and extension of Moore's law.

An oxygen vacancy-rich ZnO layer on garnet electrolyte enables dendrite-free solid state lithium metal batteries

An oxygen vacancy-rich ZnO (Ov-ZnO) layer is deposited on garnet electrolyte, which not only remove the surfafical Li 2 CO 3 , but also in-situ forms an Li + -conductive Li x ZnO interphase. Li symmetric cells with this Ov-ZnO-coated garnet exhibit an ultralow cell resistance and a record-high critical current density of 1.4 mA cm −2 ever reported without lithium dendrite at room temperature. • A layer of ZnO with oxygen vacancies is coated on the surface of garnet electrolyte. • A low interfacial resistance of 55 Ω cm 2 is achieved without melting lithium. • The reaction mechanism of the interphase on garnet is investigated in detail. • The strategy can be extended to other metal oxides with oxygen vacancies. The huge interfacial resistance caused by Li 2 CO 3 on garnet (LLZO) electrolyte and the lithium-dendrite growth through garnet greatly hinder the development of solid-state batteries (SSBs). Here, both the problems are simultaneously addressed through a general strategy of engineering garnet pellet with a layer of ZnO with oxygen vacancies (O V -ZnO). The O V -ZnO not only protects LLZO from being exposed to wet air, but also reacts spontaneously with lithium-metal to in-situ form an ionic conducting Li x ZnO interphase. The as-formed interphase improves the Li/LLZO contact, reduces the huge interface resistance caused by Li 2 CO 3 , suppresses the lithium-dendrite growth, and promotes the lithium transport between LLZO and Li-metal. As a result, an Li/Li symmetric cell with O V -ZnO coated LLZO pellet shows a low area specific resistance of 55 Ω cm 2 , a stable plating/stripping process for 200 h at a current density of 0.1 mA cm −2 , and a record-high critical current density of 1.4 mA cm −2 ever reported at room temperature. Moreover, this approach of coating metal oxide with oxygen vacancies on garnet electrolytes has been extended to other metal oxides, such as copper oxide (O V -CuO), titanium dioxide (O V -TiO 2 ) and indium oxide (O V -In 2 O 3 ).

A 10-nm-thick silicon oxide based high switching speed conductive bridging random access memory with ultra-low operation voltage and ultra-low LRS resistance

In this paper, a silicon oxide based conductive bridging random access memory (CBRAM) with an ultra-low operation voltage, a high switching speed, and an ultra-low resistance at low resistance state (LRS) is reported. The CBRAM has a sandwich structure with platinum and copper as electrode layers and an ultra-thin 10-nm-thick silicon oxide film as an insulating switching layer. The CBRAMs are fabricated with CMOS compatible materials and processes. DC I–V sweep characterizations show an ultra-low SET/RESET voltage of 0.35 V/−0.05 V, and the RESET voltage is the lowest among all ultra-low voltage CBRAMs. The CBRAM is capable of withstanding endurance tests with over 106 pulses of +0.4 V/−0.1 V with 1 μs pulse width, with the resistance at LRS maintaining at an ultra-low value of only 20 Ω, which is the lowest among all CBRAMs to date, and it is reduced by at least 2.95 times compared with prior studies. Meanwhile, the switching ratio between high resistance state and LRS is more than 1.49 × 104. Moreover, the switching time characterization of the CBRAM demonstrates an ultra-short SET/RESET time of 7/9 ns. The CBRAM has potential applications in high-speed, ultra-low voltage, and ultra-low power electronics.

Tailoring bimodal protein fabrics for enhanced air filtration performance

Natural material-based nanofiber air filters promise to minimize any adverse impacts on the environment after use, but the nanofiber structure causes poor airflow performance, i.e. high airflow resistance. Constructing bimodal structures reduces airflow resistance without compromising removal efficiency but has been rarely studied for natural nanofiber air filters. In this study, we fabricate bimodal protein fabric air filters and carefully tailor their bimodal structure to achieve higher removal efficiency with significantly lowered airflow resistance. The bimodal structures are generated by co-spinning of denatured zein protein in two solvent systems, via controlling the protein denaturation degree and fiber shape/size. The bimodal structures with bimodal diameter distributions are then carefully adjusted by varying the feed rates. It is revealed that a bimodal fabric shows an optimized filtration performance when the fiber diameters locate at 2.44 and 0.13 μm, reducing the airflow resistance by up to 56.47 Pa (from 84.97 Pa to 28.5 Pa) with a high PM2.5 removal efficiency of 98.43%. The bimodal fabric treated with TX-100 shows a further improved filtration performance of filtering PM0.3 of 97.01% and PM2.5 of 99.15% at an ultralow airflow resistance of 21.1 Pa. Moreover, the treated bimodal fabric presents better long-term performance and higher removal efficiency in a humid environment. This work develops a simple and viable method for fabricating and tailoring bimodal air filters made of abundant natural protein for broad applications.

Polyimide as a durable cathode for all-solid-state Li(Na)−organic batteries with boosted cell-level energy density

The integration of organic electrode materials (OEMs) with solid-state electrolytes (SSEs) is expected to build an all-solid-state battery (ASSB) with long-term sustainability, high safety, and high energy density. Despite this great promise, the cell-level energy density is still far from practically applicable, which stems from the ultrathick SSE layer and thin cathode layer used in a pellet-type ASSB design. Here, a cost-effective polyimide (PI) material was first exploited as an organic cathode for sulfide-based ASSBs. A capacity of ~190 mAh g−1 was delivered with almost no capacity decay over 300 cycles. Moreover, for the first time, a dry-film approach was introduced to manufacture a sheet-type Li−organic ASSB with an ultrathin SSE layer and a high-areal-loading PI cathode. Notably, PI is a perfect candidate for dry-film technology due to its high thermal stability and extraordinary chemical inertness toward sulfide SSEs. Remarkably, the free-standing SSE membrane was merely 46 µm thick, and an ultralow areal resistance of 3.3 Ω cm2 was achieved, more than tenfold lower than that of reported SSE pellets. One order of magnitude boost in the cell-level energy density was achieved. This work presents a significant leap in transferring organic ASSB technology from laboratory research to factory manufacturing.

Tough and extremely temperature-tolerance nanocomposite organohydrogels as ultrasensitive wearable sensors for wireless human motion monitoring

MXenes have attracted great attention due to their multifunctional properties and abundant surface terminations. However, it remains a considerable challenge to construct MXene hydrogels with high toughness and long-term sensory performance to withstand harsh environments. Herein, a multifunctional conductive organohydrogel based on 2D MXene nanosheets and ZA fibers were fabricated and then assembled wireless wearable sensors to track human movement. By introducing ternary mixture, the organohydrogels possess ultra-low temperature resistance (−81 °C) and moisture retention. Simultaneously, the interaction of alginate chains induced by Zn ions with PAM endows the organohydrogels with superior mechanics. Amazingly, the hydrogel sensor exhibited the highest pressure sensing performance (Sp1 = 782.7 kPa−1) and harsh-environment tolerance. Importantly, zinc-activated MXene nanosheet endowed the resultant with the favorable antibacterial ability and serves in organohydrogels for potential medical applications. This method provides a facile approach for designing sustainable dual-mode sensors with high toughness, antibacterial performance, all-weather availability, and wireless transmission.

Two-Dimensional Electron Gas with High Mobility Forming at BaO/SrTiO3 Interface

Two-dimensional electron gas (2DEG) with high electron mobility is highly desired to study the emergent properties and to enhance future device performance. Here we report the formation of 2DEG with high mobility at the interface between rock-salt BaO and perovskite SrTiO3. The interface consists of the ionically compensated BaO1 – δ layer and the electronically compensated TiO2 layer, which is demonstrated as a perfect interface without lattice mismatch. The so-formed interface features metallic conductivity with ultralow square resistance of 7.3 × 10−4 Ω/◻ at 2 K and high residual resistance ratios R 300 K/R 2 K up to 4200. The electron mobility reaches 69000 cm2⋅V−1⋅s−1 at 2 K, leading to Shubnikov–de Haas oscillations of resistance. Density functional theory calculations reveal that the effective charge transfers from BaO to the Ti 3dxy orbital occur at the interface, leading to the conducting TiO2 layer. Our work unravels that BaO can adapt itself by removing oxygen to minimize the lattice mismatch and to provide substantial carriers to SrTiO3, which is the key to forming 2DEGs with high mobility at the interfaces.