Mesoporous Piezoelectric Polymer Composite Films with Tunable Mechanical Modulus for Harvesting Energy from Liquid Pressure Fluctuation

Harvesting mechanical energy from biological systems possesses great potential for in vivo powering implantable electronic devices. In this paper, a development of flexible piezoelectric nanogenerator (NG) is reported based on mesoporous poly(vinylidene fluoride) (PVDF) films. Monolithic mesoporous PVDF is fabricated by a template‐free sol–gel‐based approach at room temperature. By filling the pores of PVDF network with poly(dimethylsiloxane) (PDMS) elastomer, the composite's modulus is effectively tuned over a wide range down to the same level of biological systems. A close match of the modulus between NG and the surrounding biological component is critical to achieve practical integration. Upon deformation, the composite NG exhibits appreciable piezoelectric output that is comparable to or higher than other PVDF‐based NGs. An artificial artery system is fabricated using PDMS with the composite NG integrated inside. Effective energy harvesting from liquid pressure fluctuation (simulating blood pressure fluctuation) is successfully demonstrated. The simple and effective approach for fabricating mesoporous PVDF with tunable mechanical properties provides a promising route toward the development of self‐powered implantable devices.     

Energy Harvesting for Nanostructured Self‐Powered Photodetectors

Harvesting the available forms of energies in the environment to create self‐powered nanosystems is now becoming a technological reality. Self‐powered nanodevices and nanosystems are expected to play a crucial role in the future development of nanotechnology because of their specific role in fundamental studies and nanotechnological applications, mainly due to their size‐dependent properties and independent, sustainable, maintainance‐free operation. As a new field in self‐powered nanotechnology‐related research, self‐powered photodetectors have been developed which exhibit a much faster photoresponse and higher photosensitivity than the conventional photoconductor‐based photodetectors. Herein, the energy‐havesting techniques are discussed and their prospects for application in self‐powered photodetectors are summarized. Moreover, potential future directions of this research area are highlighted.     

Performance Enhancement of Flexible Piezoelectric Nanogenerator via Doping and Rational 3D Structure Design For Self‐Powered Mechanosensational System

With the rapid development of the Internet of things (IoT), flexible piezoelectric nanogenerators (PENG) have attracted extensive attention for harvesting environmental mechanical energy to power electronics and nanosystems. Herein, porous piezoelectric fillers with samarium/titanium‐doped BiFeO₃ (BFO) are prepared by a freeze‐drying method, and then silicone rubber is filled into the microvoids of the piezoelectric ceramics, forming a unique structure based on silicone rubber matrix with uniformly distributed piezoelectric ceramic. When subjected to external force stimulation, compared with conventional piezocomposite films found on undoped BFO without a porous structure, the PENG possesses higher stress transfer ability and thus boosts output performance. The notable enhancement in the stress transfer ability and piezoelectric potential is proven by COMSOL simulations. The PENG can exhibit a maximum open‐circuit voltage (V_oc) of 16 V and short‐circuit current (I_sc) of 2.8 µA, which is 5.3 and 5.6 times higher than those of conventional piezocomposite films, respectively. The PENG can be used as a triggering signal to control the operation of fire extinguishers and household appliances. This work not only expands the application scope of lead‐free piezoelectric ceramic for energy harvesting, but also provides a novel solution for self‐powered mechanosensation and shows great potential application in IoT.     

Super‐Flexible Nanogenerator for Energy Harvesting from Gentle Wind and as an Active Deformation Sensor

Using an Al‐foil of thickness ≈18 μm as a substrate and electrode, a piezoelectric nanogenerator (NG) that is super‐flexible in responding to the wavy motion of a very light wind is fabricated using ZnO nanowire arrays. The NG is used to harvest the energy from a waving flag, demonstrating its high flexibility and excellent conformability to be integrated into fabric. The NG is applied to detect the wrinkling of a human face, showing its capability to serve as an active deformation sensor that needs no extra power supply. This strategy may provide a highly promising platform as energy harvesting devices and self‐powered sensors for practical use wherever movement is available.     

Performance Optimization of Vertical Nanowire‐based Piezoelectric Nanogenerators

The integrated nanogenerator (NG) based on vertical nanowire (NW) arrays is one of the dominant designs developed to harvest mechanical energy using piezoelectric nanostructures. Finite element method (FEM) simulations of such a NG are developed using ZnO NWs in compression mode to evaluate its performances in term of piezoelectric potential generated, capacitance, induced mechanical energy, output electrical energy, and efficiency. This evaluation is essential to correctly understand NG operation. Three main issues are highlighted. The mechanical and electrical structures of the NG as an integrated system are optimized, and strategies for concentrating the mechanical strain field in the NWs and increasing the force sensitivity are developed. In addition, the influence of NWs length and diameter on NG performances is investigated. The optimization results in a piezoelectric nano composite material where global performances are improved by mean of long and thin NWs.     

Piezoelectric polymer films as power converters for human powered electronics

Piezoelectric polymer film material allows for conversion of mechanical energy into electrical energy that can be used for supplying electronic devices. While this method does not allow obtaining large useful power, recent advances in electronic technology, in particular wide availability of submicron low-power CMOS processes, have made feasible the idea of using piezoelectric polymers as power converters for human powered electronics. This concept allows to overcome the necessity of using battery as a power source, which is one of the main obstacles to widespread adoption of wearable computing devices. Of particular interest is harvesting energy from walking, which can be achieved by using piezoelectric polymers. In this paper maximum power has been calculated that can be drawn from walking energy owing to application of the copolymer polyethylene–polypropylene (PE–PP) shoe insole. The amount of electric energy obtained from a PE–PP foil of a thickness of 11 μm for a single step of a duration of 1 s – that is equivalent to a frequency of 1 Hz – amounts to 340 nJ.     

Nano/Microrobots Meet Electrochemistry

Artificial autonomous self‐propelled nano and microrobots are an important part of contemporary technology. They are typically self‐powered, taking chemical energy from their environment and converting it to motion. They can move in complex environments and channels, deliver cargo, perform nanosurgery, act as chemotaxis and perform sense‐and‐act actions. The electrochemistry is closely interwoven within this field. In the case of self‐electrophoretically driven nano/microrobots, electrochemical mechanism has been the basis of power, which translates chemical energy to motion. Electrochemistry is also a major tool for the fabrication of these micro and nanodevices. Electrochemistry and electric fields can be used for the directing of nanorobots and for detection of their positions. Ultimately, nano and microrobots can dramatically improve performances of electrochemical sensors and biosensors, as well as of the energy generating devices. Here, all aspects in the fundamentals and applications of electrochemistry in the realm of nano‐ and microrobots are reviewed.     

基于压电陶瓷的人体能量收集系统的研制

为利用压电材料收集人体能量,设计了一种人体能量收集系统,它可在人行走过程中产生电能,该机构被安装在人腿的膝盖部位,选择性地在腿部摆动结束阶段连续地按压电陶瓷片参与发电,另外还设计了压电发电装置的能量存储与控制电路,并实验了其发电特性,该装置适合给假肢或其他便携式医学设备充电。     

Tribotronics for Active Mechanosensation and Self‐Powered Microsystems

Tribotronics has attracted great attention as a new research field that encompasses the control and tuning of semiconductor transport by triboelectricity. Here, tribotronics is reviewed in terms of active mechanosensation and human–machine interfacing. As a fundamental unit, contact electrification field‐effect transistors are analyzed, in which the triboelectric potential can be used to control electrical transport in semiconductors. Several tribotronic functional devices have been developed for active control and information sensing, which has demonstrated triboelectricity‐controlled electronics and established active mechanosensation for the external environment. In addition, the universal triboelectric power management strategy and the triboelectric nanogenerator‐based constant sources are also reviewed, in which triboelectricity can be managed by electronics in the reverse action. With the implantation of triboelectric power management modules, the harvested triboelectricity by various kinds of human kinetic and environmental mechanical energy can be effectively managed as a power supply for self‐powered microsystems. In terms of the research prospects for interactions between triboelectricity and semiconductors, tribotronics is expected to demonstrate significant impact and potential applications in micro‐electro‐mechanical systems/nano‐electro‐mechanical systems (MEMS/NEMS), flexible electronics, robotics, wireless sensor network, and Internet of Things.     

In Vivo Self‐Powered Wireless Transmission Using Biocompatible Flexible Energy Harvesters

Additional surgeries for implantable biomedical devices are inevitable to replace discharged batteries, but repeated surgeries can be a risk to patients, causing bleeding, inflammation, and infection. Therefore, developing self‐powered implantable devices is essential to reduce the patient's physical/psychological pain and financial burden. Although wireless communication plays a critical role in implantable biomedical devices that contain the function of data transmitting, it has never been integrated with in vivo piezoelectric self‐powered system due to its high‐level power consumption (microwatt‐scale). Here, wireless communication, which is essential for a ubiquitous healthcare system, is successfully driven with in vivo energy harvesting enabled by high‐performance single‐crystalline (1 ? x )Pb(Mg_1/3Nb_2/3)O₃?(x )Pb(Zr,Ti)O₃ (PMN‐PZT). The PMN‐PZT energy harvester generates an open‐circuit voltage of 17.8 V and a short‐circuit current of 1.74 µA from porcine heartbeats, which are greater by a factor of 4.45 and 17.5 than those of previously reported in vivo piezoelectric energy harvesting. The energy harvester exhibits excellent biocompatibility, which implies the possibility for applying the device to biomedical applications.     

FDSOI Process Technology for Subthreshold-Operation Ultralow-Power Electronics

Ultralow-power electronics will expand the technological capability of handheld and wireless devices by dramatically improving battery life and portability. In addition to innovative low-power design techniques, a complementary process technology is required to enable the highest performance devices possible while maintaining extremely low power consumption. Transistors optimized for subthreshold operation at 0.3 V may achieve a 97% reduction in switching energy compared to conventional transistors. The process technology described in this article takes advantage of the capacitance and performance benefits of thin-body silicon-on-insulator devices, combined with a workfunction engineered mid-gap metal gate.      

Dynamic Photomask‐Assisted Direct Ink Writing Multimaterial for Multilevel Triboelectric Nanogenerator

Triboelectric nanogenerator (TENG) devices are extensively studied as a mechanical energy harvester and self‐powered sensor for wearable electronics and physiological monitoring. However, the conventional TENG fabrication involving assembling steps and using the single property of matrix material suffers from simple devices shape and a single level of mechanical response for sensing and energy harvesting. Here, the printed multimaterial matrix for multilevel mechanical‐responsive TENG with on‐demand reconfiguration of shape is reported. A multimaterial 3D printing approach by using dynamic photomask‐assisted direct ink writing printing together with a two‐stage curing hybrid ink is first developed. Multimaterial structures with location‐specific properties, such as tensile modulus, failure stress, and glass transition temperature for controlled deformation, crack propagation path, and sequential shape memory, are directly printed. The printed multimaterial structure with sequential deformation behavior is used to fabricate a multilevel‐TENG (mTENG) device for multiple level mechanical energy harvesters and sensors. It is demonstrated that the mTENG can be embedded in shoe insoles to achieve both comfortable wearing and motion state monitoring. This work provides a new approach to combine multimaterial 3D printing with TENG devices for functional wearable electronics as energy harvester and sensors.     

Kinetic Energy Harvesting Using Piezoelectric and Electromagnetic Technologies—State of the Art

This paper presents the latest progress in kinetic energy harvesting for wide applications ranging from implanted devices and wearable electronic devices to mobile electronics and self-powered wireless network nodes. The advances in energy harvesters adopting piezoelectric and electromagnetic transduction mechanisms are presented. Piezoelectric generators convert mechanical strain on the active material to electric charge while electromagnetic generators make use of the relative motion between a conductor and a magnetic flux to induce charge in the conductor. The existent kinetic piezoelectric generators including human-powered and vibration-based devices are comprehensively addressed. In addition, the electromagnetic generators which include resonant, rotational, and “hybrid” devices are reviewed. In the conclusion part of this paper, a comparison between the transduction methods and future application trends is given.      

Wearable and Implantable Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) are a promising technology to convert mechanical energy to electrical energy based on coupled triboelectrification and electrostatic induction. With the rapid development of functional materials and manufacturing techniques, wearable and implantable TENGs have evolved into playing important roles in clinic and daily life from in vitro to in vivo. These flexible and light membrane‐like devices have the potential to be a new power supply or sensor element, to meet the special requirements for portable electronics, promoting innovation in electronic devices. In this review, the recent advances in wearable and implantable TENGs as sustainable power sources or self‐powered sensors are reviewed. In addition, the remaining challenges and future possible improvements of wearable and implantable TENG‐based self‐powered systems are discussed.     

Liquid‐Metal Electrode for High‐Performance Triboelectric Nanogenerator at an Instantaneous Energy Conversion Efficiency of 70.6%

Harvesting ambient mechanical energy is a key technology for realizing self‐powered electronics, which has tremendous applications in wireless sensing networks, implantable devices, portable electronics, etc. The currently reported triboelectric nanogenerator (TENG) mainly uses solid materials, so that the contact between the two layers cannot be 100% with considering the roughness of the surfaces, which greatly reduces the total charge density that can be transferred and thus the total energy conversion efficiency. In this work, a liquid‐metal‐based triboelectric nanogenerator (LM‐TENG) is developed for high power generation through conversion of mechanical energy, which allows a total contact between the metal and the dielectric. Due to that the liquid–solid contact induces large contacting surface and its shape adaptive with the polymer thin films, the LM‐TENG exhibits a high output charge density of 430 μC m^?2, which is four to five times of that using a solid thin film electrode. And its power density reaches 6.7 W m^?2 and 133 kW m^?3. More importantly, the instantaneous energy conversion efficiency is demonstrated to be as high as 70.6%. This provides a new approach for improving the performance of the TENG for special applications. Furthermore, the liquid easily fluctuates, which makes the LM‐TENG inherently suitable for vibration energy harvesting.     

On energy‐efficient aggregation routing and scheduling in IEEE 802.15.4‐based wireless sensor networks

In wireless sensor networks, continued operation of battery‐powered devices plays a crucial role particularly in remote deployment. The lifetime of a wireless sensor is primarily dependent upon battery capacity and energy efficiency. In this paper, reduction of the energy consumption of heterogeneous devices with different power and range characteristics is introduced in the context of duty scheduling, dynamic adjustment of transmission ranges, and the effects of IEEE 802.15.4‐based data aggregation routing. Energy consumption in cluster‐based networks is modeled as a mixed‐integer linear and nonlinear programming problem, an NP‐hard problem. The objective function provides a basis by which total energy consumption is reduced. Heuristics are proposed for cluster construction (Average Energy Consumption and the Maximum Number of Source Nodes) and data aggregation routing (Cluster‐based Data Aggregation Routing) such that total energy consumption is minimized. The simulation results demonstrate the effectiveness of balancing cluster size with dynamic transmission range. The heuristics outperform other modified existing algorithms by an average of 15.65% for cluster head assignment, by an average of 22.1% for duty cycle scheduling, and by up to 18.6% for data aggregation routing heuristics. A comparison of dynamic and fixed transmission ranges for IEEE 802.15.4‐based wireless sensor networks is also provided. Copyright © 2012 John Wiley & Sons, Ltd.     

High‐Temperature BiScO3‐PbTiO3 Piezoelectric Vibration Energy Harvester

Conventionally, effective mechanical vibration energy harvesting is based on (Pb,Zr)TiO₃ (PZT) ceramics, poly(vinylidene fluoride) (PVDF) polymers or PVDF/PZT or other piezoelectric composite materials, and their working temperature is normally limited to room temperature (R‐T) or below 150 °C. Here, bismuth scandium lead titanate (BiScO₃‐PbTiO₃, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high‐temperature (H‐T) vibration energy harvesting. Experimental results show that it exhibits an excellent H‐T piezoelectricity, converting mechanical vibration energy into electric power effectively in a wide temperature range from R‐T till 250 °C. This research shows the BSPT piezoelectric energy harvester having the potential application for self‐power source of wireless sensor network system in high temperature circumstance.     

超声无线输能通道的PSPICE等效电路研究

根据压电晶片厚度振动一维等效电路、传输线理论和超声传播理论提出一种PSPICE等效电路模型.该模型利用有损传输线可对压电晶片的机械损耗过程进行模拟仿真.利用该模型对超声无线输能系统声电转换通道进行了PSPICE等效电路建模和仿真,不仅得到了快速可靠的计算结果,而且简化了超声无线输能系统的电路设计过程.该方法为研究超声无线输能系统提供了有效可靠的理论和技术基础.     

Cell Generator: A Self‐Sustaining Biohybrid System Based on Energy Harvesting from Engineered Cardiac Microtissues

Biohybrid soft robotic devices present unique advantages for designing biologically active machines that can dynamically sense and interact with complex bioelectrical signals. Here, a controllable cell‐based machine is developed that harvests energy from arrays of beating cardiomyocytes to generate electricity for biomedical microscale robotic applications. The “Cell Generator” device is based on an array of piezoelectric microcantilevers wrapped with 3D patterned cardiac cells. Spontaneous contraction of the engineered cardiac constructs provides the source of mechanical energy for electricity generation. It is demonstrated that a single “Cell Generator” unit with 40 cantilevers can output peak voltages of ≈70 mV, and a larger array of 540 cantilevers can directly generate a pulsed output as high as ≈1 V. When integrated with an electrical rectification and storage circuit, it is further shown that the “Cell Generator” can provide functional outputs and work as a self‐powered neural stimulator to evoke action potentials in cultured neuronal networks. This demonstration of “Cell Generator” technology provides an innovative perspective of exploiting live biological powering system on biomedical microscale robotic devices in the human body.     

Hybrid Smart Fiber with Spontaneous Self‐Charging Mechanism for Sustainable Wearable Electronics

Smart wearable electronics that are fabricated on light‐weight fabrics or flexible substrates are considered to be of next‐generation and portable electronic device systems. Ideal wearable and portable applications not only require the device to be integrated into various fiber form factors, but also desire self‐powered system in such a way that the devices can be continuously supplied with power as well as simultaneously save the acquired energy for their portability and sustainability. Nevertheless, most of all self‐powered wearable electronics requiring both the generation of the electricity and storing of the harvested energy, which have been developed so far, have employed externally connected individual energy generation and storage fiber devices using external circuits. In this work, for the first time, a hybrid smart fiber that exhibits a spontaneous energy generation and storage process within a single fiber device that does not need any external electric circuit/connection is introduced. This is achieved through the employment of asymmetry coaxial structure in an electrolyte system of the supercapacitor that creates potential difference upon the creation of the triboelectric charges. This development in the self‐charging technology provides great opportunities to establish a new device platform in fiber/textile‐based electronics.