Transient Electronics Research Articles

Gelatin Biogel–Liquid Metal Composite Transient Circuits for Recyclable Flexible Electronics

AbstractTransient electronics with degradability or dissolvability on demand possess remarkable characteristics for wearable, bioelectronic, and implanted electronic devices. While synthetic materials have made significant progress in degradability and stretchability, they suffer from intrinsic limitations, including low degradation rates, poor mechanical compliance, and high production cost, which restrict the growth of transient electronic devices. Herein, a versatile fabrication strategy is presented for transient electronics that combine a resilient biopolymer substrate (gelatin biogels) with liquid metal (Galinstan). The circuits made from gelatin biogel‐based and liquid metal are mechanically resilient and durable, exhibiting good compliance with irregular and deformable surfaces, and thus can withstand long‐term exposure to dynamic deformation (about 60 000 cycles at a strain of 50%). More importantly, gelatin biogels are naturally derived and endowed with thermally reversible gelling, which enables on‐demand rapid dissolution and recycling of the materials. As a proof‐of‐concept, transient circuit‐based capacitive sensors, which can be degraded within 20 s, are fabricated for monitoring finger touching, morse code generation, and electrical touchpad. Such a strategy provides a guideline for designing transient electronics with a combination of biopolymer gels and liquid metal, and this approach is anticipated to find applications in human–machine interfaces and wearable devices.

From Droplets to Devices: Recent Advances in Liquid Metal Droplet Enabled Electronics

AbstractLiquid metals, particularly non‐toxic gallium‐based alloys, have emerged as promising materials for future soft electronics due to their unique properties, including fluidity, excellent electrical and thermal conductivities, and surface reactivity. They demonstrate adaptability, responsivity, and self‐healing abilities, offering a platform for innovative electronic devices. Embodied in a droplet form factor, gallium‐based liquid metal droplets (LMDs) combine the traits of liquid metals with the advantages of miniaturized structures, including high surface tension, high surface area, high mobility, and surface functionalization. This review discusses the inherent properties of LMDs, which have driven substantial research interest across various fields, such as sensors, robotics, electronic circuits, energy harvesters, drug delivery, and microfluidics systems, among others. Effective fabrication and processing techniques are detailed for LMDs, illustrating their role in applications previously challenging with conventional materials, such as reconfigurable, self‐healing, and transient electronics. Existing challenges and future directions in this growing field are discussed. This extensive review seeks to further the understanding of LMDs and their potential, offering a roadmap for their journey from a niche interest to a key material in various electronic devices.

Synergistic promotion between tolerant polymer electrode and super-conductive polyelectrolyte enables anti-damage transient wearable electronics

Manufacturing highly durable and transient materials is urgently needed to achieve optimal performances in wearable electronics. Here, a comprehensive methodology to enhance the durability and transience of wearable electronics by utilizing polypyrrole/vermiculite/polysaccharide (PPy/VMT/AF) electrodes and acid-assisted polyacrylamide (HPAM) electrolytes. The mechanical/thermal/electrochemical properties of integrated electrodes are boosting by introducing negatively charged vermiculite in conductive polymer-polysaccharide, which can be completely degrade after 90 days. Pre-gel drying shrinkage and rehydration were utilized to prepare polyacrylamide hydrogel with frost resistance and ultrahigh conductivity (increased 32.2 times as compared to traditional polyacrylamide). The synergism between PPy/VMT/AF and HPAM enables flexible solid-state supercapacitors with exceptional electrochemical stability even under serious damage such as puncturing, burning and freeze. In addition, the fabricated self-powered pressure sensor realizes ML-assisted human motion recognition with an accuracy of 95.7 %. This work opens up a new perspective on future directions for multifunctional platforms for wearable electronic devices.

Advances in Bioresorbable Materials and Electronics.

Transient electronic systems represent an emerging class of technology that is defined by an ability to fully or partially dissolve, disintegrate, or otherwise disappear at controlled rates or triggered times through engineered chemical or physical processes after a required period of operation. This review highlights recent advances in materials chemistry that serve as the foundations for a subclass of transient electronics, bioresorbable electronics, that is characterized by an ability to resorb (or, equivalently, to absorb) in a biological environment. The primary use cases are in systems designed to insert into the human body, to provide sensing and/or therapeutic functions for timeframes aligned with natural biological processes. Mechanisms of bioresorption then harmlessly eliminate the devices, and their associated load on and risk to the patient, without the need of secondary removal surgeries. The core content focuses on the chemistry of the enabling electronic materials, spanning organic and inorganic compounds to hybrids and composites, along with their mechanisms of chemical reaction in biological environments. Following discussions highlight the use of these materials in bioresorbable electronic components, sensors, power supplies, and in integrated diagnostic and therapeutic systems formed using specialized methods for fabrication and assembly. A concluding section summarizes opportunities for future research.

Highly Stretchable, Biodegradable, and Recyclable Green Electronic Substrates.

As a steady stream of electronic devices being discarded, a vast amount of electronic substrate waste of petroleum-based nondegradable polymers is generated, raising endless concerns about resource depletion and environmental pollution. With coupled reagent (CR)-grafted artificial marble waste (AMW@CR) as functional fillers, polylactic acid (PLA)-based highly stretchable biodegradable green composite (AMW@CR-SBGC) is prepared, with elongation at break up to more than 250%. The degradation mechanism of AMW@CR-SBGC is deeply revealed. AMW@CR not only contributed to the photodegradation of AMW@CR-SBGC but also significantly promoted the water degradation of AMW@CR-SBGC. More importantly, AMW@CR-SBGC showed great potential as sustainable green electronic substrates and AMW@CR-SBGC-based electronic skin can simulate the perception of human skin to strain signals. The outstanding programmable degradability, recyclability, and reusability of AMW@CR-SBGC enabled its application in transient electronics. As the first demonstration of artificial marble waste in electronic substrates, AMW@CR-SBGC killed three birds with one stone in terms of waste resourcing, e-waste reduction, and saving nonrenewable petroleum resources, opening up vast new opportunities for green electronics applications in areas such as health monitoring, artificial intelligence, and security.

Electrohydrodynamic Printed PEDOT:PSS/Graphene/PVA Circuits for Sustainable and Foldable Electronics

AbstractThe generation of electronic waste (e‐waste) poses a significant environmental challenge, necessitating strategies to extend electronics’ lifespan and incorporate eco‐friendly materials to enable their rapid degradation after disposal. Foldable electronics utilizing eco‐friendly materials offer enhanced durability during operation and degradability at the end of their life cycle. However, ensuring robust physical adhesion between electrodes/circuits and substrates during the folding process remains a challenge, leading to interface delamination and electronic failure. In this study, electrohydrodynamic (EHD) printing is employed as a cost‐effective method to fabricate the eco‐friendly foldable electronics by printing PEDOT:PSS/graphene composite circuits onto polyvinyl alcohol (PVA) films. The morphology and electrical properties of the printed patterns using inks with varying graphene and PEDOT:PSS weight ratios under different printing conditions are investigated. The foldability of the printed electronics is demonstrated, showing minimal resistance variation and stable electronic response even after four folds (16 layers) and hundreds of folding and unfolding cycles. Additionally, the application of printed PEDOT:PSS/graphene circuit is presented as a resistive temperature sensor for monitoring body temperature and respiration behavior. Furthermore, the transient features and degradation of the PEDOT:PSS/graphene/PVA based foldable electronics are explored, highlighting the potential promise as transient electronics in reducing electronic waste.

A Fully Biodegradable and Biocompatible Ionotronic Skin for Transient Electronics

AbstractWearable electronics have impacted many aspects of human life including health monitoring, disease diagnosis, and human‐machine interfacing. However, the rapid development also accelerates the generation of electronic waste (e‐waste), which is threatening the health of ecological systems. Accordingly, high‐performance biodegradable materials suitable for transient electronics are highly demanded and challenging. In this work, a fully biodegradable and biocompatible ionotronic skin is designed based on double‐network natural polyelectrolytes derivatives. It consists of carboxylated chitosan (CCS) and sulfobetaine methacrylate (SBMA) polymerized in glycerol and water followed by cross‐linking with hydrogen bonds and electrostatic attraction (namely SBMAX‐CCSY‐Glyz). By macromolecular engineering, the ionotronic skin exhibits high ionic conductivity, good compliance with skin, as well as complete degradability, which is capable of transient measurement of electrophysiology. Applied on the sciatic nerve of bullfrog, it can accurately record action potentials and fully degrade in only 3 days without any residue. Such biodegradable and biocompatible ionotronic skin will shed light on the design of ionotronic materials for future transient electronics.

Direct printing of conductive polymer PEDOT:PSS for foldable transient electronics

With the increased demand on portability, electronics have progressed from rudimentary flexible electronics to foldable electronics. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a conductive polymer, is a promising material for achieving foldable electronics, due to its mechanical stability. In foldable electronics, however, inadequate physical adhesion between electrodes and substrates under folding deformation has been a challenge. It can cause interfacial delamination and electronic failure during the folding and unfolding processes. In this study, electrohydrodynamic (EHD) printing is utilized for the fast, low-cost, and high-resolution fabrication of PEDOT:PSS circuits onto polyvinyl alcohol (PVA) films to improve the interface binding force for foldable electronics. The morphology and electrical properties of PEDOT:PSS patterns with different printed conditions were experimentally investigated. The adhesion between the printed PEDOT:PSS circuits and the PVA film was characterized by tape adhesion test, and the electrical property remained almost unchanged after 50 peeling tests. We demonstrated excellent foldability of the printed electronics. After 4 folds (16 layers), the resistance of PEDOT:PSS circuits varied minimally, and the external LED lights remained operational while folding and unfolding. Moreover, using the water soluble and degradable PVA substrate, the printed circuits can be simply dissolved in water, which provide a promising approach toward transient electronics and green electronics, and reduce the electronic waste.

Flexible conductive energetic film based on energetic ionic liquids and carbon nanotubes for information security transient electronics

Transient electronics is an emerging class of functional electronics designed to address problems such as potential data leakage and information theft. In order to meet the unification of transient technology and electronics, we prepared a flexible conductive energetic film by assembling energetic ionic liquids (EILs) loaded single-walled carbon nanotubes (SWNTs) and CuO functionalized multi-walled carbon nanotubes (MWNTs). It was found that the interaction between EILs and SWNTs maintains the high conductivity of SWNTs and strengthens the flexibility of the film. The introduce of CuO functional MWNTs enhance the detonation performance of the films by catalyzing EILs combustion. Therefore, obtained flexible conductive energetic film has good conductivity (63.67 S/cm), high energy release (8037 kJ/kg), and high flexibility (1000 bends). It is confirmed that flexible conductive energetic film can meet the requirement of low-voltage operation and high-voltage self-destruction by replacing traditional circuit in an electronic device. The prepared transient chip is able to ignited in 10 ms and completely self-destruct within 0.7 s.

Organic electrochemical transistors printed from degradable materials as disposable biochemical sensors

Transient electronics hold promise in reducing electronic waste, especially in applications that require only a limited lifetime. While various degradable electronic and physical sensing devices have been proposed, there is growing interest in the development of degradable biochemical sensors. In this work, we present the development of an organic electrochemical transistor (OECT) with degradable electrodes, printed on an eco- and bioresorbable substrate. The influence of the design and materials for the contacts, channel and gate of the transducer, namely poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) and carbon, is systematically evaluated for the development of OECT-based transient biosensors. The sensing capabilities of the electrochemical transistors are demonstrated with ionic solutions as well as for the enzyme-based detection of glucose. The disposable OECTs show comparable performance to their non-degradable counterparts. Their integration with highly conductive degradable and printable zinc tracks is studied for the realization of interconnects. These eco-friendly OECTs may find applications as disposable and sustainable biochemical sensors, and constitute a step towards bioresorbable biosensors.

Recent Progress in Transient Energy Storage using Biodegradable Materials

With the development of wireless sensor networks, electrical waste that remains in the environment is an inevitable issue in achieving sustainability and progress in electronics. Transient electronics that disappear after a prescribed time are of interest in electronics and material sciences. Such devices comprise naturally sourced materials that degrade without harmful or toxic substances during biodegradation. Although there are reports on transient electronic devices, including transistors, sensors, and radio frequency circuits, insufficient research has been conducted on the energy storage essential for operating transient devices. This review highlights the recent progress in developing transient energy storage. First, materials for transient energy storage, including conductors, electrolytes, and gels, are introduced. Second, transient supercapacitors, pseudocapacitors, primary batteries, and secondary batteries, are described and summarized. Finally, this review concludes and discusses the prospect of transient energy storage. The continuous progress of transient batteries and integration with transient devices are promising for sustainable electronics in the future.

Printed Electronics in Radiofrequency Energy Harvesters and Wireless Power Transfer Rectennas for IoT Applications

AbstractThe Internet of Things is currently one of the fastest‐growing branches in electronics. The development of energy storage systems and the miniaturization of dedicated printed circuit boards significantly influence that growth. However, the need for batteries and traditional printed circuit boards still limits devices' minimum size, weight, and cost, narrowing the application area. Energy harvesters and wireless power transfer systems fabricated with printed electronics can significantly reduce such devices' weight, size, and cost. Printed electronics technology provides scalable tools for many electronics applications, shortening the validation time and enabling new low‐cost or disposable solutions on lightweight and flexible substrates embedded inside 3D printed structures and directly on device housings. Energy harvesting and wireless power transfer systems in electronic devices can provide enough power to minimize battery capacity and size or even eliminate the need for batteries in low‐power applications. This review presents an adaptation of printed electronics technology in the fabrication of radio frequency energy harvesters and wireless power transfer rectennas for IoT applications. Last, perspectives for development towards greater integration with microsystems, transient electronics with ecofriendly materials, adaptation for next‐generation telecommunication systems, and 3D structural electronics solutions are briefly discussed.

Biocompatible, breathable and degradable microbial cellulose based triboelectric nanogenerator for wearable transient electronics

Advances in the processing of natural biomaterials have brought to the fore new approaches for the development of biofriendly and sustainable triboelectric nanogenerators (TENGs). In particular, bacterial cellulose (BC)-based TENGs have attracted considerable attention even though they still lack the key combination for transient wearable electronics. Herein, we report on a novel and facile method for in situ chemical modification of BC for the fabrication of degradable, breathable and biocompatible triboelectric nanogenerators (TENG). To achieve that, nanocoatings of polydopamine, polypyrrole or SiO2 have been used to decorate BC nanofibrils and thus tune the surface potential of the BC layer. Such a modification enables the repositioning of BC in the triboelectric series, allowing for the fabrication of various BC-based TENG devices. Polydopamine based BC TENG is found to exhibit superior performance (when coupled with a PVDF as negative triboelectric) with a maximum output voltage of ∼1010 V and a power density of ∼8.7 W/m2, a 7-fold enhancement in the power density as compared to pristine BC (VOC = 530 V and Pout = 1.1 W/m2). It is worthmentioning that all the nanocoated-BC films are found to be breathable, bio-/hemo-compatible and degradable, fulfilling the main criteria for transient electronics. As a proof of concept, we also demonstrate an on-body biomechanical energy harvester based on a single electrode All-BC TENG with the capability to generate an output voltage of 40 V upon physical motion. This TENG technology provides a unique combination of properties and has the potential to be implemented in wearables electronics and in vivo applications.

Degradable Green Polymers, Green Nanopolymers and Green Nanocomposites Derived from Natural Systems: Statistics and Headways

Nowadays, actively researching and developing degradable green materials are efficient means to move towards the future advanced technologies and industries. In this article, we review the state of the art in important aspects of degradable green polymers especially green nanopolymers from natural sources and derived nanomaterials. Consequently, the fundamentals, cataloguing and properties of degradable green polymers or green nanopolymers obtained from natural resources have been presented. Green nanopolymers and derivative green nanocomposites are natural degradable materials. In this article, we also deliver numerous technological applications of the degradable green nanopolymers and derived materials such as transient electronics, film/coating and membrane/packaging, environmental protection and sustainability, and biomedical applications. The resulting green nanocomposites have been found effective to resolve current ecological issues. Moreover, the challenges and future of the natural degradable green nanopolymers and green nanocomposites have been investigated. However, the research and advancement of technical degradable materials with industrial and commercial applications yet have along way to go.

Biodegradable natural chitosan coating films-based flexible resistive switching memory for transient electronics

Three flexible transparent transient memristors based on degradable natural chitosan coating films are reported. The Mg/Ag-doped chitosan/ITO sandwich structures were prepared by spin coating and drop coating, respectively. The plane structure device was also prepared. Three kinds of device exhibit different memory behaviors, namely, bipolar resistive switching behavior and butterfly resistive switching behavior accompanied by capacitance and negative resistance effect. The elucidated behavior of the bipolar resistive switching can be attributed to filament conduction. The behavior of the butterfly resistive switching is attributed to interface effects. In addition, the three devices have a large on/off ratio and long data retention time, showing promising non-volatile memory characteristics in flexible memory applications. The switching mechanism was evaluated by Schottky emission, hopping and direct tunneling. The transient memristor device prepared in this paper has excellent transient characteristics and controllable performance. This work reveals the potential of biodegradable flexible electronic devices.

Recent Progress and Future Prospects in Transient Polymer Electronics

Transient electronics is a rapidly growing field that focuses on the development of electronic materials that are intentionally degraded to environmentally and physiologically safe byproducts after a well-defined period of operation. The limited time frame of these materials makes them potential candidates for use in areas such as biomedicine and wearable electronics as well as mitigating the growing problem of electronic waste. Polymer-based transient electronics is attracting increasing interest due to its many advantages, including extensive chemical modification capabilities for transience and functionality, biocompatibility, and flexible and stretchable formats for electronics. In this Perspective, we discuss recent advances in the field of transient polymer electronics, highlighting existing strategies for degradation: the use of composites of biodegradable polymers with conducting polymers, the synthesis of copolymers/block copolymers or graft copolymers of conducting polymers with biodegradable polymers, the synthesis of fully (bio)degradable conjugated polymers with degradable conjugated linkers, and transience via dissolution of the conjugated polymers. We then highlight the applications of transient electronics based on conducting polymers. Finally, we provide an outlook on the future prospects in the field of transient polymer electronics and the challenges that need to be overcome for transient electronics to fulfill its promise in future electronic devices.

Biodegradable, transparent, and antibacterial alginate-based triboelectric nanogenerator for energy harvesting and tactile sensing

The utilization of natural biomaterials in the construction of triboelectric nanogenerators (TENG) has significant implications for the advancement of sustainable self-powered devices. Sodium alginate (SA), an eco-friendly and biodegradable triboelectric material with excellent transparency, is considered an ideal material for wearable TENGs. In this work, we report a biodegradable, transparent, and antibacterial SA-based TENG for mechanical energy harvesting and self-powered tactile sensing. The addition of glycerol, an environment-friendly additive, can enhance flexibility and adhesiveness of the SA, which resulted in well-transferred AgNWs/SA electrodes with high transparency and conductivity. The major parameters that affect the output performance of the fabricated TENG are investigated, including the frequency, thickness and area of the triboelectric layers. The output voltage, transferred charge, and peak power of the TENG could reach up to 53 V, 18 nC, and 4 μW, respectively, which is sufficient to power small electronic devices. In addition, the fabricated TENG device also shows excellent antibacterial and biodegradable capabilities. Finally, the TENG is demonstrated to be an effective self-powered tactile sensor for pressure mapping, human movement monitoring, and wearable human–machine interfacing. This work provides a new strategy to design flexible transparent TENGs with biodegradable SA and paves the way for developing next-generation self-powered transient electronics.

Laser‐Triggered Degradation of Silicon Circuits by Lithiation and Moisture Uptake for On‐Demand Transient Electronics

Data security risks of unauthorized access of confidential information have attracted considerable attention. Transient electronics capable of physical disappearance or disintegration upon external stimuli could potentially offer an alternative solution at the device level. Despite great advances, smart, efficient, wireless, and nonrecoverable degradation of foundry‐compatible silicon (Si)‐integrated circuit (IC) chips remains a challenge. Herein, a laser‐triggered degradation of Si circuits by lithiation and moisture uptake is proposed. By integrating IC chips with a small amount of lithium sources and a fluidic reservoir consisting of hygroscopic materials, on‐demand, wireless, rapid, and complete degradation of Si IC chips built at 600 nm node is achieved upon activation by laser irradiation. This work paves a new route to accomplish smart, tether‐free, and thorough degradation of devices compatible with existing foundry processes, offering an essential baseline for the development of intelligent transient electronics for secured hardware.

Fabric-like Electrospun PVAc-Graphene Nanofiber Webs as Wearable and Degradable Piezocapacitive Sensors.

Flexible piezocapacitive sensors utilizing nanomaterial-polymer composite-based nanofibrous membranes offer an attractive alternative to more traditional piezoelectric and piezoresistive wearable sensors owing to their ultralow powered nature, fast response, low hysteresis, and insensitivity to temperature change. In this work, we propose a facile method of fabricating electrospun graphene-dispersed PVAc nanofibrous membrane-based piezocapacitive sensors for applications in IoT-enabled wearables and human physiological function monitoring. A series of electrical and material characterization experiments were conducted on both the pristine and graphene-dispersed PVAc nanofibers to understand the effect of graphene addition on nanofiber morphology, dielectric response, and pressure sensing performance. Dynamic uniaxial pressure sensing performance evaluation tests were conducted on the pristine and graphene-loaded PVAc nanofibrous membrane-based sensors for understanding the effect of two-dimensional (2D) nanofiller addition on pressure sensing performance. A marked increase in the dielectric constant and pressure sensing performance was observed for graphene-loaded spin coated membrane and nanofiber webs respectively, and subsequently the micro dipole formation model was invoked to explain the nanofiller-induced dielectric constant enhancement. The robustness and reliability of the sensor have been underscored by conducting accelerated lifetime assessment experiments entailing at least 3000 cycles of periodic tactile force loading. A series of tests involving human physiological parameter monitoring were conducted to underscore the applicability of the proposed sensor for IoT-enabled personalized health care, soft robotics, and next-generation prosthetic devices. Finally, the easy degradability of the sensing elements is demonstrated to emphasize their suitability for transient electronics applications.

Ultra-stretchable and biodegradable elastomers for soft, transient electronics

As rubber-like elastomers have led to scientific breakthroughs in soft, stretchable characteristics-based wearable, implantable electronic devices or relevant research fields, developments of degradable elastomers with comparable mechanical properties could bring similar technological innovations in transient, bioresorbable electronics or expansion into unexplored areas. Here, we introduce ultra-stretchable, biodegradable elastomers capable of stretching up to ~1600% with outstanding properties in toughness, tear-tolerance, and storage stability, all of which are validated by comprehensive mechanical and biochemical studies. The facile formation of thin films enables the integration of almost any type of electronic device with tunable, suitable adhesive strengths. Conductive elastomers tolerant/sensitive to mechanical deformations highlight possibilities for versatile monitoring/sensing components, particularly the strain-tolerant composites retain high levels of conductivities even under tensile strains of ~550%. Demonstrations of soft electronic grippers and transient, suture-free cardiac jackets could be the cornerstone for sophisticated, multifunctional biodegradable electronics in the fields of soft robots and biomedical implants.