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Recent experiments with a carbon nanotube (CNT) system confirmed that the innertube can oscillate back-and-forth even under a room-temperature excitation. This demonstration of relative motion suggests that it is now feasible to build a CNT-based molecular memory cell (MC), and the key to bring the concept to reality is the precision control of the moving tube for sustained and reliable read/write (RW) operations. Here, we show that by using a 2-section outertube design, we are able to suitably recalibrate the system energetics and obtain the designed performance characteristics of a MC. Further, the resulting energy modification enables the MC to operate as a non-volatile memory element at room temperatures. Our paper explores a fundamental understanding of a MC and its response at the molecular level to roadmap a novel approach in memory technologies that can be harnessed to overcome the miniaturization limit and memory volatility in memory technologies. [ABSTRACT FROM AUTHOR]

A self-powered, sliding electrification based quasi-static triboelectric sensor (QS-TES) for detecting angle from rotating motion is reported. This innovative, cost-effective, simply-designed QS-TES has a two-dimensional planar structure, which consists of a rotator coated with four channel coded Cu foil material and a stator with a fluorinated ethylenepropylene film. On the basis of coupling effect between triboelectrification and electrostatic induction, the sensor generates electric output signals in response to mechanical rotating motion of an object mounted with the sensor. The sensor can read and remember the absolute angular position, angular velocity, and acceleration regardless being continuously monitored or segmented monitored. Under the rotation speed of 100 r min−1, the output voltage of the sensor reaches as high as 60 V. Given a relatively low threshold voltage of ±0.5 V for data processing, the robustness of the device is guaranteed. The resolution of the sensor is 22.5° and can be further improved by increasing the number of channels. Triggered by the output voltage signal, the rotating characteristics of the steering wheel can be real-time monitored and mapped by being mounted to QS-TES. This work not only demonstrates a new principle in the field of angular measurement but also greatly expands the applicability of triboelectric nanogenerator as self-powered sensors. [ABSTRACT FROM AUTHOR]

Biosensors are powerful analytical tools for biology and biomedicine, with applications ranging from drug discovery to medical diagnostics, food safety, and agricultural and environmental monitoring. Typically, biological recognition receptors, such as enzymes, antibodies, and nucleic acids, are immobilized on a surface, and used to interact with one or more specific analytes to produce a physical or chemical change, which can be captured and converted to an optical or electrical signal by a transducer. However, many existing biosensing methods rely on chemical, electrochemical and optical methods of identification and detection of specific targets, and are often: complex, expensive, time consuming, suffer from a lack of portability, or may require centralised testing by qualified personnel. Given the general dependence of most optical and electrochemical techniques on labelling molecules, this review will instead focus on mechanical and electrical detection techniques that can provide information on a broad range of species without the requirement of labelling. These techniques are often able to provide data in real time, with good temporal sensitivity. This review will cover the advances in the development of mechanical and electrical biosensors, highlighting the challenges and opportunities therein. [ABSTRACT FROM AUTHOR]

Modern electronic devices, particularly those intended for wearable or human health monitoring applications, require high levels of flexibility and stretchability. Hence devices, as well as interconnects, need to be capable of retaining functionality even when being mechanically deformed. Most approaches towards achieving this rely on printing or transferring structures onto elastomeric substrates that can withstand stretching. However, the processing involved can often be cumbersome, and the structures themselves tend to suffer from poor fatigue and/or are limited by the mechanical properties of the underlying substrate. Here, we have developed a novel aerosol jet printing technique capable of building fully freestanding functional structures layer by layer, which are robust and reliable upon thousands of stretching cycles. The process involves printing a combination of layers of different materials with the desired functionality, onto a substrate coated with a sacrificial film that is subsequently dissolved to release the printed structure. Using this method, we demonstrate freestanding conductive wires that can be used as stretchable interconnects/electrodes, and that also function as strain‐sensors. Additionally, we show that a freestanding capacitive structure functions as a robust, stretchable humidity sensor, paving the way for the development of other multilayer, multifunctional stretchable devices and sensors. [ABSTRACT FROM AUTHOR]

Triboelectric motion sensors, based on the generation of a voltage across two dissimilar materials sliding across each other as a result of the triboelectric effect, have generated interest due to the relative simplicity of the typical grated device structures and materials required. However, these sensors are often limited by poor spatial and/or temporal resolution of motion due to limitations in achieving the required device feature sizes through conventional lithography or printing techniques. Furthermore, the reliance on metallic components that are relatively straightforward to pattern into fine features limits the possibility to develop transparent sensors. Polymers would allow for transparent devices, but these materials are significantly more difficult to pattern into fine features when compared to metals. Here, an aerosol‐jet printing (AJP) technique is used to develop triboelectric sensors using a wide variety of materials, including polymers, which can be directly printed into finely featured grated structures for enhanced sensitivity to displacement and speed of motion. A detailed investigation is presented highlighting the role of material selection and feature size in determining the overall resolution of the resulting motion sensor. A three‐channel rotary sensor is also presented, demonstrating the versatility of the AJP technique in developing more complex triboelectric motion sensors. Aerosol‐jet printing is used to develop triboelectric motion sensors, based on the generation of a voltage across two dissimilar materials sliding across each other as a result of the triboelectric effect. A wide variety of materials, including polymers, can be directly printed into fine‐featured grated structures for enhanced sensitivity to displacement and speed of motion. [ABSTRACT FROM AUTHOR]

A new membrane-based triboelectric sensor (M-TES) is presented as a self-powered pressure change sensor. It generates a voltage induced by surface triboelectric charges in response to an air pressure change. Extremely high detection resolutions of 0.34 Pa and 0.16 Pa are achieved when the air pressure increases and decreases in a small region away from the ambient standard atmosphere pressure, respectively, indicating an excellent sensitivity. By integrating the M-TES with a signal processing unit, we demonstrate practical applications of the device in sensing footsteps, respirations, and heartbeat, which suggests widespread use of the M-TES in fields of security surveillance, chemical engineering, geography research, environment monitoring, and personal healthcare. [ABSTRACT FROM AUTHOR]

The applications of a single-layer triboelectric nanogenerator (TENG) may be challenged by its lower output current, and a possible solution is to use three-dimensional (3D) integrated multilayered TENGs. However, the most important point is to synchronize the outputs of all the TENGs so that the instantaneous output power can be maximized. Here, a multi-layered stacked TENG is reported as a cost-effective, simple, and robust approach for harvesting ambient vibration energy. With superior synchronization, the 3D-TENG produces a short-circuit current as high as 1.14 mA, and an open-circuit voltage up to 303 V with a remarkable peak power density of 104.6 W m−2. As a direct power source, it is capable of simultaneously lighting up 20 spot lights (0.6 W ea.) as well as a white G16 globe light. Furthermore, compared with the state-of-the-art vibration energy harvesters, the 3D-TENG has an extremely wide working bandwidth up to 36 Hz in low frequency range. In addition, with specific dimensional design, the 3D-TENG is successfully equipped inside a ball with a diameter of 3 inches, using which 32 commercial LEDs are simultaneously lighted up via hand shaking, exhibiting great potential of scavenging the abundant but wasted kinetic energy when people play basketball, football, baseball, and so on. [ABSTRACT FROM AUTHOR]

This article describes a simple, cost-effective, andscalable approachto fabricate a triboelectric nanogenerator (NG) with ultrahigh electricoutput. Triggered by commonly available ambient mechanical energysuch as human footfalls, a NG with size smaller than a human palmcan generate maximum short-circuit current of 2 mA, delivering instantaneouspower output of 1.2 W to external load. The power output correspondsto an area power density of 313 W/m2and a volume powerdensity of 54 268 W/m3at an open-circuit voltageof ∼1200 V. An energy conversion efficiency of 14.9% has beenachieved. The power was capable of instantaneously lighting up asmany as 600 multicolor commercial LED bulbs. The record high poweroutput for the NG is attributed to optimized structure, proper materialsselection and nanoscale surface modification. This work demonstratedthe practicability of using NG to harvest large-scale mechanical energy,such as footsteps, rolling wheels, wind power, and ocean waves. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) as a severe acute respiratory syndrome infection has spread rapidly across the world since its emergence in 2019 and drastically altered our way of life. Patients who have recovered from COVID-19 may still face persisting respiratory damage from the virus, necessitating long-term supervision after discharge to closely assess pulmonary function during rehabilitation. Therefore, developing portable spirometers for pulmonary function tests is of great significance for convenient home-based monitoring during recovery. Here, we propose a wireless, portable pulmonary function monitor for rehabilitation care after COVID-19. It is composed of a breath-to-electrical (BTE) sensor, a signal processing circuit, and a Bluetooth communication unit. The BTE sensor, with a compact size and light weight of 2.5 cm3 and 1.8 g respectively, is capable of converting respiratory biomechanical motions into considerable electrical signals. The output signal stability is greater than 93% under 35%–81% humidity, which allows for ideal expiration airflow sensing. Through a wireless communication circuit system, the signals can be received by a mobile terminal and processed into important physiological parameters, such as forced expiratory volume in 1 s (FEV 1) and forced vital capacity (FVC). The FEV 1 /FVC ratio is then calculated to further evaluate pulmonary function of testers. Through these measurement methods, the acquired pulmonary function parameters are shown to exhibit high accuracy (>97%) in comparison to a commercial spirometer. The practical design of the self-powered flow spirometer presents a low-cost and convenient method for pulmonary function monitoring during rehabilitation from COVID-19. • We develop a low-cost and convenient method for pulmonary function monitoring during rehabilitation from COVID-19. • It is composed of a lightweight breath-to-electrical sensor, a signal processing circuit, and a Bluetooth communication unit. • The output signal stability is greater than 93% under 35%–81% humidity, which allows for ideal expiration airflow sensing. • A wireless communication system receives signals from a mobile terminal and converts them into pulmonary parameters. • The FEV1/FVC ratio is then calculated to further evaluate pulmonary function of testers with high accuracy of >97%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Additively manufactured conformable microfluidic force sensor to measure forces during joint replacement. • Quantitative force data from sensors could aid precise implant positioning and balance. • Sensor design optimised using finite element modelling and calibrated within a 3D printed model hip implant. • High sensitivity demonstrated at typical forces experienced during hip replacements. • Powerful new surgical tool to aid implant positioning, increasing the lifetime of hip replacements. Balancing forces within weight-bearing joints such as the hip during joint replacement is essential for implant longevity. Minimising implant failure and the corresponding need for expensive and difficult revision surgery is vital to both improve the quality of life of the patient and lighten the burden on overstretched healthcare systems. However, balancing forces during total hip replacements is currently subjective and entirely dependent on surgical skill, as there are no sensors currently on the market that are capable of providing quantitative force feedback within the small and complex geometry of the hip joint. Here, we solve this unmet clinical need by presenting a thin and conformable microfluidic force sensor, which is compatible with the standard surgical procedure. The sensors are fabricated via additive manufacturing, using a combination of 3D and aerosol-jet printing. We optimised the design using finite element modelling, then incorporated and calibrated our sensors in a 3D printed model hip implant. Using a bespoke testing rig, we demonstrated high sensitivity at typical forces experienced following implantation of hip replacements. We anticipate that these sensors will aid soft tissue balancing and implant positioning, thereby increasing the longevity of hip replacements. These sensors thus represent a powerful new surgical tool for a range of orthopaedic procedures where balancing forces is crucial. [ABSTRACT FROM AUTHOR]

By combining contact-mode atomicforce microscopy (AFM) and scanningKevin probe microscopy (SKPM), we demonstrated an in situ method forquantitative characterization of the triboelectrification processat the nanoscale. We systematically characterized the triboelectriccharge distribution, multifriction effect on charge transfer, as wellas subsequent charge diffusion on the dielectric surface: (i) theSiO2surface can be either positively or negatively chargedthrough triboelectric process using Si-based AFM probes with and withoutPt coating, respectively; (ii) the triboelectric charges accumulatedfrom multifriction and eventually reached to saturated concentrationsof (−150 ± 8) μC/m2and (105 ± 6)μC/m2, respectively; (iii) the charge diffusion coefficientson SiO2surface were measured to be (1.10 ± 0.03)× 10–15m2/s for the positive chargeand (0.19 ± 0.01) × 10–15m2/s for the negative charges. These quantifications will facilitatea fundamental understanding about the triboelectric and de-electrificationprocess, which is important for designing high performance triboelectricnanogenerators. In addition, we demonstrated a technique for nanopatterningof surface charges without assistance of external electric field,which has a promising potential application for directed self-assemblyof charged nanostructures for nanoelectronic devices. [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]

Aiming at harvesting ambient mechanicalenergy for self-poweredsystems, triboelectric nanogenerators (TENGs) have been recently developedas a highly efficient, cost-effective and robust approach to generateelectricity from mechanical movements and vibrations on the basisof the coupling between triboelectrification and electrostatic induction.However, all of the previously demonstrated TENGs are based on verticalseparation of triboelectric-charged planes, which requires sophisticateddevice structures to ensure enough resilience for the charge separation,otherwise there is no output current. In this paper, we demonstrateda newly designed TENG based on an in-plane charge separation processusing the relative sliding between two contacting surfaces. UsingPolyamide 6,6 (Nylon) and polytetrafluoroethylene (PTFE) films withsurface etched nanowires, the two polymers at the opposite ends ofthe triboelectric series, the newly invented TENG produces an open-circuitvoltage up to ∼1300 V and a short-circuit current density of4.1 mA/m2with a peak power density of 5.3 W/m2, which can be used as a direct power source for instantaneouslydriving hundreds of serially connected light-emitting diodes (LEDs).The working principle and the relationships between electrical outputsand the sliding motion are fully elaborated and systematically studied,providing a new mode of TENGs with diverse applications. Comparedto the existing vertical-touching based TENGs, this planar-slidingTENG has a high efficiency, easy fabrication, and suitability formany types of mechanical triggering. Furthermore, with the relationshipbetween the electrical output and the sliding motion being calibrated,the sliding-based TENG could potentially be used as a self-powereddisplacement/speed/acceleration sensor. [ABSTRACT FROM AUTHOR]

The triboelectric effect is knownfor many centuries and it isthe cause of many charging phenomena. However, it has not been utilizedfor energy harvesting until very recently.(1-5) Here we developed a new principle of triboelectricgenerator (TEG) based on a fully contacted, sliding electrificationprocess, which lays a fundamentally new mechanism for designing universal,high-performance TEGs to harvest diverse forms of mechanical energyin our daily life. Relative displacement between two sliding surfacesof opposite triboelectric polarities generates uncompensated surfacetriboelectric charges; the corresponding polarization created a voltagedrop that results in a flow of induced electrons between electrodes.Grating of linear rows on the sliding surfaces enables substantialenhancements of total charges, output current, and current frequency.The TEG was demonstrated to be an efficient power source for simultaneouslydriving a number of small electronics. The principle established inthis work can be applied to TEGs of different configurations thataccommodate the needs of harvesting energy and/or sensing from diversemechanical motions, such as contacted sliding, lateral translation,and rotation/rolling. [ABSTRACT FROM AUTHOR]