Multifunctional Electronics Research Articles

A biodegradable cellulose-based flame-retardant triboelectric nanogenerator for fire warning

Triboelectric nanogenerator (TENG) is a type of disruptive high-entropy energy technology for the era of internet of things that drives the ubiquitous innovations of flexible/wearable electronics and sensor networks. However, developing a flexible TENG with a high sensitivity temperature response and fire warning capabilities is challenging. Here, we demonstrate a flexible, biodegradable, single electrode cellulose-based TENG with flame retardancy (FR-TENG) that is fabricated by biocompatible black phosphorus (BP) and phytic acid (PA) as flame retardants. The corresponding peak heat release rate and the total heat release rate values of FR-TENG are reduced by 64.6% and 47.6% compared with pure nanocellulose film, respectively, and the limiting oxygen index is increased to 39.1%. The FR-TENG exhibits an output of 116 V and 3.02 mA·m−2 at 2 Hz, indicating the application prospect of source for wearable electronics. An exciting feature of the FR-TENG is its resistance response to temperature with a high thermal index of 3779.16 K in the range of 35–150 ℃, which can be used as a temperature sensor to achieve quickly respond to temperature changes and fire warnings within 5 s. Therefore, the cellulose-based FR-TENG provides an idea to develop advanced multifunctional wearable electronics with potential applicability as sensors and fire alarms for firefighting and industrial applications.

Multi-functional multi-gate one-transistor process-in-memory electronics with foundry processing and footprint reduction

Logic gates are fundamental components of integrated circuits, and integration strategies involving multiple logic gates and advanced materials have been developed to meet the development requirements of high-density integrated circuits. However, these strategies are still far from being widely applicable owing to their incompatibility with the modern silicon-based foundry lines. Here, we propose a silicon-foundry-line-based multi-gate one-transistor design to simplify the conventional multi-transistor logic gates into one-transistor gates, thus reducing the circuit footprint by at least 40%. More importantly, the proposed configuration could simultaneously provide the multi-functionalities of logic gates, memory, and artificial synapses. In particular, our design could mimic the artificial synapses in three dimensions while simultaneously being implemented by standard silicon-on-insulator process technology. The foundry-line-compatible one-transistor design has great potential for immediate and widespread applications in next-generation multifunctional electronics.

Strain-Driven Auto-Detachable Patterning of Flexible Electrodes.

Flexible electrodes that are multilayer, multimaterial, and conformal are pivotal for multifunctional wearable electronics. Traditional electronic circuits manufacturing requires substrate-supported transfer printing, which limits their multilayer integrity and device conformability on arbitrary surfaces. Herein, a "shrinkage-assisted patterning by evaporation" (SHAPE) method is reported, by employing evaporation-induced interfacial strain mismatch, to fabricate auto-detachable, freestanding, and patternable electrodes. The SHAPE method utilizes vacuum-filtration of polyaniline/bacterial cellulose (PANI/BC) ink through a masked filtration membrane to print high-resolution, patterned, and multilayer electrodes. The strong interlayer hydrogen bonding ensures robust multilayer integrity, while the controllable evaporative shrinking property of PANI/BC induces mismatch between the strains of the electrode and filtration membrane at the interface and thus autodetachment of electrodes. Notably, a 500-layer substrateless micro-supercapacitor fabricated using the SHAPE method exhibits an energy density of 350 mWh cm-2 at a power density of 40mW cm-2 , 100 times higher than reported substrate-confined counterparts. Moreover, a digital circuit fabricated using the SHAPE method functions stably on a deformed glove, highlighting the broad wearable applications of the SHAPE method.

Multi-functional platform based on amorphous Ge2Sb2Te5 thin films for photo/thermodetection and non-volatile memory applications

As a result of the copious interest and development in multifunctional electronics, the need for a multifunctional platform with a stable and unique performance has become one of the most important research concerns. In this embodiment, the amorphous Ge2Sb2Te5 (a-GST) thermally evaporated phase-change thin films are utilized for photo/thermodetection applications. The structural, compositional, and topographical methodologies confirm the amorphous nature with smooth surface topology and average particle size of about 31 ± 10 nm. Furthermore, the optical properties of the deposited a-GST revealed the broadband absorption spectrum with indirect energy gap and Urbach energy of about 0.54 eV and 380 meV, respectively. Furthermore, the dispersion and electronic parameters of the deposited films are determined. The switchable resistivity properties of Au/a-GST/Au are evaluated, and the phase change transition is observed in the temperature range (413–463) K. Moreover, the microelectronic parameters and interface features, in addition to the charge carriers' dynamics in the fabricated Ag/a-GTS/n-Si/Au–Sb heterojunction, are interpreted and analyzed in detail. Besides, the thermodetection capability of the fabricated heterojunction is evaluated in the temperature range (303–573) K. The estimated values of the thermosensitivity of about – (28.02 ± 1) and – (3.60 ± 0.13) mV/K at driving activation current of 600 μA for the two phases regions, respectively. Additionally, the photodetection performance of the implemented architecture is tested under halogen illumination of intensity (20–100) mW/cm2. The fabricated device shows a remarkably stable light signal response with responsivity, specific detectivity, and trise/tfall of about 203.1 mA/W, 2.84 × 109Jones, and 267 ms/84 ms, respectively. Ultimately, based on the recorded results, the Au/a-GST/n-Si/Au–Sb heterojunction is suggested for multifunctional applications with promising performance.

Breathable and Skin‐Conformal Electronics with Hybrid Integration of Microfabricated Multifunctional Sensors and Kirigami‐Structured Nanofibrous Substrates

AbstractSkin‐integrated soft electronics have attracted extensive research attention due to their potential utility for fitness monitoring, disease management, human–machine interfaces, and other applications. Although many materials and device components are explored for the construction of skin‐integrated systems, achieving multifunctional sensor platform combined with good breathability and conformability on the skin remains difficult. This challenge is partly due to the processing incompatibility between planar‐fabricated microelectronics and biocompatible porous substrates. Here, a fabrication strategy that can overcome this limitation, leading to large‐area multifunctional skin electronics with breathability and conformability required for wearable applications, is reported. In this scheme, a hybrid integration of high‐performance microfabricated sensors and nanofibrous soft substrates is made possible with stamp‐based transferring techniques combined with electrospinning. The resulting membrane devices exhibit tissue‐like mechanical properties with high permeability for vapor transport. In addition, kirigami structures can be introduced into these membranes, providing high stretchability and 3D conformability for large‐area integration on the skin. The multifunctional sensors array allow for spatiotemporal measurement of bioelectrical signals, temperature, skin hydration, and potentially many other physiological parameters. The robust performance and manufacturing scalability provided by these multifunctional skin electronics may create further opportunities for the development of advanced wearable systems.

Ultrafast-response and broad-spectrum polarization sensitive photodetector based on Bi1.85In0.15S3 nanowire

Alloying of semiconductors is a good strategy to manipulate their electronic band structures, which can broaden the photoresponse range of the corresponding optoelectronic devices. In addition, building a Schottky diode and improving the crystal quality of the channel semiconductor can improve the photoresponse speed of the optoelectronic device. Here, we report the design and preparation of Bi1.85In0.15S3 nanowires by a facile chemical vapor transport method. The individual Bi1.85In0.15S3 nanowire photodetectors realize excellent photoresponse in a broadband range from solar-blind deep ultraviolet (266 nm) to near-infrared (830 nm), and the obtained maximum external photoresponsivity of 95.99 A/W and detectivity of about 3.52×1011 Jones at 638 nm. Furthermore, the photodetectors also exhibit the ultrafast photoresponse speed with the rise time of 190 ns and the fall time of 180 ns, owing to the high crystal quality and the Schottky contacts between the Au electrodes and nanowires. In addition, the photoresponse of photodetectors is polarization angle sensitive in a broadband range from 266 to 808 nm, and the obtained maximum dichroic ratio is 3.54 at 808 nm, which results from the structural anisotropy of the Bi1.85In0.15S3 crystal. These performances are superior to the reported Bi2S3, In2S3, and other Bi or In sulfide nanowire photodetectors. The results render (BixIn1−x)2S3 photodetectors have significant application potentials in multifunctional optoelectronics and electronics.

Healable, Recyclable, and Multifunctional Soft Electronics Based on Biopolymer Hydrogel and Patterned Liquid Metal.

Recent years have witnessed the rapid development of sustainable materials. Along this line, developing biodegradable or recyclable soft electronics is challenging yet important due to their versatile applications in biomedical devices, soft robots, and wearables. Although some degradable bulk hydrogels are directly used as the soft electronics, the sensing performances are usually limited due to the absence of distributed conducting circuits. Here, sustainable hydrogel-based soft electronics (HSE) are reported that integrate sensing elements and patterned liquid metal (LM) in the gelatin-alginate hybrid hydrogel. The biopolymer hydrogel is transparent, robust, resilient, and recyclable. The HSE is multifunctional; it can sense strain, temperature, heart rate (electrocardiogram), and pH. The strain sensing is sufficiently sensitive to detect a human pulse. In addition, the device serves as a model system for iontophoretic drug delivery by using patterned LM as the soft conductor and electrode. Noncontact detection of nearby objects is also achieved based on electrostatic-field-induced voltage. The LM and biopolymer hydrogel are healable, recyclable, and degradable, favoring sustainable applications and reconstruction of the device with new functions. Such HSE with multiple functions and favorable attributes should open opportunities in next-generation electronic skins and hydrogel machines.

Self-assembled growth and magnetic properties of Fe and FeTiO3 core–Sr(Ti,Fe)O3 shell nanocomposites

In this study, a promising method for the modulation of the microstructure, composition, and magnetic properties of thin films fabricated by co-sputtering metallic Fe and oxide SrTiO3 targets is proposed. The proposed method can potentially be applied in multifunctional electronics. The flat surface morphology was observed in the thin film sputtered under a low power for the Fe target, whereas micro-height rods were fabricated on an uneven layer at a higher power. Strong magnetic anisotropy was not observed in the co-sputtered thin films because of the randomly oriented growth of the magnetic rods. Detailed microstructural and compositional studies using high-resolution transmission electron microscopy and scanning transmission electron microscopy revealed that self-assembled nanocomposites with three components were grown with a core–shell structure, in which Fe and FeTiO3 phases grew in the Sr(Ti,Fe)O3 matrix. This report provides an insight into designing multifunctional metal–metal oxide nanocomposites with single-step co-sputtering, which is capable of adjusting the composition and geometry of the nanocomposites.

Interchannel coupling induced gapless modes in multichannel zero-line systems

In bilayer graphene, the application of a perpendicular electric field breaks the inversion symmetry to open a bulk band gap to harbor the quantum valley Hall effect. When the field varies spatially, a topologically confined mode (also named the zero-line mode) arises along the zero-field line. In this work, we theoretically investigate the electronic transport properties of the multichannel zero-line systems. The finite-size effect in topological systems (e.g., quantum Hall effect, topological insulators) often induces a topologically trivial gap to realize a normal insulator. To our surprise, we find that the coupling between neighboring zero lines can give rise to striking electronic properties depending on the number of channels $m$, i.e., a trivial band gap for even $m$, whereas a nontrivial gapless mode for odd $m$. We further show that these findings apply to various ribbon orientations. A general effective model is constructed to provide a clear physical picture of the emergence of gapless modes. In the end, a gate-tunable device is proposed to function as a switch with controllable current partitions. We believe that our findings are experimentally accessible, and have potential practical applications in designing multifunctional valley-based electronics.

In-situ/operando characterization techniques for organic semiconductors and devices

Abstract The increasing demands of multifunctional organic electronics require advanced organic semiconducting materials to be developed and significant improvements to be made to device performance. Thus, it is necessary to gain an in-depth understanding of the film growth process, electronic states, and dynamic structure-property relationship under realistic operation conditions, which can be obtained by in-situ/operando characterization techniques for organic devices. Here, the up-to-date developments in the in-situ/operando optical, scanning probe microscopy, and spectroscopy techniques that are employed for studies of film morphological evolution, crystal structures, semiconductor-electrolyte interface properties, and charge carrier dynamics are described and summarized. These advanced technologies leverage the traditional static characterizations into an in-situ and interactive manipulation of organic semiconducting films and devices without sacrificing the resolution, which facilitates the exploration of the intrinsic structure-property relationship of organic materials and the optimization of organic devices for advanced applications.

Highly Stretchable and Sensitive Multimodal Tactile Sensor Based on Conductive Rubber Composites to Monitor Pressure and Temperature

Stretchable and flexible tactile sensors have been extensively investigated for a variety of applications due to their outstanding sensitivity, flexibility, and biocompatibility compared with conventional tactile sensors. However, implementing stretchable multimodal sensors with high performance is still a challenge. In this study, a stretchable multimodal tactile sensor based on conductive rubber composites was fabricated. Because of the pressure-sensitive and temperature-sensitive effects of the conductive rubber composites, the developed sensor can simultaneously measure pressure and temperature, and the sensor presented high sensitivity (0.01171 kPa−1 and 2.46–30.56%/°C) over a wide sensing range (0–110 kPa and 30–90 °C). The sensor also exhibited outstanding performance in terms of processability, stretchability, and repeatability. Furthermore, the fabricated stretchable multimodal tactile sensor did not require complex signal processing or a transmission circuit system. The strategy for stacking and layering conductive rubber composites of this work may supply a new idea for building multifunctional sensor-based electronics.

2D transistors rapidly printed from the crystalline oxide skin of molten indium

Ultrathin single-nm channels of transparent metal oxides offer unparalleled opportunities for boosting the performance of low power, multifunctional thin-film electronics. Here we report a scalable and low-temperature liquid metal printing (LMP) process for unlocking the ultrahigh mobility of 2-dimensional (2D) InOx. These continuous nanosheets are rapidly (60 cm s−1) printed over large areas (30 cm2) directly from the native oxide skin spontaneously formed on molten indium. These nanocrystalline LMP InOx films exhibit unique 2D grain morphologies leading to exceptional conductivity as deposited. Quantum confinement and low-temperature oxidative postannealing control the band structure and electronic density of states of the 2D InOx channels, yielding thin-film transistors with ultrahigh mobility (μ0 = 67 cm2 V−1s−1), excellent current saturation, and low hysteresis at temperatures down to 165 °C. This work establishes LMP 2D InOx as an ideal low-temperature transistor technology for high-performance, large area electronics such as flexible displays, active interposers, and thin-film sensors.

High-Performance Flexible Heater With Command-Responding Function Attained by Direct Laser Writing on Nomex Paper

Multifunctional flexible electronics have been a hot spot in scientific research and technology development. From the view of practical application, high-performance flexible heating devices with the capability to respond to commands are an urgent need for thermal management. Herein, we propose a strategy for multifunctional integration by assembling two pieces of laser-scribed Nomex paper, thus enabling the combination of heating and sensing modules. On account of the good electrothermal and piezoresistive properties of laser-induced graphene, the device can generate high steady-state temperature with a low voltage excitation and recognize valid commands from users finger to switch between operating states. Besides, the fast and efficient fabrication method entirely based on direct laser writing technology is another unique advantage.

Ultra-antifreeze, ultra-stretchable, transparent, and conductive hydrogel for multi-functional flexible electronics as strain sensor and triboelectric nanogenerator

Ultra-antifreeze, ultra-stretchable, transparent, and conductive hydrogel for multi-functional flexible electronics as strain sensor and triboelectric nanogenerator

Tailoring neuroplasticity in flexible perovskite QDs-based optoelectronic synaptic transistors by dual modes modulation

For the achievement of robust neuromorphic computing with simple device integration and low energy consumption, the development of artificial synaptic devices incorporating multiple excitation modes has attracted wide interests. In this regard, a multi-functional and energy-efficient CsPbBr3 quantum dots-based optoelectronic synaptic transistor is designed capable of realizing required synaptic plasticity with both photonic and electric modulation modes in one device. Important synaptic behaviors, including excitatory post-synaptic current and paired-pulse facilitation, are simulated utilizing both photonic and electric stimulations. Furthermore, the transition of short-term plasticity (STP) to long-term plasticity (LTP) can also be implemented through either the adjustment of input photonic pulses or the co-modulation of photonic and electric operations. The excellent tunability between STP and LTP of the synaptic device further leads to the STP-based “Morse-code” optical decoding scheme and LTP-based simulation of visual object recognition. More significantly, the synergistic modulation of photonic and electric operations enables the implementation of logic functions. The multi-functional optoelectronic synaptic transistors are also mechanically flexible, and no distinct synaptic performance variation is observed even when the bending radius of the devices is down to 1 mm. This work suggests a new path for developing flexible and multifunctional neuromorphic electronics.

Band-like Transport of Charge Carriers in Oriented Two-Dimensional Conjugated Covalent Organic Frameworks

A tunable topology and a porous network make π-conjugated covalent organic frameworks (COFs) a new class of organic semiconductors for optoelectronic, smart sensing, and catalytic applications. Although some of the COFs exhibit enhanced electric conductivity with a high charge carrier mobility, the nature and pathways of charge transport still remain elusive. In order to unveil the transport mechanism, herein, we have developed crystalline π-conjugated COFs using planar building blocks, and a wafer-scale self-supporting thin film was grown, which could be transferred onto any of the desired substrates. The COF film was found to be highly oriented and exhibited a high in-plane electronic conductivity. The conductivity was almost independent of temperature with an ultra-low activation energy of 14.3 meV, approaching a band-like transport of charge carriers within the crystalline domains. The COF films also showed a high photoresponsivity in electronic conduction against a complete visible range, demonstrated as a flexible photodetector device. This work represents a thorough investigation of the mechanism and direction of charge transport in crystalline π-conjugated COF semiconductors, which suggests their feasibility as key active materials in multi-functional organic electronics.

Efficient and Stable Quantum‐Dot Light‐Emitting Diodes Enabled by Tin Oxide Multifunctional Electron Transport Layer

AbstractZinc oxide (ZnO) based nanoparticles (NPs) are the most commonly used electron transport layer (ETL) materials in quantum dot light‐emitting diodes (QLEDs). However, numerous defects, severe quenching, and poor stability of ZnO NPs limit the commercialization of QLEDs. Herein, tin oxide (SnO2) NPs are prepared as a substitute to ZnO. The obtained SnO2 NPs exhibit high conductivity, good transparency, and excellent stability, thus enabling them to be applied as multifunctional ETLs for various structured QLEDs, e.g., 1) as a phase tuning layer to tune the microcavity effect in inverted QLEDs, 2) as a thick protection layer to improve the stability of noninverted QLEDs, 3) as a sputtering buffer layer to protect the functional layers from the ion bombardment damage in transparent QLEDs, and 4) as an internal light extraction layer to enhance the light coupling efficiency of top‐emitting QLEDs. With the multifunctional SnO2 ETL, the resultant QLEDs are highly efficient (external quantum efficiency of 27.6%) and stable (half lifetime of 323 h at 4,459 cd m−2), which are comparable and even better than ZnMgO based devices. The results suggest that SnO2 is a promising ETL material for realizing efficient and stable QLEDs.

Implantable Thermal Therapeutic Device with Precise Temperature Control Enabled by Foldable Electronics and Heat-Insulating Pads.

Thermal therapy has continued to attract the attention of researchers and clinicians due to its important applications in tumor ablation, wound management, and drug release. The lack of precise temperature control capability in traditional thermal treatment may cause the decrease of therapeutic effect and thermal damage to normal tissues. Here, we report an implantable thermal therapeutic device (ITTD), which offers precise closed loop heating, in situ temperature monitoring, and thermal protection. The ITTD features a multifunctional foldable electronics device wrapped on a heat-insulating composite pad. Experimental and numerical studies reveal the fundamental aspects of the design, fabrication, and operation of the ITTD. In vivo experiments of the ITTD in thermal ablation for antitumor demonstrate that the proposed ITTD is capable of controlling the ablation temperature precisely in real time with a precision of at least 0.7°C and providing effective thermal protection to normal tissues. This proof-of-concept research creates a promising route to develop ITTD with precise temperature control capability, which is highly desired in thermal therapy and other disease diagnosis and treatments.

Two-dimensional van der Waals heterostructures (vdWHs) with band alignment transformation in multi-functional devices.

Two-dimensional van der Waals heterostructures (vdWHs) with tunable band alignment have the potential to be benignant in the development of minimal multi-functional and controllable electronics, but they have received little attention thus far. It is crucial to characterize and control the band alignment in semiconducting vdWHs, which determines the electronic and optoelectronic properties. The future success of optoelectronic devices will require improved electronic property control techniques, such as using an external electric field or strain engineering, to change the electronic structures directly. Herein, we review heterostructures fabricated as transition metal dichalcogenides (TMDCs) as one of their constituent monolayers with other notable 2D materials that can transfer from type-II to type-III (type-III > type-II) band alignment when a biaxial strain or electric field is applied.

Conductive hydrogels with 2D/2D β-NiS/Ti3C2Tx heterostructure for high-performance supercapacitor electrode materials

To obtain a flexible supercapacitor with excellent capacitance, good mechanical properties while maintaining self-healing ability, β-NiS/Ti 3 C 2 T x with 2D/2D heterostructure was synthesized by hydrothermal reaction and introduced as filler to the polymer hydrogel PAA/CS(PC) network. Through mechanical and self-healing performance tests, it was found that the hydrogel electrode had high tensile properties with tensile strain up to 566% and excellent self-healing properties with efficiency as high as 84%. The electrode not only exhibits a specific capacitance of 10.92 F/g at a current density of 6 mA/g, but also still shows an excellent stability of 87% at a high current density of 20 mA/g for 2000 cycles. This novel hydrogel facilitates the further development of multifunctional, smart and flexible electronics.