Icariin has the potential to induce the differentiation of bone marrow mesenchymal stem cells into brown fat cells via PDE5A inhibition.

Background: Bone marrow mesenchymal stem cells (BMMSCs) possess the ability of adipogenic differentiation. Icariin (ICA) is a prenylated flavonol glycoside with diverse pharmacological activities and has been reported to promote osteogenic differentiation of BMMSCs. Nevertheless, the effects of ICA on BMMSC adipogenic differentiation into brown fat cells are still unclear. This study aimed to explore the effects and mechanistic basis of ICA on the differentiation of BMMSCs into brown fat cells. Methods: Oil Red-O staining assay was applied to detect the adipogenic differentiation of BMMSCs after induction. RT-qPCR and Western blot were conducted to detect the expression of lipogenic markers PPARγ and FABP4 as well as the brown fat biomarkers BMP7, PGC-1α, and UCP1 in BMMSCs. Moreover, phosphodiesterase-5A (PDE5A) expression in BMMSCs treated with ICA was measured by RT-qPCR and Western blot. Results: ICA promoted the adipogenic differentiation of BMMSCs and increased the expression levels of lipogenic markers PPARγ and FABP4 and the brown fat biomarkers BMP7, PGC-1α, and UCP1 during the adipogenic differentiation of BMMSCs. Furthermore, PDE5A was identified as a target of ICA, and its expression was reduced by ICA treatment. Moreover, PDE5A inhibition enhanced BMP7, PGC-1α, and UCP1 levels in BMMSCs. Additionally, overexpression of PDE5A notably reversed the effects of ICA in the differentiation of BMMSCs into brown fat cells. Conclusion: ICA induces the differentiation of BMMSCs into brown fat cells via PDE5A inhibition, highlighting the therapeutic value of ICA for treating obesity-related diseases.

Self-Powered Wireless Temperature and Vibration Monitoring System by Weak Vibrational Energy for Industrial Internet of Things.

Developing self-powered smart wireless sensor networks by harvesting industrial environmental weak vibration energy remains a challenge and an impending need for enabling the widespread rollout of the industrial internet of things (IIoT). This work reports a self-powered wireless temperature and vibration monitoring system (WTVMS) based on a vibrational triboelectric nanogenerator (V-TENG) and a piezoelectric nanogenerator (PENG) for weak vibration energy collection and information sensing. Therein, the V-TENG can scavenge weak vibration energy down to 80 µm to power the system through a power management module, while the PENG is able to supply the frequency signal to the system by a comparison circuit. In an industrial vibration environment where the vibration frequency and amplitude are 20 Hz and 100 µm, respectively, the WTVMS can upload temperature and frequency information on the equipment to the cloud in combination with the narrowband IoT technology to realize real-time information monitoring. Furthermore, the WTVMS can work continuously for more than 2 months, during which the V-TENG can operate up to 100 million cycles, achieving ultrahigh stability and durability. By integrating weak vibration energy harvesting and active sensing technology, the WTVMS can be used for real-time online monitoring and early fault diagnosis of vibration equipment, which has great application prospects in industrial production, machinery manufacturing, traffic transportation, and intelligent IIoT.

Near-Zero Quiescent Power Sound Wake-Up and Identification System Based on a Triboelectric Nanogenerator.

Sound monitoring has been widely used in the field of the Internet of Things (IoT), in which the sensors are mainly powered by batteries with high power consumption and limited life. Here, a near-zero quiescent power sound wake-up and identification system based on a triboelectric nanogenerator (TENG) is proposed, in which the sound TENG (S-TENG) is used for ambient sound energy harvesting and system activation. Once the sound intensity is higher than 65 dB, the converted and stored electric energy by the S-TENG can wake up the system within 0.5 s. By integrating a deep learning technique, the system is used for identifying sound sources, such as drilling, child playing, dog barking, and street music. In the active mode, the sound signals are recorded by a microelectromechanical systems (MEMS) microphone and then sent to a remote computer for sound recognition through a wireless transmitter within 2.8 s. In the standby mode, the ambient sound is not enough to wake up the system, and the quiescent power consumption is only 55 nW. This work provides a triboelectric sensor-based ultralow quiescent power sound wake-up system, which has shown excellent application prospects in smart homes, unmanned monitoring, and the Internet of Things.

An ultraweak mechanical stimuli actuated single electrode triboelectric nanogenerator with high energy conversion efficiency.

Triboelectric nanogenerator (TENG) as a new energy harvester has attracted significant attention due to its excellent output performance and high energy conversion efficiency at low-frequency, small-amplitude and weak-force compared with a traditional electromagnetic generator. Here, an ultraweak mechanical stimuli actuated single electrode triboelectric nanogenerator (UMA-TENG) has been studied with an atomic force microscope. The electrical output and force curve of UMA-TENG were studied at first, as well as the maximum output performance and highest energy conversion efficiency. Then the influence of the driving frequency, separation distance and motion amplitude was investigated, respectively. Moreover, by introducing an external switch to reach a cycle of maximized energy output, the maximum energy conversion efficiency of the UMA-TENG was up to 73.6% with an input mechanical energy of 48 pJ. This work demonstrates that the TENG shows excellent performance in ultraweak mechanical stimuli and could broaden the applications of the TENG in sensors, actuators, micro-robotics, micro-electro-mechanical-systems, and wearable electronics.

Friction-Dominated Carrier Excitation and Transport Mechanism for GaN-Based Direct-Current Triboelectric Nanogenerators.

The semiconductor triboelectric nanogenerator (TENG) based on the tribovoltaic effect has the characteristics of direct current and high current density, but the energy transfer and conversion mechanism is not completely clear. Here, a series of gallium nitride (GaN)-based semiconductor direct-current TENGs (SDC-TENGs) are investigated for clarifying the carrier excitation and transport mechanism. During the friction process, the external output current always flows from GaN to silicon or aluminum, regardless of the direction of the built-in electric field, because of the semiconductor types. These results reveal that the carrier transport direction is dominated by the interfacial electric field formed by triboelectrification, which is also verified under different bias voltages. Moreover, the characteristics dependent on the frictional force have been systematically investigated under different normal forces and frictional modes. The open-circuit voltage and short-circuit current of SDC-TENG are both increased with a larger frictional force, which shows that the more severe friction results in both a larger interface electric field and more excited carriers. The maximum voltage can reach 25 V for lighting up a series of LEDs, which is enhanced by four times compared to the cutting-edge reported SDC-TENGs. This work has clarified the friction-dominated carrier excitation and transport mechanism for the tribovoltaic effect, which demonstrates the great potential of semiconductor materials for frictional energy recovery and utilization.

Self-Powered and Autonomous Vibrational Wake-Up System Based on Triboelectric Nanogenerators and MEMS Switch.

With the extensive application of wireless sensing nodes, the demand for sustainable energy in unattended environments is increasing. Here, we report a self-powered and autonomous vibrational wake-up system (SAVWS) based on triboelectric nanogenerators and micro-electromechanical system (MEMS) switches. The energy triboelectric nanogenerator (E-TENG) harvests vibration energy to power the wireless transmitter through a MEMS switch. The signal triboelectric nanogenerator (S-TENG) controls the state of the MEMS switch as a self-powered accelerometer and shows good linearity in the acceleration range of 1-4.5 m/s2 at 30 Hz with a sensitivity of about 14.6 V/(m/s2). When the acceleration increases, the S-TENG turns on the MEMS switch, and the wireless transmitter transmits an alarm signal with the energy from E-TENG, using only 0.64 mJ. Using TENGs simultaneously as an energy source and a sensor, the SAVWS provides a self-powered vibration monitoring solution for unattended environments and shows extensive applications and great promise in smart factories, autonomous driving, and the Internet of Things.

Semiconductor Contact-Electrification-Dominated Tribovoltaic Effect for Ultrahigh Power Generation.

The semiconductor direct-current triboelectric nanogenerator (SDC-TENG) based on the tribovoltaic effect is promising for developing a new semiconductor energy technology with high power density. Here, the first SDC-TENG built using gallium nitride (GaN) and bismuth telluride (Bi2 Te3 ) for ultrahigh-power generation is reported. During the friction process, an additional interfacial electric field is formed by continuous contact electrification (CE), and abundant electron-hole pairs are excited and move directionally to form a junction current that is always internally from Bi2 Te3 to GaN, regardless of the semiconductor type. The peak open-circuit voltage can reach up to 40 V and the power density is 11.85 W m-2 (average value is 9.23 W m-2 ), which is approximately 200 times higher than that of previous centimeter-level SDC-TENGs. Moreover, compared to traditional polymer TENGs under the same conditions, the average power density is remarkably improved by over 40 times. This study provides the first evidence of CE on the tribovoltaic effect and sets the normalized power density record for TENGs, which demonstrates a great potential of the tribovoltaic effect for energy harvesting and sensing.

Power Backpack for Energy Harvesting and Reduced Load Impact.

Long-distance walking with heavy loads is often needed when going hiking or for field rescue, which is prone to cumulative fatigue. There is also a great need for labor-saving and biomechanical energy harvesting in daily life for extended security and communication needs. Here, we report a load-suspended backpack for harvesting the wasted energy of human motion based on a triboelectric nanogenerator (TENG). Two elastomers are incorporated into the backpack to decouple the synchronous movement of the load and the human body, which results in little or no extra accelerative force. With such a design, through theoretical analysis and field experiments, the backpack can realize a reduction of 28.75 % in the vertical oscillation of the load and 21.08 % in the vertical force on the wearer, respectively. Meanwhile, the mechanical-to-electric energy conversion efficiency is modeled and calculated to be 14.02 % under normal walking conditions. The designed backpack has the merits of labor-saving and shock absorption as well as electricity generation, which has the promising potential to be a power source for small-scale wearable and portable electronics, GPS systems, and other self-powered health care sensors.

Triboelectric nanogenerators for human-health care.

Since the world's first triboelectric nanogenerator (TENG) was proposed in 2012, numerous TENG-based devices and equipment have sprung up in various fields. In particular, TENG has great potential in the field of human-health care due to its small size, self-powered and low cost. With the continuous deepening of TENG research, its structure, function and technical concept are becoming more and more abundant. In order to summarize the progress and development status of TENG in health care, based on the different types of applications subdirection, this paper reviews the TENG-based research work of this field in recent eight years. The characteristics of various types of TENG-based applications and their corresponding technologies are introduced and analyzed, under the comparison of their structure and performance. This review is dedicated to provide reference and inspiration for the future development and innovation of TENG for health care.

Distributed mobile ultraviolet light sources driven by ambient mechanical stimuli.

Due to the natural characteristics of high voltage output, Triboelectric Nanogenerators (TENGs) have huge advantages in many fields. Here, we have proposed a concept of Mobile ultraviolet light sources (Mobile-UV) driven by TENG, without any additional circuits. For this system, analysis of electric characteristics, optical emission spectra, and COMSOL simulation were carried out to promote the performance. Subsequently, we have developed exploratory applications in the fields of bio-sterilization, chemical detection, and UV-curing, which proved the versatility and effectiveness. This work offers a promising, portable, effective, and safe supplement to traditional ultraviolet light sources, and will enrich the diversity of the ultraviolet application based on the reach of existing technologies.