Bias-Free Cardiac Monitoring Capsule.

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Patients often fail to recognize the early signs of CVDs, which display irregularities in cardiac contractility and may ultimately lead to heart failure. Therefore, continuously monitoring the abnormal changes in cardiac contractility might represent a novel approach to long-term CVD surveillance. In this study, we introduce a zero-power consumption and implantable bias-free cardiac monitoring capsule (BCMC) based on the triboelectric effect for cardiac contractility monitoring in situ. The output performance of BCMC has been improved over 10 times with nanoparticle self-adsorption method. This device can be implanted into the right ventricle of swine using catheter intervention to detect the change of cardiac contractility and corresponding CVDs. The physiological signals can be wirelessly transmitted to a mobile terminal for analysis through the acquisition and transmission module. This work will contribute to a new option for precise monitoring and early diagnosis of CVDs. This article is protected by copyright. All rights reserved.

A self-powered intracardiac pacemaker in swine model.

Harvesting biomechanical energy from cardiac motion is an attractive power source for implantable bioelectronic devices. Here, we report a battery-free, transcatheter, self-powered intracardiac pacemaker based on the coupled effect of triboelectrification and electrostatic induction for the treatment of arrhythmia in large animal models. We show that the capsule-shaped device (1.75 g, 1.52 cc) can be integrated with a delivery catheter for implanting in the right ventricle of a swine through the intravenous route, which effectively converts cardiac motion energy to electricity and maintains endocardial pacing function during the three-week follow-up period. We measure in vivo open circuit voltage and short circuit current of the self-powered intracardiac pacemaker of about 6.0 V and 0.2 µA, respectively. This approach exhibits up-to-date progress in self-powered medical devices and it may overcome the inherent energy shortcomings of implantable pacemakers and other bioelectronic devices for therapy and sensing.

Self-encapsulated ionic fibers based on stress-induced adaptive phase transition for non-contact depth-of-field camouflage sensing.

Ionically conductive fibers have promising applications; however, complex processing techniques and poor stability limit their practicality. To overcome these challenges, we proposed a stress-induced adaptive phase transition strategy to conveniently fabricate self-encapsulated hydrogel-based ionically conductive fibers (se-HICFs). se-HICFs can be produced simply by directly stretching ionic hydrogels with ultra-stretchable networks (us-IHs) or by dip-drawing from molten us-IHs. During this process, stress facilitated the directional migration and evaporation of water molecules in us-IHs, causing a phase transition in the surface layer of ionic fibers to achieve self-encapsulation. The resulting sheath-core structure of se-HICFs enhanced mechanical strength and stability while endowing se-HICFs with powerful non-contact electrostatic induction capabilities. Mimicking nature, se-HICFs were woven into spider web structures and camouflaged in wild environments to achieve high spatiotemporal resolution 3D depth-of-field sensing for different moving media. This work opens up a convenient route to fabricate stable functionalized ionic fibers.

A Self-Powered Wearable Sensor for Continuous Wireless Sweat Monitoring.

Wireless wearable sweat analysis devices can monitor biomarkers at the molecular level continuously and in situ, which is highly desired for personalized health care. The miniaturization, integration, and wireless operation of sweat sensors improve the comfort and convenience while also bringing forward new challenges for power supply technology. Herein, a wireless self-powered wearable sweat analysis system (SWSAS) is designed that effectively converts the mechanical energy of human motion into electricity through hybrid nanogenerator modules (HNGMs). The HNGM shows stable output characteristics at low frequency with a current of 15 mA and a voltage of 60 V. Through real-time on-body sweat analysis powered by HNGM, the SWSAS is demonstrated to selectively monitor biomarkers (Na+ and K+ ) in sweat and wirelessly transmit the sensing data to the user interface via Bluetooth.

A Self-Powered Optogenetic System for Implantable Blood Glucose Control.

Diabetes treatment and rehabilitation are usually a lifetime process. Optogenetic engineered designer cell-therapy holds great promise in regulating blood glucose homeostasis. However, portable, sustainable, and long-term energy supplementation has previously presented a challenge for the use of optogenetic stimulation in vivo. Herein, we purpose a self-powered optogenetic system (SOS) for implantable blood glucose control. The SOS consists of a biocompatible far-red light (FRL) source, FRL-triggered transgene-expressing cells, a power management unit, and a flexible implantable piezoelectric nanogenerator (i-PENG) to supply long-term energy by converting biomechanical energy into electricity. Our results show that this system can harvest energy from body movement and power the FRL source, which then significantly enhanced production of a short variant of human glucagon-like peptide 1 (shGLP-1) in vitro and in vivo. Indeed, diabetic mice equipped with the SOS showed rapid restoration of blood glucose homeostasis, improved glucose, and insulin tolerance. Our results suggest that the SOS is sufficiently effective in self-powering the modulation of therapeutic outputs to control glucose homeostasis and, furthermore, present a new strategy for providing energy in optogenetic-based cell therapy.

Artificial tactile perception smart finger for material identification based on triboelectric sensing.

Tactile perception includes the direct response of tactile corpuscles to environmental stimuli and psychological parameters associated with brain recognition. To date, several artificial haptic-based sensing techniques can accurately measure physical stimuli. However, quantifying the psychological parameters of tactile perception to achieve texture and roughness identification remains challenging. Here, we developed a smart finger with surpassed human tactile perception, which enabled accurate identification of material type and roughness through the integration of triboelectric sensing and machine learning. In principle, as each material has different capabilities to gain or lose electrons, a unique triboelectric fingerprint output will be generated when the triboelectric sensor is in contact with the measured object. The construction of a triboelectric sensor array could further eliminate interference from the environment, and the accuracy rate of material identification was as high as 96.8%. The proposed smart finger provides the possibility to impart artificial tactile perception to manipulators or prosthetics.

Self-Powered Force Sensors for Multidimensional Tactile Sensing.

A tactile sensor is the centerpiece in human-machine interfaces, enabling robotics or prosthetics to manipulate objects dexterously. Specifically, it is crucial to endow the sensor with the ability to detect and distinguish normal and shear forces in real time, so that slip detection and more complex control could be achieved during the interaction with objects. Here, a self-powered multidirectional force sensor (SMFS) based on triboelectric nanogenerators with a three-dimensional structure is proposed for sensing and analysis of normal and shear forces in real time. Four polydimethylsiloxane (PDMS) cylinders act as the force sensing structure of the SMFS. A flexible tip array made of carbon black/MXene/PDMS composites is used to generate triboelectric signals when the SMFS is driven by an external force. The SMFS can sense multidimensional force due to the adaptability of the PDMS cylinders and detect tiny force due to the sensitivity of the flexible tips. A small shear force as low as 50 mN could be recognized using the SMFS. The direction of the externally applied force could be recognized by analyzing the location and output voltage amplitude of the SMFS. Moreover, the tactile sensing applications, including reagent weighing and force direction perception, are also achieved by using the SMFS, which demonstrates the potential in promoting developments of self-powered wearable sensors, human-machine interactions, electronic skin, and soft robotic applications.

Self-Powered Gesture Recognition Wristband Enabled by Machine Learning for Full Keyboard and Multicommand Input.

Virtual reality is a brand-new technology that can be applied extensively. To realize virtual reality, certain types of human-computer interaction equipment are necessary. Existing virtual reality technologies often rely on cameras, data gloves, game pads, and other equipment. These equipment are either bulky, inconvenient to carry and use, or expensive to popularize. Therefore, the development of a convenient and low-cost high-precision human-computer interaction device can contribute positively to the development of virtual reality technology. In this study, a gesture recognition wristband that can realize a full keyboard and multicommand input is developed. The wristband is convenient to wear, low in cost, and does not affect other daily operations of the hand. This wristband is based on physiological anatomy as well as aided by active sensor and machine learning technology; it can achieve a maximum accuracy of 92.6% in recognizing 26 letters. This wristband offers broad application prospects in the fields of gesture command recognition, assistive devices for the disabled, and wearable electronics.

A Gyroscope Nanogenerator with Frequency Up-Conversion Effect for Fitness and Energy Harvesting.

Converting the mechanical energy of human motion into electricity is considered an ideal energy supply solution for portable electronics. However, low-frequency human movement limits conversion efficiency of conventional energy harvesting devices, which is difficult to provide sustainable power for portable electronic devices. Herein, a fitness gyroscope nanogenerator (fg-NG) based on a triboelectric nanogenerator (TENG) and electromagnetic generator (EMG) is developed that can convert low-frequency wrist motion into high-frequency rotation by using the frequency up-conversion effect of the gyroscope. Remarkably, the fg-NG can reach a rotational speed of over 8000 rpm by hand, increasing the frequency by more than 280 times. The fg-NG can continuously and stably output a current of 17 mA and a voltage of 70 V at frequency of 220-230 Hz. The fg-NG is demonstrated to consistently power a hygrothermograph, smart bracelet, and mobile phone. Also, it can be applicated to a self-powered intelligent training system, showing its immense application potential in portable electronics and wireless Internet of Things devices.

Ultra-Stretchable and Fast Self-Healing Ionic Hydrogel in Cryogenic Environments for Artificial Nerve Fiber.

Self-healing materials behave with irreplaceable advantages in biomimetic intelligent robots (BIR) for avoiding or reducing safety hazards and economic losses from accidental damage during service. However, the self-healing ability is unreservedly lost and even becomes rigid and fragile in the cryogenic environment where BIR are precisely needed. Here, the authors report a versatile ionic hydrogel with fast self-healing ability, ultra-stretchability, and stable conductivity, even at -80 °C. The hydrogel is systematically optimized to improve a hydrogen-bonded network nanostructure, coordinated achieving a quick self-healing ability within 10 min, large deformation tolerance of over 7000%, superior conductivity of 11.76 S cm-1 and anti-freezing ability, which is difficult to obtain simultaneously. Such a hydrogel provides new opportunities for artificial electronic devices in harsh environments. As a prospective application, they fabricate an artificial nerve fiber by mimicking the structure and functions of the myelinated axon, exhibiting the property of fast and potential-gated signal transmission. This artificial nerve fiber is integrated into a robot for demonstrating a real-time high fidelity and high throughput information interaction under big deformation and cryogenic temperature. The hydrogel and bionic device will bring pioneering functions for robots and open a broad application scenario in extreme conditions.

A Self-Powered Triboelectric Hybrid Coder for Human-Machine Interaction.

Human-machine interfaces have penetrated various academia and industry fields such as smartphones, robotic, virtual reality, and wearable electronics, due to their abundant functional sensors and information interaction methods. Nevertheless, most sensors' complex structural design, monotonous parameter detection capability, and single information coding communication hinder their rapid development. As the frontier of self-powered sensors, the triboelectric nanogenerator (TENG) has multiple working modes and high structural adaptability, which is a potential solution for multi-parameter sensing and miniaturizing of traditional interactive electronic devices. Herein, a self-powered hybrid coder (SHC) based on TENG is reported to encode two action parameters of touch and press, which can be used as a smart interface for human-machine interaction. The top-down hollow structure of the SHC, not only constructs a compositing mode to generate stable touch and press signals but also builds a hybrid coding platform for generating action codes in synergy mode. When a finger touches or presses the SHC, Morse code and Gray code can be transmitted for text information or remote control of electric devices. This self-powered coder is of reference value for designing an alternative human-machine interface and having the potential to contribute to the next generation of highly integrated portable smart electronics.

Stretchable, Self-Healing, and Skin-Mounted Active Sensor for Multipoint Muscle Function Assessment.

Assessment of muscle function is an essential indicator for estimating elderly health, evaluating motor function, and instructing rehabilitation training, which also sets urgent requirements for mechanical sensors with superior quantification, accuracy, and reliability. To overcome the rigidity and vulnerability of traditional metallic electrodes, we synthesize an ionic hydrogel with large deformation tolerance and fast self-healing ability. And we propose a stretchable, self-healing, and skin-mounted (Triple S) active sensor (TSAS) based on the principles of electrostatic induction and electrostatic coupling. The skin modulus-matched TSAS provides outstanding sensing properties: maximum output voltage of 78.44 V, minimal detection limit of 0.2 mN, fast response time of 1.03 ms, high signal-to-noise ratio and excellent long-term service stability. In training of arm muscle, the functional signals of biceps and triceps brachii muscles as well as the joint dexterity of bending angle can be acquired simultaneously through TSAS. The signal can also be sent wirelessly to a terminal for analysis. With the characteristics of high sensitivity, reliability, convenience, and low-cost, TSAS shows its potential to be the next-generation procedure for real-time assessment of muscle function and rehabilitation training.

An Ultra-Simple Charge Supplementary Strategy for High Performance Rotary Triboelectric Nanogenerators.

Free-standing rotary triboelectric nanogenerators (rTENG) can accomplish special tasks which require both high voltage and high frequency. However, the reported high performance rTENG all have complex structures for output enhancement. In this work, an ultra-simple strategy to build high performance rTENG is developed. With only one small paper strip added to the conventional structure, the output of the TENG is promoted hugely. The voltage is triplicated to 2.3 kV, and the current and charge are quintupled to 133 µA and 197 nC, respectively. The small paper strip, with the merits of ultra-simplicity, wide availability, easy accessibility and low cost, functions as a super-effective charge supplement. This simple and delicate structure enables ultra-high durability with the 2.3 kV voltage output 100% maintained after 1 000 000 cycles. This charge supplementary strategy is universally effective for many other materials, and decouples the output enhancement from any friction or contact on the metal electrodes, emphasizing a critical working principle for the rTENG. Atmospheric cold plasma is generated using the paper strip rTENG (ps-rTENG), which demonstrates strong ability to do bacteria sterilization. This simple and persistent charge supplementary strategy can be easily adopted by other designs to promote the output even further.

A Stretchable, Self-Healable Triboelectric Nanogenerator as Electronic Skin for Energy Harvesting and Tactile Sensing.

Electronic skin that is deformable, self-healable, and self-powered has high competitiveness for next-generation energy/sense/robotic applications. Herein, we fabricated a stretchable, self-healable triboelectric nanogenerator (SH-TENG) as electronic skin for energy harvesting and tactile sensing. The elongation of SH-TENG can achieve 800% (uniaxial strain) and the SH-TENG can self-heal within 2.5 min. The SH-TENG is based on the single-electrode mode, which is constructed from ion hydrogels with an area of 2 cm × 3 cm, the output of short-circuit transferred charge (Qsc), open-circuit voltage (Voc), and short-circuit current (Isc) reaches ~6 nC, ~22 V, and ~400 nA, and the corresponding output power density is ~2.9 µW × cm-2 when the matching resistance was ~140 MΩ. As a biomechanical energy harvesting device, the SH-TENG also can drive red light-emitting diodes (LEDs) bulbs. Meanwhile, SH-TENG has shown good sensitivity to low-frequency human touch and can be used as an artificial electronic skin for touch/pressure sensing. This work provides a suitable candidate for the material selection of the hydrogel-based self-powered electronic skin.

Human Motion Driven Self-Powered Photodynamic System for Long-Term Autonomous Cancer Therapy.

Long-term and low-dose photodynamic therapy for treating tumors requires a sustainable energy supply. The power source technology of batteries and wireless charging for driving a light-emitting diode (LED) may cause inconveniences during treatment. In addition, the development of telemedicine and Internet medicine put forward higher demands on treatment methods, such as better patient compliance and autonomous management. Here, we show a self-powered photodynamic therapy (s-PDT) system with two different irradiation modes that can be autonomously managed by patients. The as-fabricated s-PDT system based on a twinning structured piezoelectric nanogenerator is powered by energy harvested from body motion and realizes effective tumor tissue killing and inhibition. As demonstrated at the cellular level, the s-PDT system can significantly suppress tumor cell growth with the pulsed light stimulation mode. When the miniature LED was implanted subcutaneously in mice with transplanted tumors, the s-PDT system led to significant antitumor effects by irradiation with intermittent continuous light stimulation mode for 12 days, and an 87.46% tumor inhibition rate was obtained. This innovative s-PDT system combined with two treatment modes may provide a great opportunity to develop wearable/implantable and self-controllable devices for long-term photodynamic therapy, which would be a promising method for clinical cancer treatment.

Flexible and stretchable dual mode nanogenerator for rehabilitation monitoring and information interaction.

Motion recognition and information interaction sensors with flexibility and stretchability are key functional modules as interactive media between the mechanical motions and electric signals in an intelligent robotic and rehabilitation training system. Nanogenerators have many useful applications in the field of intelligent interaction, with the advantages of a self-powered sensing ability, easy fabrication, considerable sensitivity and reliability. However, the singularity of the sensing mode limits its applications. Hence, in this research, a flexible and stretchable dual mode nanogenerator (FSDM-NG) for human motion sensing and information interaction, based on the integration of piezoelectric and triboelectric principles was developed. In piezoelectric mode, the FSDM-NG can effectively monitor the bending angle of joints (finger, wrist and elbow) from 30° to 90°. In triboelectric mode, text and logic information transfer are encoded using Morse code and logic gates, respectively. In addition, the device has good adhesion and biosafety, and is robust which makes it work normally even in under water environments. Combining these two sensing mechanisms, multiple modes of sensing from touch and stretch based on the FSDM-NG can be achieved for information interaction in real time. The proposed sensor has the potential to be adapted for more complex sensing, which may provide new applications for intelligent interaction of robots and in the rehabilitation training field.

Customization of Conductive Elastomer Based on PVA/PEI for Stretchable Sensors.

Conductive, stretchable, environmentally-friendly, and strain-sensitive elastomers are attracting immense research interest because of their potential applications in various areas, such as human-machine interfaces, healthcare monitoring, and soft robots. Herein, a binary networked elastomer is reported based on a composite hydrogel of polyvinyl alcohol (PVA) and polyethyleneimine (PEI), which is demonstrated to be ultrastretchable, mechanically robust, biosafe, and antibacterial. The mechanical stretchability and toughness of the hydrogels are optimized by tuning the constituent ratio and water content. The optimal hydrogel (PVA2 PEI1 -75) displays an impressive tensile strain as high as 500% with a corresponding tensile stress of 0.6 MPa. Furthermore, the hydrogel elastomer is utilized to fabricate piezoresistive sensors. The as-made strain sensor displays seductive capability to monitor and distinguish multifarious human motions with high accuracy and sensitivity, like facial expressions and vocal signals. Therefore, the elastomer reported in this study holds great potential for sensing applications in the era of the Internet of Things (IoTs).

Fabrication of Concentric Carbon Nanotube Rings and Their Application on Regulating Cell Growth.

The carbon nanotube (CNT) pattern plays an important role in various electronic devices and biological fields for its superior conductivity and biocompatibility. Herein, we fabricated regularly arranged concentric multiwalled carbon nanotube (MWCNT) rings in a Petri dish by evaporation-driven self-assembly technology. By adjusting the dispersion ratio, heating temperature, and solution volume, various MWCNT rings with different shapes and morphologies were obtained. The variation law of ring radius, formation range, and ring numbers was processed with statistical analysis. With fine adjustment of parameters, the control of desired MWCNT rings can be achieved for further scientific researches. By culturing L929 cells with these rings, oriented cell growth along the rings was achieved, which is of significance for cell regulation, tissue repairing, and related biological applications.

A bionic stretchable nanogenerator for underwater sensing and energy harvesting.

Soft wearable electronics for underwater applications are of interest, but depend on the development of a waterproof, long-term sustainable power source. In this work, we report a bionic stretchable nanogenerator for underwater energy harvesting that mimics the structure of ion channels on the cytomembrane of electrocyte in an electric eel. Combining the effects of triboelectrification caused by flowing liquid and principles of electrostatic induction, the bionic stretchable nanogenerator can harvest mechanical energy from human motion underwater and output an open-circuit voltage over 10 V. Underwater applications of a bionic stretchable nanogenerator have also been demonstrated, such as human body multi-position motion monitoring and an undersea rescue system. The advantages of excellent flexibility, stretchability, outstanding tensile fatigue resistance (over 50,000 times) and underwater performance make the bionic stretchable nanogenerator a promising sustainable power source for the soft wearable electronics used underwater.

Body-Integrated Self-Powered System for Wearable and Implantable Applications.

The human body has an abundance of available energy from the mechanical movements of walking, jumping, and running. Many devices such as electromagnetic, piezoelectric, and triboelectric energy harvesting devices have been demonstrated to convert body mechanical energy into electricity, which can be used to power various wearable and implantable electronics. However, the complicated structure, high cost of production/maintenance, and limitation of wearing and implantation sites restrict the development and commercialization of the body energy harvesters. Here, we present a body-integrated self-powered system (BISS) that is a succinct, highly efficient, and cost-effective method to scavenge energy from human motions. The biomechanical energy of the moving human body can be harvested through a piece of electrode attached to skin. The basic principle of the BISS is inspired by the comprehensive effect of triboelectrification between soles and floor and electrification of the human body. We have proven the feasibility of powering electronics using the BISS in vitro and in vivo. Our investigation of the BISS exhibits an extraordinarily simple, economical, and applicable strategy to harvest energy from human body movements, which has great potential for practical applications of self-powered wearable and implantable electronics in the future.