Tribotronic Logic Circuits and Basic Operations

A Degradable Tribotronic Transistor for Self-Destructing Intelligent Package e-Labels

Recently, discarded electronic products have caused serious environmental pollution and information security issues, which have attracted widespread attention. Here, a degradable tribotronic transistor (DTT) for self-destructing intelligent package e-labels has been developed, integrated by a triboelectric nanogenerator and a protonic field-effect transistor with sodium alginate as a dielectric layer. The triboelectric potential generated by external contact electrification is used as the gate voltage of the organic field-effect transistor, which regulates carrier transport through proton migration/accumulation. The DTT has successfully demonstrated its output characteristics with a high sensitivity of 0.336 mm-1 and a resolution of over 100 μm. Moreover, the DTT can be dissolved in water within 3 min and completely degraded in soil within 12 days, demonstrating its excellent degradation characteristics, which may contribute to environmental protection. Finally, an intelligent package e-label based on the modulation of the DTT is demonstrated, which can display information about the package by a human touch. The e-label will automatically fail due to the degradation of the DTT over time, achieving the purpose of information confidentiality. This work has not only presented a degradable tribotronic transistor for package e-labels but also exhibited bright prospects in military security, information hiding, logistics privacy, and personal affairs.

TMDC ternary alloy-based triboelectric nanogenerators with giant photo-induced enhancement

Multifunctional self-powered energy harvesting devices have attracted significant attention for wearable, portable, IoT and healthcare devices. In this study, we report transition metal dichalcogenide (TMDC) ternary alloy (Mo0.5W0.5S2)-based self-powered photosensitive vertical triboelectric nanogenerator (TENG) devices, where the ternary alloy functions both as a triboelectric layer and as a photoabsorbing material. The scalable synthesis of the highly crystalline Mo0.5W0.5S2 ternary alloy can overcome the limitations of binary TMDCs (MoS2, WS2) by utilizing its superior optical characteristics, enabling this semiconductor-based TENG device to simultaneously exhibit photoelectric and triboelectric properties. Benefiting from visible light absorption, this vertical TENG device generates higher triboelectric outputs and exhibits excellent power harvesting properties under visible light illumination. The open circuit voltage and short circuit currents of the devices under illumination (410 nm, 525 μW cm-2) are enhanced by 62% and 253%, respectively, while in the darkness, a very high photoresponsivity of ∼45.5 V mW-1 (voltage mode) is exhibited, indicating the superior energy harvesting potential under ultralow illumination. Furthermore, the energy harvesting ability from regular human activities and the operation as artificial e-skin expands the multi-functionality of this TENG device, paving a pathway for simultaneous mechanical and photonic energy harvesting with self-powered sensing.

Self-Powered Sensing in Wearable Electronics─A Paradigm Shift Technology

With the advancements in materials science and micro/nanoengineering, the field of wearable electronics has experienced a rapid growth and significantly impacted and transformed various aspects of daily human life. These devices enable individuals to conveniently access health assessments without visiting hospitals and provide continuous, detailed monitoring to create comprehensive health data sets for physicians to analyze and diagnose. Nonetheless, several challenges continue to hinder the practical application of wearable electronics, such as skin compliance, biocompatibility, stability, and power supply. In this review, we address the power supply issue and examine recent innovative self-powered technologies for wearable electronics. Specifically, we explore self-powered sensors and self-powered systems, the two primary strategies employed in this field. The former emphasizes the integration of nanogenerator devices as sensing units, thereby reducing overall system power consumption, while the latter focuses on utilizing nanogenerator devices as power sources to drive the entire sensing system. Finally, we present the future challenges and perspectives for self-powered wearable electronics.

Highly Stretchable Graphene Scrolls Transistors for Self-Powered Tribotronic Non-Mechanosensation Application

Owing to highly desired requirements in advanced disease diagnosis, therapy, and health monitoring, noncontact mechanosensation active matrix has drawn considerable attention. To satisfy the practical demands of high energy efficiency, in this report, combining the advantage of multiparameter monitoring, high sensitivity, and high resolution of active matrix field-effect transistor (FET) with triboelectric nanogenerators (TENG), we successfully developed the tribotronic mechanosensation active matrix based on tribotronic ion gel graphene scrolls field-effect transistors (GSFET). The tribopotential produced by TENG served as a gate voltage to modulate carrier transport along the semiconductor channel and realized self-powered ability with considerable decreased energy consumption. To achieve high spatial utilization and more pronounced responsivity of the dielectric of this transistor, ion gel was used to act as a triboelectric layer to conduct friction and contact electrification with external materials directly to produce triboelectric charges to power GFET. This tribopotential-driving device has excellent tactile sensing properties with high sensitivity (1.125 mm^-1), rapid response time (~16 ms), and a durability operation of thousands of cycles. Furthermore, the device was transparent and flexible with the capability of spatially mapping touch stimuli and monitoring real-time temperature. Due to all these unique characteristics, this novel noncontact mechanosensation GSFET active matrix provided a new method for self-powered E-skin with promising potential for self-powered wearable devices and intelligent robots.

A Flexible Tribotronic Artificial Synapse with Bioinspired Neurosensory Behavior

As key components of artificial afferent nervous systems, synaptic devices can mimic the physiological synaptic behaviors, which have attracted extensive attentions. Here, a flexible tribotronic artificial synapse (TAS) with bioinspired neurosensory behavior is developed. The triboelectric potential generated by the external contact electrification is used as the ion-gel-gate voltage of the organic thin film transistor, which can tune the carriers transport through the migration/accumulation of ions. The TAS successfully demonstrates a series of synaptic behaviors by external stimuli, such as excitatory postsynaptic current, paired-pulse facilitation, and the hierarchical memory process from sensory memory to short-term memory and long-term memory. Moreover, the synaptic behaviors remained stable under the strain condition with a bending radius of 20 mm, and the TAS still exhibits excellent durability after 1000 bending cycles. Finally, Pavlovian conditioning has been successfully mimicked by applying force and vibration as food and bell, respectively. This work demonstrates a bioinspired flexible artificial synapse that will help to facilitate the development of artificial afferent nervous systems, which is great significance to the practical application of artificial limbs, robotics, and bionics in future.

Triboelectric Potential Powered High-Performance Organic Transistor Array

Triboelectric potential gated transistors have inspired various applications toward mechanical behavior controlled logic circuits, multifunctional sensors, artificial sensory neurons, etc. Their rapid development urgently calls for high-performance devices and corresponding figure of merits to standardize the tribotronic gating properties. Organic semiconductors paired with solution processability promise low-cost manufacture of high-performance tribotronic transistor devices/arrays. Here, we demonstrate a record high-performance tribotronic transistor array composed of an integrated triboelectric nanogenerator (TENG) and a large-area device array of C8-BTBT-PS transistors. The working mechanism of effective triboelectric potential gating is elaborately explained from the aspect of conjugated energy bands of the contact-electrification mediums and organic semiconductors. Driven by the triboelectric potential, the tribotronic transistor shows superior properties of record high current on/off ratios (>10⁸), a steep subthreshold swing (29.89 μm/dec), high stability, and excellent reproducibility. Moreover, tribotronic logic devices modulated by mechanical displacement have also been demonstrated with good stability and a high gain of 1260 V/mm. The demonstrated large-area tribotronic transistor array of organic semiconductor exhibits record high performance and offers an effective R&D platform for mechano-driven electronic terminals, interactive intelligent system, artificial robotic skin, etc.

Tactile tribotronic reconfigurable p-n junctions for artificial synapses

The emulation of biological synapses with learning and memory functions and versatile plasticity is significantly promising for neuromorphic computing systems. Here, a robust and continuously adjustable mechanoplastic semifloating-gate transistor is demonstrated based on an integrated graphene/hexagonal boron nitride/tungsten diselenide van der Waals heterostructure and a triboelectric nanogenerator (TENG). The working states (p-n junction or n⁺-n junction) can be manipulated and switched under the sophisticated modulation of triboelectric potential derived from mechanical actions, which is attributed to carriers trapping and detrapping in the graphene layer. Furthermore, a reconfigurable artificial synapse is constructed based on such mechanoplastic transistor that can simulate typical synaptic plasticity and implement dynamic control correlations in each response mode by further designing the amplitude and duration. The artificial synapse can work with ultra-low energy consumption at 74.2 fJ per synaptic event and the extended synaptic weights. Under the synergetic effect of the semifloating gate, the synaptic device can enable successive mechanical facilitation/depression, short-/long-term plasticity and learning-experience behavior, exhibiting the mechanical behavior derived synaptic plasticity. Such reconfigurable and mechanoplastic features provide an insight into the applications of energy-efficient and real-time interactive neuromodulation in the future artificial intelligent system beyond von Neumann architecture.

Self-powered bifunctional sensor based on tribotronic planar graphene transistors

With the development of material science, micro-nano-fabrication and microelectronics, the higher level requirements are posed on the electronic skins (E-skin). The lower energy consumption and multiple functions are the imperative requirements to spurred scientists and mechanists to make joint efforts to meet. To achieve lower energy consumption, a promising energy-harvesting style of triboelectric nanogenerators (TENG) is incorporated into the field effect transistors (FETs) to play the important role for sensor. For bifunctional sensor, to harness the difficult for reflecting the magnitude of frequency, we resorted to synaptic transistors to achieve more intelligentization. Furthermore, with regards to the configuration of FET, we continued previous work: using the electrolyte gate dielectrics of FET-ion gel as the electrification layer to achieve high efficient, compact and extensively adoption for mechanosensation. The working principle of the GFET was based on the coupling effects of the FET and the TENG. This newly emerged self-powered sensor would offer a new platform for lower power consumption sensor for human-machine interface and intelligent robot.

Fiber-Shaped Triboiontronic Electrochemical Transistor

Contact electrification-activated triboelectric potential offers an efficient route to tuning the transport properties in semiconductor devices through electrolyte dielectrics, i.e., triboiontronics. Organic electrochemical transistors (OECTs) make more effective use of ion injection in the electrolyte dielectrics by changing the doping state of the semiconductor channel. However, the mainstream flexible/wearable electronics and OECT-based devices are usually modulated by electrical signals and constructed in conventional geometry, which lack direct and efficient interaction between the external environment and functional electronic devices. Here, we demonstrate a fiber-shaped triboiontronic electrochemical transistor with good electrical performances, including a current on/off ratio as high as ≈1286 with off-current at ~nA level, the average threshold displacements (D_th) of 0.3 mm, the subthreshold swing corresponding to displacement (SS_D) at 1.6 mm/dec, and excellent flexibility and durability. The proposed triboiontronic electrochemical transistor has great potential to be used in flexible, functional, and smart self-powered electronic textile.

Triboelectric micromotors actuated by ultralow frequency mechanical stimuli

A high-speed micromotor is usually actuated by a power source with high voltage and frequency. Here we report a triboelectric micromotor by coupling a micromotor and a triboelectric nanogenerator, in which the micromotor can be actuated by ultralow-frequency mechanical stimuli. The performances of the triboelectric micromotor are exhibited at various structural parameters of the micromotor, as well as at different mechanical stimuli of the triboelectric nanogenerator. With a sliding range of 50 mm at 0.1 Hz, the micromotor can start to rotate and reach over 1000 r min⁻¹ at 0.8 Hz. The maximum operation efficiency of the triboelectric micromotor can reach 41%. Additionally, the micromotor is demonstrated in two scanning systems for information recognition. This work has realized a high-speed micromotor actuated by ultralow frequency mechanical stimuli without an external power supply, which has extended the application of triboelectric nanogenerator in micro/nano electromechanical systems, intelligent robots and autonomous driving.

High-speed electrostatic micromotors with low energy consumption are attractive for small-scale electromechanical systems, but applications are limited by power supplies. Here the authors use a triboelectric nanogenerator for actuation of a high-speed micromotor by low-frequency mechanical stimuli.

Controlling Surface Charge Generated by Contact Electrification: Strategies and Applications

Contact electrification is the phenomenon in which charge is generated on the surfaces of materials after they come into contact. The surface charge generated has traditionally been known to cause a vast range of undesirable consequences in our lives and in industry; on the other hand, it can also give rise to many types of useful applications. In addition, there has been a lot of interest in recent years for fabricating devices and materials based on regulating a desired amount of surface charge. It is thus important to understand the general strategies for increasing, decreasing, or controlling the surface charge generated by contact electrification. Herein, the fundamental mechanisms for influencing the amount of charge generated, the methods used for implementing these mechanisms, and some of the recent interesting applications that require regulating the amount of surface charge generated by contact electrification, are briefly summarized.

Triboelectric Series of 2D Layered Materials

Recently, as applications based on triboelectricity have expanded, understanding the triboelectric charging behavior of various materials has become essential. This study investigates the triboelectric charging behaviors of various 2D layered materials, including MoS₂ , MoSe₂ , WS₂ , WSe₂ , graphene, and graphene oxide in a triboelectric series using the concept of a triboelectric nanogenerator, and confirms the position of 2D materials in the triboelectric series. It is also demonstrated that the results are obviously related to the effective work functions. The charging polarity indicates the similar behavior regardless of the synthetic method and film thickness ranging from a few hundred nanometers (for chemically exfoliated and restacked films) to a few nanometers (for chemical vapor deposited films). Further, the triboelectric charging characteristics could be successfully modified via chemical doping. This study provides new insights to utilize 2D materials in triboelectric devices, allowing thin and flexible device fabrication.

Pyro-phototronic nanogenerator based on flexible 2D ZnO/graphene heterojunction and its application in self-powered near infrared photodetector and active analog frequency modulation

Even though 2D ZnO has been utilized for enhanced self-powered sensing by strain modulation due to its piezoelectric property, study on utilizing the pyroelectric property of ZnO remains unexplored. The piezoelectric property of 2D ZnO works on mechanical strain, which disrupts the structure of ZnO leading to the failure of the device. For a pyroelectric nanogenerator, the temperature difference can be triggered by an external light source, which does not disrupt the ZnO structure and also avoids the need for physical bending/pressing, as in the case of a piezoelectric nanogenerator. This work represents the first demonstration of the fabrication of a flexible 2D ZnO/Gr pyro-phototronic diode where the pyro-potential generated in the 2D ZnO due to the near infrared (NIR) illumination adds to or subtracts from the built-in electric field of the heterojunction and modulates the depletion region of the heterojunction thereby enabling bias-free operation. Furthermore, the variation in the depletion width of the heterojunction was utilized as a variable capacitor in the frequency modulator, wherein, with the increasing intensity, the frequency of oscillations increased from 9.8 to 10.42 MHz. The work presented provides an alternative approach for a self-powered NIR photodetector and the utilization of the same at circuit level, having potential applications in the fields of optothermal detection, electronic tuning circuits, etc.

Self-Powered Electrostatic Adsorption Face Mask Based on a Triboelectric Nanogenerator

The physical filtration mechanism of a traditional face mask has a low removal efficiency of ultrafine particulates in the size range of 10-1000 nm, which are badly harmful to human health. Herein, a novel self-powered electrostatic adsorption face mask (SEA-FM) based on the poly(vinylidene fluoride) electrospun nanofiber film (PVDF-ESNF) and a triboelectric nanogenerator (TENG) driven by respiration (R-TENG) is developed. The ultrafine particulates are electrostatically adsorbed by the PVDF-ESNF, and the R-TENG can continually provide electrostatic charges in this adsorption process by respiration. On the basis of the R-TENG, the SEA-FM shows that the removal efficiency of coarse and fine particulates is higher than 99.2 wt % and the removal efficiency of ultrafine particulates is still as high as 86.9 wt % after continually wearing for 240 min and a 30-day interval. This work has proposed as a new method of wearable air filtration and may have great prospects in human health, self-powered electronics, and wearable devices.

An alginate film-based degradable triboelectric nanogenerator

Alginate, as a natural linear polysaccharide derived from brown sea algae, has the advantage of low toxicity, good biocompatibility, and biodegradability, which has aroused wide interests in recent years. In this study, a degradable triboelectric generator based on an alginate film is presented. The calcium alginate film, which is prepared by a simple freeze-drying method and a crosslinking reaction, has a form of porous structures that are beneficial for triboelectric power generation. The fabricated TENG has a stable output performance with a maximum voltage, current, and power of 33 V, 150 nA, and 9.5 μW, respectively. The performances of the TENG were investigated at different thicknesses of the calcium alginate film and various concentrations of the sodium alginate solution, as well as the degradability of the film with different thicknesses and temperatures. In addition, the TENG was designed for harvesting water wave energy in a low-frequency range from 1 to 4 Hz. This study is promising to provide new insights to develop degradable and eco-friendly TENG based on ocean plants and expand the application range in blue energy.

A degradable triboelectric generator based on an alginate film has been proposed, which can be used to harvest water wave energy.

Bioinspired Tribotronic Resistive Switching Memory for Self-Powered Memorizing Mechanical Stimuli

Haptic memory, from the interaction of skin and brain, can not only perceive external stimuli but also memorize it after removing the external stimuli. For the mimicry of human sensory memory, a self-powered artificial tactile memorizing system was developed by coupling bionic electronic skin and nonvolatile resistive random access memory (RRAM). The tribotronic nanogenerator is utilized as electronic skin to transform the touching signal into electric pulse, which will be programmed into the artificial brain: RRAM. Because of the advanced structural designs and accurate parameter matching, including the output voltages and the resistances in different resistive states, the artificial brain can be operated in self-powered mode to memorize the touch stimuli with the responsivity up to 20 times. For demonstrating the application potential of this system, it was fabricated as an independently addressed matrix to realize the memorizing of motion trace in two-dimensional space. The newly designed self-powered nonvolatile system has broad applications in next-generation high-performance sensors, artificial intelligence, and bionics.

Flexible Organic Tribotronic Transistor for Pressure and Magnetic Sensing

Flexible electronics has attracted enormous interest in wearable electronics and human-machine interfacing. Here, a flexible organic tribotronic transistor (FOTT) without a top gate electrode has been demonstrated. The FOTT is fabricated on a flexible polyethylene terephthalate film using the p-type pentacene and poly(methyl methacrylate)/Cytop composites as the conductive channel and dielectric layer, respectively. The charge carriers can be modulated by the contact electrification between the dielectric layer and a mobile triboelectric layer. Based on the fabricated FOTT, pressure and magnetic sensors have been developed, respectively, that exhibit great sensitivity, fast response time, and excellent stability. The FOTT in this simple structure shows bright potentials of tribotronics in human-machine interaction, electronic skins, wearable electronics, intelligent sensing, and so on.

Tribotronic Tuning Diode for Active Analog Signal Modulation

Realizing active interaction with external environment/stimuli is a great challenge for current electronics. In this paper, a tribotronic tuning diode (TTD) is proposed by coupling a variable capacitance diode and a triboelectric nanogenerator in free-standing sliding mode. When the friction layer is sliding on the device surface for electrification, a reverse bias voltage is created and applied to the diode for tuning the junction capacitance. When the sliding distance increases from 0 to 25 mm, the capacitance of the TTD decreases from about 39 to 8 pF. The proposed TTD has been integrated into analog circuits and exhibited excellent performances in frequency modulation, phase shift, and filtering by sliding a finger. This work has demonstrated tunable diode and active analog signal modulation by tribotronics, which has great potential to replace ordinary variable capacitance diodes in various practical applications such as signal processing, electronic tuning circuits, precise tuning circuits, active sensor networks, electronic communications, remote controls, flexible electronics, etc.

Graphene Tribotronics for Electronic Skin and Touch Screen Applications

Graphene tribotronics is introduced for touch-sensing applications such as electronic skins and touch screens. The devices are based on a coplanar coupling of triboelectrification and current transport in graphene transistors. The touch sensors are ultrasensitive, fast, and stable. Furthermore, they are transparent and flexible, and can spatially map touch stimuli such as movement of a ball, multi-touch, etc.

Tribotronic Transistor Array as an Active Tactile Sensing System

Large-scale tactile sensor arrays are of great importance in flexible electronics, human-robot interaction, and medical monitoring. In this paper, a flexible 10 × 10 tribotronic transistor array (TTA) is developed as an active tactile sensing system by incorporating field-effect transistor units and triboelectric nanogenerators into a polyimide substrate. The drain-source current of each tribotronic transistor can be individually modulated by the corresponding external contact, which has induced a local electrostatic potential to act as the conventional gate voltage. By scaling down the pixel size from 5 × 5 to 0.5 × 0.5 mm², the sensitivities of single pixels are systematically investigated. The pixels of the TTA show excellent durability, independence, and synchronicity, which are suitable for applications in real-time tactile sensing, motion monitoring, and spatial mapping. The integrated tribotronics provides an unconventional route to realize an active tactile sensing system, with prospective applications in wearable electronics, human-machine interfaces, fingerprint identification, and so on.

Tribotronic Enhanced Photoresponsivity of a MoS2 Phototransistor

Molybdenum disulfide (MoS₂) has attracted a great attention as an excellent 2D material for future optoelectronic devices. Here, a novel MoS₂ tribotronic phototransistor is developed by a conjunction of a MoS₂ phototransistor and a triboelectric nanogenerator (TENG) in sliding mode. When an external friction layer produces a relative sliding on the device, the induced positive charges on the back gate of the MoS₂ phototransistor act as a "gate" to increase the channel conductivity as the traditional back gate voltage does. With the sliding distance increases, the photoresponsivity of the device is drastically enhanced from 221.0 to 727.8 A W^-1 at the 100 mW cm^-2 UV excitation intensity and 1 V bias voltage. This work has extended the emerging tribotronics to the field of photodetection based on 2D material, and demonstrated a new way to realize the adjustable photoelectric devices with high photoresponsivity via human interfacing.

Theoretical Study of Triboelectric-Potential Gated/Driven Metal-Oxide-Semiconductor Field-Effect Transistor

Triboelectric nanogenerator has drawn considerable attentions as a potential candidate for harvesting mechanical energies in our daily life. By utilizing the triboelectric potential generated through the coupling of contact electrification and electrostatic induction, the "tribotronics" has been introduced to tune/control the charge carrier transport behavior of silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET). Here, we perform a theoretical study of the performances of tribotronic MOSFET gated by triboelectric potential in two working modes through finite element analysis. The drain-source current dependence on contact-electrification generated triboelectric charges, gap separation distance, and externally applied bias are investigated. The in-depth physical mechanism of the tribotronic MOSFET operations is thoroughly illustrated by calculating and analyzing the charge transfer process, voltage relationship to gap separation distance, and electric potential distribution. Moreover, a tribotronic MOSFET working concept is proposed, simulated and studied for performing self-powered FET and logic operations. This work provides a deep understanding of working mechanisms and design guidance of tribotronic MOSFET for potential applications in micro/nanoelectromechanical systems (MEMS/NEMS), human-machine interface, flexible electronics, and self-powered active sensors.

Flexible Organic Tribotronic Transistor Memory for a Visible and Wearable Touch Monitoring System

A new type of flexible organic tribotronic transistor memory is proposed, which can be written and erased by externally applied touch actions as an active memory. By further coupling with an organic light-emitting diode (OLED), a visible and wearable touch monitoring system is achieved, in which touch triggering can be memorized and shown as the emission from the OLED.