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Abstract The field of bioelectronics is developing exponentially. There is now a drive to interface electronics with biology for the development of new technologies to improve our understanding of electrical forces in biology. This builds on our recently published work in which we show wireless electrochemistry could be used to grow bioelectronic functional circuitry in 2D cell layers. To date our ability to merge electronics with in situ with biology is 3D limited. In this study, we aimed to further develop the wireless electrochemical approach for the self-assembly of microwires in situ with custom-designed and fabricated 3D cancer spheroids. Unlike traditional electrochemical methods that rely on direct electrical connections to induce currents, our technique utilises bipolar electrodes that operate independently of physical wired connections. These electrodes enable redox reactions through the application of an external electric field. Specifically, feeder electrodes connected to a power supply generate an electric field, while the bipolar electrodes, not physically connected to the feeder electrodes, facilitate the reduction of silver ions from the solution. This process occurs upon applying a voltage across the feeder electrodes, resulting in the formation of self-assembled microwires between the cancer spheroids.Thereby, creating interlinked bioelectronic circuitry with cancer spheroids. We demonstrate that a direct current was needed to stimulate the growth of conductive microwires in the presence of cell spheroids. Microwire growth was successful when using 50 V (0.5 kV/cm) of DC applied to a single spheroid of approximately 800 µm in diameter but could not be achieved with alternating currents. This represents the first proof of the concept of using wireless electrochemistry to grow conductive structures with 3D mammalian cell spheroids.

Polarization‐sensitive solar‐blind ultraviolet (UV) photodetectors are essential in both civilian and military applications. 1D perovskites derivative Rb2CuCl3 holds promise for polarization‐sensitive solar‐blind UV photodetectors due to its wide direct bandgap, anisotropic crystal structure, and long carrier lifetime. However, no studies on the polarization properties of Rb2CuCl3 are reported. Here, the electronic structural anisotropy of Rb2CuCl3 is confirmed by calculating the partial charge density distribution in the ac‐plane and bc‐plane. Then, the Raman‐active modes and corresponding atomic vibration modes are explored within the bc‐plane through joint experimental and theoretical Raman spectroscopy. Besides, angle‐resolved Raman, photoluminescence, and absorption spectroscopy reveal the intriguing anisotropic photoelectric characteristics of Rb2CuCl3 microwires (MWs). By using single Rb2CuCl3 MW as the photoactive layer, a polarization‐sensitive solar‐blind UV photodetector is fabricated, showing high photoresponsivity of 78 mA W−1 and photocurrent anisotropy ratio of ≈1.7 at 265 nm. Importantly, the proposed photodetectors without encapsulation exhibit excellent stability in ambient air, retaining the original photocurrent after two months, showcasing practical applicability. This study underscores the promise of Rb2CuCl3 for high‐performance polarization‐sensitive solar‐blind UV photodetectors, contributing valuable insights into its electronic structure, photoelectric properties, and practical applicability. [ABSTRACT FROM AUTHOR]

The effects of metal/non-metal ratio (M/NM ​= ​ x : 1) on the microstructure and magnetocaloric properties of promising melt-extracted Mn–Fe–P–Si microwires with short heat treatment have been investigated here. More Fe 2 P principal phase, which is considered favorite for magnetocaloric effect (MCE), should achieve at low M/NM ratio and the fraction of Fe 2 P phase increased with the reduction of x. Meanwhile, the (Mn, Fe) 3 Si impurity phase is formed for x ​= ​2.00–1.90 whereas change to (Mn, Fe) 5 Si 3 structure for x ​= ​1.85. It's worth noting that a metal deficiency resulted in the thermal hysteresis (T hys) and the magnetic hysteresis loss (W y) decreased by ∼40 ​%., The magnetic transition temperature (T tran), peak value of isothermal magnetic entropy change (− Δ S iso peak), refrigerant capacity (RC) and effective refrigerant capacity (RCE) first increased then decreased with the decrease of x , and reached the maximums at x ​= ​1.90, i.e., 370 ​K, 26.0 ​J ​kg−1 ​K−1, 367.4 and 339.8 ​J ​kg−1, respectively. Therefore, the customizable microstructure and magnetic properties of the melt-extracted (MnFe) x (P 0.5 Si 0.5) microwires will be achievable effectively by tuning M/NM ratio x , and optimized Mn–Fe–P–Si compounds with novel thermomagnetic properties will be obtained. [Display omitted] • The (MnFe) x (P 0.5 Si 0.5) microwires were fabricated by melt-extracted method. • The high amount of Fe 2 P phase would be obtained by reducing the M/NM. • The ​− ​ Δ S iso peak is −26.0 ​J ​kg−1 ​K−1 (5 ​T) for the wires with x ​= ​1.90. [ABSTRACT FROM AUTHOR]

The field of bioelectronics is developing exponentially. There is now a drive to interface electronics with biology for the development of new technologies to improve our understanding of electrical forces in biology. This builds on our recently published work in which we show wireless electrochemistry could be used to grow bioelectronic functional circuitry in 2D cell layers. To date our ability to merge electronics with in situ with biology is 3D limited. In this study, we aimed to further develop the wireless electrochemical approach for the self-assembly of microwires in situ with custom-designed and fabricated 3D cancer spheroids. Unlike traditional electrochemical methods that rely on direct electrical connections to induce currents, our technique utilises bipolar electrodes that operate independently of physical wired connections. These electrodes enable redox reactions through the application of an external electric field. Specifically, feeder electrodes connected to a power supply generate an electric field, while the bipolar electrodes, not physically connected to the feeder electrodes, facilitate the reduction of silver ions from the solution. This process occurs upon applying a voltage across the feeder electrodes, resulting in the formation of self-assembled microwires between the cancer spheroids.Thereby, creating interlinked bioelectronic circuitry with cancer spheroids. We demonstrate that a direct current was needed to stimulate the growth of conductive microwires in the presence of cell spheroids. Microwire growth was successful when using 50 V (0.5 kV/cm) of DC applied to a single spheroid of approximately 800 µm in diameter but could not be achieved with alternating currents. This represents the first proof of the concept of using wireless electrochemistry to grow conductive structures with 3D mammalian cell spheroids. [ABSTRACT FROM AUTHOR]

This article demonstrates scalable production of liquid metal (LM)-based microwires through the thermal drawing of extrudates. These extrudates were first co-extruded using a eutectic alloy of gallium and indium (EGaIn) as a core element and a thermoplastic elastomer, styrene–ethylene/butylene–styrene (SEBS), as a shell material. By varying the feed speed of the co-extruded materials and the drawing speed of the extrudate, it was possible to control the dimensions of the microwires, such as core diameter and shell thickness. How the extrusion temperature affects the dimensions of the microwire was also analyzed. The smallest microwire (core diameter: 52 ± 14 μm and shell thickness: 46 ± 10 μm) was produced from a drawing speed of 300.1 mm s−1 (the maximum attainable speed of the apparatus used), SEBS extrusion speed of 1.50 mm3 s−1, and LM injection rate of 5 × 105 μL s−1 at 190 °C extrusion temperature. The same extrusion condition without thermal drawing generated significantly large extrudates with a core diameter of 278 ± 26 μm and shell thickness of 430 ± 51 μm. The electrical properties of the microwires were also characterized under different degrees of stretching and wire kinking deformation which proved that these LM-based microwires change electrical resistance as they are deformed and fully self-heal once the load is removed. Finally, the sewability of these microwires was qualitatively tested by using a manual sewing machine to pattern microwires on a traditional cotton fabric. [ABSTRACT FROM AUTHOR]

The concept of solderability is rigorously defined, accompanied by the proposal of quantitative criteria for its assessment. A comprehensive categorization of solderable materials into three distinct groups—namely, easily solderable, moderately solderable, and unsolderable—is proposed based on solderability parameters. Practical recommendations are given for the effective deployment of solderability testing methodologies across a spectrum of materials and electronic components. Detailed expositions are offered on the methods employed in the evaluation of solderability, encompassing solder immersion, measurement of solder spreading area, and assessment of capillary penetration into gaps. Schematic representations of these evaluation techniques, alongside descriptions of the requisite apparatus for their implementation, are presented. Furthermore, tabulated data on the solder spreading factors for diverse categories of chemical and electroplated coatings, including hot tinning, are given. Prolonged storage may lead to the formation of oxide films on the surface of coatings, thereby deteriorating solderability. To enhance the quality of electroplated coatings, it is recommended to employ periodic currents in nonstationary electrolysis modes during the deposition of electroplated coatings. [ABSTRACT FROM AUTHOR]

In this chapter, we comprehensively discuss the primary varieties of solders and fluxes utilized in the fabrication of electrical connections within electronic modules. Particular emphasis is placed on the challenges associated with the use of lead-free soldering materials. A potential resolution to these challenges involves the modification of solder compositions, potentially transitioning towards nanoscale architectures. A promising avenue of exploration lies in the utilization of water-based fluxes and flux gels. Water-based fluxes containing surfactant additives offer notable advantages, particularly in their application via spray mechanisms. They exhibit robust stability and mitigate thermal shock occurrences during soldering operations. Furthermore, we delve into the characteristics of solder pastes employed in the surface mounting of electronic modules, elucidating their application methodologies, operational considerations, and optimal storage practices. Additionally, we provide a comprehensive overview of conductive adhesives utilized in the formation of contact connections. The chapter also examines the primary types of mounting microwires employed in ultrasonic and thermosonic microwelding processes, alongside outlining the role of protective liquids in the cleaning of connections. [ABSTRACT FROM AUTHOR]

Introduction: Many invasive and noninvasive neurotechnologies are being developed to help treat neurological pathologies and disorders. Making a brain implant safe, stable, and efficient in the long run is one of the requirements to conform with neuroethics and overcome limitations for numerous promising neural treatments. A main limitation is low biocompatibility, characterized by the damage implants create in brain tissue and their low adhesion to it. This damage is partly linked to friction over time due to the mechanical mismatch between the soft brain tissue and the more rigid wires.Methods: Here, we performed a short biocompatibility assessment of bio-inspired intra-cortical implants named “Neurosnooper” made of a microelectrode array consisting of a thin, flexible polymer–metal–polymer stack with microwires that mimic axons. Implants were assembled into poly-lactic-glycolic acid (PLGA) biodegradable needles for their intra-cortical implantation.Results and Discussion: The study of glial scars around implants, at 7 days and 2 months post-implantation, revealed a good adhesion between the brain tissue and implant wires and a low glial scar thickness. The lowest corresponds to electrode wires with a section size of 8 μm × 10 μm, compared to implants with the 8 μm × 50 μm electrode wire section size, and a straight shape appears to be better than a zigzag. Therefore, in addition to flexibility, size and shape parameters are important when designing electrode wires for the next generation of clinical intra-cortical implants.

ObjectiveDecoding neural activity has been limited by the lack of tools available to record from large numbers of neurons across multiple cortical regions simultaneously with high temporal fidelity. To this end, we developed the Argo system to record cortical neural activity at high data rates.ApproachHere we demonstrate a massively parallel neural recording system based on platinum-iridium microwire electrode arrays bonded to a CMOS voltage amplifier array. The Argo system is the highest channel count in vivo neural recording system, supporting simultaneous recording from 65 536 channels, sampled at 32 kHz and 12-bit resolution. This system was designed for cortical recordings, compatible with both penetrating and surface microelectrodes.Main resultsWe validated this system through initial bench testing to determine specific gain and noise characteristics of bonded microwires, followed by in-vivo experiments in both rat and sheep cortex. We recorded spiking activity from 791 neurons in rats and surface local field potential activity from over 30 000 channels in sheep.SignificanceThese are the largest channel count microwire-based recordings in both rat and sheep. While currently adapted for head-fixed recording, the microwire-CMOS architecture is well suited for clinical translation. Thus, this demonstration helps pave the way for a future high data rate intracortical implant.

GaN‐based materials are the hottest research topic in UV photodetectors (PDs) because of their low operating voltage, small volume, long lifetime, high‐temperature resistance, and low energy consumption. However, there are still fundamental issues to be overcome, and the most important issue is to get a photoconductive gain. In this paper, the following new approaches are provided to innovatively improve the photoconductive gain of UV PDs in GaN‐based materials. First, the aspect ratio of the 1D GaN microwire (MW) structure is dramatically improved by analyzing the pulse growth mechanism using the metal‐organic vapor deposition system. Second, the comprehensive strain behavior in the MW epitaxial growth system is successfully analyzed. Third, the fabricated metal‐semiconductor‐metal‐based MW UV PD shows photoresponsivity and sensitivity of 28.365 A W−1 and 93.16%, respectively, at the −2 V bias, which significantly outperforms the conventional structures in the UV region. Finally, a trap‐assisted Poole–Frenkel effect‐based energy bandgap mechanism, that allows the defect level formed by lattice mismatch between the substrate and GaN to be used as an electron carrier path, is newly defined. This study will present the direction of future UV PDs by providing a new MW structure based on GaN materials, a third‐generation semiconductor. [ABSTRACT FROM AUTHOR]

Microstructure and mechanical properties of in situ Cu-7.7Nb microcomposite (MC) wires manufactured by cold drawing with intermediate heat treatment (HT) have been studied. The evolution of Nb filaments morphology under various steps of deformation and modes of intermediate HT have been studied by the SEM and TEM methods. According to X-ray analysis, internal microstresses accumulate in the niobium filaments of the drawn MC, leading to a decrease in ductility. After heat treatment, the ductility of the wire increases significantly, since the microstresses in the niobium decrease even at the lowest HT temperature. The strength of the composite decreases under the HT because of negative changes in morphology and interface density of Nb filaments. The <110>Nb texture is stable under the HT up to 800 °C. The Nb filaments morphology and semi-coherent boundaries at Cu/Nb interfaces are restored under the post-HT cold drawing, leading to a sharp increase in the strength of the MC wire. Reducing the niobium concentration to 7.7%Nb relative to the traditional MC with 16–20%Nb and the recovery of the wire ductility under the HT makes it possible to obtain long-scale high-strength microwires with an extremely small diameter of 0.05 mm and high ultimate tensile strength of 1227 MPa. [ABSTRACT FROM AUTHOR]

Recently, lead halide perovskites arouse intensive attentions in photoelectric fields owing to their low trap state density, high carrier mobility, large extinction coefficient, and low‐temperature solution processing technique. However, their future commercial development is severely hampered by the lead toxicity and instability. Although lead‐free metal‐halide perovskites recently have been extensively studied in optoelectronics, their low‐dimensional counterparts can further expand their novel optical and electronic properties for potential applications. In this work, the planar growth of one‐dimensional (1D) CsAg2I3 single‐crystal microwires (MWs) on diverse substrates by space‐confined method is reported. The growth kinetic process of CsAg2I3 single‐crystal MWs is elucidated by in situ observation. Furthermore, the CsAg2I3 single‐crystal MWs exhibit potential applications in ultraviolet light photodetectors as a photoactive layer. The fabricated heterojunction photodetector exhibits pronounced photoelectric performances working in self‐powered mode, including a specific detectivity of 2.09 × 108 Jones, a high responsivity of 26.5 mA W−1, and fast response speed of 258.43/289.32 ms under light illumination of 265 nm, due to the high crystallinity and effective photogenerated carrier transfer. This study provides a vital insight into the rational design of low‐dimensional perovskites for versatile optoelectronic applications. [ABSTRACT FROM AUTHOR]

Solid-state magnetic refrigeration, based on the magnetocaloric effect, is a promising, highly energy-efficient, and environmentally friendly cooling technology. High-entropy metallic glasses (HE-MGs) have attracted increasing interests due to their excellent magneto-caloric properties across a wide temperature range. In this work, we successfully prepared three rare-earth (RE) based HE-MGs microwires and investigated their structural and magnetocaloric properties. The Gd 25 Dy 25 Co 25 Al 25 , Tb 20 Gd 20 Dy 20 Co 20 Al 20 , and Ho 20 Gd 20 Dy 20 Co 20 Al 20 microwires exhibit an amorphous structure with good glass forming ability. They undergo a second-order phase transition from ferromagnetic to paramagnetic states around Curie temperatures of ∼61 K, ∼63 K, and ∼ 47 K, respectively. The peak magnetic entropy change (-Δ S M) for these HE-MGs microwires range from 8.2 J kg−1 K−1 to 10.2 J kg−1 K−1 under a 5 T magnetic field change. Furthermore, the refrigeration capacities of these microwires are evaluated to be between 504 J kg−1 and 507 J kg−1 (5 T), demonstrating their exceptional cooling efficiency. Additionally, this study provides valuable insights for the further research and development of RE-containing HE-MGs, paying the way for optimized materials tailored for advanced magnetic refrigeration applications. [Display omitted] • GdDyCoAl-based high-entropy metallic glass microwires were fabricated successfully. • Maximum magnetic entropy changes 8.2–10.2 J kg−1 K−1 for 5 T were reached. • A second-order phase transition from ferromagnetic to paramagnetic state was obtained. • Refrigeration capacities 504 J kg−1-507 J kg−1 for 5 T were achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Partial amorphization under 120 ns laser impulse observed in DyPrFeCoB microwires. • The amorphized layer exhibits an almost periodic radial domain structure. • Laser impulse restores initially amorphous state disappeared under thermal annealing. • Laser causes surface amorphization at a depth of ∼1 µm. • The surface amorphous layer protects MEMS microdevices from aggressive environments. Magnetic microcombs are necessary in microrobotics, MEMS technologies, actuator and magnetic flow analyzer industries. Usually, magnetic microcombs are artificial linear magnets of periodic shape. We propose another type of microcombs based of microwires, where periodicity of magnetization is caused by equidistant alternation of natural domains. We have demonstrated the presence of quasi-periodic radial magnetization and the effect of temperature and magnetic field on magnetic relief in PrDyFeCoB microwires. Accurate analysis of chemical, phase and structural composition of the microwires allowed us to reveal necessary conditions for the creation of periodical magnetic relief. Annealing affects magnetic relief and changes structure of initially amorphous microwires. Crystal structure of inclusions enriched with Fe and Co instead of Dy and Pr is body-centered cubic (BCC), while the bulk of the microwire has tetragonal structure. We have found laser stimulated amorphization of surface of PrDy-FeCo-B microwires. Partial restoration of the amorphous structure in polycrystalline microwires under single laser pulse of irradiation of 1mJ power and 120 ns duration has been found in 1–2 μm depth. [ABSTRACT FROM AUTHOR]

GaN nano- and microwires have gained increasing interest due to their unique geometry and flexibility, and have already been successfully applied in optoelectronics. One important advantage is their superior crystalline quality in comparison to their thin-film counterparts. Beside this, GaN is also known for its high radiation hardness, owed to the large displacement energy of the atoms in its crystal lattice and efficient dynamic annealing properties. In this work, single GaN core–shell p–n junction microwires have been processed into radiation detectors and the induced damage effects on the electrical and optoelectrical characteristics, when irradiating the detectors with 1 and 2 MeV protons, have been studied. By measuring the dark and photocurrent as a function of the irradiation fluence we show that for fluences up to 1 × 1 0 14 protons/cm2 there is no significant modification of any of the parameters and that serious degradation only occurs for fluences above 1 × 1 0 15 protons/cm2. Furthermore, we also observe that the dark current decays at a lower irradiation fluence with respect to the photocurrent due to the different impact of the created irradiation defects on the properties of the neutral region and the p–n junction. As a consequence, the signal-to-noise ratio of the detector is strongly enhanced, especially when applying a higher reverse bias. Thermal treatments furthermore show that the degree of recovery of the properties of the detectors is strongly dependent on the irradiation fluence. The detector irradiated with a fluence of 5 × 1 0 14 protons/cm2 almost completely retrieved its pre-irradiation characteristics whereas the detector irradiated with 5 × 1 0 15 protons/cm2 only showed a minimal recovery. • Properties of the microwires are not modified up to a fluence of 1 × 1014 protons/cm2. • For a fluence of 1 × 1015 protons/cm2 the properties are more severely affected. • The dark current decays at a lower fluence than the iono- and photocurrent. • A strong enhancement of the signal-to-noise ratio is observed. • Samples irradiated with lower fluence show very good recovery of their properties. [ABSTRACT FROM AUTHOR]

Ga2O3 has been regarded as a promising material for solar-blind detection due to its ultrawide bandgap and low growth cost. Although semiconductor microwires (MWs) possess unique optical and electronic characteristics, the performances of photodetectors developed from Ga2O3 MWs are still less than satisfactory. Herein, we demonstrate high-performance solar-blind photodetectors based on Sn-doped Ga2O3 MWs, possessing a light/dark current ratio of 107 and a responsivity of 2,409 A/W at 40 V. Moreover, a 1 × 10 solar-blind photodetector linear array is developed based on the Sn-doped Ga2O3 MWs via a patterned-electrodes method. And clear solar-blind images are obtained by using the photodetector array as the imaging unit of a solar-blind imaging system. The results provide a convenient way to construct high-performance solar-blind photodetector arrays based on Ga2O3 MWs, and thus may push forward their future applications. [ABSTRACT FROM AUTHOR]

Micro/nano optoelectronic devices based on curved substrates play a significant role in the development of wearable devices, electronic skin, conformal sensors, conformal antennas, and soft robots. However, the current fabrication processes are oriented toward planar micro/nano devices, and the fabrication of such devices on curved substrates is challenging. Herein, a temperature‐gradient‐assisted nanoimprint‐based in situ micro/nano‐crystal growth method is proposed to fabricate high‐quality curved perovskite microwire crystal (MWC) arrays on curved surfaces. Based on this curved perovskite MWC array without bending‐induced defects, high‐performance curved photodetectors (responsivity = 414 A W−1, detectivity = 1.2 × 1014 Jones, and external quantum efficiency over 140 000%) with extraordinary stability (85% of original performance maintained for more than 2 years) are fabricated to realize a curved imaging device. These results provide insights into the application of high‐performance perovskite photodetectors in nonconformal optical systems. [ABSTRACT FROM AUTHOR]

X‐ray detectors are used widely, but they suffer from short operational stability and insufficient absorptivity of X‐ray photons. Here, a strategy for room‐temperature, solution‐grown δ‐CsPbI3 monocrystalline microwires exhibiting one of the highest linear X‐ray absorption coefficients among known semiconductors is reported. In a metal–semiconductor–metal architecture, δ‐CsPbI3 demonstrates one of the lowest detectable X‐ray dose rates at 33.3 nGyair s−1, enabled by its exceptionally low dark current density of 12 pA mm−2. The detector remains stable following a continuous operation for a total accumulated dose of 1.44 × 106 Gyair, which is equivalent to 720 million chest X‐ray scans. The 1D crystalline nature of δ‐CsPbI3 enables a high X‐ray imaging resolution of 12.4 line pairs per millimeter (lp mm−1). [ABSTRACT FROM AUTHOR]

The Utah array powers cutting‐edge projects for restoration of neurological function, such as BrainGate, but the underlying electrode technology has itself advanced little in the last three decades. Here, advanced dual‐side lithographic microfabrication processes is exploited to demonstrate a 1024‐channel penetrating silicon microneedle array (SiMNA) that is scalable in its recording capabilities and cortical coverage and is suitable for clinical translation. The SiMNA is the first penetrating microneedle array with a flexible backing that affords compliancy to brain movements. In addition, the SiMNA is optically transparent permitting simultaneous optical and electrophysiological interrogation of neuronal activity. The SiMNA is used to demonstrate reliable recordings of spontaneous and evoked field potentials and of single unit activity in chronically implanted mice for up to 196 days in response to optogenetic and to whisker air‐puff stimuli. Significantly, the 1024‐channel SiMNA establishes detailed spatiotemporal mapping of broadband brain activity in rats. This novel scalable and biocompatible SiMNA with its multimodal capability and sensitivity to broadband brain activity will accelerate the progress in fundamental neurophysiological investigations and establishes a new milestone for penetrating and large area coverage microelectrode arrays for brain–machine interfaces. [ABSTRACT FROM AUTHOR]

Single‐crystalline micro‐/nanostructures based on organic stimulus‐responsive materials have attracted wide interests for their unique functional roles in various photonic applications including optical wave guiding, optical vapor sensing, and miniaturized lasing. Yet one imminent challenge is to pattern micro‐/nanostructured organic 1D arrays with controlled geometry, precise alignment, and pure crystallographic orientation owing to the uncontrollable dewetting dynamics in the solution processes. Herein, a smart assembly method is employed to regulate a confined crystallization of organic molecules. Sensitive, stable, and reproducible optical 1D‐array vapor sensors can detect the alkaline and acidic vapors based on the proton transfer process. As‐fabricated vapor sensors based on organic 1D arrays also selectively identify four similar amine vapors. Meanwhile, based on these 1D microstructure arrays, high‐performing Fabry–Pérot resonators with deep‐red laser emission, a low lasing threshold of 0.31 µJ, and high quality factor Q (≈2243) are realized. Owing to these multiple functions, organic microwire arrays not only provide intrinsic insight into optical vapor sensing but also offer guidance for the development of miniaturized lasers with specific functionalities, which show considerable potential in multifunctional photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Amorphous glass-coated microwires with positive magnetostriction are composite material with very fast domain wall (DW) propagation that can reach up to 18 km/s. Previously it was shown that such high DW velocity can be explained by the tilted orientation of a DW in static or quasi-static experimental conditions. Here we perform time-resolved observation of a DW in propagation. The shape of a DW is studied via magneto-optical Kerr effect (MOKE) imaging. Time-resolved MOKE microscope operating in the single-shot regime and a static mode is used to ascertain the role of surface pinning on DW velocity fluctuation. It is shown that a tilted DW undergoes complex DW distortions on a local scale. [ABSTRACT FROM AUTHOR]

Nanostructured ultraviolet (UV) light sources represent a growing research field in view of their potential applications in wearable optoelectronics or medical treatment devices. In this work, we report the demonstration of the first flexible UV-A light emitting diode (LED) based on AlGaN/GaN core-shell microwires. The device is based on a composite microwire/poly(dimethylsiloxane) (PDMS) membrane with flexible transparent electrodes. The electrode transparency in the UV range is optimized: namely, we demonstrate that single-walled carbon nanotube electrodes provide a stable electrical contact to the membrane with high transparency (70% at 350 nm). The flexible UV-A membrane demonstrating electroluminescence around 345 nm is further applied to excite Zn-Ir-BipyPDMS luminophores: the UV-A LED is combined with the elastic luminophore-containing membrane to produce a visible amber emission from 520 to 650 nm. The obtained results pave the way for flexible inorganic light-emitting diodes to be employed in sensing, detection of fluorescent labels, or light therapy.

1D metal halide perovskites (MHPs) are known as excellent candidates for fabricating high‐performance optoelectronic devices, ranging from lasers to photodetectors (PDs). Nevertheless, their inherent limitations, such as high binding energy and limited carrier mobility, have restricted their further improvement in performance. To tackle this issue, hybrid MHP microwires (MWs) are fabricated by combining MHP MWs and an organic semiconductor via a facile self‐assembly method, forming a radial heterojunction. Meanwhile, an ultrathin insulating organic layer is introduced as an interlayer between MHP MWs and the organic semiconductor. The synthesized hybrid MWs are further applied in rigid and flexible PDs, which demonstrated a high light/dark current on‐off ratio (>2 × 105), a high responsivity (>400 A W−1), and robust bending stability. These impressive results make the hybrid MHP MWs with the unique radial heterostructure promising building blocks for high‐performance future optoelectronics. [ABSTRACT FROM AUTHOR]

The manipulation of microstructure from the growth stage is desired in perovskite materials to improve the environmental stability and enhance the perovskite‐based device performance. Herein, the traditional challenges of self‐assembly of multifunctional perovskite nano/microwires (MWs) are overcome by developing a new nanocrystal strategy to intelligently build self‐inlaid jagged CsPbBr3 MWs for photodetectors (PDs) with a combination of improved light‐harvesting capability, heat dissipation, and humidity stability. With a collection of compelling features, the as‐constructed PDs deliver an ultralow dark current of 10−12 A, excellent response speed of 26 ms, superior detectivity (D*) of 1.9 × 1012 Jones, and peak external quantum efficiency of 939%. Furthermore, attributing to the interlocking–protecting effect of the self‐inlaid monocrystalline CsPbBr3 nanostructure, the CsPbBr3 MW PDs display improved stability against heat and humidity with promoted heat dissipation ability at 60 °C and 97% photocurrent retention under 80% humidity treatment for 200 min, respectively. This work represents a significant advancement in developing high‐performance and environmentally stable PDs.

Through designing the composition and processing approach, the non-equiatomic (Gd36Tb20Co20Al24)100-xFex (x = 0, 1, 2 and 3 at.%) high-entropy-metallic-glass (HE-MG) alloy microwires were successfully fabricated by melt-extraction technique. The microstructure and magnetocaloric properties of the microwires were systematically investigated. The microwires possess tunable Curie temperatures, i.e. 81–108 K, above the typical rare-earth (RE) containing HE-MG reports. The high Curie temperatures are attributed to the designed composition. Magnetocaloric response peak values of Fe-containing GdTbCoAl alloy microwires range 7.6–8.9 J kg−1 K−1 (5 T), which are comparable to those of many outstanding RE-containing magnetocaloric HE-MGs. The characteristics of the melt-extraction method, combining with compositional effects, favor the formation of amorphous and nanocrystalline phases. The increase in the cooling efficiency for microwires with higher Fe content can be attributed to the broadening of the Curie temperature distribution induced by the composition difference between nanocrystalline phase and amorphous matrix. The designed composition and the melt-extraction processing approach for Fe-containing GdTbCoAl alloys can tune their Curie temperatures towards a temperature range of natural gas liquefaction and improve their magnetocaloric properties. This demonstrates that Fe-containing GdTbCoAl HE-MG composite microwires have great potential as high-performance magnetic refrigerants.

Meta-magnetic shape-memory alloys combine ferroelastic order with ferromagnetic order and exhibit attractive multifunctional properties, but they are extremely brittle, showing hardly any tensile deformability, which impedes their practical application. Here, for the first time, an Ni–Cu–Co–Mn–In microwire has been developed that simultaneously exhibits a magnetic field-induced first-order meta-magnetic phase transition and huge tensile superelasticity. A temperature-dependent in situ synchrotron high-energy X-ray diffraction investigation reveals that the martensite of this Ni43.7Cu1.5Co5.1Mn36.7In13 microwire shows a monoclinic six-layered modulated structure and the austenite shows a cubic structure. This microwire exhibits an oligocrystalline structure with bamboo grains, which remarkably reduces the strain incompatibility during deformation and martensitic transformation. As a result, huge tensile superelasticity with a recoverable strain of 13% is achieved in the microwire. This huge tensile superelasticity is in agreement with our theoretical calculations based on the crystal structure and lattice correspondence of austenite and martensite and the crystallographic orientation of the grains. Owing to the large magnetization difference between austenite and martensite, a pronounced magnetic field-induced magnetostructural transition is achieved in the microwire, which could give rise to a variety of magnetically driven functional properties. For example, a large magnetocaloric effect with an isothermal entropy change of 12.7 J kg−1 K−1 (under 5 T) is obtained. The realization of magnetic-field- and tensile-stress-induced structural transformations in the microwire may pave the way for exploiting the multifunctional properties under the coupling of magnetic field and stress for applications in miniature multifunctional devices.

Organic‐inorganic hybrid perovskites are promising semiconductors for high‐performance field‐effect transistors because of their excellent charge carrier transport, but hybrid perovskites used in field‐effect transistors are not diverse enough and the field‐effect performances are always not satisfactory at room temperature and in the dark and air. Herein, we prepared CH3NH3PbI3 microwires through a transformation from CH3NH3PbI3 bulk single crystals and fabricated ambipolar field‐effect transistors based on them. At room temperature and in the dark and air, the field‐effect mobility can reach to 1.8×10−3 cm2V−1 s−1, which is two orders of magnitude higher than that of CH3NH3PbI3 polycrystalline film based field‐effect transistors under the same condition, indicating that CH3NH3PbI3 microwires have potential for use in ambipolar transistors. [ABSTRACT FROM AUTHOR]

Micro/nanowire light‐emitting diodes (LEDs) have inspired considerable research interests due to their potential applications in microdisplays and micro/nano‐optoelectronic integrated systems. Herein, a single InGaN/GaN multiple‐quantum‐well (MQW) microwire‐based flexible LED with high‐efficiency current injection and spreading is fabricated, and the performance modulation of the device by external strain is further studied. The results show that under external compressive strains, the output power is enhanced and the peak wavelength is blue shifted; on the contrary, the output power declines and the peak wavelength is red shifted under stretch strains. Compared with strain‐free devices, the flexible LED achieves the best performance at a − 1% compressive strain, with external quantum efficiency (EQE) increasing by 14.2% and efficiency droop reducing by 17.9%. The effective improvements are attributed to external strain‐induced piezoelectric polarization charges presented at local junctions/interfaces tuning the energy band. Herein, an efficient external modulation of light emission properties in a single InGaN/GaN MQW microwire LED is presented. [ABSTRACT FROM AUTHOR]

Radial junctions on crystalline silicon (c‐Si) microwire structures considerably reduce the diffusion length of photoinduced minority carriers required for energy generation by decoupling light absorption and carrier separation in orthogonal spatial directions. Hence, radial junctions mitigate the need for high‐purity materials, and thus reduce the fabrication cost of c‐Si solar cells. In this study, the formation of dopant‐free radial junctions from atomic layer deposition (ALD) of Al2O3 on an n‐c‐Si microwire surface is reported. ALD‐Al2O3 generates a p+ inversion layer, which eventually forms the radial junction on the n‐c‐Si surface. The width of depletion region induced by the p+ inversion layer is calculated from PC1D simulation as 900 nm. The fabricated dopant‐free radial junction c‐Si solar cells exhibit a power conversion efficiency of 20.1%, which is higher than those of previously reported microwire‐based radial junction solar cells. Notably, internal quantum efficiencies of over 90% are obtained in the 300–980 nm wavelength region, thereby verifying the successful formation of radial junctions. [ABSTRACT FROM AUTHOR]

A method to prepare TEM specimens from metallic microwires and based on conventional twin‐jet electropolishing is introduced. The wire is embedded in an opaque epoxy resin medium and the hardened resin is mechanically polished to reveal the wire on both sides. The resin containing wire is then cut into discs of the appropriate size. The obtained embedded wire is electropolished in a conventional twin‐jet electropolishing machine until electron transparency in large areas without radiation damage is achieved. [ABSTRACT FROM AUTHOR]

Introduction: Many invasive and noninvasive neurotechnologies are being developed to help treat neurological pathologies and disorders. Making a brain implant safe, stable, and efficient in the long run is one of the requirements to conform with neuroethics and overcome limitations for numerous promising neural treatments. A main limitation is low biocompatibility, characterized by the damage implants create in brain tissue and their low adhesion to it. This damage is partly linked to friction over time due to the mechanical mismatch between the soft brain tissue and the more rigid wires. Methods: Here, we performed a short biocompatibility assessment of bio-inspired intra-cortical implants named "Neurosnooper" made of a microelectrode array consisting of a thin, flexible polymer-metal-polymer stack with microwires that mimic axons. Implants were assembled into poly-lactic-glycolic acid (PLGA) biodegradable needles for their intra-cortical implantation. Results and Discussion: The study of glial scars around implants, at 7 days and 2 months post-implantation, revealed a good adhesion between the brain tissue and implant wires and a low glial scar thickness. The lowest corresponds to electrode wires with a section size of 8 μm × 10 μm, compared to implants with the 8 μm × 50 μm electrode wire section size, and a straight shape appears to be better than a zigzag. Therefore, in addition to flexibility, size and shape parameters are important when designing electrode wires for the next generation of clinical intra-cortical implants., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Darlot, Villard, Salam, Rousseau and Piret.)

New compound magnetic material based on parallel continuous ferromagnetic microwires (e.g., based on cobalt) embedded in a body made of polymeric material can potentially offer significant mechanical advantages over well-known fragile ferrite in some applications where the magnetic material has to withstand mechanical vibrations. The diameter of the magnetic microwires is minimal (3–60  $\mu$ m) compared to the rest of the dimensions (80–300 mm) and the number of microwires is in the order of 1000 s. It requires extremely fine meshes, then brute force simulation by the finite element method is not possible. In this article, a method to overcome this limitation is proposed, which is based on the substitution of the original material by a homogenous material that behaves, in a macroscopic sense, as the compound material. The physical properties of the homogeneous material are obtained in different spatial directions, due to the inherent anisotropy of the compounded magnetic component, through analytical equations. [ABSTRACT FROM AUTHOR]

An inhomogeneous elastocaloric effect has been found and investigated in the present Cu–Al–Mn shape memory microwires by using the combined technique of infrared thermography and electron backscatter diffraction. Upon unloading, a reversible temperature change of ~5 K has been detected within the 5 mm gauge length. Inhomogeneous temperature distribution can be directly observed on the surface of microwires through infrared thermography measurement. Different regions of the microwires, involving bi-crystalline, oligo-crystalline, single-crystalline and poly-crystalline grain architectures, display different eCE cyclic stability, which can be ascribed to the heterogeneous grain architectures, the discrepancy of grain orientation and the varied neighboring grain constraints. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The realization of electrically pumped emitters at micro and nanoscale, especially with flexibility or special shapes is still a goal for prospective fundamental research and application. Herein, zinc oxide (ZnO) microwires were produced to investigate the luminescent properties affected by stress. To exploit the initial stress, room temperature in situ elastic bending stress was applied on the microwires by squeezing between the two approaching electrodes. A novel unrecoverable deformation phenomenon was observed by applying a large enough voltage, resulting in the formation of additional defects at bent regions. The electrical characteristics of the microwire changed with the applied bending deformation due to the introduction of defects by stress. When the injection current exceeded certain values, bright emission was observed at bent regions, ZnO microwires showed illumination at the bent region priority to straight region. The bent emission can be attributed to the effect of thermal tunneling electroluminescence appeared primarily at bent regions. The physical mechanism of the observed thermoluminescence phenomena was analyzed using theoretical simulations. The realization of electrically induced deformation and the related bending emissions in single microwires shows the possibility to fabricate special-shaped light sources and offer a method to develop photoelectronic devices.

• Cylindrical shape of sample is responsible for peculiar magneto-optical contrast. • Surface shape of a magnetic domain wall in microwire is studied by two detectors. • The domain wall has an inclined shape with strong surface distortions. Thin magnetic cylinders are in focus of interest due to peculiar features of domain wall motion like absence of the Walker breakdown. Here, we propose an experimental technique based on magneto-optical Kerr effect that allows surface studies of a domain wall shape in thin microwires. Our setup is optimized for characteristic optical and magneto-optical features of thin magnetic cylinders. Time-resolved measurements of a magnetic contrast along the circumference of wire are used to reconstruct a three-dimensional image of a surface domain wall shape. Our measurements confirmed a tilted shape of domain wall, in agreement with previous observations of microwires with positive magnetostriction alloy. The experimental technique represents a new way for direct visualizations of a surface magnetism of thin cylinders in optical range. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a systematic growth behavior of Cu, Ni and Cu/Ni microwire arrays in porous silicon (PSi) templates is presented. After preparation of PSi templates via anodizing in HF solution, such microwires are successfully grown into PSi templates by electrodeposition method. Systematic scanning electron microscopy (SEM) imaging reveals that Cu seed nucleation occurs at the bottom and Ni seed nucleation starts on the wall of the silicon pores. The different growth models are explained according to the observed diffusion coefficients of ionic elements in electrodeposition baths. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were used to further observe the structural characteristics of the grown microwires. We believe that this work can be used in developing microwires with desired structural characteristics. Highlights • Deposition of Cu, Ni, and Cu/Ni microwires within porous Si was investigated • Nucleation of Cu seed occurred at the bottom of silicone pores • Nucleation of Ni seed started on the wall of silicone pores [ABSTRACT FROM AUTHOR]

Abstract Detection of viral infection is commonly performed using serological techniques like the enzyme-linked immunosorbent assay (ELISA) to detect antibody responses. Such assays may also be used to determine the infection phase based on isotype prevalence. However, ELISAs demonstrate limited sensitivity and are difficult to perform at the point of care. Here, we present a novel technique for label-free, rapid detection of ultra-low concentrations of virus specific antibodies. We have developed a simple, robust capacitive biosensor using microwires coated with Zika or Chikungunya virus envelope antigen. With little discernable nonspecific binding, the sensor can detect as few as 10 antibody molecules in a small volume (10 molecules/30 µL) within minutes. It can also be used to rapidly, specifically, and accurately determine the isotype of antigen-specific antibodies. Finally, we demonstrate that anti-Zika virus antibody can be sensitively and specifically detected in dilute mouse serum and can be isotyped using the sensor. Overall, our findings suggest that our microwire sensor platform has the potential to be used as a reliable, sensitive, and inexpensive diagnostic tool to detect immune responses at the point of care. Highlights • A capacitance sensing system was developed that can detect as few as 10 anti-Zika or anti-Chikungunya virus specific monoclonal antibodies with almost no cross-reactivity. • The system accurately determined the isotype of antibodies targeting Zika or Chikungunya virus antigen. • The system could to detect Zika virus specific antibodies in immunized mouse serum as few as 4-days post-immunization. • This system has the potential to be developed into a simple yet robust diagnostic platform for pathogen antibody detection and isotype determination. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • One-dimensional Ni microwires were synthesized by two-step MFI method. • Ni particles turned from nanospheres to microwires for magnetic field. • Brownian motion and magnetic moments affected the morphology of Ni microwires. • The length increased with magnetic field, while the diameter decreased. • The magnetic field improved the spontaneous magnetization of Ni microwires. Abstract One-dimensional nickel (Ni) microwires were synthesized by the magnetic-field-induced (MFI) microemulsion-hydrothermal method using Ni nanospheres as seeds. The influence of the chemical conditions and magnetic field on the morphology and magnetic properties of Ni microwires were investigated by X-Ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The strength of magnetic field greatly affected the morphology and magnetic properties of Ni microwires. The growth and morphology of Ni microwires depended on the competition between Brownian motion and magnetic dipole moments from magnetic field. The larger nanoparticles with the higher magnetic moments preferred to form one-dimensional Ni microwires and their length increased up to several millimeters with the increasing magnetic field strength, while the average diameter of Ni microwires decreased. Furthermore, the easy magnetization direction of Ni microwires was parallel to the direction of magnetic field and the Ni microwires axis. [ABSTRACT FROM AUTHOR]

One of the most important challenges in the fabrication of Cu x O microstructures via the electrochemical method is formation of long, regular and well-packed microwires with good adhesion on the Cu substrate and to achieve better photoelectrochemical properties, which can be potentially applied in solar-driven water splitting and CO 2 conversion to light hydrocarbons. In this paper, Cu 2 O photoelectrode has been fabricated by direct anodization of the Cu foil, then CuO microwires (MWs) was formed by calcination process. The effect of the applied potential (10–40 V), sodium fluoride content in the electrolyte (0.2–0.5% wt.) as well as calcination conditions (400–500 °C, 60–360 min) on the morphology, phase composition, optical and photoelectrochemical properties was investigated. The highest photocurrent response was −0.71 mA cm−2 for the sample 0.35%_10V_400 °C_60min with 0.83 μm length and 154 nm diameter. The mechanism of the photocurrent generation process in the presence of Cu x O/Cu under UV–Vis irradiation was proposed. Thin films of CuO MWs/Cu 2 O were produced on the surface of Cu plates by anodic oxidation. A tendency of increase in the number and length of microwires was observed with the increase in NaF concentration and the increase in the voltage applied during anodization. A mechanism for the synthesis and photoexcitation of the obtained samples was also proposed. [Display omitted] • Optimization of the Cu anodization - voltage (10–40 V); NaF conc. (0.2–0.5% wt.); calcination (400–500 °C, 60–360 min). • Tendency to increase the length and number and decreasing diameter of the microwires with increasing NaF conc. and voltage. • Increasing the photocurrent response 1.65 timer comparing to calcinated pristine Cu plate. • Proposed mechanism of the photocurrent generation process in the presence of Cu x O/Cu under the UV–Vis irradiation. [ABSTRACT FROM AUTHOR]

This paper presents two types of metal insulator field effect transistors (MISFETs) devices fabricated from Si microwires through a new manufacturing route involving a combination of printing and microfabrication technologies. Si microwires, developed through standard photolithography and etching steps, are transferred from a silicon on insulator wafer onto polyimide using stamp-assisted transfer printing. The MISFETs are then obtained by spray coating the dielectric layer and metal contact layer. Spray coating has been introduced here for the first time for deposition of organic dielectric on transfer printed Si microwires. Two groups of the devices are fabricated, one based on a single Si microwire and the other based on the array of 15 microwires of similar dimensions. The variations in the output response of the two groups of devices has been investigated. The devices based on array of microwires are observed to have less variation in the output response, with lesser standard deviations as compared to MISFETs made from single Si microwires.

Coating microelectrodes with conductive polymer is widely recognized to decrease impedance and improve performance of implantable neural devices during recording and stimulation. A concern for wide-spread use of this approach is shelf-life, i.e., the electrochemical stability of the coated microelectrodes prior to use. In this work, we investigated the possibility of using the freeze-drying process in order to retain the native low impedance state and, thereby, improve the shelf-life of conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT)-PSS modified neural electrodes. Control PEDOT-PSS coated microelectrodes demonstrated a significant increase in impedance at 1 kHz after 41–50 days of room temperature storage. Based on equivalent circuit modeling derived from electrochemical impedance spectroscopy, this increase in impedance could be largely attributed to a decrease in the interfacial capacitance consistent with a collapse and closing of the porous structure of the polymeric coating. Time-dependent electrochemical impedance measurements revealed higher stability of the freeze-dried coated microelectrodes compared to the controls, such that impedance values after 41–50 days appeared to be indistinguishable from the initial levels. This suggests that freeze drying PEDOT-PSS coated microelectrodes correlates with enhanced electrochemical stability during shelf storage.

Molecular design and crystallinity control are important issues for the development of high‐performance organic optoelectronic devices. Here, a highly photo‐responsive n‐type organic small molecular semiconductor, (2Z,2′Z)‐3,3′‐(2,5‐dimethoxy‐1,4‐phenylene)bis(2‐(3,5‐bis(trifluoro‐methyl)phenyl)acrylonitrile) (DM‐R), was synthesized and the photoelectronic properties of self‐assembled DM‐R microwire organic phototransistors (MW‐OPTs) were studied. Significant enhancement in the electron mobility (μe) of MW‐OPTs (μe: 0.16 cm2 V−1 s−1) was observed as compared to thin‐film‐OPTs (μe: 2.7×10−3 cm2 V−1 s−1), most likely due to the single‐crystalline nature of the self‐assembled MWs. Moreover, the photoresponsivity of MW‐OPTs showed 23.53 (A W−1), which was 130 times higher than that of thin‐film OPTs (0.18 A W−1). Furthermore, the MW‐OPTs exhibited stable photoswitching properties and a faster charge accumulation/release rate than those of thin‐film OPTs. The results obtained herein demonstrate a facile solution‐based approach for the fabrication of high‐performance n‐type organic MW‐OPTs and provide a systematic analysis platform of the photo‐generated charge carrier dynamics. High‐performancen‐type organic phototransistors (OPTs) have been developed by utilizing self‐assembled microwires of a distyrylbenzene derivative. These OPTs exhibit significantly enhanced optoelectronic performance compared to the thin‐film‐based OPTs due to the high crystallinity of the organic microwires. This study provides a systematic analysis platform of the photo‐generated charge carrier dynamics in OPTs. [ABSTRACT FROM AUTHOR]