Search

A comprehensiveinvestigation was carried out on n-type ZnO nanowiresfor studying the temperature dependence of the piezotronic effectfrom 77 to 300 K. In general, lowering the temperature results ina largely enhanced piezotronic effect. The experimental results showthat the behaviors can be divided into three groups depending on thecarrier doping level or conductivity of the ZnO nanowires. For nanowireswith a low carrier density (<1017/cm3at77 K), the pieozotronic effect is dominant at low temperature fordictating the transport properties of the nanowires; an opposite changeof Schottky barrier heights at the two contacts as a function of temperatureat a fixed strain was observed for the first time. At a moderate doping(between 1017/cm3and 1018/cm3at 77 K), the piezotronic effect is only dominant at onecontact, because the screening effect of the carriers to the positivepiezoelectric polarization charges at the other end (for n-type semiconductors).For nanowires with a high density of carriers (>1018/cm3at 77 K), the piezotronic effect almost vanishes.This studynot only proves the proposed fundamental mechanism of piezotroniceffect, but also provides guidance for fabricating piezotronic devices. [ABSTRACT FROM AUTHOR]

We present that the electroluminescence (EL) propertiesof Mg-doped p-type GaN thin films can be tuned bythe piezo-phototroniceffect via adjusting the minority carrier injection efficiency atthe metal–semiconductor (M–S) interface by strain inducedpolarization charges. The device is a metal–semiconductor–metalstructure of indium tin oxide (ITO)–GaN–ITO. Under differentstraining conditions, the changing trend of the transport propertiesof GaN films can be divided into two types, corresponding to the different c-axis orientations of the films. An extreme value was observedfor the integral EL intensity under certain applied strain due tothe adjusted minority carrier injection efficiency by piezoelectriccharges introduced at the M–S interface. The external quantumefficiency of the blue EL at 430 nm was changed by 5.84% under differentstraining conditions, which is 1 order of magnitude larger than thechange of the green peak at 540 nm. The results indicate that thepiezo-phototronic effect has a larger impact on the shallow acceptorstates related EL process than on the one related to the deep acceptorstates in p-type GaN films. This study has greatsignificance on the practical applications of GaN in optoelectronicdevices under a working environment where mechanical deformation isunavoidable such as for flexible/printable light emitting diodes. [ABSTRACT FROM AUTHOR]

We demonstrate the first electric field induced transverse deflection of a single-crystal, free-standing ZnO microbelt as a result of converse piezoelectric effect. For a microbelt growing along the c-axis, a shear stress in the a-cplane can be induced when an electric field Eis applied along the a-axis of the wurtzite structure. As amplified by the large aspect ratio of the microbelt that grows along the c-axis, the strain localized near the root can be detected via the transverse deflection perpendicular to the ZnO microbelt. After an experimental approach was carefully designed and possible artifacts were ruled out, the experimentally observed degree of deflection of the microbelt agrees well with the theoretically expected result. The device demonstrated has potential applications as transverse actuators/sensors/switches and electric field induced mechanical deflectors. [ABSTRACT FROM AUTHOR]

[Display omitted] • DHA inhibited the tumor growth by inducing cell cycle arrest and promoting apoptosis in NSCLC cells. • DHA reduced the expression level of receptor tyrosine kinase (RTK)-like orphan receptor 1 (ROR1). • ROR1 played a crucial role in promoting the activity of STAT3 signaling. • ROR1 may serve as a crucial molecular target mediating DHA-induced STAT3 inhibition in NSCLC. In non-small cell lung cancer (NSCLC), identifying a component with certain molecular targets can aid research on cancer treatment. Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin which induced the anti-cancer effects via the STAT3 signaling pathway, but the underlying molecular mechanism is still elusive. In this study, we first proved that DHA prohibits the growth of tumors both in vitro and in vivo. Data from transcriptomics showed that DHA reduced the expression level of the genes involved in cell cycle-promoting and anti-apoptosis, and most importantly, DHA restricted the expression level of receptor tyrosine kinase-like orphan receptor 1 (ROR1) which has been reported to have abnormal expression on tumor cells and had close interaction with STAT3 signaling. Then, we performed comprehensive experiments and found that DHA remarkably decreased the expression of ROR1 at both mRNA and protein levels and it also diminished the phosphorylation level of STAT3 in NSCLC cell lines. In addition, our data showed that exogenously introduced ROR1 could significantly enhance the phosphorylation of STAT3 while blocking ROR1 had the opposite effects indicating that ROR1 plays a critical role in promoting the activity of STAT3 signaling. Finally, we found that ROR1 overexpression could partially reverse the decreased activity of STAT3 induced by DHA which indicates that DHA-induced anti-growth signaling is conferred, at least in part, through blocking ROR1-mediated STAT3 activation. In summary, our study indicates that in NSCLC, ROR1 could be one of the critical molecular targets mediating DHA-induced STAT3 retardation. [ABSTRACT FROM AUTHOR]

Flexible electrochemical biosensors used for sweat analysis have aroused great interests in the field of intelligent instruments. Due to the complexity of body fluids, development of ultrasensitive and miniaturized sensors for analysis of sweat is always challengeable. In this research, we fabricate a sensitive and flexible sensor for real-time monitoring of glucose and lactate in sweat at micromolar level and millimolar level by using gold nanopine needles (AuNNs) as the signal amplification strategy. A flexible chip with gold electrode arrays was fabricated in a standard semi-conductor laboratory. AuNNs were deposited on the working electrode by electrochemical deposition method. Enzyme immobilization was carried out on the electrode surface via a cross-linker poly(ethylene glycol) diglycidylether (PEGDE), which is an important component of redox hydrogels capable of retaining the activity of the enzyme to a greater extent than other linkers like glutaraldehyde. The catalytic behavior of AuNNs under different conditions was investigated. The as-fabricated electrochemical sweat biosensor was found to achieve low detection limit down to 7 μmol L−1 for glucose, 54 μmol L−1 for lactate, respectively. The sensor also exhibited great selectivity, reproducibility and stability. In addition, human sweat samples were analyzed by the sensor, indicating its potential applications in determination of glucose and lactate as a wearable skin sensor. • A flexible electrochemical sensor is fabricated. • Au nanostructure is utilized for signal amplification. • Both glucose and lactate in sweat are detected. • High sensitivity is achieved due to Au nanostructure. • The developed sensor shows satisfactory selectivity. [ABSTRACT FROM AUTHOR]

Electronic devices with configurability to providing multiple functions are of great interests for their superior adaptability to the ever-changing and multifarious application scenarios. Here, we report flexible integrated circuits (ICs) possessing configurable functions constructed with dual-material gate (DMG) devices based on carbon nanotube thin films, which can serve as either transistors or diodes, on a 2-μm-thick parylene substrate. When configured as a transistor, the DMG device has great advantages over the normal-gated (NG) devices regarding the current on/off ratio (I on / I off), the subthreshold swing (SS) and the drain-induced barrier lowering (DIBL) due to the regulated energy band distribution in channel area. When operating as a diode, a typical DMG device demonstrates a sufficient rectification ratio of 8 × 10 4 and a diode-on-current of over 26 μA. Scalable manufacturing of DMG devices was also demonstrated with great uniformity both in diode and transistor configurations. Finally, multifunctional integrated circuits, which can dynamically switch their function from rectifier to follower or from OR gate to voltage adder by changing controlling signals, were constructed. The functional-configurability, together with scalable manufacturing and the realization on ultrathin flexible substrates, will open up great opportunity for the future environmentally-adaptive system in the field of flexible electronics. Image 1 [ABSTRACT FROM AUTHOR]

The piezophototronic effect is known as a three-way coupling between piezoelectric polarization, semiconductor property, and optical excitation in piezoelectric semiconductor materials to modify their energy band structures by strain-induced piezoelectric polarization charges, and thus to tune/control their optoelectronic processes of charge carrier generation, separation, recombination, and transport. In this work, the temperature dependence of the piezophototronic effect in wurtzite-structured CdS nanowires is investigated from 77 to 300 K. The piezophototronic effect is enhanced by over 550% under lower temperature due to the increased effective piezoelectric polarization surface/interface charges resulting from the reduced screening effect by decreased mobile charge carriers in CdS nanowires. Optoelectronic performances of CdS nanowires are systematically investigated under various light illuminations, strains, and temperatures. By analyzing the corresponding band diagrams, the piezophototronic effect is found to dominate the transport and separation processes of charge carriers. This study presents in-depth fundamental understanding about the piezophototronic effect and provides guidance for its future applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Single-electrode triboelectric nanogenerators (SETENGs) significantly expand the application of triboelectric nanogenerators in various circumstances, such as touch-pad technologies. In this work, a theoretical model of SETENGs is presented with in-depth interpretation and analysis of their working principle. Electrostatic shield effect from the primary electrode is the main consideration in the design of such SETENGs. On the basis of this analysis, the impacts of two important structural parameters, that is, the electrode gap distance and the area size, on the output performance are theoretically investigated. An optimized electrode gap distance and an optimized area size are observed to provide a maximum transit output power. Parallel connection of multiple SETENGs with micro-scale size and relatively larger spacing should be utilized as the scaling-up strategy. The discussion of the basic working principle and the influence of structural parameters on the whole performance of the device can serve as an important guidance for rational design of the device structure towards the optimum output in specific applications. [ABSTRACT FROM AUTHOR]

We introduce an innovative designof a disk triboelectric nanogenerator(TENG) with segmental structures for harvesting rotational mechanicalenergy. Based on a cyclic in-plane charge separation between the segmentsthat have distinct triboelectric polarities, the disk TENG generateselectricity with unique characteristics, which have been studied byconjunction of experimental results with finite element calculations.The role played by the segmentation number is studied for maximizingoutput. A distinct relationship between the rotation speed and theelectrical output has been thoroughly investigated, which not onlyshows power enhancement at high speed but also illuminates its potentialapplication as a self-powered angular speed sensor. Owing to the nonintermittentand ultrafast rotation-induced charge transfer, the disk TENG hasbeen demonstrated as an efficient power source for instantaneouslyor even continuously driving electronic devices and/or charging anenergy storage unit. This work presents a novel working mode of TENGsand opens up many potential applications of nanogenerators for harvestingeven large-scale energy. [ABSTRACT FROM AUTHOR]

Harvesting thermoelectric energy mainly relies on theSeebeck effectthat utilizes a temperature difference between two ends of the devicefor driving the diffusion of charge carriers. However, in an environmentthat the temperature is spatially uniform without a gradient, thepyroelectric effect has to be the choice, which is based on the spontaneouspolarization in certain anisotropic solids due to a time-dependenttemperature variation. Using this effect, we experimentally demonstratethe first application of pyroelectric ZnO nanowire arrays for convertingheat energy into electricity. The coupling of the pyroelectric andsemiconducting properties in ZnO creates a polarization electric fieldand charge separation along the ZnO nanowire as a result of the time-dependentchange in temperature. The fabricated nanogenerator has a good stability,and the characteristic coefficient of heat flow conversion into electricityis estimated to be ∼0.05–0.08 Vm2/W. Ourstudy has the potential of using pyroelectric nanowires to convertwasted energy into electricity for powering nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: Relying on the piezopotential created in ZnO under straining, nanogenerators, piezotronics and piezo-phototronics developed based on laterally bonded nanowires on a polymer substrate have been reviewed. The principle of the nanogenerator is a transient flow of electrons in external load as driven by the piezopotential created by dynamic straining. By integrating the contribution made by millions of nanowires, the output voltage has been raised to 1.2V. Consequently, self-powered nanodevices have been demonstrated. This is an important platform technology for the future sensor network and the internet of things. Alternatively, the piezopotential can act as a gate voltage that can tune/gate the transport process of the charge carriers in the nanowire, which is a gate-electrode free field effect transistor (FET). The device fabricated based on this principle is called the piezotronic device. Piezo-phototronic effect is about the tuning and controlling of electro-optical processes by strain induced piezopotential. The piezotronic, piezophotonic and pieozo-phototronic devices are focused on low frequency applications in areas involving mechanical actions, such as MEMS/NEMS, nanorobotics, sensors, actuators and triggers. [ABSTRACT FROM AUTHOR]

Flexible sensors have attracted increasing research interest due to their broad application potential in the fields of human–computer interaction, medical care, sports monitoring, etc. Constructing an integrated sensor system with high performance and being capable of discriminating different stimuli remains a challenge. Here, we proposed a flexible integrated sensor system for motion monitoring that can measure bending strain and pressure independently with a low-cost and simple fabrication process. The resistive bending strain sensor in the system is fabricated by sintering polyimide (PI), demonstrating a gauge factor of 9.54 and good mechanical stability, while the resistive pressure sensor is constructed based on a composite structure of silver nanowires (AgNWs) and polydimethylsiloxane (PDMS)-expandable microspheres with a tunable sensitivity and working range. Action recognition is demonstrated by attaching the flexible integrated sensor system on the wrist with independent strain and pressure information recorded from corresponding sensors. It shows a great application potential in motion monitoring and intelligent human–machine interfaces. [ABSTRACT FROM AUTHOR]

A wearable electronic system constructed with multiple sensors with different functions to obtain multidimensional information is essential for making accurate assessments of a person's condition, which is especially beneficial for applications in the areas of health monitoring, clinical diagnosis, and therapy. In this work, using polyimide films as substrates and Pt as the constituent material of serpentine structures, flexible temperature and angle sensors were designed that can be attached to the surface of an object or the human body for monitoring purposes. In these sensors, changes in temperature and bending angle are converted into variations in resistance through thermal resistance and strain effects with a sensitivity of 0.00204/°C for temperatures in the range of 25 to 100 °C and a sensitivity of 0.00015/° for bending angles in the range of 0° to 150°. With an appropriate layout design, two sensors were integrated to measure temperature and bending angles simultaneously in order to obtain decoupled, compensated, and more accurate information of temperature and angle. Finally, the system was tested by being attached to the surface of a knee joint, demonstrating its application potential in disease diagnosis, such as in arthritis assessment. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerator (TENG) is a newly arisen technology for mechanical energy harvesting from the environment, such as raindrops, wind, tides, and so on. It has attracted widespread attention in flexible electronics to serve as self-powered sensors and energy-harvesting devices because of its flexibility, durability, adaptability, and multi-functionalities. In this work, we fabricated a tubular flexible triboelectric nanogenerator (TF-TENG) with energy harvesting and human motion monitoring capabilities by employing polydimethylsiloxane (PDMS) as construction material, and fluorinated ethylene propylene (FEP) films coated with Cu as the triboelectric layer and electrode, serving in a free-standing mode. The tube structure has excellent stretchability that can be stretched up to 400%. Modifying the FEP films to obtain a superhydrophobic surface, the output performance of TF-TENG was increased by at least 100% compared to an untreated one. Finally, as the output of TF-TENG is sensitive to swing angle and frequency, demonstration of real-time monitoring of human motion state was realized when a TF-TENG was worn on the wrist. [ABSTRACT FROM AUTHOR]

There are numerous works that report wirelessly controlling the locomotion of soft robots through a single actuation method of light or magnetism. However, coupling multiple driving modes to improve the mobility of robots is still in its infancy. Here, we present a soft multi-legged millirobot that can move, climb a slope, swim and detect a signal by near-infrared irradiation (NIR) light or magnetic field dual actuation. Due to the design of the feet structure, our soft millirobot incorporates the advantages of a single actuation mode of light or magnetism. Furthermore, it can execute a compulsory exercise to sense a signal and analyze the ambience fluctuation in a narrow place. This work provides a novel alternative for soft robots to achieve multimode actuation and signal sensing. [ABSTRACT FROM AUTHOR]

Although two-dimensional (2D) layered molybdenum disulfide (MoS2) has widespread electrical applications in catalysis, energy storage, and photodetection, there are few reports available regarding sputtered MoS2 for piezoresistive sensors. In this research, we found that the resistance of magnetron sputtered MoS2 on a flexible substrate changed significantly and regularly when pressure was applied. Scanning electron microscope (SEM) and atomic force microscope (AFM) images revealed an MoS2 micro-grain-like structure comprising nano-scale particles with grooves between the particles. Chemical characterization data confirmed the successful growth of amorphous MoS2 on a polydimethylsiloxane (PDMS) substrate. A micro-thickness film flexible sensor was designed and fabricated. In particular, the sensor with a 1.5 μm thick polydimethylsiloxane (PDMS) substrate exhibited the best resistance performance, displaying a maximum ΔR/R of 70.39 with a piezoresistive coefficient as high as 866.89 MPa−1 while the pressure was 0.46 MPa. A proposed flexible pressure sensor based on an MoS2 film was also successfully used as a wearable pressure sensor to measure plantar pressure and demonstrated good repeatability. The results showed that the thin film pressure sensor had good piezoresistive performance and high sensitivity. [ABSTRACT FROM AUTHOR]

Chemical and biological sensors have attracted great interest due to their importance in applications of healthcare, food quality monitoring, environmental monitoring, etc. Carbon nanotube (CNT)-based field-effect transistors (FETs) are novel sensing device configurations and are very promising for their potential to drive many technological advancements in this field due to the extraordinary electrical properties of CNTs. This review focuses on the implementation of CNT-based FETs (CNTFETs) in chemical and biological sensors. It begins with the introduction of properties, and surface functionalization of CNTs for sensing. Then, configurations and sensing mechanisms for CNT FETs are introduced. Next, recent progresses of CNTFET-based chemical sensors, and biological sensors are summarized. Finally, we end the review with an overview about the current application status and the remaining challenges for the CNTFET-based chemical and biological sensors. [ABSTRACT FROM AUTHOR]

Degradable Electronics: Wafer-Scale High-Yield Manufacturing of Degradable Electronics for Environmental Monitoring (Adv. Funct. In article number 1905518, Youfan Hu and co-workers develop a wafer-scale high-yield manufacturing process for degradable electronics with a degradable system for real-time environmental monitoring. High device yields, high-uniformity, and great performance are achieved simultaneously, which provide new opportunities for degradable electronics for next-generation ecofriendly sensing platforms for the coming Internet of Things era. [Extracted from the article]

Degradable electronics that dissolve or disintegrate in the environment after completing target functions are highly desirable due to great capabilities to eliminate the disposal, retrieval, and recycling of electronic waste worldwide. Constructing electronic systems on water‐soluble substrates via transfer printing technology has emerged as a promising approach toward this goal. However, the current approach suffers from low yields and thus hinders the complexity and scale of the obtained system in practical applications. Here, a wafer‐scale manufacturing process is proposed for degradable systems with high yields. As a demonstration, chips based on carbon nanotube thin films are 100% successfully transferred to water‐soluble substrates with an average device yield of 96.6%. Great uniformity is also obtained in the transferred thin‐film transistors (TFTs) and integrated circuits with a minimum standard deviation of 55 and 60 mV in the threshold voltage of TFTs and switching threshold voltage of inverters, respectively. System‐level demonstration of real‐time environmental monitoring is implemented in a simulated ecosystem together with a degradation demonstration under artificial rain. With its combined great performance, processing robustness, and high yields, this technology provides new opportunities for batch manufacturing of degradable electronics and next‐generation ecofriendly sensing platforms for the coming Internet of Things era. [ABSTRACT FROM AUTHOR]

By introducing stretchability and/or deformability to planar electronics, devices can conformably attach to 3D curved surfaces with minimal invasiveness, which is of great interest for next‐generation wearables in clinical and biological applications. Here, a feasible route is demonstrated to generate deformable 3D structures as a robust platform to construct electronic systems by utilizing silver nanowires/parylene hybrid films in a way analogous to the art of kirigami. The hybrid films exhibit outstanding electrical conductivity along with decent optical transparency, flexibility, and long‐term stability. These merits enable these films to work as electrodes for electrocardiogram recording with comparable accuracy to a commercial counterpart, and to fabricate a 7‐GHz monopole antenna with good omni‐directionality and a peak gain of 1.35 dBi. More importantly, a general scheme for constructing 3D deformable electronic systems is presented, including unique patterning procedures and rational cut designs inspired by kirigami. As an example, deformable transparent humidity sensors are fabricated to work on elbows and finger joints for sweating monitoring. The strategy demonstrated here for 3D deformable system construction is versatile and holds great promise for future advanced health monitoring at diverse and complex epidermal surfaces. 3D deformable electronic systems are constructed by utilizing silver nanowires/parylene hybrid films in a way similar to the art of kirigami. This combines unique patterning procedures and rational cut designs, providing a general platform for physiological signal monitoring on curved biological surface. A deformable transparent humidity sensor for sweating monitoring on the elbow and finger joint is demonstrated. [ABSTRACT FROM AUTHOR]

In article number 1801070, Youfan Hu and co‐workers construct 3D deformable electronic systems for physiological monitoring on curved surfaces by utilizing silver nanowires/parylene hybrid films in a way inspired by kirigami. Unique patterning procedures and rational cut designs are combined to transform planar electronic systems into a tunable 3D form. As an example, a deformable transparent humidity sensor for sweat monitoring was demonstrated on an elbow and finger joint. [ABSTRACT FROM AUTHOR]

Review: [86 refs. [ABSTRACT FROM AUTHOR]