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Unipolar brush cells (UBCs) are excitatory interneurons in the cerebellar cortex that receive mossy fiber (MF) inputs and excite granule cells. The UBC population responds to brief burst activation of MFs with a continuum of temporal transformations, but it is not known how UBCs transform the diverse range of MF input patterns that occur in vivo. Here, we use cell-attached recordings from UBCs in acute cerebellar slices to examine responses to MF firing patterns that are based on in vivo recordings. We find that MFs evoke a continuum of responses in the UBC population, mediated by three different types of glutamate receptors that each convey a specialized component. AMPARs transmit timing information for single stimuli at up to 5 spikes/s, and for very brief bursts. A combination of mGluR2/3s (inhibitory) and mGluR1s (excitatory) mediates a continuum of delayed, and broadened responses to longer bursts, and to sustained high frequency activation. Variability in the mGluR2/3 component controls the time course of the onset of firing, and variability in the mGluR1 component controls the duration of prolonged firing. We conclude that the combination of glutamate receptor types allows each UBC to simultaneously convey different aspects of MF firing. These findings establish that UBCs are highly flexible circuit elements that provide diverse temporal transformations that are well suited to contribute to specialized processing in different regions of the cerebellar cortex. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries represent a significant component of the field of energy storage, with a diverse range of applications in consumer electronics, portable devices, and numerous other fields. In view of the growing concerns about the safety of batteries, it is of the utmost importance to develop a sensor that is capable of accurately monitoring the internal temperature of lithium-ion batteries. External sensors are subject to the necessity for additional space and ancillary equipment. Moreover, external sensors cannot accurately measure internal battery temperature due to packaging material interference, causing a temperature discrepancy between the interior and surface. Consequently, this study presents an integrated temperature sensor within the battery, based on PT1000 resistance temperature detector (RTD). The sensor is integrated with the anode via a flexible printed circuit (FPC), simplifying the assembly process. The PT1000 RTD microsensor's temperature is linearly related to resistance (R = 3.71T + 1003.86). It measures about 15 °C temperature difference inside/outside the battery. On short-circuit, the battery's internal temperature rises to 27 °C in 10 s and 32 °C in 20 s, measured by the sensor. A battery with the PT1000 sensor retains 89.8% capacity under 2 C, similar to the normal battery. Furthermore, a PT1000 temperature array sensor was designed and employed to enable precise monitoring and localization of internal temperature variations. [ABSTRACT FROM AUTHOR]

Flexible integrated circuits (FlexICs) have drawn increasing attention, particularly in remote sensors and wearables operating in a limited power budget. Here, we present an ultra-low power timer designed to wake-up an external circuit periodically, from a deep-sleep state into an active state, thereby largely reducing the system power consumption. We achieved this with a circuit topology that exploits the transistor's leakage current to generate a low frequency wake-up signal. This topology is compatible with IC technologies where only n-type transistors are available. The design was implemented with the sustainable FlexIC process of PragmatIC, that is based on Indium Gallium Zinc Oxide (IGZO) thin-film transistors. Our timer generates mean wake-up frequency of 0.24 ± 0.15 Hz, with a mean power consumption of 26.7 ± 14.1 nW. In this paper, we provide details of the Wake-Up timer's design and performance at different supply voltages, under temperature variations and different light conditions. [ABSTRACT FROM AUTHOR]

We propose a non-magnetic transparent heating film based on silver nanowires (Ag-NWs) for application in spin-exchange relaxation-free (SERF) magnetic field measurement devices. To achieve ultra-high sensitivity in atomic magnetometers, the atoms within the alkali metal vapor cell must be maintained in a stable and uniform high-temperature environment. Ag-NWs, as a transparent conductive material with exceptional electrical conductivity, are well suited for this application. By employing high-frequency AC heating, we effectively minimize associated magnetic noise. The experimental results demonstrate that the proposed heating film, utilizing a surface heating method, can achieve temperatures exceeding 140 °C, which is sufficient to vaporize alkali metal atoms. The average magnetic flux coefficient of the heating film is 0.1143 nT/mA. Typically, as the current increases, a larger magnetic field is generated. When integrated with the heating system discussed in this paper, this characteristic can effectively mitigate low-frequency magnetic interference. In comparison with traditional flexible printed circuits (FPC), the Ag-NWs heating film exhibits a more uniform temperature distribution. This magnetically transparent heating film, leveraging Ag-NWs, enhances atomic magnetometry and presents opportunities for use in chip-level gyroscopes, atomic clocks, and various other atomic devices. [ABSTRACT FROM AUTHOR]

The purpose of the experiment was to indicate which element of the production process of flexible printed circuit boards is optimal in terms of the reliability of final products. According to the Taguchi method, in the experiment, five factors with two levels each were chosen for the subsequent analysis. These included the number of conductive layers, the thickness of the laminate layer, the type of the laminate, the diameter of the plated holes, and the current density in the galvanic bath. The reliability of the PCBs in the produced variations was verified using the Interconnect Stress Test environmental test. The qualitatively best variant of the board construction was indicated using the signal-to-noise ratio and the analysis of variance method for each factor. The factors determined to be the most important in terms of reliability were the number of conductive layers and the current density in the galvanic bath. The optimal variant of the board construction was two conductive layers on a polyimide laminate, where the laminate layer was 100 μm thick, the hole diameter was equal to 0.4 mm, and current density was 2 A/dm2 in the galvanic bath. Therefore, the plated experiment indicated the factors needed to obtain a high-quality product with a low failure rate. [ABSTRACT FROM AUTHOR]

Plasma processes are critical for achieving precise device fabrication in semiconductor manufacturing. However, polymer accumulation during processes like plasma etching can cause chamber contamination, adversely affecting plasma characteristics and process stability. This study focused on developing a real-time sensor system for diagnosing chamber contamination by quantitatively monitoring polymer accumulation. A quartz crystal sensor integrated with flexible printed circuit boards was designed to measure the frequency shifts corresponding to polymer thickness changes. An impedance probe was also employed to monitor variations in the plasma discharge characteristics. The sensor demonstrated high reliability with a measurement scatter of 2.5% despite repeated plasma exposure. The experimental results revealed that polymer accumulation significantly influenced the plasma impedance, and this correlation was validated through real-time monitoring and scanning electron microscopy (SEM). The study further showed that the sensor could detect the transition point of the plasma state changes under varying process gas conditions, enabling the early detection of potential process anomalies. These findings suggest that the developed sensor system can be crucial for diagnosing plasma and chamber conditions, providing valuable data for optimizing preventive maintenance schedules. This advancement offers a pathway for improving process reliability and extending the operational lifetime of semiconductor manufacturing equipment. [ABSTRACT FROM AUTHOR]

In response to the issue of providing a wireless power supply to the magnetic focusing rotor torque and torsion sensors on the rotating shaft systems, loose-coupled transformers (LCTs) are difficult to disassemble and install due to their large size. In addition, their large mass has a significant impact on the dynamic balance of the shaft system. Consequently, in this paper, a structural design of an flexible printed circuit (FPC)-stacked receiving coil is proposed, with its mathematical model, physical model, and simulation model established. The optimal structure is obtained by simulating the coil-induced voltage under different structural parameters through COMSOL electromagnetic simulation. Through modal simulation analysis of the rotor in ANSYS, it is found that the FPC-stacked receiving coil has less impact on the dynamic balance of the rotating shaft system. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) semiconductors, combining remarkable electrical properties and mechanical flexibility, offer fascinating opportunities for flexible integrated circuits (ICs). Despite notable progress, so far the showcased 2D flexible ICs have been constrained to basic logic gates and ring oscillators with a maximum integration scale of a few thin film transistors (TFTs), creating a significant disparity in terms of circuit scale and functionality. Here, we demonstrate medium-scale flexible ICs integrating both combinational and sequential elements based on 2D molybdenum disulfide (MoS2). By co-optimization of the fabrication processes, flexible MoS2 TFTs with high device yield and homogeneity are implemented, as well as flexible NMOS inverters with robust rail-to-rail operation. Further, typical IC modules, such as NAND, XOR, half-adder and latch, are created on flexible substrates. Finally, a medium-scale flexible clock division module consisting of 112 MoS2 TFTs is demonstrated based on an edge-triggered Flip-Flop circuit. Our work scales up 2D flexible ICs to medium-scale, showing promising developments for various applications, including internet of everything, health monitoring and implantable electronics. Flexible integrated circuits (ICs) based on 2D semiconductors hold promise for various applications, but their scale has so far remained limited to a low number of devices. Here, the authors report the fabrication of medium-scale flexible ICs integrating both combinational and sequential elements based on 2D MoS2 transistors. [ABSTRACT FROM AUTHOR]

Due to their flexibility, high conductivity, stability, monodispersity, and ease of processing; polypyrrole‐based conductive inks hold significant advancements in printing, biomedical and electronic applications. These inks enable innovative solutions in flexible electronics, wearable devices, sensors, and energy storage systems and also facilitate high‐quality printed films on various rigid and flexible substrates, supporting diverse applications from flexible circuits to smart textiles. Notably, in biomedicine, they exhibit excellent biocompatibility, and cell adhesion, aiding in tissue engineering and stem cell therapies. They serve as bioinks for 3D printing free‐standing scaffolds, showing potential for creating electrically active tissue constructs. Additionally, polypyrrole inks are crucial for developing highly specific and sensitive sensors for detecting gases, chemicals, and biological analytes and efficient energy storage devices like supercapacitors. As research progresses, these inks are pivotal in the future of lightweight, flexible, portable, and wearable electronic materials and devices. This review covers a general overview of various types of polypyrrole‐based conductive inks, highlighting their major applications and impacts. [ABSTRACT FROM AUTHOR]

Traditional circuit board fabrication schemes are not directly applicable to the production of flexible, multi‐material circuits. This article reports a technique, microfluidic directed material patterning, which combines soft microfluidic stamps and low‐temperature solution‐phase deposition to generate multi‐material circuits on flexible, non‐planar polymeric supports. Specifically, metallic and semiconductive traces are combined on commodity plastic films to yield functional photosensitive circuits that can be used in the spectrophotometric detection and concentration measurement of microdroplets on 3D "e‐plates." The photoresistive material cadmium sulfide is used in these circuits because it is suitable for visible light detection and it can be deposited directly from aqueous solutions following established bath deposition procedures. This method can produce colorimetric devices capable of quantifying micromolar concentrations of Allura Red in microdroplets of Kool‐Aid. This technique presents the opportunity for producing single‐use or low‐use disposable/recyclable devices for flexible 3D sensors and detectors following a convenient, low‐waste fabrication scheme. The general capabilities of this approach, in terms of substrate geometry and device layout (e.g., the number, area, and pattern of photoresistive elements), can be applied to the design and manufacture of more intricate, multiplexed devices supportive of advanced and/or specialized functions that go beyond those reported in this initial demonstration. [ABSTRACT FROM AUTHOR]

AbstractThe planar flexible Koch fractal eddy current probe exhibits high consistency in detecting short cracks in all orientations. However, it is limited by a weak signal caused by the small number of coil turns. This paper utilizes multilayer flexible circuit board technology to address the issue. The probe is designed with a mutual inductance coil structure and is arranged on a 10-layer flexible circuit board. This board includes one layer for the excitation coil and nine layers for the pick-up coil. The probe’s performance was studied through C-scan experiments, which examined cracks of varying depths, widths, orientations, and lengths. The experimental results show that the probe can detect minimum crack sizes of 0.5 mm × 0.15 mm × 1 mm for 5083-aluminum alloy, 3 mm × 0.15 mm × 1 mm for GH4169 superalloy, and 1 mm × 0.15 mm × 1 mm for Q235 steel. The results demonstrate that the flexible fractal eddy current probe has significant advantages in detecting small cracks. [ABSTRACT FROM AUTHOR]

ABSTRACT This work presents an experimental characterization of a novel clocked regenerative comparator with oxide TFT (a‐IGZO) technology on a flexible substrate. The circuit functionality is demonstrated as a wide range duty‐cycle PWM signal generator with a triangular input signal. The regenerative latch in the comparator is implemented with diode‐load–based inverters. The proposed circuit has shown a linear variation in the duty‐cycle from 12% to 84%, when the reference voltage (Vref$$ {V}_{ref} $$) is varied from 0.5 to 3.3 V, respectively, in the clocked comparator. Further, a reliable operation is observed up to an input signal frequency of 2 kHz at a supply voltage of 4 V, with a power dissipation of 20 μ$$ \upmu $$ W. This circuit would find potential applications in wearable bio‐medical and neuromorphic computational systems. [ABSTRACT FROM AUTHOR]

In order to ensure the service reliability of flexible electronic products, flexible electronic interconnection wires need to have good conductivity and good resistance and mechanical reliability. In this study, Ag microwire samples were prepared on flexible substrates by aerosol inkjet printing. The electrical tests show that the resistivity of the Ag microwire treated by high-density pulsed electric current was reduced. At the same time, the bending resistance tests show that the resistance of Ag microwire changes less when treated by high-density pulsed electric current under the same bending angle. Thus, the electrical conductivity and flexural behavior of the samples can be simultaneously enhanced by applying high-density pulsed electric current. After pulsing under the specified electrical parameters, the microstructure of the Ag microwire was denser, and the grain distribution was more uniform owing to the decrease in grain porosity, which was caused by atomic filling. The atomic diffusion was controlled directionally by the electron wind and Joule thermal effect. Ultimately, a significant accumulation of Ag atoms occurred, healing the voids and cracks. The technique holds promise for utilization in the realm of flexible printed circuits. [ABSTRACT FROM AUTHOR]

Flexible wearable electronic devices play a vital role in daily monitoring, medical diagnosis, and human‐computer interaction, and such devices have a great demand for portability, integration, comfort, and self‐power. In this study, a triboelectric nanogenerator integrated into a flexible chest belt is proposed as a displacement sensor to monitor the displacement and frequency of thoracic expansion. Based on three parallel interpolation electrode structures with phase differences, the Triboelectric Nanogenerators's(TENG) output signal pulse number can characterize the sliding displacement, with a resolution of more than 1 mm and a durability of more than 700,000 cycles. Based on the flexible printed circuit processing technology, the volume of the sensor is less than 8.5 cm3, and the weight is less than 3.2 g, which improves the portability of the device. Based on wireless radio frequency technology, the collected signals are transmitted to the upper computer, and then the monitoring of respiratory physiological signals and the human‐machine synchronous control of the ventilator are achieved within the overshoot of 1.5% and the control error of 5% through a simulation machine. This work provides a sensing method for daily and medical respiratory monitoring and demonstrates the enormous potential of frictional electric sensors in intelligent medical applications. [ABSTRACT FROM AUTHOR]

Functional soft materials, especially hydrogels have been widely developed to achieve various soft structures and machines. However, synthetic hydrogels commonly show formula‐dependent mechanical properties to fulfill the requirements of mechanical elasticity, stiffness, toughness, and tearing‐resistance for adapting to complex application scenario. Inspired by heterostructures and materials found in nature such as leaves and insect wings, a sequential photopolymerization process combined with site‐selective patterning exposure is reported to prepare programmable hydrogels with locally heterogeneous reinforcement skeletons, i.e., interpenetrating double networks. The heterogeneous interface between soft matrices and stiff skeletons is seamlessly interlocked through strong multiple hydrogen bonds induced by phase transition. By harnessing the size, shape, and distribution of the patterned stiff skeletons, a wide range of mechanical properties of hydrogels including modulus (0.32–5.92 MPa), toughness (0.15–18 kJ m−2), dissipated energy (1–100 kJ m−3), impact resistance, and mechanical anisotropy can be readily sculpted within one material system without needing design and optimization of the complex and elusive material formulation on demand. It is believed that this simple yet powerful method relying on heterogenous patterning would guide the development of functional hydrogel materials with programmable mechanical properties toward potential engineering applications, such as damping and flexible circuits. [ABSTRACT FROM AUTHOR]

The integration of pressure quantification and visualization enhances pressure perception, accuracy, and efficiency. Current solutions require improvements in quantization accuracy, structural simplicity, and integration. We proposed a novel photonic skin comprising a 3 × 1 flexible optical fiber combiner, integrating red, green, and blue light emitting diode (LED) chips through three flexible optical fibers. Under pressure, changes in the optical fibers' transmission loss alter the output light intensity ratio, thus inducing a color shift at the combiner's output. This visible change can be precisely quantified using a color sensor chip. Performance metrics include sensing range up to 33N, sensitivity between 0.04 and 0.24 dB N−1, detection limit below 0.08 N, response time of 500 ms, recovery time of 400 ms, and durability exceeding 2000 cycles. A compact flexible circuit board manages light source driving, data acquisition, and wireless communication, forming a wearable photonic skin system. This system enables visual recognition and quantitative measurement of pressure across diverse scenarios, including different tactile modes, multi‐position pressure, finger bending, and neck movement. For oral occlusion force detection, the spatial separation of the sensing and visualization areas enables the system to simultaneously provide accurate measurements and intuitive visual assessment. [ABSTRACT FROM AUTHOR]

Peripheral nerve injury significantly impairs sensory and motor functions, leading to diminished quality of life. Traditional treatments like nerve suturing and grafting often have limited efficacy and require long recovery. Recent advances in electrical stimulation technology show promise in speeding nerve repair, but current devices usually require lengthy surgeries, risking secondary nerve injury from prolonged nerve exposure during electrode installation and removal. This study introduces a portable, absorbable electrical stimulation system (PAESS) that integrates a battery‐free, wirelessly powered flexible printed circuit board chip with a biodegradable organic electrode. PAESS enables multiple self‐administered nerve stimulation without the need for electrode installation or removal. Using animal models, its electrical performance, biocompatibility, and efficacy in nerve repair are evaluated. The findings indicate a considerable enhancement in the recovery of nerve function, as demonstrated by improved electrophysiological measurements, decreased muscle atrophy, and positive histological results. Transcriptomic analysis indicates that the PAESS initiates the nerve regeneration process. This research presents an innovative platform for electrical stimulation, laying the groundwork for exploring electrical parameters and their mechanisms. This may deepen understanding of nerve regeneration and foster innovation in therapies. [ABSTRACT FROM AUTHOR]

Aiming at the micrometeoroid/orbital debris (MMOD) collision problem for space structures, this paper proposes a self-sensing aluminum/aramid hybrid laminate for detection of MMOD collision event and identification of its associated damage. A co-curing method is used to fabricate the hybrid laminate while carbon nanotube (CNT) film and flexible printed circuit (FPC) are embedded in the laminate as sensing layer. By injecting tiny currents into the CNT film before and after MMOD collision and collecting the corresponding boundary voltages, electrical resistance tomography (ERT) is employed to reconstruct tomographic image of the conductivity change caused by MMOD collision and provide information about the damage. Experimental studies have conducted to perform ballistic high velocity impacts to simulate MMOD collision to three self-sensing hybrid laminates. The results have demonstrated that, the CNT film has good sensing performance, and the reconstructed image of conductivity changes can reflect the location and approximate size of the damage, validating the effectiveness of the proposed self-sensing hybrid laminate and providing a new way for space structures to detect MMOD collisions. [ABSTRACT FROM AUTHOR]

This investigation presents an analytical model optimized for predicting the curve of Flexible Printed Circuits (FPCs), aiming to enhance design precision within the burgeoning realm of flexible electronics. By modifying the bending Mises stresses derived from the finite element model (FEM), an almost linear relationship was established between the deformed FPC curvature and its length. The analytical model, based on the trend of the FPC curve, integrates differential equations, the Jacobian matrix, and an iterative process. The model's performance, marked by its remarkable efficiency, is rigorously compared with Finite Element Method simulations. The results show a negligible error between the two methods, with the predicted results for different types of FPC curves proving to be highly accurate. The study's insights advocate for the model's adoption in practical applications, suggesting a paradigm shift towards more agile and efficient design methodologies in flexible electronics engineering. [ABSTRACT FROM AUTHOR]

In this paper for the first time, we have studied various structures of nanosheet field-effect transistors (NSFET) and the effect of various devices and process parameters such as nanosheet width, length, interspacing, S/D doping, channel doping, random dopant fluctuations studied on these device structures. Comparative analysis has been done between JL-NSFET, GS-JL-NSFET, JL-SiGeNSFET and JL-GS-SiGeNSFET in terms of analog parameters. Nanosheet-based FETs are likely to be the successor of FinFET beyond the 5-nm node. NSFETs have better control over gate, variable sheet width and more current per device footprint which gives them the advantage of circuit design versatility. NSFET offers better gate control, better current and switching per device footprint. NSFETs are preferred over NWFETs due to better electrostatics, greater channel widths, decreased SCEs and increased device reliability. Above 5 nm technology nodes, stacked nanosheet (NS) GAAFETs are expected to replace FinFETs as they have improved gate control, variable sheet width and substantial current per device footprint, which allows for flexible circuit design. The GAA nanosheet (NS) FETs outperform FinFETs and NWFETs while requiring just straightforward fabrication techniques. NSFETs increase the effective width of the channel while maintaining sufficient current drivability in the specified footprint to provide enhanced electrostatic integrity, better per chip density and enhanced power performances.Comparative analysis in terms of various analog parameters like Ion, Ioff, Ion/Ioff ratio, sub-threshold slope and the effect of various device parameters were carried out for JL-NSFET, JL-GS-NSFET, JL-SiGeNSFET and JL-GS-SiGeNSFET. [ABSTRACT FROM AUTHOR]

Hemodialysis (HD) is widely considered to be the primary means of kidney replacement therapy for end-stage renal disease, involving millions of patients worldwide. The utilization of continuous non-invasive sensors for blood property detection can achieve an adequacy assessment of the dialysis process, which is of great significance for determining the optimal treatment time, ensuring the treatment effect, and improving the quality of life of patients. In this work, a microwave metamaterial sensor is reported for HD based on spoof localized surface plasmons (LSPs). The spoof LSPs sensor is fabricated from a 21 × 12 × 0.043 mm3 thin film, which is conformally attached to the exterior of the pipeline in the dialysis circuit. This attachment design allows for continuous, non-invasive monitoring of variations in the blood's permittivity of patients. The proposed sensor design is compatible with standard flexible printed circuit technology, allowing for low-cost and large-scale manufacturing. In the frequency range of 3–6 GHz, three resonance modes based on spoof LSPs can be used for liquid sensing with a maximum sensitivity of 0.39%. This study is expected to foster research and application of microwave metamaterial sensors in the biomedical field. [ABSTRACT FROM AUTHOR]

The interaction of laser radiation with matter is considered. Marking of non-metallic materials re- quires heating below the softening point, heat treatment requires heating to temperatures above the phase transformation temperature, laser cutting of metals occurs with heating above the melting point, and engraving occurs above the melting or evaporation point. The choice of a laser for a certain type of processing is determined by the specific impact of laser radiation on a given material and the characteristics of the technological task at hand. Laser radiation in the UV range with a wavelength of λ = 355 nm, which can be obtained through third harmonic generation, is increasingly used in industry. Recommendations are pro- vided for the use of low-power pulsed UV lasers for marking, engraving, cutting of metallic and non- metallic materials and surface hardening of steels. The paper presents the results of a study of the effect of laser radiation wavelength on metal engraving. The studies show that engraving with a beam with a radiation wavelength of λ = 0.355 µm allows obtaining a high-quality image without melting the surface. Due to the fact that radiation with a wavelength of λ = 0.35 µm is equally well absorbed by metals and dielectrics, UV-lasers can be used for separation operations in microelectronics, for example, for cutting flexible printed circuit boards with high quality. Reducing the diameter of the focus spot of the UV-laser compared to the focus of the CO2-laser makes it possible to reduce the radiation power and perform better cutting. Comparison of thermal strengthening of steels by volume hardening, laser hardening with melting, laser hardening by UV-radiation showed high efficiency of hardening by UV-radiation. Laser processing in the UV-range is rationally used for local surface hardening of fuel equipment parts, cutting tools [ABSTRACT FROM AUTHOR]

Cardiac mapping is a crucial procedure for diagnosing and treating cardiac arrhythmias. Still, current clinical techniques face limitations including insufficient electrode coverage, poor conformability to complex heart chamber geometries, and high costs. This study explores the design, testing, and validation of a 64-electrode soft robotic catheter that addresses these challenges in cardiac mapping. A dual-layer flexible printed circuit board (PCB) was designed and integrated with sensors into a soft robotic sensor array (SRSA) assembly. Design considerations included flex PCB layout, routing, integration, conformity to heart chambers, sensor placement, and catheter durability. Rigorous SRSA in vitro testing evaluated the burst/leakage pressure, block force for electrode contact, mechanical integrity, and environmental resilience. For in vivo validation, a porcine model was used to demonstrate the successful deployment, conformability, and acquisition of electrograms in both the ventricles and atria. This catheter-deployable SRSA represents a meaningful step towards translating the integration of soft robotic actuators and stretchable electronics for clinical use, showcasing the unique mechanical and electrical performance that these designs enable. The high-density electrode array enabled rapid 2 s data acquisition with detailed spatial and temporal resolution, as illustrated by the clear and consistent cardiac signals recorded across all electrodes. The future of this work will lie in enabling high-density, anatomically conformable devices for detailed cardiac mapping to guide ablation therapy and other interventions. [ABSTRACT FROM AUTHOR]

The rising flexible and intelligent electronics greatly facilitate the noninvasive and timely tracking of physiological information in telemedicine healthcare. Meticulously building bionic-sensitive moieties is vital for designing efficient electronic skin with advanced cognitive functionalities to pluralistically capture external stimuli. However, realistic mimesis, both in the skin's three-dimensional interlocked hierarchical structures and synchronous encoding multistimuli information capacities, remains a challenging yet vital need for simplifying the design of flexible logic circuits. Herein, we construct an artificial epidermal device by in situ growing Cu3(HHTP)2 particles onto the hollow spherical Ti3C2Tx surface, aiming to concurrently emulate the spinous and granular layers of the skin's epidermis. The bionic Ti3C2Tx@Cu3(HHTP)2 exhibits independent NO2 and pressure response, as well as novel functionalities such as acoustic signature perception and Morse code-encrypted message communication. Ultimately, a wearable alarming system with a mobile application terminal is self-developed by integrating the bimodular senor into flexible printed circuits. This system can assess risk factors related with asthmatic, such as stimulation of external NO2 gas, abnormal expiratory behavior and exertion degrees of fingers, achieving a recognition accuracy of 97.6% as assisted by a machine learning algorithm. Our work provides a feasible routine to develop intelligent multifunctional healthcare equipment for burgeoning transformative telemedicine diagnosis. Highlights: A smart wearable alarming system integrated artificial epidermal device for pluralistically identifying asthmatic attack risk factors, achieving a 97.6% classification accuracy as assisted by machine learning algorithm. A meticulous mimicry both in the advanced structural attributes and encoding information abilities of the skin was adopted to design a novel artificial epidermal device by integrating conductive Cu3(HHTP)2 coupled with spherical Ti3C2Tx. The bioinspired Ti3C2Tx@Cu3(HHTP)2 sensors can independently perceive NO2 gas and pressure-triggered stimuli. [ABSTRACT FROM AUTHOR]

This paper proposes a stacked-capacitor pixel circuit for flexible AMOLED (Active Matrix-Organic Light Emitting Diode) displays based on the a-IGZO (Amorphous-Indium Gallium Zinc Oxide) TFT (Thin Film Transistor). A calibrated HSPICE level-61 a-IGZO TFT model is used for CAD simulations. The proposed design compensates for V TH shifts in the TFT by employing a stacked capacitor configuration for threshold voltage detection. The simulated results show a percentage error in the OLED current of less than 0.04% for a maximum tensile and compressive strain of 0.3%. The circuit can suppress the error in OLED current to 1.83% for a V TH shift in the range of 0 V to 2.1 V, from the nominal 0.7 V, with an input data voltage of 15 V. Therefore, the proposed pixel circuit topology proves to be a highly reliable pixel architecture which can be effectively used in AMOLED displays. [ABSTRACT FROM AUTHOR]

This work demonstrates the application of urea-powered paper-based fuel cells (PFCs) with Hydrogen Peroxide (H2O2) as the oxidant to drive a flexible electronic circuit (ring oscillator (RO)), for the first time. Herein, the electrochemical performance of four different PFCs has been studied by employing non-precious electrodes as the anode and cathode. These are the membraneless PFC with (i) Toray carbon paper (CP) (ii) Nickel (Ni)-mesh (iii) Nickel Cobalt nanoparticles supported on reduced Graphene Oxide loaded on the CP (Ni Co@rGo@CP) and (iv) membrane-based PFC with Ni Co@rGo@CP as the electrodes. In each PFC the same electrode is employed on both the sides. A single membraneless-PFC with Ni-Co@rGo@CP as electrodes delivered a peak power density (Pmax) of 55 µW cm−2, maximum current density (Jmax) of 371 µA cm−2 and an open-circuit voltage (OCV) of 0.7 V at 3 M urea. While, a single membrane-based PFC assembled on an anion exchange membrane with Ni-Co@rGo@CP electrodes, delivered a Pmax of ≈70 µW cm−2 and Jmax of ≈500 µA cm−2 at an OCV of 0.7 V with 3 M urea. Subsequently, a stack of two membrane-based PFCs delivered an OCV of ≈1.4 V for 400 s. Finally, this stack is employed as a power source to drive a RO. The measured frequency and peak-to-peak voltage are 37.52 kHz and 1.04 V, respectively. This demonstration opens a window to implement self-contained flexible electronic system using PFCs as the power source with minimal e-waste. [ABSTRACT FROM AUTHOR]

In hard disk drive (HDD) manufacturing, a reflow soldering process (RSP) employs heat generated at the welding tip (WT) to bond tiny electrical components for assembling an HDD. Generally, the heat was generated by an electric current applied to the WT. This article reports a feasibility study of using hot air based on computational fluid dynamics (CFD), a choice to assist heat generation. First, the WT and hot air tube (HAT) prototypes were designed and created. The HAT is a device that helps to supply hot air directly to generate heat at the WT. Then, the experiment was established to measure the temperature (T) supplied by the hot air. The measure results were employed to validate the CFD results. Next, the prototype HAT was used to investigate the T generated at the WT by CFD. The comparison revealed that the T measured by the experiment was in the 106.2 °C–133.5 °C range and that the CFD was in the 107.3 °C–136.6 °C range. The maximum error of the CFD results is 2.3% compared to the experimental results, confirming the credibility of the CFD results and methodology. The CFD results revealed that the operating conditions, such as WT, HAT designs, hot air inlet velocity, and inlet temperature, influence the T. Last, examples of suitable operating conditions for using hot air were presented, which confirmed that hot air is a proper choice for a low-temperature RPS. [ABSTRACT FROM AUTHOR]

Dynamic and agile locomotion in legged robots enables them to overcome obstacles and navigate complex and unstructured terrain. However, the leg mechanisms and actuators needed for versatile locomotion are much more challenging to manufacture and integrate in sub‐gram scale robots. Herein, Picotaur, a 15.4 mg hexapedal robot with legs that enable various locomotion tasks such as turning, climbing 3D‐printed stairs, and pushing loads for the first time at these size scales, is presented. 3D printing with two‐photon polymerization enables the manufacture of electrostatically driven 2 degrees of freedom legs on a robot body made from a flexible printed circuit board. Based on simple control inputs, Picotaur can achieve alternating tripod gaits, reaching speeds up to 57 mm (7.2 body lengths) per second, as well as pronking gaits to tackle a wider variety of terrain. This approach to manufacturing and controlling legged robots at smaller scales provides a path forward toward robots that can be used for practical applications ranging from inspection to exploration and rival the performance of insects at similar size scales. [ABSTRACT FROM AUTHOR]

Metal micro/nanoparticle ink-based printed circuits have shown promise for promoting the scalable application of flexible electronics due to enabling superhigh metallic conductivity with cost-effective mass production. However, it is challenging to activate printed metal-particle patterns to approach the intrinsic conductivity without damaging the flexible substrate, especially for high melting-point metals. Here, we report a pressure-constrained sonication activation (PCSA) method of the printed flexible circuits for more than dozens of metal (covering melting points from room temperature to 3422 °C) and even nonmetallic inks, which is integrated with the large-scale roll-to-roll process. The PCSA-induced synergistic heat-softening and vibration-bonding effect of particles can enable multilayer circuit interconnection and join electronic components onto printed circuits without solder within 1 s at room temperature. We demonstrate PCSA-based applications of 3D flexible origami electronics, erasable and foldable double-sided electroluminescent displays, and custom-designed and large-area electronic textiles, thus indicating its potential for universality in flexible electronics. It is challenging to activate the flexible printed metal circuit to approach the intrinsic conductivity with minimal damage to the substrate. Here, the authors report a large-scale pressure-constrained sonication activation method for various metals and non-metallic inks. [ABSTRACT FROM AUTHOR]

Erectile dysfunction (ED) is a prevalent type of sexual dysfunction, and continuous monitoring of penile tumescence and rigidity during spontaneous nocturnal erections is crucial for its diagnosis and classification. However, the current clinical standard device, limited by its active mechanical load, is bulky and nonwearable and strongly interferes with erections, which compromises both monitoring reliability and patient compliance. Here, we report a wearable adaptive rigidity monitoring (WARM) system that employs a measurement principle without active loads, allowing for the assessment of penile tumescence and rigidity through a specifically designed elastic dual-ring sensor. The dual-ring sensor, comprising two strain-sensing rings with distinct elastic moduli, provides high resolution (0.1%), robust mechanical and electrical stability (sustaining over 1000 cycles), and strong interference resistance. An integrated flexible printed circuit (FPC) collects and processes sensing signals, which are then transmitted to the host computer via Bluetooth for ED assessment. Additionally, we validated the WARM system against the clinical standard device using both a penile model and healthy volunteers, achieving high consistency. Furthermore, the system facilitates the continuous evaluation of penile erections during nocturnal tumescence tests with concurrent sleep monitoring, demonstrating its ability to minimize interference with nocturnal erections. In conclusion, the WARM system offers a fully integrated, wearable solution for continuous, precise, and patient-friendly measurement of penile tumescence and rigidity, potentially providing more reliable and accessible outcomes than existing technologies. [ABSTRACT FROM AUTHOR]

This study presents a novel method to fabricate scalable photovoltaic fibers (PVFs) by leveraging crystalline silicon (c‐Si) solar cell technology, known for its high‐power conversion efficiency (PCE), stable performance, and low cost. The c‐Si PVF is built on a flexible circuit strip as narrow as 400 µm, and c‐Si cells as small as 0.35 mm2 are surface‐mounted on the strip. The cells are diced from an interdigitated back‐contact c‐Si solar cell (≈153 cm2). A c‐Si PVF including a 1 mm2 cell reaches PCE up to 9.6% and 11.0% under simulated AM 1.5G illumination without and with encapsulation, respectively, the highest reported for c‐Si PVFs, while a 1.5 ft‐long fiber produces ≈37 mW m−1. Additionally, the PVF can tolerate bending fatigue with no sign of performance loss after 8000 bending cycles. To demonstrate practical applicability, the c‐Si PVFs are also woven into textile swatches. They deliver ≈10 mW cm−2 under a halogen lamp and successfully power a light‐emitting‐diode. This PVF technology is scalable with regards to both achieving thin fibers and its compatibility with roll‐to‐roll fabrication processes. The fiber concept presented here can also be extended to any chip‐scale surface mountable devices, enabling cell‐agnostic fiber technologies for multifunctional electronic textiles. [ABSTRACT FROM AUTHOR]

This research unveils a transformative methodology for fabricating flexible printed circuit boards (PCBs), focusing on the unique attributes of filter paper substrates. A meticulous parametric exploration scrutinizes critical aspects such as buckling resistance, charging current, plating time, and electrode configurations for copper electroplating. Key findings highlight the exceptional stability of copper electroplating on filter paper, exhibiting robust resistance against environmental variations and bending angles spanning +180° to −180°. Utilizing higher pencil grade material and maintaining a minimum 4 cm distance with a voltage range of 3 to 1.44 V ensures uniform, controlled plating without burning, optimizing the electrode area below 1 cm2 for enhanced practicality. The research underscores the longevity and durability of copper‐plated filter paper, with negligible resistance changes even after 1000 folds. Over a year, the shelf‐life assessment emphasizes the excellent stability of electroplated filter paper. Practical applications, including fully functional circuits and a bio‐degradable piano, underscore the versatility and real‐world feasibility of the proposed electroplating technique. [ABSTRACT FROM AUTHOR]

Deep learning techniques provide a new approach to the design and optimization of electromagnetic metamaterials. This study used a convolutional neural network and long short-term memory (CNN–LSTM) hybrid network to design and optimize a broadband metamaterial reflective linear polarization converter. The data augmentation method was also employed in few-shot learning to reduce optimization costs and improve model prediction performance. With the inverse prediction, a linear polarization converter that perfectly covers the Ku-band was obtained and fabricated with flexible printed circuit technology. Both simulation and experimental results indicate that this network can accurately predict the structural parameters. The polarization converter not only achieves remarkable broadband polarization conversion efficiency spanning the 2.2–18 GHz range but also maintains precise cross-polarization control across the entire Ku-band. The mean polarization conversion ratio in the Ku-band was calculated to be an impressive 99.69%. Finally, the mechanism of polarization conversion and the influence of each structural parameter on its performance further verify the optimality of the inverse design model. The use of CNN–LSTM deep learning methods significantly simplified the design process of electromagnetic metamaterials, reducing design costs while ensuring high design precision and excellent performance. [ABSTRACT FROM AUTHOR]

In hard disk drive (HDD) manufacturing, a reflow soldering process (RSP) implements heat generated by the welding tip to melt a solder ball for bonding the following essential HDD components: a flexible printed circuit (FPC) and a printed circuit cable (PCC). Since the mentioned components are tiny and comprise many thin material layers, an experiment to study thermal and mechanical responses is complex and not worth it. Therefore, a static state multiphysics consisting of thermal analysis (TA) and structural analysis (SA) was employed to investigate both responses. First, the experiment was established to mimic the RSP, measuring the temperature generated by the actual welding tip. Then, the measured temperature was defined as the boundary conditions with the pressing force (F) for the TA and SA based on the actual operating conditions. As expected, the TA results revealed the temperature distribution in the HDD components, which was consistent with the theory and results from previous work and confirmed this work's credibility. Significantly, the SA reported severe total deformation (δ) in FPC's top and bottom ends. The maximum δ was 0.72–0.88 mm for the F of 0–1 N. The stronger the F, the greater the δ. This research highlights that multiphysics can investigate both responses in HDD components as slight as 0.1–100 microns thick, which can be used to develop a high-efficacy RSP. [ABSTRACT FROM AUTHOR]

Modified polyimide (MPI) flexible printed circuits (FPCs) are used as chip carrier boards. The quality of the FPC directly affects the reliability of the integrated circuit. Furthermore, micro-holes are critical components of FPCs. In this study, an ultraviolet (UV) femtosecond laser is used to drill micro-holes in double-layer flexible circuit boards with MPI as the substrate. The morphology of the micro-hole wall in the copper foil and MPI layer is observed, and the effects of the laser processing parameters on the diameter and depth of the micro-holes are analyzed. The drilling process and mechanism of micro-holes obtained using a UV femtosecond laser in MPI FPCs are discussed. The results show that the morphology of femtosecond laser-machined copper is closely related to the laser energy, and a periodic structure is observed during the machining process. Copper, MPI, and copper oxides are the most common molten deposits in micro-holes during drilling. The depth of the micro-holes increases with an increase in the energy of a single pulse, scanning time, and scanning overlap rate of the laser beam. However, the diameter exhibits no discernible alteration. The material removal rate increased significantly when laser processing was applied to the MPI resin layer. [ABSTRACT FROM AUTHOR]

The construction of flexible circuits is a crucial and challenging aspect in the design and fabrication of fabric‐based flexible electronics, which hold significant potential for various applications. In this study, we successfully developed high‐precision and durable fabric‐based flexible circuits by ingeniously combining ultraviolet light (UV)‐curing technology with chemical plating. Specifically, a UV coating containing Ag/Fe3O4 catalysts was applied onto polyester fabric surface, followed by printing the designed circuit structure diagram onto the fabric using UV light‐directed curing of the coating, and fabric‐based flexible circuits were then fabricated through chemical plating process. The fabric‐based flexible circuits exhibit only minimal increases in resistance following durability testing, including bending (8000 times), abrasion (2000 times), high and low temperature stability (−30 to 60°C), and high temperature/humidity stability (65°C, RH = 95%, 48 h), which remains consistently stable. This developed technology holds immense potential across various applications for smart wearable devices. [ABSTRACT FROM AUTHOR]

We implement a distributed Bragg reflector (DBR) laser diode (LD) package with low-magnetic field generation. The package consists of a commercial 795 nm DBR LD chip, a thermo-electric cooler (TEC), a thermistor, a flexible printed circuit board (FPCB) which cancels the magnetic field emitted by the TEC current flow, and a non-magnetic aluminum case. We confirm that the magnetic dipole moment of our low-magnetic package body is about three orders of magnitude smaller than that of a commercial DBR laser package. Moreover, it is shown that our compensating FPCB, the effectiveness of which is supported by computer simulations, reduces the magnetic field magnitude by a factor of 2.2. The FPCB also reduces the magnetic field gradient emitted by the TEC current flow so that gradient-induced spin relaxations are suppressed in applications. A portable optically pumped atomic magnetometer (OPAM) utilizing two low-magnetic packages as light sources is reported as an application of the package and shows a 0.30 pT/Hz1/2 level magnetic sensitivity at a 69 μT external magnetic field; in contrast, the OPAM utilizing the commercial packages showed a magnetic sensitivity of 0.87 pT/Hz1/2. [ABSTRACT FROM AUTHOR]

Flexible tactile sensors play important roles in many areas, like human-machine interface, robotic manipulation, and biomedicine. However, their flexible form factor poses challenges in their integration with wafer-based devices, commercial chips, or circuit boards. Here, we introduce manufacturing approaches, device designs, integration strategies, and biomedical applications of a set of flexible, modular tactile sensors, which overcome the above challenges and achieve cooperation with commercial electronics. The sensors exploit lithographically defined thin wires of metal or alloy as the sensing elements. Arranging these elements across three-dimensional space enables accurate, hysteresis-free, and decoupled measurements of temperature, normal force, and shear force. Assembly of such sensors on flexible printed circuit boards together with commercial electronics forms various flexible electronic systems with capabilities in wireless measurements at the skin interface, continuous monitoring of biomechanical signals, and spatial mapping of tactile information. The flexible, modular tactile sensors expand the portfolio of functional components in both microelectronics and macroelectronics. [ABSTRACT FROM AUTHOR]

Metal oxide films are essential in most electronic devices, yet they are typically deposited at elevated temperatures by using slow, vacuum-based processes. We printed native oxide films over large areas at ambient conditions by moving a molten metal meniscus across a target substrate. The oxide gently separates from the metal through fluid instabilities that occur in the meniscus, leading to uniform films free of liquid residue. The printed oxide has a metallic interlayer that renders the films highly conductive. The metallic character of the printed films promotes wetting of trace amounts of evaporated gold that would otherwise form disconnected islands on conventional oxide surfaces. The resulting ultrathin (<10 nanometers) conductors can be patterned into flexible circuits that are transparent, mechanically robust, and electrically stable, even at elevated temperatures. [ABSTRACT FROM AUTHOR]

It remains a huge challenge to efficiently recycle the printed circuit boards (PCBs) because of the diversity and complexity of the PCBs in terms of material composition. The recycling of PCBs highly depends on the design of the polymers that make up the polymer substrates and conductive pastes. Herein, closed‐loop recyclable plastics for use as the polymer substrates and for the preparation of the conductive pastes are fabricated by dynamically cross‐linking phenylboronic acid‐functionalized poly(methylmethacrylate) (PMMA‐B) and poly(urea‐urethane) (PUU‐B) with boroxines. The closed‐loop recyclable plastic, which is denoted as PMMA‐PUU exhibits a breaking strength of 71.0 MPa and Young's modulus of 1.8 GPa. Because of the dynamic nature of boroxines, the PMMA‐PUU0.6 plastic can be depolymerized in the N, N‐dimethylacetamide/ethanol mixture solvent. The depolymerized PMMA and PUU can be efficiently recovered in high yields and purity through their solubility differences in selective solvents. Conductive pastes suitable for printing of electrical circuits are fabricated through complexation of Ag particles with PMMA‐PUU. PCBs composed of PMMA‐PUU substrates and PMMA‐PUU‐based conductive pastes are flexible, healable, and recyclable. The closed‐loop recycling of the PCBs enables the collection of highly purified Ag particles, PMMA‐B, and PUU‐B monomers even when the PCBs are mixed with polymer wastes. [ABSTRACT FROM AUTHOR]

Wound infections pose a major healthcare issue, affecting the well‐being of millions of patients worldwide. Effective intervention and on‐site detection are important in wound management. However, current approaches are hindered by time‐consuming analysis and a lack of technology for real‐time monitoring and prompt therapy delivery. In this study, a smart wound patch system (SWPS) designed for wireless closed‐loop and in‐situ wound management is presented. The SWPS integrates a microfluidic structure, an organic electrochemical transistor (OECT) based sensor, an electrical stimulation module, and a miniaturized flexible printed circuit board (FPCB). The OECT incorporates a bacteria‐responsive DNA hydrogel‐coated gate for continuous monitoring of bacterial virulence at wound sites. Real‐time detection of OECT readings and on‐demand delivery of electrical cues to accelerate wound healing is facilitated by a mobile phone application linked with an FPCB containing low‐power electronics equipped with parallel sensing and stimulation circuitry. In this proof‐of‐concept study, the functionality of the SWPS is validated and its application both in vitro and in vivo is demonstrated. This proposed system expands the arsenal of tools available for effective wound management and enables personalized treatment. [ABSTRACT FROM AUTHOR]

Electrical and mechanical integration approaches are essential for emerging hybrid electronics that must robustly bond rigid electrical components with flexible circuits and substrates. However, flexible polymeric substrates and circuits cannot withstand the high temperatures used in traditional electronic processing. This constraint requires new strategies to create flexible materials that simultaneously achieve high electrical conductivity, strong adhesion, and processibility at low temperature. Here, an electrically conductive adhesive is introduced that is flexible, electrically conductive (up to 3.25×105 S m−1) without sintering or high temperature post‐processing, and strongly adhesive to various materials common to flexible and stretchable circuits (fracture energy 350

Monitoring neural activity in the central nervous system often utilizes silicon-based microelectromechanical system (MEMS) probes. Despite their effectiveness in monitoring, these probes have a fragility issue, limiting their application across various fields. This study introduces flexible printed circuit board (FPCB) neural probes characterized by robust mechanical and electrical properties. The probes demonstrate low impedance after platinum coating, making them suitable for multiunit recordings in awake animals. This capability allows for the simultaneous monitoring of a large population of neurons in the brain, including cluster data. Additionally, these probes exhibit no fractures, mechanical failures, or electrical issues during repeated-bending tests, both during handling and monitoring. Despite the possibility of using this neural probe for signal measurement in awake animals, simply applying a platinum coating may encounter difficulties in chronic tests and other applications. Furthermore, this suggests that FPCB probes can be advanced by any method and serve as an appropriate type of tailorable neural probes for monitoring neural systems in awake animals. [ABSTRACT FROM AUTHOR]

Peripheral nerve modulation via electrical stimulation shows promise for treating several diseases, but current approaches lack selectivity, leading to side effects. Exploring selective neuromodulation with commercially available nerve cuffs is impractical due to their high cost and limited spatial resolution. While custom cuffs reported in the literature achieve high spatial resolutions, they require specialized microfabrication equipment and significant effort to produce even a single design. This inability to rapidly and cost-effectively prototype novel cuff designs impedes research into selective neuromodulation therapies in acute studies. To address this, we developed a reproducible method to easily create multi-channel epineural nerve cuffs for selective fascicular neuromodulation. Leveraging commercial flexible printed circuit (FPC) technology, we created cuffs with high spatial resolution (50 μm) and customizable parameters like electrode size, channel count, and cuff diameter. We designed cuffs to accommodate adult mouse or rat sciatic nerves (300–1500 μm diameter). We coated the electrodes with PEDOT:PSS to improve the charge injection capacity. We demonstrated selective neuromodulation in both rats and mice, achieving preferential activation of the tibialis anterior (TA) and lateral gastrocnemius (LG) muscles. Selectivity was confirmed through micro-computed tomography (μCT) and quantified through a selectivity index. These results demonstrate the potential of this fabrication method for enabling selective neuromodulation studies while significantly reducing production time and costs compared to traditional approaches. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue of the journal Micromachines on wearable and implantable bio-MEMS devices and applications. The editorial highlights the importance of these devices in health monitoring, disease treatment, and human-machine interaction. The special issue includes six articles, five of which are original research papers and one is a review article. The articles cover various topics such as novel design methods, fabrication techniques, algorithms for signal detection and recognition, and applications for detecting biomarkers and monitoring chronic diseases. The goal of the special issue is to showcase the advancements and opportunities in this field and their potential to improve people's lives. [Extracted from the article]

The performance improvement of CMOS computer fails to meet the enormous data processing requirement of artificial intelligence progressively. The memristive neural network is one of the most promising circuit hardwares to make a breakthrough. This paper proposes a novel memristive synaptic circuit that is composed of four MOS transistors and one memristor (4T1M). The 4T1M synaptic circuit provides flexible control strategies to change memristance or respond to the input signal. Applying the 4T1M synaptic circuit as the cell of memristive crossbar array, based on the structure and algorithm of the back-propagation (BP) neural network, this paper proposes circuit design of the memristive crossbar-based BP neural network. By reusing the 4T1M memristive crossbar array, the computations in the forward-propagation process and back-propagation process of BP neural network are accomplished on the memristive crossbar-based circuit to accelerate the computing speed. The 4T1M memristive crossbar array can change all the cells' memristance at a time, accordingly, the memristive crossbar-based BP neural network can realize synchronous memristance adjustment. The proposed memristive crossbar-based BP neural network is then evaluated through experiments involving XOR logic operation, iris classification, and MNIST handwritten digit recognition. The experimental results present fewer iterations or higher classification accuracies. Further, the comprehensive comparisons with the existing memristive BP neural networks highlight the advantages of the proposed memristive crossbar-based BP neural network, which achieves the fastest memristance adjustment speed using relatively few components. [ABSTRACT FROM AUTHOR]

As a stress hormone existing in the human body, cortisol can reflect the psychological stress and health status in daily life, and is a potential biomarker of the body's stress response. To effectively collect sweat and accurately identify the target, this paper reports a flexible wearable cortisol detection device with outstanding reliability and sensitivity. Molecular imprinted polymer (MIP) ensures cortisol specificity. And carbon nanotubes (CNT) on electrodes increase sensitivity, expanding the detection range to 10−3 to 104 nM, with sensitivity at 189.2 nA/lg(nM). In addition, porous chitosan hydrogel (PCSH) collects sweat effectively, its adhesive properties and 80% swelling rate offer a low-cost alternative to microfluidics. Flexible printed circuit board (FPCB) and serpentine electrode (SE) ensure device durability. This non-invasive, highly sensitive device offers a novel method for mental stress monitoring and clinical diagnosis, advancing human physiological state monitoring. [ABSTRACT FROM AUTHOR]

Aramid nanofibers (ANFs) are a strong and heat‐resistant nanomaterial that can be isolated from commercial para‐aramid fibers, which allow a bottom‐up self‐assembly to form ordered macroscale structures like ANF films. However, the anisotropic nature of high aspect ratio ANFs is not fully exploited when fabricating ANF films for the optimal mechanical properties. In this research, direct ink writing (DIW) is applied to produce ANF‐assembled films with arbitrary shapes, and the shear‐induced alignment of ANFs can follow the printing path direction. Therefore, controlled alignment of ANFs following the computer‐programmed printing pattern is achieved by DIW, which provides a path for the application of topology and nanofiber alignment optimization in nanofiber‐assembled films. In addition, the resulting DIW ANF films exhibit outstanding Young's modulus of 8.39 GPa, tensile strength of 198 MPa, and tensile toughness of 19.4 MJ m−3 in the alignment direction, together with a wide working temperature range up to 440 °C without losing 50% of its room temperature storage modulus. Moreover, the demonstrated self‐joining ability, rollability, and lamination processability of the DIW ANF films expand their potential applications toward high‐temperature ultrathin tubes, substrates for flexible printed circuit boards, and three‐dimensional all‐ANF lightweight structural parts in extreme environments. [ABSTRACT FROM AUTHOR]

Transient electronics with degradability or dissolvability on demand possess remarkable characteristics for wearable, bioelectronic, and implanted electronic devices. While synthetic materials have made significant progress in degradability and stretchability, they suffer from intrinsic limitations, including low degradation rates, poor mechanical compliance, and high production cost, which restrict the growth of transient electronic devices. Herein, a versatile fabrication strategy is presented for transient electronics that combine a resilient biopolymer substrate (gelatin biogels) with liquid metal (Galinstan). The circuits made from gelatin biogel‐based and liquid metal are mechanically resilient and durable, exhibiting good compliance with irregular and deformable surfaces, and thus can withstand long‐term exposure to dynamic deformation (about 60 000 cycles at a strain of 50%). More importantly, gelatin biogels are naturally derived and endowed with thermally reversible gelling, which enables on‐demand rapid dissolution and recycling of the materials. As a proof‐of‐concept, transient circuit‐based capacitive sensors, which can be degraded within 20 s, are fabricated for monitoring finger touching, morse code generation, and electrical touchpad. Such a strategy provides a guideline for designing transient electronics with a combination of biopolymer gels and liquid metal, and this approach is anticipated to find applications in human–machine interfaces and wearable devices. [ABSTRACT FROM AUTHOR]

A series of ester-linked tetracarboxylic dianhydrides containing multiple para-phenylene units (TA-pPhs) was synthesized to obtain novel modified polyimides, namely poly(ester imide)s (PEsIs). The flame retardancy and film toughness of PEsIs tended to deteriorate with the structural extension of the repeating units (or monomers) via ester groups. To identify the structural factors necessary for achieving the highest flame retardancy rank (UL-94, V-0), we systematically investigated the structure–property relationships of a series of TA-pPh-based PEsIs. Among them, a PEsI derived from para-quaterphenylene-containing TA-pPh (TA-DPQP) and p-phenylenediamine (p-PDA) exhibited the best property combination, featuring an extremely high glass transition temperature (Tg), very low linear coefficient of thermal expansion (CTE), low water uptake (WA), ultralow linear coefficient of humidity (hygroscopic) expansion (CHE), unexpectedly high film toughness, and excellent flame retardancy (V-0 rank). Moreover, we examined the effects of substituents of TA-pPh and discussed the mode of action for the increased film toughness. This study also investigated the structure–property relationship for a series of PEsIs derived from isomeric naphthalene-containing tetracarboxylic dianhydrides. Some of the PEsIs obtained in this study, such as the TA-DPQP/p-PDA system, hold promise as novel high-temperature dielectric substrates for use in flexible printed circuits. [ABSTRACT FROM AUTHOR]