Processing Techniques for Bioresorbable Nanoparticles in Fabricating Flexible Conductive Interconnects

Accelerable Self-Sintering of Solvent-Free Molybdenum/Wax Biodegradable Composites for Multimodally Transient Electronics

Biodegradable conductive composites are key materials or components for printable transient electronics that can be fabricated in a low-cost and high-efficiency manner, thereby boosting their wide applications in biomedical engineering, hardware security, and environmental-friendly electronics. Continuous efforts in this area still lie in the development of strategies for highly conductive, safe, and reliable biodegradable conductive composite materials and devices. This paper introduces molybdenum/wax composites for multimodally printable transient electronics in which multiple transience modes including dissolution-induced degradation and thermally triggered degradation are available. Systematic experiments demonstrate several advantages and unique properties of this material system, including solvent-free fabrication, self-sintering behavior, and long-term and high conductivity via accelerable self-sintering treatment and rehealing capabilities. Notably, the immersion of molybdenum/wax composites in phosphate buffer solution can provide both positive effects (accelerated self-sintering-dominated) and negative effects (degradation-dominated) on their electrical conductivities. Mechanism analyses reveal the basis for balancing the degradation and accelerated self-sintering processes. The presented demonstrations foreshadow opportunities of the developed molybdenum/wax composites in rehealable electronics, on-demand smart transient electronics with multiple transience modes, and many other related unusual applications.

Water-Sintered Transient Nanocomposites Used as Electrical Interconnects for Dissolvable Consumer Electronics

Rapid development of electronic technology shortens the development time for new products and accelerates the obsolescence of consumer electronics, resulting in the explosive growth of electronic waste that is difficult to recycle and hazardous to the environment and human health. Transient electronics that can dissolve in water may potentially be adopted to tackle the issues of electronic waste; however, promising approaches to yield large-scale and high-performance transient consumer electronics have not yet been developed. Here, the joint effect of galvanic corrosion and redeposition has been utilized to develop bimetallic transient nanocomposites, which can be printed and water-sintered to yield high-performance transient PCB circuits with excellent electrical conductivity and mechanical robustness. The entire sintering process requires no external energy and strict environmental conditions. The achieved PCB circuits offer a conductivity of 307,664.4 S/m that is among the highest in comparison with other printed transient circuits. The supreme performance of the transient circuits eventually leads to the first dissolvable smartwatch that offers the same functions and similar performance as conventional smartwatches and dissolves in water within 40 h. The joint effect of galvanic corrosion and redeposition between two metals with distinct activities leads to novel nanocomposites and processing techniques of transient electronics. The resulting high-performance transient devices may reshape the appearance of consumer electronics and reform the electronics recycling industry by reducing recycling costs and minimizing environmental pollution and health hazard.

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.

Poly(lactic acid)-Based Ink for Biodegradable Printed Electronics With Conductivity Enhanced through Solvent Aging

Biodegradable electronics is a rapidly growing field, and the development of controllably biodegradable, high-conductivity materials suitable for additive manufacturing under ambient conditions remains a challenge. In this report, printable conductive pastes that employ poly(lactic acid) (PLA) as a binder and tungsten as a conductor are demonstrated. These composite conductors can provide enhanced stability in applications where moisture may be present, such as environmental monitoring or agriculture. Post-processing the printed traces using a solvent-aging technique increases their conductivity by up to 2 orders of magnitude, with final conductivities approaching 5000 S/m. Such techniques could prove useful when thermal processes including heating or laser sintering are limited by the temperature constraints of typical biodegradable substrates. Both accelerated oxidative and hydrolytic degradation of the printed composite conductors are examined, and a fully biodegradable capacitive soil moisture sensor is fabricated and tested.

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.

Soft Material-Enabled Electronics for Medicine, Healthcare, and Human-Machine Interfaces

Soft material-enabled electronics offer distinct advantages over conventional rigid and bulky devices for numerous wearable and implantable applications. Soft materials allow for seamless integration with skin and tissues due to the enhanced mechanical flexibility and stretchability. Wearable devices with multiple sensors offer continuous, real-time monitoring of biosignals and movements, which can be applied for rehabilitation and diagnostics, among other applications. Soft implantable electronics offer similar functionalities, but with improved compatibility with human tissues. Biodegradable soft implantable electronics are also being developed for transient monitoring, such as in the weeks following surgeries. New composite materials, integration strategies, and fabrication techniques are being developed to further advance soft electronics. This paper reviews recent progresses in these areas towards the development of soft material-enabled electronics for medicine, healthcare, and human-machine interfaces.

Manufacturing and Characterization of Zn-WC as Potential Biodegradable Material

This work presents the manufacturing and characterization of zinc-tungsten carbide (Zn-WC) nanocomposite as a potential biodegradable material. A highly homogeneous WC nanoparticle dispersion in a Zn matrix was achieved by molten salt assisted stir casting followed with hot rolling. The Vickers microhardness and ultimate tensile strength of zinc were enhanced more than 50% and 87%, respectively, with the incorporation of up to 4.4 vol. % WC nanoparticles. Additionally, Zn-WC nanocomposite retained high ductility (> 65%). However, the electrical and thermal conductivities were reduced by 12% and 21%, respectively. The significant enhancement in mechanical strength makes nanoparticle-reinforced zinc a promising candidate material for biodegradable metallic implants for a wide range of clinical applications, including orthopaedic and cardiovascular implants as well as bioresorbable electronics.