A three-dimensional liquid diode for soft, integrated permeable electronics.

Wearable electronics with great breathability enable a comfortable wearing experience and facilitate continuous biosignal monitoring over extended periods1-3. However, current research on permeable electronics is predominantly at the stage of electrode and substrate development, which is far behind practical applications with comprehensive integration with diverse electronic components (for example, circuitry, electronics, encapsulation)4-8. Achieving permeability and multifunctionality in a singular, integrated wearable electronic system remains a formidable challenge. Here we present a general strategy for integrated moisture-permeable wearable electronics based on three-dimensional liquid diode (3D LD) configurations. By constructing spatially heterogeneous wettability, the 3D LD unidirectionally self-pumps the sweat from the skin to the outlet at a maximum flow rate of 11.6 ml cm-2 min-1, 4,000 times greater than the physiological sweat rate during exercise, presenting exceptional skin-friendliness, user comfort and stable signal-reading behaviour even under sweating conditions. A detachable design incorporating a replaceable vapour/sweat-discharging substrate enables the reuse of soft circuitry/electronics, increasing its sustainability and cost-effectiveness. We demonstrated this fundamental technology in both advanced skin-integrated electronics and textile-integrated electronics, highlighting its potential for scalable, user-friendly wearable devices.

Bioelectronics for electrical stimulation: materials, devices and biomedical applications.

Bioelectronics is a hot research topic, yet an important tool, as it facilitates the creation of advanced medical devices that interact with biological systems to effectively diagnose, monitor and treat a broad spectrum of health conditions. Electrical stimulation (ES) is a pivotal technique in bioelectronics, offering a precise, non-pharmacological means to modulate and control biological processes across molecular, cellular, tissue, and organ levels. This method holds the potential to restore or enhance physiological functions compromised by diseases or injuries by integrating sophisticated electrical signals, device interfaces, and designs tailored to specific biological mechanisms. This review explains the mechanisms by which ES influences cellular behaviors, introduces the essential stimulation principles, discusses the performance requirements for optimal ES systems, and highlights the representative applications. From this review, we can realize the potential of ES based bioelectronics in therapy, regenerative medicine and rehabilitation engineering technologies, ranging from tissue engineering to neurological technologies, and the modulation of cardiovascular and cognitive functions. This review underscores the versatility of ES in various biomedical contexts and emphasizes the need to adapt to complex biological and clinical landscapes it addresses.

Implantable Electronic Medicine Enabled by Bioresorbable Microneedles for Wireless Electrotherapy and Drug Delivery.

A combined treatment using medication and electrostimulation increases its effectiveness in comparison with one treatment alone. However, the organic integration of two strategies in one miniaturized system for practical usage has seldom been reported. This article reports an implantable electronic medicine based on bioresorbable microneedle devices that is activated wirelessly for electrostimulation and sustainable delivery of anti-inflammatory drugs. The electronic medicine is composed of a radio frequency wireless power transmission system and a drug-loaded microneedle structure, all fabricated with bioresorbable materials. In a rat skeletal muscle injury model, periodic electrostimulation regulates cell behaviors and tissue regeneration while the anti-inflammatory drugs prevent inflammation, which ultimately enhance the skeletal muscle regeneration. Finally, the electronic medicine is fully bioresorbable, excluding the second surgery for device removal.

Transient, Implantable, Ultrathin Biofuel Cells Enabled by Laser-Induced Graphene and Gold Nanoparticles Composite.

Transient power sources with excellent biocompatibility and bioresorablility have attracted significant attention. Here, we report high-performance, transient glucose enzymatic biofuel cells (TEBFCs) based on the laser-induced graphene (LIG)/gold nanoparticles (Au NPs) composite electrodes. Such LIG electrodes can be easily fabricated from polyimide (PI) with an infrared CO2 laser and exhibit a low impedance (16 Ω). The resulted TEBFC yields a high open circuit potential (OCP) of 0.77 V and a maximum power density of 483.1 µW/cm2. The TEBFC not only exhibits a quick response time that enables reaching the maximum OCP within 1 min but also owns a long lifetime over 28 days in vitro. The excellent biocompatibility and transient performance from in vitro and in vivo tests allow long-term implantation of TEBFCs in rats for energy harvesting. The TEBFCs with advanced processing methods provide a promising power solution for transient electronics.

[Application of electronic skin in healthcare and virtual reality].

Electronic skin has shown great application potential in many fields such as healthcare monitoring and human-machine interaction due to their excellent sensing performance, mechanical properties and biocompatibility. This paper starts from the materials selection and structures design of electronic skin, and summarizes their different applications in the field of healthcare equipment, especially current development status of wearable sensors with different functions, as well as the application of electronic skin in virtual reality. The challenges of electronic skin in the field of wearable devices and healthcare, as well as our corresponding strategies, are discussed to provide a reference for further advancing the research of electronic skin.

A sensitive H2O2 biosensor based on carbon nanotubes/tetrathiafulvalene and its application in detecting NADH.

Reduced nicotinamide adenine dinucleotide (NADH) plays a pivotal role in the electron-transfer chain of biological system. Analysis of many biological markers is based on the detection of the enzymatically generated NADH. In this paper, a sensitive hydrogen peroxide (H2O2) biosensor, fabricated by carbon nanotubes (CNTs)/tetrathiafulvalene (TTF)/horseradish peroxidase (HRP), was applied for detecting the NADH in a buffer containing methylene blue (MB) at low operating potential of - 0.3 V (vs. Ag/AgCl). Since the NADH could be oxidized by MB to release H2O2, the electrochemical biosensor enables to detect the NADH in the MB buffer. And the low working potential made the biosensor avoid the interference from other electroactive substances. Linear response ranges from 10 µM to 790 µM, with a sensitivity of 4.76 µA mM-1 and a detection limit of 1.53 µM were obtained under the optimum conditions. The proposed sensor provided a promising approach for sensitively detecting the NADH.

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.

Battery-free, wireless, and electricity-driven soft swimmer for water quality and virus monitoring.

Miniaturized mobile electronic system is an effective candidate for in situ exploration of confined spaces. However, realizing such system still faces challenges in powering issue, untethered mobility, wireless data acquisition, sensing versatility, and integration in small scales. Here, we report a battery-free, wireless, and miniaturized soft electromagnetic swimmer (SES) electronic system that achieves multiple monitoring capability in confined water environments. Through radio frequency powering, the battery-free SES system demonstrates untethered motions in confined spaces with considerable moving speed under resonance. This system adopts soft electronic technologies to integrate thin multifunctional bio/chemical sensors and wireless data acquisition module, and performs real-time water quality and virus contamination detection with demonstrated promising limits of detection and high sensitivity. All sensing data are transmitted synchronously and displayed on a smartphone graphical user interface via near-field communication. Overall, this wireless smart system demonstrates broad potential for confined space exploration, ranging from pathogen detection to pollution investigation.

Wearable bio-adhesive metal detector array (BioMDA) for spinal implants.

Dynamic tracking of spinal instrumentation could facilitate real-time evaluation of hardware integrity and in so doing alert patients/clinicians of potential failure(s). Critically, no method yet exists to continually monitor the integrity of spinal hardware and by proxy the process of spinal arthrodesis; as such hardware failures are often not appreciated until clinical symptoms manifest. Accordingly, herein, we report on the development and engineering of a bio-adhesive metal detector array (BioMDA), a potential wearable solution for real-time, non-invasive positional analyses of osseous implants within the spine. The electromagnetic coupling mechanism and intimate interfacial adhesion enable the precise sensing of the metallic implants position without the use of radiation. The customized decoupling models developed facilitate the precise determination of the horizontal and vertical positions of the implants with incredible levels of accuracy (e.g., <0.5 mm). These data support the potential use of BioMDA in real-time/dynamic postoperative monitoring of spinal implants.

Multi-functional adhesive hydrogel as bio-interface for wireless transient pacemaker.

Traditional temporary cardiac pacemakers (TCPs), which employ transcutaneous leads and external wired power systems are battery-dependent and generally non-absorbable with rigidity, thereby necessitating surgical retrieval after therapy and resulting in potentially severe complications. Wireless and bioresorbable transient pacemakers have, hence, emerged recently, though hitting a bottleneck of unfavorable tissue-device bonding interface subject to mismatched mechanical modulus, low adhesive strength, inferior electrical performances, and infection risks. Here, to address such crux, we develop a multifunctional interface hydrogel (MIH) with superior electrical performance to facilitate efficient electrical exchange, comparable mechanical strength to natural heart tissue, robust adhesion property to enable stable device-tissue fixation (tensile strength: ∼30 kPa, shear strength of ∼30 kPa, and peel-off strength: ∼85 kPa), and good bactericidal effect to suppress bacterial growth. Through delicate integration of this versatile MIH with a leadless, battery-free, wireless, and transient pacemaker, the entire system exhibits stable and conformal adhesion to the beating heart while enabling precise and constant electrical stimulation to modulate the cardiac rhythm. It is envisioned that this versatile MIH and the proposed integration framework will have immense potential in overcoming key limitations of traditional TCPs, and may inspire the design of novel bioelectronic-tissue interfaces for next-generation implantable medical devices.

A fully integrated breathable haptic textile.

Wearable haptics serve as an enhanced media to connect humans and VR/robots. The inevitable sweating issue in all wearables creates a bottleneck for wearable haptics, as the sweat/moisture accumulated in the skin/device interface can substantially affect feedback accuracy, comfortability, and create hygienic problems. Nowadays, wearable haptics typically gain performance at the cost of sacrificing the breathability, comfort, and biocompatibility. Here, we developed a fully integrated breathable haptic textile (FIBHT) to solve these trade-off issues, where the FIBHT exhibits high-level integration of 128 pixels over the palm, great stretchability of 400%, and superior permeability of over 657 g/m2/day (moisture) and 40 mm/s (air). It is a stand-alone haptic system totally composed of stretchable, breathable, and bioadhesive materials, which empowers it with precise, sweating/movement-insensitive and dynamic feedback, and makes FIBHT powerful for virtual touching in broad scenarios.

Wearable and battery-free wound dressing system for wireless and early sepsis diagnosis.

Sepsis is a severe organ dysfunction typically caused by wound infection which leads to septic shock, organ failure or even death if no early diagnosis and property medical treatment were taken. Herein, we report a soft, wearable and battery-free wound dressing system (WDS) for wireless and real-time monitoring of wound condition and sepsis-related biomarker (procalcitonin [PCT]) in wound exudate for early sepsis detection. The battery-free WDS powered by near-field communication enables wireless data transmission, signal processing and power supply, which allows portable intelligent wound caring. The exudate collection associates with soft silicone based microfluidic technologies (exudate collection time within 15 s), that can filtrate contamination at the cell level and enable a superior filtration rate up to 95% with adopting microsphere structures. The battery-free WDS also includes state-of-the-art biosensors, which can accurate detect the pH value, wound temperature, and PCT level and thus for sepsis diagnosis. In vivo studies of SD rats prove the capability of the WDS for continuously monitoring wound condition and PCT concentration in the exudate. As a result, the reported fully integrated WDS provides a potential solution for further developing wearable, multifunctional and on-site disease diagnosis.

Thin, soft, 3D printing enabled crosstalk minimized triboelectric nanogenerator arrays for tactile sensing.

With the requirements of self-powering sensors in flexible electronics, wearable triboelectric nanogenerators (TENGs) have attracted great attention due to their advantages of excellent electrical outputs and low-cost processing routes. The crosstalk effect between adjacent sensing units in TENGs significantly limits the pixel density of sensor arrays. Here, we present a skin-integrated, flexible TENG sensor array with 100 sensing units in an overall size of 7.5 cm × 7.5 cm that can be processed in a simple, low-cost, and scalable way enabled by 3D printing. All the sensing units show good sensitivity of 0.11 V/kPa with a wide range of pressure detection from 10 to 65 kPa, which allows to accurately distinguish various tactile formats from gentle touching (as low as 2 kPa) to hard pressuring. The 3D printing patterned substrate allows to cast triboelectric layers of polydimethylsiloxane in an independent sensing manner for each unit, which greatly suppresses the cross talk arising from adjacent sensing units, where the maximum crosstalk output is only 10.8%. The excellent uniformity and reproducibility of the sensor array offer precise pressure mapping for complicated pattern loadings, which demonstrates its potential in tactile sensing and human-machine interfaces.

Ultrathin, Soft, Bioresorbable Organic Electrochemical Transistors for Transient Spatiotemporal Mapping of Brain Activity.

A critical challenge lies in the development of the next-generation neural interface, in mechanically tissue-compatible fashion, that offer accurate, transient recording electrophysiological (EP) information and autonomous degradation after stable operation. Here, an ultrathin, lightweight, soft and multichannel neural interface is presented based on organic-electrochemical-transistor-(OECT)-based network, with capabilities of continuous high-fidelity mapping of neural signals and biosafety active degrading after performing functions. Such platform yields a high spatiotemporal resolution of 1.42 ms and 20 µm, with signal-to-noise ratio up to ≈37 dB. The implantable OECT arrays can well establish stable functional neural interfaces, designed as fully biodegradable electronic platforms in vivo. Demonstrated applications of such OECT implants include real-time monitoring of electrical activities from the cortical surface of rats under various conditions (e.g., narcosis, epileptic seizure, and electric stimuli) and electrocorticography mapping from 100 channels. This technology offers general applicability in neural interfaces, with great potential utility in treatment/diagnosis of neurological disorders.

Skin-Integrated Wireless Odor Message Delivery Electronics for the Deaf-blind.

Deaf-blindness limits daily human activities, especially interactive modes of audio and visual perception. Although the developed standards have been verified as alternative communication methods, they are uncommon to the nondisabled due to the complicated learning process and inefficiency in terms of communicating distance and throughput. Therefore, the development of communication techniques employing innate sensory abilities including olfaction related to the cerebral limbic system processing emotions, memories, and recognition has been suggested for reducing the training level and increasing communication efficiency. Here, a skin-integrated and wireless olfactory interface system exploiting arrays of miniaturized odor generators (OGs) based on melting/solidifying odorous wax to release smell is introduced for establishing an advanced communication system between deaf-blind and non-deaf-blind. By optimizing the structure design of the OGs, each OG device is as small as 0.24 cm3 (length × width × height of 11 mm × 10 mm × 2.2 mm), enabling integration of up to 8 OGs on the epidermis between nose and lip for direct and rapid olfactory drive with a weight of only 24.56 g. By generating single or mixed odors, different linked messages could be delivered to a user within a short period in a wireless and programmable way. By adopting the olfactory interface message delivery system, the recognition rates for the messages have been improved 1.5 times that of the touch-based method, while the response times were immensely decreased 4 times. Thus, the presented wearable olfactory interface system exhibits great potential as an alternative message delivery method for the deaf-blind.

Soft, miniaturized, wireless olfactory interface for virtual reality.

Recent advances in virtual reality (VR) technologies accelerate the creation of a flawless 3D virtual world to provide frontier social platform for human. Equally important to traditional visual, auditory and tactile sensations, olfaction exerts both physiological and psychological influences on humans. Here, we report a concept of skin-interfaced olfactory feedback systems with wirelessly, programmable capabilities based on arrays of flexible and miniaturized odor generators (OGs) for olfactory VR applications. By optimizing the materials selection, design layout, and power management, the OGs exhibit outstanding device performance in various aspects, from response rate, to odor concentration control, to long-term continuous operation, to high mechanical/electrical stability and to low power consumption. Representative demonstrations in 4D movie watching, smell message delivery, medical treatment, human emotion control and VR/AR based online teaching prove the great potential of the soft olfaction interface in various practical applications, including entertainment, education, human machine interfaces and so on.

Thin, soft, wearable system for continuous wireless monitoring of artery blood pressure.

Continuous monitoring of arterial blood pressure (BP) outside of a clinical setting is crucial for preventing and diagnosing hypertension related diseases. However, current continuous BP monitoring instruments suffer from either bulky systems or poor user-device interfacial performance, hampering their applications in continuous BP monitoring. Here, we report a thin, soft, miniaturized system (TSMS) that combines a conformal piezoelectric sensor array, an active pressure adaptation unit, a signal processing module, and an advanced machine learning method, to allow real wearable, continuous wireless monitoring of ambulatory artery BP. By optimizing the materials selection, control/sampling strategy, and system integration, the TSMS exhibits improved interfacial performance while maintaining Grade A level measurement accuracy. Initial trials on 87 volunteers and clinical tracking of two hypertension individuals prove the capability of the TSMS as a reliable BP measurement product, and its feasibility and practical usability in precise BP control and personalized diagnosis schemes development.

Intelligent Soft Sweat Sensors for the Simultaneous Healthcare Monitoring and Safety Warning.

Intelligent monitoring human physiological information in real time raises the demand for skin-integrated electronics, as which is a flexible format and can be mounted onto the curved human skin for noninvasive healthcare monitoring. The biofluid such as sweat from skin contains abundant biomarkers reflecting body health conditions. Here, a skin-integrated sweat monitor with six biosensors embedded for the detection of NH4 + , Na+ , glucose, pH, skin impedance, and surface temperature is described, which could decode the information in the fresh sweat generated during exercising. Furthermore, the system also includes an innovative safety warning mechanism, which is based on a miniaturized actuator to provide mechanical stimuli, and coupled with six changeable colors light emitting diodes corresponding to the six biosensors for providing simultaneous safety alarming to users. The self-developed microfluidics system with a hydrophilic surface allows to enhance the sweat collection rate. Meanwhile, microfluidic filters can reduce the interruption of skin debris during biosignal monitoring. These state-of-art biosensors can real-time monitor health related signals with excellent linearity and specificity. The skin-integrated sweat monitor system exhibits a great potential in human healthcare monitoring and medical treatment.

Wireless, battery-free, multifunctional integrated bioelectronics for respiratory pathogens monitoring and severity evaluation.

The rapid diagnosis of respiratory virus infection through breath and blow remains challenging. Here we develop a wireless, battery-free, multifunctional pathogenic infection diagnosis system (PIDS) for diagnosing SARS-CoV-2 infection and symptom severity by blow and breath within 110 s and 350 s, respectively. The accuracies reach to 100% and 92% for evaluating the infection and symptom severity of 42 participants, respectively. PIDS realizes simultaneous gaseous sample collection, biomarker identification, abnormal physical signs recording and machine learning analysis. We transform PIDS into other miniaturized wearable or portable electronic platforms that may widen the diagnostic modes at home, outdoors and public places. Collectively, we demonstrate a general-purpose technology for rapidly diagnosing respiratory pathogenic infection by breath and blow, alleviating the technical bottleneck of saliva and nasopharyngeal secretions. PIDS may serve as a complementary diagnostic tool for other point-of-care techniques and guide the symptomatic treatment of viral infections.

Electronic skin as wireless human-machine interfaces for robotic VR.

The coronavirus pandemic has highlighted the importance of developing intelligent robotics to prevent infectious disease spread. Human-machine interfaces (HMIs) give a chance of interactions between users and robotics, which play a significant role in teleoperating robotics. Conventional HMIs are based on bulky, rigid, and expensive machines, which mainly focus on robots/machines control, but lack of adequate feedbacks to users, which limit their applications in conducting complicated tasks. Therefore, developing closed-loop HMIs with both accurate sensing and feedback functions is extremely important. Here, we present a closed-loop HMI system based on skin-integrated electronics, whose electronics compliantly interface with the whole body for wireless motion capturing and haptic feedback via Bluetooth, Wireless Fidelity (Wi-Fi), and Internet. The integration of visual and haptic VR via skin-integrated electronics together into a closed-loop HMI for robotic VR demonstrates great potentials in noncontact collection of bio samples, nursing infectious disease patients and many others.