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Directional freezing and drying under stretching are combined to fabricate hierarchical hydrogel scaffolds with a clustered and oriented structure, which guides the alignment and orientation of fibroblasts and chondrocytes.

Wearable exoskeletons are developing rapidly due to their superiority in improving human ability and efficiency. The construction of a multifunctional exoskeleton system relies on an efficient continuous energy supply and various high-performance sensors. Here, a magnetic-driven piezoelectric cantilever generator (MPCG) array is designed for energy harvesting and angle sensing of joint motions. Combining theoretical derivation and experimental characterization, it is found that the nonlinear magnetic force acting on the cantilever structure will cause the phenomenon of frequency upconversion, which greatly improves the output of the MPCG. The experiment successfully proves the feasibility of using the MPCG array as an energy-harvesting module to collect energy from human joint motions and power an RH/temp sensor. Furthermore, the MPCG array can also be used to sense the rotation angle and angular velocity. By integrating with a wireless data acquisition and transmission module and supporting software, a wearable joint rehabilitation monitoring and assessment system is built, which can measure the activities of the joint in real time and evaluate the flexion degree. The demonstrated wearable exoskeleton system for joint motion energy harvesting and joint angle sensing is of great value for the construction of a multifunctional exoskeleton system and wearable smart rehabilitation equipment.

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.

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.

Exchange bias (EB) has extremely important applications in spintronics, researchers have proposed various means to manipulate it. This work realizes the regulation of the EB field in Co/IrMn films sputtered on LiNbO3 substrate by the surface acoustic wave (SAW). The experimental results show that in the out-of-plane and in-plane EB of Co/IrMn films, both the coercivity and the EB field decrease with the increase of the SAW power. The dynamic strain field provided by the SAW transfer to the magnetic films changes the arrangement of the magnetic moments in the Co layer and IrMn layer, the rearrangement of magnetic moments leads to a reduction in the EB field. Our experiments provide an approach to manipulate the EB field, opening a potential avenue for manipulating antiferromagnetic moments in the future.

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

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.

In the field of exercise physiology, it is of great significance to monitor human body motion status and physiological functions for assessing physical quality and training load. However, the wearable electronics as the mainstream monitoring solution have power consumption and bulk-size issues that limit sustainable operation. Here, we present a multi-mode stretchable and wearable triboelectric nanogenerator (msw-TENG) for biomechanical energy harvesting and physiological functions sensing. The msw-TENG fabricated by a liquid metal and silicone achieves stretchable and highly conductive characteristics at the same time, and realizes conformal contact with skin. The msw-TENG mainly includes contact separation/stretch/press modes, which can be randomly transformed according to the actual applications. The device converts the biomechanical energy of limb movement into electrical energy for directly lighting up commercial LEDs. Additionally, the radial artery pulse signal, joint bending angle and limb stability can be detected in real-time. As a multifunctional biomedical active sensor that is exempt from needing an extra power source, the proposed msw-TENG holds great potentials in the future of exercise monitoring and rehabilitation therapy.

Promoting the differentiation of osteoblasts is critical to maintain bone homeostasis for treatment osteoporosis and fracture healing. For these orthopedic diseases, a portable, highly patient compliance therapy device remains a great challenge. Here, we proposed a biomechanical-energy-driven shape memory piezoelectric nanogenerator (sm-PENG) that integrated with fixation splint to promote osteogenic differentiation. The pulsed direct current (DC) generated from the sm-PENG effectively promote MC3T3-E1 preosteoblast cell proliferation, orientation and increase intracellular calcium ion. At the same time, the ALP activity of cells is also improved by pulsed-DC under long-term culture conditions. Ultimately, increasing calcium deposition, extracellular matrix mineralization and osteogenesis. Our work demonstrates the potential of sm-PENG as a power source for pulsed-DC stimulation of bone repair, and shows great prospect self-powered and portable electronic medical device.

High efficiency and wide bandwidth are the main optimization directions for energy harvester. Based on flexoelectric theory, this paper presents a micro cantilever vibration energy harvester (VEH) with a broad bandwidth which achieved by collisions of two beams. The nanocrystalline graphene (NCG) is selected as base layer because its quality factor (Q factor) is highest compared with common materials, which means its energy loss in progress of power conversion is lowest and device has a high sensitivity to external excitation. Considering flexoelectric effect, based on Hamilton’s principle and Hertz contact force model, the electromechanical coupling equations are obtained. Numerical simulations are conducted. Output voltages of upper and lower beam are calculated respectively and the frequency response curve of the power density is obtained. It has been found that the maximum output voltage of flexoelectric energy harvester is almost 5 times that of piezoelectric energy harvester when the thickness of substrate layer is 400 nm. The effects of some parameters, such as resistance, gap distance between two beams, and tip mass, on the performance of harvester are studied. It indicates that the working bandwidth of the VEH has increased approximately fourfold, and the output power density is improved in some case due to collision of two beams, which has been verified by experiment. This work designs a novel efficient micro VEH and provides a theoretical basis for structure optimization.

In this paper, an auto-tuning piezoelectric energy harvester (PEH) based on the cantilever plate is presented by attaching a box to each corner of the free sides and placing a ball in each box. The prototype and supporting experimental fixtures were designed and manufactured. A series of hammering experiments are carried out to measure the natural frequency of the device according to different whole centroid position of the two balls. Seven excitation frequencies are selected to perform auto-tuning experiments, respectively. The two balls roll automatically to make the natural frequency of the structure consistent with the excitation, thereby resonating. The device is subjected to sweeping experiments. It can be seen from open circuit voltage-frequency and power-frequency diagrams that the auto-tuning PEH has a wider work frequency band as TFB and outputs higher voltage and power compared to cases where balls are fixed.

With the development of MEMS (Micro-electro-mechanical Systems) techniques, research interest has deepened in micro piezoelectric harvesting device, which can supply electrical power for wireless sensors from ambient vibration. This paper proposes a nonlinear analysis of a micro-scale PEH (piezoelectric energy harvester), which is modeled by a micro-cantilever plate with two layers and a tip mass attached to the free end. Considering size effect and nonlinear curvature, based on strain gradient and inextensible plate theory, nonlinear dynamic equations of the micro cantilever piezoelectric energy harvester with tip mass are established by virtue of the Hamilton’s principle. The maximum output voltage of piezoelectric energy harvester with different tip mass is calculated respectively using MATLAB software. Comparative analysis confirms that an increase of K (the mass ratio of the tip mass to piezoelectric plate) reduces the natural frequency of energy harvester and significantly enhances the nonlinear phenomenon. In addition, when the mass ratio K exceeds 1, obvious superharmonic resonance phenomena generates, which considerably improves the output voltage of the proposed PEH in a lower frequency band. This study proposes an approach to enhance the output performance of micro-cantilever plate energy harvesters and broaden the bandwidth of PEH to adapt low-frequency ambient vibration.

Autonomous robots are increasingly applied in realworld environments, and expect to execute plans robustly to accomplish the assigned tasks in the presence of dynamics and uncertainties of the changing environment. The robustness of plan execution requires the robot to keep aware of plan execution status and to adapt the plan towards possible execution contingencies. Such requirements pose a great challenge for autonomous robot software in terms of the abstraction model over robot behavior patterns. Conventional abstraction models for robot behaviors generally follow the sense-model-planact and behavior-based paradigms, which show limitations in tight integration with sensory inputs and tracking execution traces of robot plans. This paper proposes an accompanying behavior model that considers robot behaviors as task-oriented and observation-based types with diverse aims, and develops the run-time mechanisms to facilitate collaboration between two types of behaviors. Additionally, we implement the model by the multi-agent approach which develops the robot software as a multi-agent system. To demonstrate the feasibility and applicability of proposed model, we conduct a case study by implementing a typical example of service scenarios, e.g., a robot that autonomously picks up and drops off dishes for remote guests in the open and dynamic environment.

The structural characteristics of three lignin samples (maple lignin, rice straw lignin and rice husk lignin) prepared by Klason method were examined by elemental analysis and FTIR. Rice husk lignin has the highest H/C ratio among the three lignins, presenting molecular formula as C 9 H 8.56 O 9.60 against C 9 H 6.98 O 8.21 for rice straw lignin and C 9 H 7.79 O 4.81 for maple lignin. Maple lignin contained more methoxyl groups due to enrichment of guaiacyl and syringyl units, while rice straw lignin and rice husk lignin contained more p -hydroxyphenyl units. Thermal degradation of the three lignin samples was investigated by thermogravimetric-Fourier transform infrared spectrometry (TG-FTIR), exhibiting three mass loss stages: the evaporation of water, the intensive evolution of aromatic compounds and the sequent release of light gases. Maple lignin was estimated to be most thermally unstable among the three lignins due to the earliest evolution of phenolic compounds, CH 4 and methanol. Distribution of the prominent products from pyrolysis of lignin was determined by Py-GC/MS, regarding the effect of lignin sources and reaction temperature (550 °C ∼ 900 °C). The cleavage of typical inter-unit linkages on lignin macromolecules under relatively low temperatures can produce the guaiacol-type and syringol-type compounds, whereas the cracking of methoxyl group and hydroxyl group might be promoted by the elevated temperature with regard to the notable increase of phenol-type compounds and aromatic hydrocarbons. The formation of aromatic hydrocarbons (such as benzene, toluene and xylene) from rice straw lignin and rice husk lignin at higher temperature was remarkably more than that from maple lignin, possibly ascribed to the vigorous dehydroxylation of the phenol-type compounds enhanced by inorganic impurities.

Lignin as the most abundant source of aromatic chemicals in nature has attracted a great deal of attention in both academia and industry. Solvolysis is one of the promising methods to convert lignin to a number of petroleum-based aromatic chemicals. The process involving the depolymerization of the lignin macromolecule and repolymerization of fragments is complicated influenced by heating methods, reaction conditions, presence of a catalyst and solvent systems. Recently, numerous investigations attempted unveiling the inherent mechanism of this process in order to promote the production of valuable aromatics. Oxidative solvolysis of lignin can produce a number of the functionalized monomeric or oligomeric chemicals. A number of research groups should be greatly appreciated with regard to their contributions on the following two concerns: (1) the cracking mechanism of inter-unit linkages during the oxidative solvolysis of lignin; and (2) the development of novel catalysts for oxidative solvolysis of lignin and their performance. Investigations on lignin oxidative solvolysis are extensively overviewed in this work, concerning the above issues and the way-forward for lignin refinery.

The structure optimization of piezoelectric energy harvester aims at frequency reduction, broadening bandwidth and increasing output mainly. This paper employs a cantilever with cavity modelled by the finite element software COMSOL Multiphysics and the effect of the cavity on transducer is studied. The first order characteristic frequency is obtained by modal analysis module and the frequency response curve is solved by frequency domain analysis module. Comparison results show that the introducing of cavity improves output voltage of energy harvester and reducing device nature frequency. Moreover, effect of the cavity size parameters such as the thickness, length and position on frequency, output and conversion rate of the harvester is studied, after that the energy harvester structure is optimized.

PEH (piezoelectric energy harvester) outputs a higher voltage when the natural frequency matches ambient vibration frequency. How to widen working frequency band is a hot issue in study of PEH. In this paper, an auto-tuning PEH is presented by attaching a box to each corner of its free sides and a ball is placed in each box. Change of the balls position makes natural frequency of PEH variable, which expands working bandwidth of the device to accommodate complex ambient vibration. Fixing the equipment on experimental platform by designing fixture, hammering experiments are carried out to measure natural frequency of the structure when balls are in different positions. It is found that the maximum and minimum natural frequencies exist in the auto-tuning PEH, which form a resonance bandwidth. Moreover, there are multiple position combinations of two balls at the same natural frequency in the range of resonance bandwidth. Fixed the apparatus on exciter by the fixture, and a constant excitation frequency is selected in the bandwidth to perform auto-tuning experiments on the instrument. It is observed that location of balls is automatically changed to make natural frequency of the system coincide with the excitation, and the law of variation in balls position is obtained. The converter is subjected to sweeping experiments through an exciter and an oscilloscope. Using voltage-frequency diagrams, it is shown that the auto-tuning PEH outputs a higher voltage and its frequency band is wider when the ball rolls freely compared to two cases where balls are fixed.

In this paper, a tunable cantilever plate structure is presented, in which a box is attached to each corner of its free sides and a ball is placed in each box. Change of the balls position makes natural frequency of the structure variable, which expands working bandwidth of the structure to accommodate the complex ambient vibration. The modal analysis of the tunable cantilever plate is carried out by the finite element software-ABAQUS. Changing the balls position, it is found that there are maximum and minimum values in the natural frequency of the self-tuning structure, which forms a resonance bandwidth. Moreover, there are multiple position combinations of two balls at the same natural frequency in the range of resonance band. The paper studies the influence of mass and geometrical dimensions of boxes and balls on the natural frequency and bandwidth. While ensuring strength and stiffness of the structure, optimal material and size parameters are selected to improve the resonant bandwidth. This provides a theoretical basis for applying the tunable structure to piezoelectric energy harvester.

Xylan-based hemicellulose sample is tested in TG-MS under He, 7% O2, 20% O2 and 60% O2, in order to underpin the understanding of thermo-degradation mechanism of hemicellulose and biomass. The mass loss history recorded by TG can be divided into two main stages: (1) low-temperature stage with the peak located at around 265°C associated with thermal cracking of hemicellulose, and (2) high-temperature stage with the peak enhanced and shifted to lower temperatures by oxygen concentration ascribed to char combustion. A number of prominently evolved ions identified by MS can be designated to acetone, acetic acid, furfural, water, CO, CO2 and so on. The releasing profile of smaller fragments (water, CO and CO2) follows the pattern of DTG curve under different oxygen concentrations (especially for that in the high temperature stage). A three-step consecutive kinetic model employing "n-order reaction function" is proposed and achieved good fit for the experimental mass loss data of thermo-oxidation of hemicellulose.