Self-powered Motion Research Articles

Incorporation of hexagonal boron nitride and multi-walled carbon nanotube for motion sensing triboelectric nanogenerators

In this study, the thermoplastic polyurethane (TPU) composite that incorporates hexagonal boron nitride (h-BN) and multi-walled carbon nanotube (MWCNT) is fabricated and employed as an electrification layer for triboelectric nanogenerators (TENG). Owing to the high elasticity of TPU, the TPU/h-BN/MWCNT composite shows high stretching ability with low Young's modulus of 2∼3 MPa, similar to that of soft tissues. The addition of h-BN efficiently helps construct the conductive network of MWCNT, and the combination of h-BN and MWCNT significantly boosts the dielectric constant of the composite. The mixture of 6 vol% of h-BN and 1.05 vol% of MWCNT exhibits an excellent combination of a real permittivity of 232 and a loss tangent of 2.4, generating the output voltage and current of 47V and 244 nA, respectively. In addition, the increase of resistance is not considerable up to 60 % tensile strain when 1.05 vol% of MWCNT exists in the TPU, and the TPU/h-BN/MWCNT composite presented a stable TENG performances under 60 % strain. Moreover, the TENG made from the TPU/h-BN/MWCNT composite successfully senses a range of complicated hand gestures by producing very distinct output voltages. Thus, it presents promising possibility as a wearable, skin mountable, and self-powered motion sensor.

All-fibrous, permeable, adhesive, and stretchable self-powered electronic skin for sign language recognition†

Self-powered human motion electronic skin (E-skin) holds significant potential for intelligent sports, healthcare, and human-machine interactions. However, the limited permeability to air and moisture, along with poor stretchability, impedes the...

Printed High-Adhesion Flexible Electrodes Based on an Interlocking Structure for Self-Powered Intelligent Movement Monitoring.

Two-dimensional transition metal carbide nitrides (MXenes) have been extensively explored in diverse areas, such as electrochemical energy storage and flexible electronics. Although the solution-processed MXene-based device has made significant achievements, it is still a challenge to develop large-scale and high-resolution printing methods for flexible printed electronics. In this work, we reported a novel strategy of a porous interlocking structure to obtain flexible MXene/laser-induced graphene (LMX) composite electrodes with enhanced adhesion and high printing resolution. In comparison to traditional printed MXene electrodes, the LMX electrode with an interlocking interface possesses enhanced mechanical properties (adhesive strength of 2.17 MPa) and comparable electrical properties (0.68 S/mm). Furthermore, owing to the outstanding stability and flexibility, the LMX-based triboelectric nanogenerator (TENG) can be used as a self-powered sensor to monitor finger-bending movement. A support vector machine (SVM)-assisted self-powered motion sensor can distinguish the bending angle with high recognition accuracy and can effectively identify different angles. The successful experience of directly printing flexible electrodes with excellent mechanical and electrical properties can be promoted to other solution-processed two-dimensional materials. Our strategy opens up a promising perspective to develop flexible and printed electronics.

Self-powered motion state monitoring system based on combined triboelectric nanogenerators for human physiological signal monitoring and energy collection

The study of self-powered motion state monitoring systems based on triboelectric nanogenerators has recently received increasing attention. In this paper, we propose a self-powered system consisting of two low-cost and simply manufactured triboelectric nanogenerators for human physiological signal monitoring and energy collection. This system can monitor the trunk information and gait information during human activities, and measure human motion status in a holistic manner. The triboelectric nanogenerator, which monitors body torso information (B-TENG), we optimize its triboelectric layer through the microstructure of sandpaper to increase its contact area with the skin. In addition, by adding iron powder into the B-TENG electrode layer, the magnetic permeability of the induction electrode is increased to improve its output performance, and its maximum open-circuit voltage can reach 44.3 V. The triboelectric nanogenerator, which is installed on the foot to monitor gait information (F-TENG), can reach an average open-circuit voltage of 205.6 V by adding a rectangular protrusion structure to the triboelectric layer. In addition, due to its high output performance (∼4700 μw), the F-TENG can collect mechanical energy generated from the soles of the feet during daily human activities and charge a 100 μF capacitor to 1.4 V within 60 s, subsequently powering the miniature electronics. During foot walking, F-TENG is able to light up more than 60 light-emitting diodes. By having the experimenters wear these two triboelectric nanogenerators, we can record the frequency and amplitude signals of the experimenter's elbow, knee, breath, and gait in real time. We also monitored three running states of the human body through these two triboelectric nanogenerators, including normal state, insufficient exercise capacity, and dyspnea. We believe that this work provides a new direction for the development of big data motion analysis and self-powered smart exercise devices.

Electric field enhancement for triboelectrification-induced electroluminescence via micro electrode units and BaTiO3 nanoparticles

Intelligent terminals demand motion sensors with high intensity and low energy consumption. Motion sensors relied on the conversion of mechanical signals into electrical signals usually need complex electric circuits. Alternatively, novel motion sensors that can convert mechanical signals into optical signals represent an intuitive way of motion sensing. Here, a high-intensity luminescent composite film is proposed with utilization of micro electrode units and high dielectric BaTiO3 nanoparticles aiming at electric field enhancement for the electroluminescence process of triboelectrification-induced electroluminescence (TIEL). It is found that the existing of electrode units would effectively enhance the produced electric field along the edge of the electrode units and thus promote the luminescent intensity. Besides, the BaTiO3 nanoparticles would elevate the dielectric constant of the luminescent composite film and a proper ratio of BaTiO3 would significantly improve the luminescent intensity. The dielectric constant of the luminescent layer would rise as the driving frequency decreases, which indicates its suitability for low frequency mechanical movement sensing. Visualized motion sensing with high intensity and excellent stability thereby can be stimulated under ultra-low pressure and low frequency mechanical movement. Hand motion and water flow can be real-timely tracked via luminescent composite films with micro electrode arrays, demonstrating its great potential in self-powered motion sensors for the broad applications in biometrics, liquid sensing, anti-counterfeiting identification, surveillance and many others.

Stretchable and biodegradable triboelectric nanogenerator based on elastomeric nanocomposites

Biologically benign, dissolvable materials-based triboelectric nanogenerators hold significant potential as a sustainable power source for bioresorbable, transient electronic systems; however poor options in materials and engineering approaches are major obstacles to the desired electrical, physical, and mechanical properties, particularly when considering operations under restrictive, demanding conditions or environments. Here, we present an elastomeric composites-based triboelectric nanogenerator with a package of completely degradable materials. Assembly of inorganic nanoparticles with high charge affinity/permittivity and micro-pyramid structures with high surface area produces enhanced charge density and power outputs over those of existing elements. Study on mechanical and biochemical characteristics validates the capability of maintaining stable, long-life electrical outputs under cyclic tests and aqueous solutions. Demonstrations of energy harvesting at an artificial knee and self-powered motion sensing at a finger joint suggest the practical feasibility in versatile areas of biomedical and eco-resorbable electronics.

Deacetylation-controlled chitin derivative imbedded WPU nanocomposite for highly powered and robust triboelectric nanogenerator

For effective triboelectric nanogenerator, it remains a major challenge to improve the intrinsic electron-donating properties of positive materials. We report a positive triboelectric nanocomposite material based on chitin, a biopolymer, embedded in a waterborne polyurethane matrix to improve the output performance, sustainability, and robustness of triboelectric nanogenerators (TENGs). This nanocomposite can increase the output performance via electron donating control through the deacetylation of chitin nanofibers. For the deacetylation of chitin, the exposed amine group can be an attractive electron donor combined with polyurethane, resulting in a higher output characteristic (210 V and 3.2 μA/cm2), as confirmed by Kelvin probe force microscopy measurements. Moreover, this nanocomposite film showed good sustainability (V/V0 = 85%) in a humid environment (85 RH%) owing to its hydrogen bonding with water molecules. The hybridized film exhibited excellent robustness (100,000 cycles of bending test, long-term stability test over 10,000 s) in two types of harsh mechanical environments. This flexible, robust TENG with a nanocomposite film can serve as a self-powered motion sensor for monitoring various human motions, such as contact pressure and sliding speed. Combined with a homemade sodium-ion potentiometric sensor, stable operation of the dehydration monitoring system was successfully demonstrated under sweating conditions.

Flexible triboelectric nanogenerators of Au-g-C3N4/ZnO hierarchical nanostructures for machine learning enabled body movement detection

Here we report the development of triboelectric nanogenerator (TENG) based self-powered human motion detector with chemically developed Au-g-C3N4/ZnO based nanocomposite on common cellulose paper platform. Compared to bare g-C3N4, the nanocomposite in the form of hierarchical morphology is found to exhibit higher output voltage owing to the contribution of Au and ZnO in increasing the dielectric constant and surface roughness. While generating power ∼3.5 μW cm−2 and sensitivity ∼3.3 V N−1, the flexible TENG, is also functional under common biomechanical stimuli to operate as human body movement sensor. When attached to human body, the flexible TENG is found to be sensitive towards body movement as well as the frequency of movement. Finally upon attaching multiple TENG devices to human body, the nature of body movement has been traced precisely using machine learning (ML) techniques. The execution of the learning algorithms like artificial neural network and random forest classifier on the data generated from these multiple sensors can yield an accuracy of 99% and 100% respectively to predict body movement with great deal of precision. The exhibition of superior sensitivity and ML based biomechanical motion recognition accuracy by the hierarchical structure based flexible TENG sensor are the prime novelties of the work.

Nanogenerator based self-powered motion monitoring for flapping wings of bio-inspired flying robots

Under the constraints of weight and power, achieving airborne monitoring of wings' flexible motion toward bio-inspired flying robots is an arduous challenge. Herein, we present a self-powered motion monitoring method based on nanogenerators to tackle this issue. First, a locally adaptable integration structure of triboelectric nanogenerator (TENG) integrated wings is proposed for the design of airborne devices. Second, a theoretical output model is developed to dynamically monitor the flapping motion of TENG-integrated wings. The proposed approach is a multi-target monitoring technique that enables the sensing of parameters, such as the flapping frequency and the flapping angles with stability. After validation, the monitoring error of the wing plane's pitch angle affected by device stability is less than 0.7°. Likewise, the maximum observed error rate for flapping frequency monitoring is about 0.1%. This technique will further enhance the intelligent airborne wing state perception for bio-inspired flying robots.

Thermogalvanic gel patch for self-powered human motion recognition enabled by photo-thermal-electric conversion

Quasi-solid-state electrolytes offer a cheap, leak-free, and scalable way to convert heat directly into electricity for wearable electronics. However, the limited temperature difference with the environment poses a challenge for the extensive application of thermoelectric gels. Currently, photo-thermal-electric (PTE) conversion is an environmentally-friendly technology to exploit the thermogalvanic effect of gels. Here, we report a smart light-driven flexible PTE gel for self-powered human motion monitoring. The whole structure takes advantage of the low thermal conductivity and high output power of poly(vinyl alcohol)/polydimethylsiloxane (PVA-PDMS) gels with Fe2+/3+ as a redox pair, together with the local surface plasmon resonance (LSPR) of Au nanoparticles (AuNPs)@SiO2-PDMS composite film. This enables simultaneous high thermogalvanic and photothermal performance, with an open circuit voltage of up to 12 mV and a short circuit current exceeding 1.25 A m−2 at a temperature difference of up to 9 °C under one sun. The PTE gel is fabricated into a proof-of-concept self-powered patch, which can actively distinguish human motions in real time by recognizing the switching of solar radiation stimulated by arm swing. This work provides thermogalvanic gels with a new opportunity in self-powered wearable sensing that may greatly promote the progress of intelligent medical electronics.

Self-Repairing and Energy-Harvesting Triboelectric Sensor for Tracking Limb Motion and Identifying Breathing Patterns.

The increasing prevalence of health problems stemming from sedentary lifestyles and evolving workplace cultures has placed a substantial burden on healthcare systems. Consequently, remote health wearable monitoring systems have emerged as essential tools to track individuals' health and well-being. Self-powered triboelectric nanogenerators (TENGs) have exhibited significant potential for use as emerging detection devices capable of recognizing body movements and monitoring breathing patterns. However, several challenges remain to be addressed in order to fulfill the requirements for self-healing ability, air permeability, energy harvesting, and suitable sensing materials. These materials must possess high flexibility, be lightweight, and have excellent triboelectric charging effects in both electropositive and electronegative layers. In this work, we investigated self-healable electrospun polybutadiene-based urethane (PBU) as a positive triboelectric layer and titanium carbide (Ti3C2Tx) MXene as a negative triboelectric layer for the fabrication of an energy-harvesting TENG device. PBU consists of maleimide and furfuryl components as well as hydrogen bonds that trigger the Diels-Alder reaction, contributing to its self-healing properties. Moreover, this urethane incorporates a multitude of carbonyl and amine groups, which create dipole moments in both the stiff and the flexible segments of the polymer. This characteristic positively influences the triboelectric qualities of PBU by facilitating electron transfer between contacting materials, ultimately resulting in high output performance. We employed this device for sensing applications to monitor human motion and breathing pattern recognition. The soft and fibrous-structured TENG generates a high and stable open-circuit voltage of up to 30 V and a short-circuit current of 4 μA at an operation frequency of 4.0 Hz, demonstrating remarkable cyclic stability. A significant feature of our TENG is its self-healing ability, which allows for the restoration of its functionality and performance after sustaining damage. This characteristic has been achieved through the utilization of the self-healable PBU fibers, which can be repaired via a simple vapor solvent method. This innovative approach enables the TENG device to maintain optimal performance and continue functioning effectively even after multiple uses. After integration with a rectifier, the TENG can charge various capacitors and power 120 LEDs. Moreover, we employed the TENG as a self-powered active motion sensor, attaching it to the human body to monitor various body movements for energy-harvesting and sensing purposes. Additionally, the device demonstrates the capability to recognize breathing patterns in real time, offering valuable insights into an individual's respiratory health.

Broadband omnidirectional piezoelectric–electromagnetic hybrid energy harvester for self-charged environmental and biometric sensing from human motion

Vibration induced by human motions features a wide frequency spectrum and spatiotemporal-variable directions. Yet, it is challenging to concurrently expand frequency bandwidth and achieve multidirectional capability for effectively human-induced biomechanical energy harvesting and biometrics sensing. In this paper, we report a piezoelectric–electromagnetic hybrid energy harvester with coupled vibrational stabilization and induced frequency-up rotational mechanisms for omnidirectional and broadband vibration energy harvesting. Experimental studies demonstrate the proposed hybrid energy harvester operates effectively over a wide excitation frequency range from 6.0 to 16.0 Hz with omnidirectional responses. The piezoelectric conversion unit can provide a maximum output power of 0.9 mW and the electromagnetic conversion unit’s maximum output power is 22.7 mW. The hybrid energy harvester satisfies the power requirements of different types of portable electronics and realizes various self-charged sensing electronics that are stimulated by human movement. Various types of human motion signals are detected by piezoelectric and electromagnetic units via machine learning techniques to realize self-powered motion monitoring. Compared with a single type of signal, the identification accuracy of the hybrid device is improved from 85.6% to 100%. The proposed energy harvester for self-powered sensing paves the way to green intelligent life such as health management, environmental monitoring and human-machine interaction.

A Piezoelectric-Driven Electrochromic/Electrofluorochromic Dual-Modal Display Device.

Electrochromic (EC) reflective displays offer great advantages in delivering information and providing visual data, but are limited in dark environments. Reflective/emissive dual-modal displays capable of electrochemically-induced color and fluorescence change simultaneously are highly desirable, especially possessing rapid response speed as well as long-term durability. Herein, an electroactive fluorescent ionic liquidbased on triphenylamine and imidazole (EFIL-TPA) has been synthesized for reflective/emissive dual-modal display. The resultant device exhibits outstanding electrochromic/electrofluorochromic (EC/EFC) performance with low driving voltage (below 1.0V), fast switching speed (0.57-1.8 s), and remarkable cycling durability (91% retention for 10000 cycles). A piezoelectric nanogenerator (PENG) driven EC/EFC integrated system is fabricated to harvest energy from human motion and visually drive the color/fluorescence change for human motion indication in both bright and dark environments. This innovative EC/EFC dual-modal display device based on EFIL-TPA supports a huge space for the development of self-powered human motion visualized indication in all-light conditions.

Eco-Friendly Garlic Tunic–Tin Oxide(II) Nanoparticle Composite-Based Triboelectric Nanogenerator for Self-Powered Human Motion Monitoring

Eco-Friendly Garlic Tunic–Tin Oxide(II) Nanoparticle Composite-Based Triboelectric Nanogenerator for Self-Powered Human Motion Monitoring

Electrospun Nanofibers Hybrid Wrinkled Micropyramidal Architectures for Elastic Self-Powered Tactile and Motion Sensors.

Conformable, sensitive, long-lasting, external power supplies-free multifunctional electronics are highly desired for personal healthcare monitoring and artificial intelligence. Herein, we report a series of stretchable, skin-like, self-powered tactile and motion sensors based on single-electrode mode triboelectric nanogenerators. The triboelectric sensors were composed of ultraelastic polyacrylamide (PAAm)/(polyvinyl pyrrolidone) PVP/(calcium chloride) CaCl2 conductive hydrogels and surface-modified silicon rubber thin films. The significant enhancement of electrospun polyvinylidene fluoride (PVDF) nanofiber-modified hierarchically wrinkled micropyramidal architectures for the friction layer was studied. The mechanism of the enhanced output performance of the electrospun PVDF nanofibers and the single-side/double-side wrinkled micropyramidal architectures-based sensors has been discussed in detail. The as-prepared devices exhibited excellent sensitivity of a maximum of 20.1 V/N (or 8.03 V/kPa) as tactile sensors to recognize a wide range of forces from 0.1 N to 30 N at low frequencies. In addition, multiple human motion monitoring was demonstrated, such as knee, finger, wrist, and neck movement and voice recognition. This work shows great potential for skin-like epidermal electronics in long-term medical monitoring and intelligent robot applications.

Photothermal Propelling and Pyroelectric Potential-Promoted Cell Internalization of Janus Nanoparticles and Pyroelectrodynamic Tumor Therapy.

Cancer phototherapy experiences limitations in tissue diffusion and cell internalization of phototherapeutic agents and dose-dependent side effects. Herein, Janus pyroelectric nanoparticles (NPs) are designed to generate self-powered motion and built-in electric fields to overcome the delivery barriers. Polydopamine (PDA) layers are partially coated on tetragonal BaTiO3 (tBT) NPs to prepare Janus tBT@PDA, and Au NPs are deposited on the PDA caps to obtain Janus tBT@PDA-Au NPs. Near-infrared (NIR) illumination of tBT@PDA-Au builds in situ pyroelectric potentials on NPs, which selectively affect the membrane potential of tumor cells rather than normal cells to enhance tumor cell internalization and produce reactive oxygen species (ROS) for pyroelectric dynamic therapy (PEDT). The asymmetric photothermal effect of the Janus NPs creates thermophoretic force to propel NP motion, which enhances tumor diffusion and cellular uptake of NPs and boosts cytotoxicity and intracellular ROS levels. The inoculation of Au NPs increases the photothermal effect, exhibits larger motion velocities, produces higher pyroelectric potentials, and elevates cellular uptake rates, resulting in significant induction of tumor cell apoptosis, suppression of tumor growth, and extension of animal survival. Thus, the concise design of tBT@PDA-Au/NIR treatment has achieved thermophoretic motion-promoted tissue diffusion, built-in electric field-enhanced cell internalization, and photothermal/PEDT-synergized antitumor efficacy.

Large-scale production of the 3D warp knitted terry fabric triboelectric nanogenerators for motion monitoring and energy harvesting

In the coming era of intelligence, the textile-based triboelectric nanogenerator (T-TENG) is considered to be one of the most important development directions to achieve flexible wearable sensing and micro/nano energy harvesting. Among them, due to excellent physical proeprties of nano/micro fibrous structure, fluff/terry /fleece/brush/fur/pile/villus/velvet structure fabrics are gradually being applied to TENG. However, the research on the relationship between the triboelectric properties of TENG and the structural parameters of fluff, as well as the fabrication of large-scale fluff TENG are very lacking. Here, a 3D warp knitted terry fabric TENG (WKTF-TENG) is mass produced by a mature warp knitted technology. The triboelectric properties of contact-separation mode, lateral-sliding mode and single electrode mode are systematically investigated by changing the height and density of the pile loops of the fabric. This study demonstrates that terry fabric is an excellent triboelectric materials for it high output and good wear resistance, especially for ateral-sliding mode. The output of WKTF-TENG even increases with the increase of working cycles due to the more fluffy and uniform distribution of fibers on the surface of the fabric. What’s more, the triboelectric properties of terry fabrics also have a great relationship with the compression properties of the pile loops. As smart textile matertail, WKTF-TENG can be usde as self-powered motion monitoring sensor and energy harvesting device. The research on the output performance of WKTF-TENG through theoretical analysis and experimental testing may provides a promising direction for fluff fabric based TENG.

Solution-processed flexible n-type S-doped Ag2Se thermoelectric generators for near-ambient-temperature energy harvest†

Among the different technologies to harvest renewable energy, thermoelectric (TE) generators (TEGs) represent a highly promising route capable of converting heat to electricity based on the Seebeck effect. Here, a new room temperature (RT) one-pot solution synthesis approach was proposed, together with a sulfur-doping strategy, to optimize the flexibility and the power factor of n-type S-doped Ag2Se TE thin films deposited by solution-processes, requiring only mild post-deposition annealing at 150 °C. Optimized S-doped flexible Ag2Se thin films exhibited a maximum power factor of ∼2058 μW/m/K2 at RT, allowing for the fabrication of flexible TEGs with a maximum power output (Pmax) of 3.98 μW under a near-RT ΔT of 31 K, equivalent to a power density of 11.06 W/m2. Multidomain applications were further demonstrated by these heavy-metal–free, flexible TEGs to harvest near-RT waste heat from laptop computers, non-concentrated sun light, and human body together with the realization of a self-powered motion detector. The current findings open promising paths for innovations on low-cost wearable smart electronics and energy harvesting.

Flexible Lead-Free Piezoelectric Ba0.94Sr0.06Sn0.09Ti0.91O3/PDMS Composite for Self-Powered Human Motion Monitoring.

Piezoelectric wearable electronics, which can sense external pressure, have attracted widespread attention. However, the enhancement of electromechanical coupling performance remains a great challenge. Here, a new solid solution of Ba1-xSrxSn0.09Ti0.91O3 (x = 0.00~0.08) is prepared to explore potential high-performance, lead-free piezoelectric ceramics. The coexistence of the rhombohedral phase, orthorhombic phase and tetragonal phase is determined in a ceramic with x = 0.06, showing enhanced electrical performance with a piezoelectric coefficient of d33~650 pC/N. Furthermore, Ba0.94Sr0.06Sn0.09Ti0.91O3 (BSST) is co-blended with PDMS to prepare flexible piezoelectric nanogenerators (PENGs) and their performance is explored. The effects of inorganic particle concentration and distribution on the piezoelectric output of the composite are systematically analyzed by experimental tests and computational simulations. As a result, the optimal VOC and ISC of the PENG (40 wt%) can reach 3.05 V and 44.5 nA, respectively, at 138.89 kPa, and the optimal sensitivity of the device is up to 21.09 mV/kPa. Due to the flexibility of the device, the prepared PENG can be attached to the surface of human skin as a sensor to monitor vital movements of the neck, fingers, elbows, spine, knees and feet of people, thus warning of dangerous behavior or incorrect posture and providing support for sports rehabilitation.

A Flexible Triboelectric Nanogenerator Integrated with CMCh-Fe/LiCl Hydrogel Electrode for Cheerleading Monitoring

Conductive hydrogel is a high-performance conductive electrode that can be used for flexible and stretchable sensors. Furthermore, the self-powered sensor devices integrated with conductive hydrogel conductive can play the role in dance posture monitoring. In this work, we proposed a carboxymethyl chitosan (CMCh)-Fe/LiCl hydrogel-based triboelectric nanogenerator (CL-TENG) to harvest human motion mechanical energy. Based on the experimental results, the average transmissivity of CMCh-Fe/LiCl hydrogel can arrive at 91.53%. Also the CMCh-Fe/LiCl hydrogel has a high rate of mechanical healing, especially at high temperatures. The CL-TENG can reach the maximum power density of 81.48[Formula: see text]mW/m2 when the external load is 200[Formula: see text]M[Formula: see text]. The open-circuit voltage ([Formula: see text]) and transferred charge ([Formula: see text]) of CL-TENG can arrive at 96[Formula: see text]V and 32.4[Formula: see text]nC, and the short-circuit current ([Formula: see text] of CL-TENG can reach 1.2[Formula: see text][Formula: see text]A. The CL-TENG can also serve as the self-powered dance motion sensor to monitor the action specifications of actors in cheerleading performance. This research will promote the development of dance pose sensors.