Intrinsically stretchable organic photovoltaics by redistributing strain to PEDOT:PSS with enhanced stretchability and interfacial adhesion.

Intrinsically stretchable organic photovoltaics have emerged as a prominent candidate for the next-generation wearable power generators regarding their structural design flexibility, omnidirectional stretchability, and in-plane deformability. However, formulating strategies to fabricate intrinsically stretchable organic photovoltaics that exhibit mechanical robustness under both repetitive strain cycles and high tensile strains remains challenging. Herein, we demonstrate high-performance intrinsically stretchable organic photovoltaics with an initial power conversion efficiency of 14.2%, exceptional stretchability (80% of the initial power conversion efficiency maintained at 52% tensile strain), and cyclic mechanical durability (95% of the initial power conversion efficiency retained after 100 strain cycles at 10%). The stretchability is primarily realised by delocalising and redistributing the strain in the active layer to a highly stretchable PEDOT:PSS electrode developed with a straightforward incorporation of ION E, which simultaneously enhances the stretchability of PEDOT:PSS itself and meanwhile reinforces the interfacial adhesion with the polyurethane substrate. Both enhancements are pivotal factors ensuring the excellent mechanical durability of the PEDOT:PSS electrode, which further effectively delays the crack initiation and propagation in the top active layer, and enables the limited performance degradation under high tensile strains and repetitive strain cycles.

Intelligent wearable olfactory interface for latency-free mixed reality and fast olfactory enhancement.

Olfaction feedback systems could be utilized to stimulate human emotion, increase alertness, provide clinical therapy, and establish immersive virtual environments. Currently, the reported olfaction feedback technologies still face a host of formidable challenges, including human perceivable delay in odor manipulation, unwieldy dimensions, and limited number of odor supplies. Herein, we report a general strategy to solve these problems, which associates with a wearable, high-performance olfactory interface based on miniaturized odor generators (OGs) with advanced artificial intelligence (AI) algorithms. The OGs serve as the core technology of the intelligent olfactory interface, which exhibit milestone advances in millisecond-level response time, milliwatt-scale power consumption, and the miniaturized size. Empowered by robust AI algorithms, the olfactory interface shows its great potentials in latency-free mixed reality (MR) and fast olfaction enhancement, thereby establishing a bridge between electronics and users for broad applications ranging from entertainment, to education, to medical treatment, and to human machine interfaces.

Janus Membrane-Based Wearable pH Sensor with Sweat Absorption, Gas Permeability, and Self-Adhesiveness.

Wearable biomedical sensors have enabled noninvasive and continuous physiological monitoring for daily health management and early detection of chronic diseases. Among biomedical sensors, wearable pH sensors attracted significant interest, as pH influences most biological reactions. However, conformable pH sensors that have sweat absorption ability, are self-adhesive to the skin, and are gas permeable remain largely unexplored. In this study, we present a pioneering approach to this problem by developing a Janus membrane-based pH sensor with self-adhesiveness on the skin. The sensor is composed of a hydrophobic polyurethane-polydimethylsiloxane porous hundreds nanometer-thick substrate and a hydrophilic poly(vinyl alcohol)-poly(acrylic acid) porous nanofiber layer. This Janus membrane exhibits a thickness of around 10 µm, providing a conformable adhesion to the skin. The simultaneous realization of solution absorption, gas permeability, and self-adhesiveness makes it suitable for long-term continuous monitoring without compromising the comfort of the wearer. The pH sensor was tested successfully for continuous monitoring for 7.5 h, demonstrating its potential for stable analysis of skin health conditions. The Janus membrane-based pH sensor holds significant promise for comprehensive skin health monitoring and wearable biomedical applications.

Permeable Bioelectronics toward Biointegrated Systems.

Bioelectronics integrates electronics with biological organs, sustaining the natural functions of the organs. Organs dynamically interact with the external environment, managing internal equilibrium and responding to external stimuli. These interactions are crucial for maintaining homeostasis. Additionally, biological organs possess a soft and stretchable nature; encountering objects with differing properties can disrupt their function. Therefore, when electronic devices come into contact with biological objects, the permeability of these devices, enabling interactions and substance exchanges with the external environment, and the mechanical compliance are crucial for maintaining the inherent functionality of biological organs. This review discusses recent advancements in soft and permeable bioelectronics, emphasizing materials, structures, and a wide range of applications. The review also addresses current challenges and potential solutions, providing insights into the integration of electronics with biological organs.

All-solution-processed ultraflexible wearable sensor enabled with universal trilayer structure for organic optoelectronic devices.

All-solution-processed organic optoelectronic devices can enable the large-scale manufacture of ultrathin wearable electronics with integrated diverse functions. However, the complex multilayer-stacking device structure of organic optoelectronics poses challenges for scalable production. Here, we establish all-solution processes to fabricate a wearable, self-powered photoplethysmogram (PPG) sensor. We achieve comparable performance and improved stability compared to complex reference devices with evaporated electrodes by using a trilayer device structure applicable to organic photovoltaics, photodetectors, and light-emitting diodes. The PPG sensor array based on all-solution-processed organic light-emitting diodes and photodetectors can be fabricated on a large-area ultrathin substrate to achieve long storage stability. We integrate it with a large-area, all-solution-processed organic solar module to realize a self-powered health monitoring system. We fabricate high-throughput wearable electronic devices with complex functions on large-area ultrathin substrates based on organic optoelectronics. Our findings can advance the high-throughput manufacture of ultrathin electronic devices integrating complex functions.

Waterproof and ultraflexible organic photovoltaics with improved interface adhesion.

Ultraflexible organic photovoltaics have emerged as a potential power source for wearable electronics owing to their stretchability and lightweight nature. However, waterproofing ultraflexible organic photovoltaics without compromising mechanical flexibility and conformability remains challenging. Here, we demonstrate waterproof and ultraflexible organic photovoltaics through the in-situ growth of a hole-transporting layer to strengthen interface adhesion between the active layer and anode. Specifically, a silver electrode is deposited directly on top of the active layers, followed by thermal annealing treatment. Compared with conventional sequentially-deposited hole-transporting layers, the in-situ grown hole-transporting layer exhibits higher thermodynamic adhesion between the active layers, resulting in better waterproofness. The fabricated 3 µm-thick organic photovoltaics retain 89% and 96% of their pristine performance after immersion in water for 4 h and 300 stretching/releasing cycles at 30% strain under water, respectively. Moreover, the ultraflexible devices withstand a machine-washing test with such a thin encapsulation layer, which has never been reported. Finally, we demonstrate the universality of the strategy for achieving waterproof solar cells.

Heavy-to-light electron transition enabling real-time spectra detection of charged particles by a biocompatible semiconductor.

The current challenge of wearable/implantable personal dosimeters for medical diagnosis and radiotherapy applications is lack of suitable detector materials possessing both excellent detection performance and biocompatibility. Here, we report a solution-grown biocompatible organic single crystalline semiconductor (OSCS), 4-Hydroxyphenylacetic acid (4HPA), achieving real-time spectral detection of charged particles with single-particle sensitivity. Along in-plane direction, two-dimensional anisotropic 4HPA exhibits a large electron drift velocity of 5 × 105 cm s-1 at "radiation-mode" while maintaining a high resistivity of (1.28 ± 0.003) × 1012 Ω·cm at "dark-mode" due to influence of dense π-π overlaps and high-energy L1 level. Therefore, 4HPA detectors exhibit the record spectra detection of charged particles among their organic counterparts, with energy resolution of 36%, (µt)e of (4.91 ± 0.07) × 10-5 cm2 V-1, and detection time down to 3 ms. These detectors also show high X-ray detection sensitivity of 16,612 µC Gyabs-1 cm-3, detection of limit of 20 nGyair s-1, and long-term stability after 690 Gyair irradiation.

A 10-micrometer-thick nanomesh-reinforced gas-permeable hydrogel skin sensor for long-term electrophysiological monitoring.

Hydrogel-enabled skin bioelectronics that can continuously monitor health for extended periods is crucial for early disease detection and treatment. However, it is challenging to engineer ultrathin gas-permeable hydrogel sensors that can self-adhere to the human skin for long-term daily use (>1 week). Here, we present a ~10-micrometer-thick polyurethane nanomesh-reinforced gas-permeable hydrogel sensor that can self-adhere to the human skin for continuous and high-quality electrophysiological monitoring for 8 days under daily life conditions. This research involves two key steps: (i) material design by gelatin-based thermal-dependent phase change hydrogels and (ii) robust thinness geometry achieved through nanomesh reinforcement. The resulting ultrathin hydrogels exhibit a thickness of ~10 micrometers with superior mechanical robustness, high skin adhesion, gas permeability, and anti-drying performance. To highlight the potential applications in early disease detection and treatment that leverage the collective features, we demonstrate the use of ultrathin gas-permeable hydrogels for long-term, continuous high-precision electrophysiological monitoring under daily life conditions up to 8 days.

Indoor Self-Powered Perovskite Optoelectronics with Ultraflexible Monochromatic Light Source.

Self-powered skin optoelectronics fabricated on ultrathin polymer films is emerging as one of the most promising components for the next-generation Internet of Things (IoT) technology. However, a longstanding challenge is the device underperformance owing to the low process temperature of polymer substrates. In addition, broadband electroluminescence (EL) based on organic or polymer semiconductors inevitably suffers from periodic spectral distortion due to Fabry-Pérot (FP) interference upon substrate bending, preventing advanced applications. Here, ultraflexible skin optoelectronics integrating high-performance solar cells and monochromatic light-emitting diodes using solution-processed perovskite semiconductors is presented. n-i-p perovskite solar cells and perovskite nanocrystal light-emitting diodes (PNC-LEDs), with power-conversion and current efficiencies of 18.2% and 15.2 cd A-1 , respectively, are demonstrated on ultrathin polymer substrates with high thermal stability, which is a record-high efficiency for ultraflexible perovskite solar cell. The narrowband EL with a full width at half-maximum of 23 nm successfully eliminates FP interference, yielding bending-insensitive spectra even under 50% of mechanical compression. Photo-plethysmography using the skin optoelectronic device demonstrates a signal selectivity of 98.2% at 87 bpm pulse. The results presented here pave the way to inexpensive and high-performance ultrathin optoelectronics for self-powered applications such as wearable displays and indoor IoT sensors.

An optical-based multipoint 3-axis pressure sensor with a flexible thin-film form.

Multipoint 3-axis tactile pressure sensing by a high-resolution and sensitive optical system provides rich information on surface pressure distribution and plays an important role in a variety of human interaction-related and robotics applications. However, the optical system usually has a bulky profile, which brings difficulties to sensor mounting and system integration. Here, we show a construction of thin-film and flexible multipoint 3-axis pressure sensor by optical methods. The sensor can detect the distribution of 3-axis pressure on an area of 3 centimeter by 4 centimeter, with a high-accuracy normal and tangential pressure sensing up to 360 and 100 kilopascal, respectively. A porous rubber is used as a 3-axis pressure-sensitive optical modulator to omit the thick and rigid focusing system without sacrificing the sensitivity. In addition, by integrating thin and flexible backlight and imager, the sensor has a total thickness of 1.5 milimeter, making it function properly even when bent to a radius of 18 milimeter.

Flexible Solution-Processed Electron-Transport-Layer-Free Organic Photovoltaics for Indoor Application.

Organic photovoltaics (OPVs) have unique advantages of low weight, mechanical flexibility, and solution processability, which make them exceptionally suitable for integrating low-power Internet of Things devices. However, achieving improved operational stability together with solution processes that are applicable to large-scale fabrication remains challenging. Their major limitation arises due to the instable factors that occur both inside the thick active film and from the ambient environment, which cannot be completely resolved via the current encapsulation techniques used for flexible OPVs. Additionally, thin active layers are highly vulnerable to point defects, which result in low yield rates and impede the laboratory-to-industry translation. In this study, flexible fully solution-processed OPVs with improved indoor efficiency and long-term operational stability than that of conventional OPVs with evaporated electrodes are achieved. Benefiting from the oxygen and water vapor permeation barrier of the spontaneously formed gallium oxide layers on the exposed eutectic gallium-indium surface, fast degradation of the OPVs with thick active layers is prevented, maintaining 93% of its initial Pmax after 5000 min of indoor operation under 1000 lx light-emitting diode (LED) illumination. Additionally, by using the thick active layer, spin-coated silver nanowires could be directly used as bottom electrodes without complicated flattening processes, thereby substantially simplifying the fabrication process and proposing a promising manufacturing technique for devices with high-throughput energy demands.

Surface-Energy-Mediated Interfacial Adhesion for Mechanically Robust Ultraflexible Organic Photovoltaics.

Insufficient interfacial adhesion is a widespread problem across multilayered devices that undermines their reliability. In flexible organic photovoltaics (OPVs), poor interfacial adhesion can accelerate degradation and failure under mechanical deformations due to the intrinsic brittleness and mismatching mechanical properties between functional layers. We introduce an argon plasma treatment for OPV devices, which yields 58% strengthening in interfacial adhesion between an active layer and a MoOX hole transport layer, thus contributing to mechanical reliability. The improved adhesion is attributed to the increased surface energy of the active layer that occurred after the mild argon plasma treatment. The mechanically stabilized interface retards the flexible device degradation induced by mechanical stress and maintains a power conversion efficiency of 94.8% after 10,000 cycles of bending with a radius of 2.5 mm. In addition, a fabricated 3 µm thick ultraflexible OPV device shows excellent mechanical robustness, retaining 91.0% of the initial efficiency after 1000 compressing-stretching cycles with a 40% compression ratio. The developed ultraflexible OPV devices can operate stably at the maximum power point under continuous 1 sun illumination for 500 min with an 89.3% efficiency retention. Overall, we validate a simple interfacial linking strategy for efficient and mechanically robust flexible and ultraflexible OPVs.

Clinical role of radiofrequency ablation for early-stage hepatocellular carcinoma in an advanced aging society.

AIM: It is unclear whether prognosis differs by age for early-stage hepatocellular carcinoma (HCC). We aimed to examine prognosis and recurrence after radiofrequency ablation (RFA) for early-stage HCC and to determine its prognostic factors for different age groups. METHODS: This retrospective study enrolled 1079 patients with initial early-stage HCC treated with RFA at two institutions. All patients in this study were divided into four groups: <70 years old (group1, n = 483), 70-74 years old (group2, n = 198), 75-79 years old (group3, n = 201), and ≥80 years old (group4, n = 197). Prognostic factors were evaluated by comparing survival and recurrence rates between each group. RESULTS: The median survival time and 5-year survival rates for each group were 113 months and 70.8% in group1, 99.2 months and 71.5% in group2, 91.3 months and 66.5% in group3, and 71 months and 52.6% in group 4, respectively. Group4 had a significantly shorter survival than the other groups (p < 0.05). There were no significant differences in recurrence-free survival among the groups. In group4, the most common cause of death was nonliver-related disease (69.4%). In all groups, modified albumin-bilirubin index grade was a factor contributing to prolonged prognosis, but only in group4 performance status (PS) was a significant factor (hazard ratio, 2.46; 95% confidence interval, 1.16-3.00; p = 0.009). CONCLUSION: For early-stage HCC in the elderly, preoperative evaluation of PS and management of other diseases could contribute to a prolonged prognosis.

Patients with Chronic Liver Disease under Surveillance for Hepatocellular Carcinoma Have a Favorable Long-Term Outcome for Pancreatic Cancer Due to Early Diagnosis and High Resection Rate.

Patients with viral hepatitis-related chronic liver disease (CLD) under surveillance for hepatocellular carcinoma (HCC) are often diagnosed with pancreatic cancer (PC) at an early stage. However, the long-term outcomes of these patients are unclear. We aimed to clarify the long-term outcomes of patients with PC with viral hepatitis-related CLD using a chart review. Data collection included the Union for International Cancer Control (UICC) stage at PC diagnosis, hepatitis B virus and hepatitis C virus status, and long-term outcomes. The distribution of the entire cohort (N = 552) was as follows: early stage (UICC 0-IB; n = 52, 9.5%) and non-early stages (UICC IIA-IV; n = 500, 90.5%). At diagnosis, the HCC surveillance group (n = 18) had more patients in the early stages than the non-surveillance group (n = 534) (50% vs. 8.0%), leading to a higher indication rate for surgical resection (72.2% vs. 29.8%) and a longer median survival time (19.0 months vs. 9.9 months). We confirmed that patients with viral hepatitis-related CLD under HCC surveillance were diagnosed with PC at an early stage. Because of the higher indication rate for surgical resection in these patients, they had favorable long-term outcomes for PC.

Metastasis from Renal Cell Carcinoma to Ectopic Pancreas Diagnosed after Resection.

We herein report a 68-year-old man who underwent nephrectomy for right renal cell carcinoma 10 years prior. He remained under regular medical observation, and abdominal computed tomography showed tumors in the head and tail of the pancreas. He was diagnosed with pancreatic metastasis from renal cell carcinoma. He underwent surgical excision. The pathologic diagnosis proved that the pancreatic tumors were metastases from renal cell carcinoma and clarified that an ectopic pancreas in the duodenum had metastases as well. To our knowledge, this is the first case of metastasis to an ectopic pancreas.

Ultrathin Fiber-Mesh Polymer Thermistors.

Flexible sensors enable on-skin and in-body health monitoring, which require flexible thermal protection circuits to prevent overheating and operate the devices safely. Here, ultrathin fiber-mesh polymer positive temperature coefficient (PTC) thermistors via electrospinning are developed. The fiber-type thermistors are composed of acrylate polymer and carbon nanofibers. The fibrous composite materials are coated with a parylene to form a core-sheath structure, which improves the repeatability of temperature characteristics. Approximately 5 µm thick fiber-type thermistors exhibit an increase in the resistance by three orders of magnitude within ≈2 °C and repeatable temperature characteristics for up to 400 cycles. The mesh structure enables the thermistor layer to be ultra-lightweight and transparent; the mesh-type thermistor operates with a fiber density of 16.5 µg cm-2 , whose fiber layer has a transmittance of more than 90% in the 400-800 nm region. By fabricating the mesh thermistor on a 1.4 µm thick substrate, the thermistor operates without degradation when wrapped around a 280 µm radius needle. Furthermore, the gas-permeable property is demonstrated by fabricating the fibrous thermistor on a mesh substrate. The proposed ultrathin mesh polymer PTC thermistors form the basis for on-skin and implantable devices that are equipped with overheat prevention.

A case of walled-off necrosis extending into the pelvic cavity successfully treated by endoscopic necrosectomy using a lumen-apposing metal stent.

A 31-year-old man developed massive walled-off necrosis extending into the pelvic cavity following severe acute alcoholic pancreatitis. Endoscopic ultrasound-guided fistula drainage was performed using a lumen-apposing metal stent, but this was insufficiently effective, and endoscopic necrosectomy was also performed, after which the patient improved. Percutaneous drainage and surgery are other options for the treatment of walled-off necrosis extending into the pelvic cavity, but a valuable case in which the patient improved with endoscopic treatment alone is presented.

Antimicrobial second skin using copper nanomesh.

The functional support and advancement of our body while preserving inherent naturalness is one of the ultimate goals of bioengineering. Skin protection against infectious pathogens is an application that requires common and long-term wear without discomfort or distortion of the skin functions. However, no antimicrobial method has been introduced to prevent cross-infection while preserving intrinsic skin conditions. Here, we propose an antimicrobial skin protection platform copper nanomesh, which prevents cross-infectionmorphology, temperature change rate, and skin humidity. Copper nanomesh exhibited an inactivation rate of 99.99% for Escherichia coli bacteria and influenza virus A within 1 and 10 min, respectively. The thin and porous nanomesh allows for conformal coating on the fingertips, without significant interference with the rate of skin temperature change and humidity. Efficient cross-infection prevention and thermal transfer of copper nanomesh were demonstrated using direct on-hand experiments.

On-skin paintable biogel for long-term high-fidelity electroencephalogram recording.

Long-term high-fidelity electroencephalogram (EEG) recordings are critical for clinical and brain science applications. Conductive liquid-like or solid-like wet interface materials have been conventionally used as reliable interfaces for EEG recording. However, because of their simplex liquid or solid phase, electrodes with them as interfaces confront inadequate dynamic adaptability to hairy scalp, which makes it challenging to maintain stable and efficient contact of electrodes with scalp for long-term EEG recording. Here, we develop an on-skin paintable conductive biogel that shows temperature-controlled reversible fluid-gel transition to address the abovementioned limitation. This phase transition endows the biogel with unique on-skin paintability and in situ gelatinization, establishing conformal contact and dynamic compliance of electrodes with hairy scalp. The biogel is demonstrated as an efficient interface for long-term high-quality EEG recording over several days and for the high-performance capture and classification of evoked potentials. The paintable biogel offers a biocompatible and long-term reliable interface for EEG-based systems.

Skin bioelectronics towards long-term, continuous health monitoring.

Skin bioelectronics are considered as an ideal platform for personalised healthcare because of their unique characteristics, such as thinness, light weight, good biocompatibility, excellent mechanical robustness, and great skin conformability. Recent advances in skin-interfaced bioelectronics have promoted various applications in healthcare and precision medicine. Particularly, skin bioelectronics for long-term, continuous health monitoring offer powerful analysis of a broad spectrum of health statuses, providing a route to early disease diagnosis and treatment. In this review, we discuss (1) representative healthcare sensing devices, (2) material and structure selection, device properties, and wireless technologies of skin bioelectronics towards long-term, continuous health monitoring, (3) healthcare applications: acquisition and analysis of electrophysiological, biophysical, and biochemical signals, and comprehensive monitoring, and (4) rational guidelines for the design of future skin bioelectronics for long-term, continuous health monitoring. Long-term, continuous health monitoring of advanced skin bioelectronics will open unprecedented opportunities for timely disease prevention, screening, diagnosis, and treatment, demonstrating great promise to revolutionise traditional medical practices.