Transient Light-Emitting Diodes Constructed from Semiconductors and Transparent Conductors that Biodegrade Under Physiological Conditions

Advances in Symbiotic Bioabsorbable Devices

Symbiotic bioabsorbable devices are ideal for temporary treatment. This eliminates the boundaries between the device and organism and develops a symbiotic relationship by degrading nutrients that directly enter the cells, tissues, and body to avoid the hazards of device retention. Symbiotic bioresorbable electronics show great promise for sensing, diagnostics, therapy, and rehabilitation, as underpinned by innovations in materials, devices, and systems. This review focuses on recent advances in bioabsorbable devices. Innovation is focused on the material, device, and system levels. Significant advances in biomedical applications are reviewed, including integrated diagnostics, tissue repair, cardiac pacing, and neurostimulation. In addition to the material, device, and system issues, the challenges and trends in symbiotic bioresorbable electronics are discussed.

Buckling Behavior Analysis of Kirigami Structure Under Tension

Flexible electronic technology has attracted great interest, where rigid and brittle semiconductor materials can withstand large deformation. In order to improve the stretchability of devices, many novel structures have been designed, such as the classical "wavy" structure, the island-bridge structure, and origami structures that achieve stretchability through creases. However, the stretchability of these structures is still not large enough. Inspired by traditional kirigami, the stretchability of devices is achieved by making various periodic cuts in the substrate while the devices are placed in the area around the cuts. The previous research mainly focused on the change in the electrical properties of the structure during the deformation process, and there were few studies on the mechanical mechanisms. Therefore, this paper studies the buckling behavior of the kirigami structure when the substrate is stretched, and its mechanism can provide guidance for practical applications.

Design and Development of Transient Sensing Devices for Healthcare Applications

With the ever-growing requirements in the healthcare sector aimed at personalized diagnostics and treatment, continuous and real-time monitoring of relevant parameters is gaining significant traction. In many applications, health status monitoring may be carried out by dedicated wearable or implantable sensing devices only within a defined period and followed by sensor removal without additional risks for the patient. At the same time, disposal of the increasing number of conventional portable electronic devices with short life cycles raises serious environmental concerns due to the dangerous accumulation of electronic and chemical waste. An attractive solution to address these complex and contradictory demands is offered by biodegradable sensing devices. Such devices may be able to perform required tests within a programmed period and then disappear by safe resorption in the body or harmless degradation in the environment. This work critically assesses the design and development concepts related to biodegradable and bioresorbable sensors for healthcare applications. Different aspects are comprehensively addressed, from fundamental material properties and sensing principles to application-tailored designs, fabrication techniques, and device implementations. The emerging approaches spanning the last 5 years are emphasized and a broad insight into the most important challenges and future perspectives of biodegradable sensors in healthcare are provided.

Silicon-based transient electronics: principles, devices and applications

Recent advances in materials science, device designs and advanced fabrication technologies have enabled the rapid development of transient electronics, which represents a class of devices or systems that their functionalities and constitutions can be partially/completely degraded via chemical reaction or physical disintegration over a stable operation. Therefore, numerous potentials, including zero/reduced waste electronics, bioresorbable electronic implants, hardware security, and others, are expected. In particular, transient electronics with biocompatible and bioresorbable properties could completely eliminate the secondary retrieval surgical procedure after their in-body operation, thus offering significant potentials for biomedical applications. In terms of material strategies for the manufacturing of transient electronics, silicon nanomembranes (SiNMs) are of great interest because of their good physical/chemical properties, modest mechanical flexibility (depending on their dimensions), robust and outstanding device performances, and state-of-the-art manufacturing technologies. As a result, continuous efforts have been made to develop silicon-based transient electronics, mainly focusing on designing manufacturing strategies, fabricating various devices with different functionalities, investigating degradation or failure mechanisms, and exploring their applications. In this review, we will summarize the recent progresses of silicon-based transient electronics, with an emphasis on the manufacturing of SiNMs, devices, as well as their applications. After a brief introduction, strategies and basics for utilizing SiNMs for transient electronics will be discussed. Then, various silicon-based transient electronic devices with different functionalities are described. After that, several examples regarding on the applications, with an emphasis on the biomedical engineering, of silicon-based transient electronics are presented. Finally, summary and perspectives on transient electronics are exhibited.

Recent Development of Implantable Chemical Sensors Utilizing Flexible and Biodegradable Materials for Biomedical Applications

Implantable chemical sensors built with flexible and biodegradable materials exhibit immense potential for seamless integration with biological systems by matching the mechanical properties of soft tissues and eliminating device retraction procedures. Compared with conventional hospital-based blood tests, implantable chemical sensors have the capability to achieve real-time monitoring with high accuracy of important biomarkers such as metabolites, neurotransmitters, and proteins, offering valuable insights for clinical applications. These innovative sensors could provide essential information for preventive diagnosis and effective intervention. To date, despite extensive research on flexible and bioresorbable materials for implantable electronics, the development of chemical sensors has faced several challenges related to materials and device design, resulting in only a limited number of successful accomplishments. This review highlights recent advancements in implantable chemical sensors based on flexible and biodegradable materials, encompassing their sensing strategies, materials strategies, and geometric configurations. The following discussions focus on demonstrated detection of various objects including ions, small molecules, and a few examples of macromolecules using flexible and/or bioresorbable implantable chemical sensors. Finally, we will present current challenges and explore potential future directions.

Advances in Wireless, Batteryless, Implantable Electronics for Real-Time, Continuous Physiological Monitoring

This review summarizes recent progress in developing wireless, batteryless, fully implantable biomedical devices for real-time continuous physiological signal monitoring, focusing on advancing human health care. Design considerations, such as biological constraints, energy sourcing, and wireless communication, are discussed in achieving the desired performance of the devices and enhanced interface with human tissues. In addition, we review the recent achievements in materials used for developing implantable systems, emphasizing their importance in achieving multi-functionalities, biocompatibility, and hemocompatibility. The wireless, batteryless devices offer minimally invasive device insertion to the body, enabling portable health monitoring and advanced disease diagnosis. Lastly, we summarize the most recent practical applications of advanced implantable devices for human health care, highlighting their potential for immediate commercialization and clinical uses.

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.

Transparent Electronics for Wearable Electronics Application

Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.

A biomaterial-silicon junction for photodetection

Bio-integrated optoelectronics can be interfaced with biological tissues, thereby offering opportunities for clinical diagnosis and therapy. However, finding a suitable biomaterial-based semiconductor to interface with electronics is still challenging. In this study, a semiconducting layer is assembled comprising a silk protein hydrogel and melanin nanoparticles (NPs). The silk protein hydrogel provides a water-rich environment for the melanin NPs that maximizes their ionic conductivity and bio-friendliness. An efficient photodetector is produced by forming a junction between melanin NP-silk and a p-type Si (p-Si) semiconductor. The observed charge accumulation/transport behavior at the melanin NP-silk/p-Si junction is associated with the ionic conductive state of the melanin NP-silk composite. The melanin NP-silk semiconducting layer is printed as an array on an Si substrate. The photodetector array exhibits uniform photo-response to illumination at various wavelengths, thus providing broadband photodetection. Efficient charge transfer between melanin NP-silk and Si provides fast photo-switching with rise and decay constants of 0.44 ​s and 0.19 ​s, respectively. The photodetector with a biotic interface comprising an Ag nanowire-incorporated silk layer as the top contact can operate when underneath biological tissue. The photo-responsive biomaterial-Si semiconductor junction using light as a stimulus offers a bio-friendly and versatile platform for artificial electronic skin/tissue.

Isotropic conductive paste for bioresorbable electronics

Bioresorbable implantable medical devices can be employed in versatile clinical scenarios that burden patients with complications and surgical removal of conventional devices. However, a shortage of suitable electricalinterconnection materials limits the development of bioresorbable electronic systems. Therefore, this study highlights a highly conductive, naturally resorbable paste exhibiting enhanced electrical conductivity and mechanical stability that can solve the existing problems of bioresorbable interconnections. Multifaceted experiments on electrical and physical properties were used to optimize the composition of pastes containing beeswax, submicron tungstenparticles, and glycofurol. These pastes embody isotropic conductive paths for three-dimensional interconnects and function as antennas, sensors, and contact pads for bioresorbable electronic devices. The degradation behavior in aqueous solutions was used to assess its stability and ability to retain electrical conductance (∼7 ​kS/m) and structural form over the requisite dissolution period. In vitro and in vivo biocompatibility tests clarified the safety of the paste as an implantable material.

Bioresorbable Nanostructured Chemical Sensor for Monitoring of pH Level In Vivo

Here, the authors report on the manufacturing and in vivo assessment of a bioresorbable nanostructured pH sensor. The sensor consists of a micrometer-thick porous silica membrane conformably coated layer-by-layer with a nanometer-thick multilayer stack of two polyelectrolytes labeled with a pH-insensitive fluorophore. The sensor fluorescence changes linearly with the pH value in the range 4 to 7.5 upon swelling/shrinking of the polymer multilayer and enables performing real-time measurements of the pH level with high stability, reproducibility, and accuracy, over 100 h of continuous operation. In vivo studies carried out implanting the sensor in the subcutis on the back of mice confirm real-time monitoring of the local pH level through skin. Full degradation of the pH sensor occurs in one week from implant in the animal model, and its biocompatibility after 2 months is confirmed by histological and fluorescence analyses. The proposed approach can be extended to the detection of other (bio)markers in vivo by engineering the functionality of one (at least) of the polyelectrolytes with suitable receptors, thus paving the way to implantable bioresorbable chemical sensors.

Natural Polymer in Soft Electronics: Opportunities, Challenges, and Future Prospects

Pollution caused by nondegradable plastics has been a serious threat to environmental sustainability. Natural polymers, which can degrade in nature, provide opportunities to replace petroleum-based polymers, meanwhile driving technological advances and sustainable practices. In the research field of soft electronics, regenerated natural polymers are promising building blocks for passive dielectric substrates, active dielectric layers, and matrices in soft conductors. Here, the natural-polymer polymorphs and their compatibilization with a variety of inorganic/organic conductors through interfacial bonding/intermixing and surface functionalization for applications in various device modalities are delineated. Challenges that impede the broad utilization of natural polymers in soft electronics, including limited durability, compromises between conductivity and deformability, and limited exploration in controllable degradation, etc. are explicitly inspected, while the potential solutions along with future prospects are also proposed. Finally, integrative considerations on material properties, device functionalities, and environmental impact are addressed to warrant natural polymers as credible alternatives to synthetic ones, and provide viable options for sustainable soft electronics.

High-Performance Carbon Nanotube-Based Transient Complementary Electronics

Transient electronics is an emerging class of electronic devices that can physically degrade or disintegrate after a stable period of service, showing a vast prospect in applications of "green" consumer electronics, hardware-secure devices, medical implants, etc. Complementary metal-oxide-semiconductor (CMOS) technology is dominant in integrated circuit design for its advantages of low static power consumption, high noise immunity, and simple design layout, which also work and are highly preferred for transient electronics. However, the performance of complementary transient electronics is severely restricted by the confined selection of transient materials and compatible fabrication strategies. Here, we report the realization of high-performance transient complementary electronics based on carbon nanotube thin films via a reliable electrostatic doping method. Under a low operating voltage of 2 V, on a 1.5 μm-thick water-soluble substrate made of poly(vinyl alcohol), the width-normalized on-state currents of the p-type and n-type transient thin-film transistors (TFTs) reach 4.5 and 4.7 μA/μm, and the width-normalized transconductances reach 2.8 and 3.7 μS/μm, respectively. Meanwhile, these TFTs show small subthreshold swings no more than 108 mV/dec and current on/off ratios above 10⁶ with good uniformity. Transient CMOS inverters, as basic circuit components, are demonstrated with a voltage gain of 24 and a high noise immunity of 67.4%. Finally, both the degradation of the active components and the disintegration of the functional system are continuously monitored with nontraceable remains after 10 and 5 h, respectively.

Paper and Salt: Biodegradable NaCl-Based Humidity Sensors for Sustainable Electronics

Flexible and thin-film humidity sensors are currently attracting the attention of the scientific community due to their portability and reduced size, which are highly useful traits for use in the Internet o Things (IoT) industry. Furthermore, in order to perform efficient and profitable mass production, it is necessary to develop a cost-effective and reproducible fabrication process and materials. Green fabrication methods and biodegradable materials would also minimize the environmental impact and create a sustainable IoT development. In this paper, flexible humidity sensors based on a common salt (NaCl) sensing layer are reported. Our sensors and the fabrication techniques employed, such as dip and spray coating, provide a biodegradable, low cost, and highly reproducible device. One of the sensors reported presents a typical resistive behaviour from 40% RH up to 85% RH with a sensitivity of −0.21 (Z/%RH). The performance of the sensors obtained with several fabrication techniques is studied and reported at multiple frequencies from 100 Hz to 10 MHz, showcasing its versatility and robustness.

Materials Chemistry of Neural Interface Technologies and Recent Advances in Three-Dimensional Systems

Advances in materials chemistry and engineering serve as the basis for multifunctional neural interfaces that span length scales from individual neurons to neural networks, neural tissues, and complete neural systems. Such technologies exploit electrical, electrochemical, optical, and/or pharmacological modalities in sensing and neuromodulation for fundamental studies in neuroscience research, with additional potential to serve as routes for monitoring and treating neurodegenerative diseases and for rehabilitating patients. This review summarizes the essential role of chemistry in this field of research, with an emphasis on recently published results and developing trends. The focus is on enabling materials in diverse device constructs, including their latest utilization in 3D bioelectronic frameworks formed by 3D printing, self-folding, and mechanically guided assembly. A concluding section highlights key challenges and future directions.

Advances in Implantable Optogenetic Technology for Cardiovascular Research and Medicine

Optogenetic technology provides researchers with spatiotemporally precise tools for stimulation, sensing, and analysis of function in cells, tissues, and organs. These tools can offer low-energy and localized approaches due to the use of the transgenically expressed light gated cation channel Channelrhodopsin-2 (ChR2). While the field began with many neurobiological accomplishments it has also evolved exceptionally well in animal cardiac research, both in vitro and in vivo. Implantable optical devices are being extensively developed to study particular electrophysiological phenomena with the precise control that optogenetics provides. In this review, we highlight recent advances in novel implantable optogenetic devices and their feasibility in cardiac research. Furthermore, we also emphasize the difficulties in translating this technology toward clinical applications and discuss potential solutions for successful clinical translation.

Bioresorbable Metals for Biomedical Applications: From Mechanical Components to Electronic Devices

Bioresorbable metals and metal alloys are of growing interest for myriad uses in temporary biomedical implants. Examples range from structural elements as stents, screws, and scaffolds to electronic components as sensors, electrical stimulators, and programmable fluidics. The associated physical forms span mechanically machined bulk parts to lithographically patterned conductive traces, across a diversity of metals and alloys based on magnesium, zinc, iron, tungsten, and others. The result is a rich set of opportunities in healthcare materials science and engineering. This review article summarizes recent advances in this area, starting with an historical perspective followed by a discussion of materials options, considerations in biocompatibility, and device applications. Highlights are in system level bioresorbable electronic platforms that support functions as diagnostics and therapeutics in the context of specific, temporary clinical needs. A concluding section highlights challenges and emerging research directions.

Bioresorbable Photonics: Materials, Devices and Applications

Bio-photonic devices that utilize the interaction between light and biological substances have been emerging as an important tool for clinical diagnosis and/or therapy. At the same time, implanted biodegradable photonic devices can be disintegrated and resorbed after a predefined operational period, thus avoiding the risk and cost associated with the secondary surgical extraction. In this paper, the recent progress on biodegradable photonics is reviewed, with a focus on material strategies, device architectures and their biomedical applications. We begin with a brief introduction of biodegradable photonics, followed by the material strategies for constructing biodegradable photonic devices. Then, various types of biodegradable photonic devices with different functionalities are described. After that, several demonstration examples for applications in intracranial pressure monitoring, biochemical sensing and drug delivery are presented, revealing the great potential of biodegradable photonics in the monitoring of human health status and the treatment of human diseases. We then conclude with the summary of this field, as well as current challenges and possible future directions.

Recent Progress on Bioresorbable Passive Electronic Devices and Systems

Bioresorbable electronic devices and/or systems are of great appeal in the field of biomedical engineering due to their unique characteristics that can be dissolved and resorbed after a predefined period, thus eliminating the costs and risks associated with the secondary surgery for retrieval. Among them, passive electronic components or systems are attractive for the clear structure design, simple fabrication process, and ease of data extraction. This work reviews the recent progress on bioresorbable passive electronic devices and systems, with an emphasis on their applications in biomedical engineering. Materials strategies, device architectures, integration approaches, and applications of bioresorbable passive devices are discussed. Furthermore, this work also overviews wireless passive systems fabricated with the combination of various passive components for vital sign monitoring, drug delivering, and nerve regeneration. Finally, we conclude with some perspectives on future fundamental studies, application opportunities, and remaining challenges of bioresorbable passive electronics.

Becoming Sustainable, The New Frontier in Soft Robotics

The advancement of technology has a profound and far-reaching impact on the society, now penetrating all areas of life. From cradle to grave, one is supported by and depends on a wide range of electronic and robotic appliances, with an ever more intimate integration of the digital and biological spheres. These advances, however, often come at the price of negatively impacting our ecosystem, with growing demands on energy, contributions to greenhouse gas emissions and environmental pollution-from production to improper disposal. Mitigating these adverse effects is among the grand challenges of the society and at the forefront of materials research. The currently emerging forms of soft, biologically inspired electronics and robotics have the unique potential of becoming not only like their natural antitypes in performance and capabilities, but also in terms of their ecological footprint. This review outlines the rise of sustainable materials in soft and bioinspired robotics, targeting all robotic components from actuators to energy storage and electronics. The state-of-the-art in biobased robotics spans flourishing fields and applications ranging from microbots operating in vivo to biohybrid machines and fully biodegradable yet resilient actuators. These first steps initiate the evolution of robotics and guide them into a sustainable future.

Recyclable and Flexible Dual-Mode Electronics with Light and Heat Management

Realizing multiple functions and sustainable manufacturing within the same electronic device would be highly attractive from a design and fabrication perspective. Here we demonstrate a recyclable dual-mode thin-film device that can perform both light emission and heat management simultaneously. The device is composed of a dissolvable emitting layer sandwiched between two undissolvable conducting films. The vertical multilayered device enables a highly flexible and foldable multicolor electroluminescent emission ranging from yellow or blue to white, and the coplanar monolayered conductor achieves tunable Joule heat temperature setting. By utilizing selective dissolution and artificial reconstruction of each layered component, the parent device shows full recyclability and reconstructability without severe performance degradation after several recycles. The proof-of concept device provides an ideal strategy to construct a multifunctional film system with recyclability and makes a significant contribution to scientific and technological advancement in low-cost sustainable electronics and optoelectronics.

Bioresorbable Materials on the Rise: From Electronic Components and Physical Sensors to In Vivo Monitoring Systems

Over the last decade, scientists have dreamed about the development of a bioresorbable technology that exploits a new class of electrical, optical, and sensing components able to operate in physiological conditions for a prescribed time and then disappear, being made of materials that fully dissolve in vivo with biologically benign byproducts upon external stimulation. The final goal is to engineer these components into transient implantable systems that directly interact with organs, tissues, and biofluids in real-time, retrieve clinical parameters, and provide therapeutic actions tailored to the disease and patient clinical evolution, and then biodegrade without the need for device-retrieving surgery that may cause tissue lesion or infection. Here, the major results achieved in bioresorbable technology are critically reviewed, with a bottom-up approach that starts from a rational analysis of dissolution chemistry and kinetics, and biocompatibility of bioresorbable materials, then moves to in vivo performance and stability of electrical and optical bioresorbable components, and eventually focuses on the integration of such components into bioresorbable systems for clinically relevant applications. Finally, the technology readiness levels (TRLs) achieved for the different bioresorbable devices and systems are assessed, hence the open challenges are analyzed and future directions for advancing the technology are envisaged.