Tailoring Food Biopolymers into Biogels for Regenerative Wound Healing and Versatile Skin Bioelectronics

An increasing utilization of wound-related therapeutic materials and skin bioelectronics urges the development of multifunctional biogels for personal therapy and health management.Nevertheless,conventional dressings and skin bioelectronics with single function,mechanical mismatches,and impracticality severely limit their widespread applications in clinical.Herein,we explore a gelling mechanism,fabrication method,and functionalization for broadly applicable food biopolymers-based biogels that unite the challenging needs of elastic yet injectable wound dressing and skin bioelectronics in a single system.We combine our biogels with functional nanomaterials,such as cuttlefish ink nanoparticles and silver nanowires,to endow the biogels with reactive oxygen species scavenging capacity and electrical conductivity,and finally realized the improvement in diabetic wound microenvironment and the monitoring of electrophysiological signals on skin.This line of research work sheds light on preparing food biopolymers-based biogels with multifunctional integration of wound treatment and smart medical treatment.

Adhesive hydrogels for bioelectronics

Benefiting from the unique advantages of superior biocompatibility,strong stability,good biodegradability,and adjustable mechanical properties,hydrogels have attracted extensive research interests in bioelectronics.However,due to the existence of an interface between hydrogels and human tissues,the transmission of electrical signals from the human tissues to the hydrogel electronic devices will be hindered.The adhesive hydrogels with adhesive properties can tightly combine with the human tissue,which can enhance the contact between the electronic devices and human tissues and reduce the contact resistance,thereby improving the performance of hydrogel electronic devices.In this review,we will discuss in detail the adhesion mechanism of adhesive hydrogels and elaborate on the design principles of adhesive hydrogels.After that,we will introduce some methods of performance evaluation for adhesive hydrogels.Finally,we will provide a perspective on the development of adhesive hydrogel bioelectronics.

Mussel‑Inspired Redox‑Active and Hydrophilic Conductive Polymer Nanoparticles for Adhesive Hydrogel Bioelectronics

Conductive polymers(CPs)are generally insoluble,and developing hydrophilic CPs is significant to broaden the applications of CPs.In this work,a mussel-inspired strategy was proposed to construct hydrophilic CP nanoparticles(CP NPs),while endowing the CP NPs with redox activity and biocompatibility.This is a universal strategy applicable for a series of CPs,including polyaniline,polypyrrole,and poly(3,4-ethylenedioxythiophene).The catechol/quinone contained sulfonated lignin(LS)was doped into various CPs to form CP/LS NPs with hydrophilicity,conductivity,and redox activity.These CP/LS NPs were used as versatile nanofillers to prepare the conductive hydrogels with long-term adhesiveness.The CP/LS NPs-incorporated hydrogels have a good conductivity because of the uniform distribution of the hydrophilic NPs in the hydrogel network,forming a well-connected electric path.The hydrogel exhibits long-term adhesiveness,which is attributed to the mussel-inspired dynamic redox balance of catechol/quinone groups on the CP/LS NPs.This conductive and adhesive hydrogel shows good electroactivity and biocompatibility and therefore has broad applications in electrostimulation of tissue regeneration and implantable bioelectronics.

Flexible energy storage devices for wearable bioelectronics

With the growing market of wearable devices for smart sensing and personalized healthcare applications,energy storage devices that ensure stable power supply and can be constructed in flexible platforms have attracted tremendous research interests.A variety of active materials and fabrication strategies of flexible energy storage devices have been intensively studied in recent years,especially for integrated self-powered systems and biosensing.A series of materials and applications for flexible energy storage devices have been studied in recent years.In this review,the commonly adopted fabrication methods of flexible energy storage devices are introduced.Besides,recent advances in integrating these energy devices into flexible self-powered systems are presented.Furthermore,the applications of flexible energy storage devices for biosensing are summarized.Finally,the prospects and challenges of the self-powered sensing system for wearable electronics are discussed.

Semi-Implantable Bioelectronics

Developing techniques to effectively and real-time monitor and regulate the interior environment of biological objects is significantly important for many biomedical engineering and scientific applications, including drug delivery, electrophysiological recording and regulation of intracellular activities. Semi-implantable bioelectronics is currently a hot spot in biomedical engineering research area, because it not only meets the increasing technical demands for precise detection or regulation of biological activities, but also provides a desirable platform for externally incorporating complex functionalities and electronic integration. Although there is less definition and summary to distinguish it from the well-reviewed non-invasive bioelectronics and fully implantable bioelectronics, semi-implantable bioelectronics have emerged as highly unique technology to boost the development of biochips and smart wearable device. Here, we reviewed the recent progress in this field and raised the concept of “Semi-implantable bioelectronics”, summarizing the principle and strategies of semi-implantable device for cell applications and in vivo applications, discussing the typical methodologies to access to intracellular environment or in vivo environment, biosafety aspects and typical applications. This review is meaningful for understanding in-depth the design principles, materials fabrication techniques, device integration processes, cell/tissue penetration methodologies, biosafety aspects, and applications strategies that are essential to the development of future minimally invasive bioelectronics.

Intelligent structured nanocomposite adhesive for bioelectronics and soft robots

The remarkable functionality of biological systems in detecting and adapting to various environmental conditions has inspired the design of the latest electronics and robots with advanced features.This review focuses on intelligent bio-inspired strategies for developing soft bioelectronics and robotics that can accommodate nanocomposite adhesives and integrate them into biological surfaces.The underlying principles of the material and structural design of nanocomposite adhesives were investigated for practical applications with excellent functionalities,such as soft skin-attachable health care sensors,highly stretchable adhesive electrodes,switchable adhesion,and untethered soft robotics.In addition,we have discussed recent progress in the development of effective fabrication methods for micro/nanostructures for integration into devices,presenting the current challenges and prospects.

Long-Range Electronic Effect-Promoted Ring-Opening Polymerization of Thioctic Acid to Produce Biomimetic Ionic Elastomers for Bioelectronics

Poly(disulfide)s have been widely used in flexible wearable electronics,smart materials,and drug delivery.The synthesis of poly(disulfide)s usually utilizes external stimuli or toxic initiators to promote the polymerization.Here,we indicated that the long-range electronic effect can significantly alter the reactivity of the disulfide group.Accordingly,we established deprotonation-promoted ring-opening polymerization of thioctic acid(TA)as a highly effective and simple method to synthesize poly(disulfide)s due to the long-range electronic effect and nucleophilic carboxylate.Without external stimuli and initiators,simple mixing of TA and deprotonation reagent,choline bicarbonate,in different ratios at room temperature rapidly produced a series of high molecular weight(up to 772 kDa)ionic liquid crystal poly(disulfide)s elastomers with room temperature self-healing ability,adjustable conductivity(2.39×10^(−2)∼0.28×10^(−2)S m^(−1)),degradability,biocompatibility,antibacterial property,and tissue-like softness(Young’s moduli ranging from 18.2±6.0 to 111.1±36.7 kPa).The experiments and density functional theory calculations also revealed the principle of long-range electronic effect to establish a new synthetic strategy of poly(disulfide)s with superior properties favorable for bioelectronics.

Chemical Approaches to Emerging Advancements in Deformable Bioelectronics:Synthesis,Device Concepts,Performance,and Applications

This mini review examines the current advances and future prospects of chemical approaches in deformable bioelectronics,emphasizing their transformative potential in healthcare and other sectors.The mini review outlines novel fabrication strategies that rely on chemical principles to create adaptable,comfortable,and durable bioelectronic devices that are capable of seamlessly integrating into the dynamic biological environment.The discussion also extends to the integration of innovative device concepts that enhance the outcomes in both sensing and modulation functionalities.Performance-enhancing strategies that use chemistry to refine the sensitivity and precision of these devices are also highlighted.Moreover,the mini review explores the emerging applications of chemically enhanced bioelectronic devices in healthcare,reflecting the potential of this field to revolutionize patient care and improve health monitoring.In the outlook section,this mini review investigates the promising future of transient and living bioelectronics,emphasizing the pivotal role of chemical approaches in their development.It additionally covers the potential of chemical techniques in powering bioelectronic devices using biological systems and discusses the prospective applications of chemically synthesized bioelectronic devices outside of healthcare.While the field has made substantial progress,this mini review also identifies challenges that must be addressed,thus underlining the necessity for continued research and chemical innovation in bioelectronics.

Microfluidics-derived microfibers in flexible bioelectronics

Flexible electronics have attracted extensive attention across a wide range of fields due to their potential for preventive medicine and early disease detection.Microfiber-based textiles,encountered in everyday life,have emerged as promising platforms with integrated sensing capabilities.Microfluidic technology has been recognized as a promising avenue for the development of flexible conductive microfibers and has made significant achievements.In this review,we provide a comprehensive overview of the state-of-the-art advancements in microfiber-based flexible electronics fabricated using microfluidic platforms.Firstly,the fundamental strategies of the microfluidic fabrication of conductive microfibers with different structures and morphologies are introduced.Subsequently,attention is then directed towards the diverse applications of these microfibers in bioelectronics.Finally,we offer a forwardlooking perspective on the future challenges about microfluidic-derived microfibers in flexible bioelectronics.

Gelatin-Based Metamaterial Hydrogel Films with High Conformality for Ultra-Soft Tissue Monitoring

Implantable hydrogel-based bioelectronics(IHB)can precisely monitor human health and diagnose diseases.However,achieving biodegradability,biocompatibility,and high conformality with soft tissues poses significant challenges for IHB.Gelatin is the most suitable candidate for IHB since it is a collagen hydrolysate and a substantial part of the extracellular matrix found naturally in most tissues.This study used 3D printing ultrafine fiber networks with metamaterial design to embed into ultra-low elastic modulus hydrogel to create a novel gelatin-based conductive film(GCF)with mechanical programmability.The regulation of GCF nearly covers soft tissue mechanics,an elastic modulus from 20 to 420 kPa,and a Poisson’s ratio from-0.25 to 0.52.The negative Poisson’s ratio promotes conformality with soft tissues to improve the efficiency of biological interfaces.The GCF can monitor heartbeat signals and respiratory rate by determining cardiac deformation due to its high conformability.Notably,the gelatin characteristics of the biodegradable GCF enable the sensor to monitor and support tissue restoration.The GCF metamaterial design offers a unique idea for bioelectronics to develop implantable sensors that integrate monitoring and tissue repair and a customized method for endowing implanted sensors to be highly conformal with soft tissues.

Device design principles and bioelectronic applications for flexible organic electrochemical transistors

Organic electrochemical transistors(OECTs) exhibit significant potential for applications in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. Expanding OECTs to the fexible devices will significantly facilitate stable contact with the skin and enable more possible bioelectronic applications. In this work,we summarize the device physics of fexible OECTs, aiming to offer a foundational understanding and guidelines for material selection and device architecture. Particular attention is paid to the advanced manufacturing approaches, including photolithography and printing techniques, which establish a robust foundation for the commercialization and large-scale fabrication. And abundantly demonstrated examples ranging from biosensors, artificial synapses/neurons, to bioinspired nervous systems are summarized to highlight the considerable prospects of smart healthcare. In the end, the challenges and opportunities are proposed for fexible OECTs. The purpose of this review is not only to elaborate on the basic design principles of fexible OECTs, but also to act as a roadmap for further exploration of wearable OECTs in advanced bio-applications.

Mussel-inspired nanozyme catalyzed conductive and self-setting hydrogel for adhesive and antibacterial bioelectronics

Adhesive hydrogels have broad applications ranging from tissue engineering to bioelectronics;however,fabricating adhesive hydrogels with multiple functions remains a challenge.In this study,a mussel-inspired tannic acid chelated-Ag(TA-Ag)nanozyme with peroxidase(POD)-like activity was designed by the in situ reduction of ultrasmall Ag nanoparticles(NPs)with TA.The ultrasmall TA-Ag nanozyme exhibited high catalytic activity to induce hydrogel self-setting without external aid.The nanozyme retained abundant phenolic hydroxyl groups and maintained the dynamic redox balance of phenol-quinone,providing the hydrogels with long-term and repeatable adhesiveness,similar to the adhesion of mussels.The phenolic hydroxyl groups also afforded uniform distribution of the nanozyme in the hydrogel network,thereby improving its mechanical properties and conductivity.Furthermore,the nanozyme endowed the hydrogel with antibacterial activity through synergistic effects of the reactive oxygen species generated via POD-like catalytic reactions and the intrinsic bactericidal activity of Ag.Owing to these advantages,the ultrasmall TA-Ag nanozyme-catalyzed hydrogel could be effectively used as an adhesive,antibacterial,and implantable bioelectrode to detect bio-signals,and as a wound dressing to accelerate tissue regeneration while preventing infection.Therefore,this study provides a promising approach for the fabrication of adhesive hydrogel bioelectronics with multiple functions via mussel-inspired nanozyme catalysis.

Laser-induced graphene for bioelectronics and soft actuators

Laser-assisted process can enable facile,mask-free,large-area,inexpensive,customizable,and miniaturized patterning of laser-induced porous graphene(LIG)on versatile carbonaceous substrates(e.g.,polymers,wood,food,textiles)in a programmed manner at ambient conditions.Together with high tailorability of its porosity,morphology,composition,and electrical conductivity,LIG can find wide applications in emerging bioelectronics(e.g.,biophysical and biochemical sensing)and soft robots(e.g.,soft actuators).In this review paper,we first introduce the methods to make LIG on various carbonaceous substrates and then discuss its electrical,mechanical,and antibacterial properties and biocompatibility that are critical for applications in bioelectronics and soft robots.Next,we overview the recent studies of LIG-based biophysical(e.g.,strain,pressure,temperature,hydration,humidity,electrophysiological)sensors and biochemical(e.g.,gases,electrolytes,metabolites,pathogens,nucleic acids,immunology)sensors.The applications of LIG in flexible energy generators and photodetectors are also introduced.In addition,LIG-enabled soft actuators that can respond to chemicals,electricity,and light stimulus are overviewed.Finally,we briefly discuss the future challenges and opportunities of LIG fabrications and applications.

Flexible bioelectronics for physiological signals sensing and disease treatment

Flexible bioelectronics,including wearable and implantable electronics,have revolutionized the way of human-machine interaction due to the fact that they can provide natural and seamless interactions with humans and keep stable and durable at strained states.As sensor elements or biomimetic actuators,flexible bioelectronics can dynamically sense and monitor physiological signals,reveal real-time physical health information and provide timely precise stimulations or treatments.Thus,the flexible bioelectronics are playing increasingly important roles in human-health monitoring and disease treatment,which will significantly change the future of healthcare as well as our relationships with electronics.This review summarizes recent major progress in the development of flexible substrates or encapsulation materials,sensors,circuits and energy-autonomous powers toward digital healthcare monitoring,emphasizing its role in biomedical applications in vivo and problems in practical applications.A future perspective into the challenges and opportunities in emerging flexible bioelectronics designs for the next-generation healthcare monitoring systems is also presented.

Structures,properties,and challenges of emerging 2D materials in bioelectronics and biosensors

Bioelectronics are powerful tools for monitoring and stimulating biological and biochemical processes,with applications ranging from neural interface simulation to biosensing.The increasing demand for bioelectronics has greatly promoted the development of new nanomaterials as detection platforms.Recently,owing to their ultrathin structures and excellent physicochemical properties,emerging two-dimensional(2D)materials have become one of the most researched areas in the fields of bioelectronics and biosensors.In this timely review,the physicochemical structures of the most representative emerging 2D materials and the design of their nanostructures for engineering highperformance bioelectronic and biosensing devices are presented.We focus on the structural optimization of emerging 2D material-based composites to achieve better regulation for enhancing the performance of bioelectronics.Subsequently,the recent developments of emerging 2D materials in bioelectronics,such as neural interface simulation,biomolecular/biomarker detection,and skin sensors are discussed thoroughly.Finally,we provide conclusive views on the current challenges and future perspectives on utilizing emerging 2D materials and their composites for bioelectronics and biosensors.This review will offer important guidance in designing and applying emerging 2D materials in bioelectronics,thus further promoting their prospects in a wide biomedical field.

Potential of eNose Technology for Monitoring Biological CO_(2) Conversion Processes

Electronic nose(eNose) is a modern bioelectronic sensor for monitoring biological processes that convert CO_(2) into valueadded products, such as products formed during photosynthesis and microbial fermentation. eNose technology uses an array of sensors to detect and quantify gases, including CO_(2), in the air. This study briefly introduces the concept of eNose technology and potential applications thereof in monitoring CO_(2) conversion processes. It also provides background information on biological CO_(2) conversion processes. Furthermore, the working principles of eNose technology vis-à-vis gas detection are discussed along with its advantages and limitations versus traditional monitoring methods. This study also provides case studies that have used this technology for monitoring biological CO_(2) conversion processes. eNose-predicted measurements were observed to be completely aligned with biological parameters for R~2 values of 0.864, 0.808, 0.802, and 0.948. We test eNose technology in a variety of biological settings, such as algae farms or bioreactors, to determine its effectiveness in monitoring CO_(2) conversion processes. We also explore the potential benefits of employing this technology vis-à-vis monitoring biological CO_(2) conversion processes, such as increased reaction efficiency and reduced costs versus traditional monitoring methods. Moreover, future directions and challenges of using this technology in CO_(2) capture and conversion have been discussed. Overall, we believe this study would contribute to developing new and innovative methods for monitoring biological CO_(2) conversion processes and mitigating climate change.

Active Micro-Nano-Collaborative Bioelectronic Device for Advanced Electrophysiological Recording

The development of precise and sensitive electrophysiological recording platforms holds the utmost importance for research in the fields of cardiology and neuroscience.In recent years,active micro/nano-bioelectronic devices have undergone significant advancements,thereby facilitating the study of electrophysiology.The distinctive configuration and exceptional functionality of these active micro-nano-collaborative bioelectronic devices offer the potential for the recording of high-fidelity action potential signals on a large scale.In this paper,we review three-dimensional active nano-transistors and planar active micro-transistors in terms of their applications in electroexcitable cells,focusing on the evaluation of the effects of active micro/nano-bioelectronic devices on electrophysiological signals.Looking forward to the possibilities,challenges,and wide prospects of active micro-nano-devices,we expect to advance their progress to satisfy the demands of theoretical investigations and medical implementations within the domains of cardiology and neuroscience research.

From biomimicry to bioelectronics:Smart materials for cardiac tissue engineering

Effective strategies in cardiac tissue engineering require matrices that recapitulate the mechanical,topographic and electrical cues present in the native extracellular matrix.In this review,we discuss recent efforts in materials science and nanotechnology to achieve functional three-dimensional(3D)scaffolds that modulate and monitor cardiac tissue function.We consider key design considerations,including choice of biopolymer matrix,cell sources,and delivery methods for eventual therapies.We then discuss how solid-state nanomaterials may be integrated within these systems to provide unique electrical and nanotopographic cues that improve electromechanical synchrony.We describe how these approaches may be extended to complex,spatially heterogeneous constructs using 3D bioprinting techniques.Finally,we describe how scaffold materials may be augmented with bioelectronic components to achieve hybrid myocardium that monitors or controls electrophysiological activity.Collectively,these approaches provide a framework for achieving cardiac tissues with tunable,rationally-designed functionalities.We discuss future prospects and remaining challenges for clinical translation.

Recent progress on smart hydrogels for biomedicine and bioelectronics

The increasing development of biomedicine and bioelectronics has highlighted the requirement for smart materials that can respond to changes in physical and chemical properties under external environments,such as magnetic fields,electric fields,and temperature.Accordingly,hydrogels have been widely evaluated as promising candidates for smart materials owing to their intriguing structures comprising a cross‐linked network of polymer chains with interstitial spaces filled with solvent water.This feature endows hydrogels with soft and wet characteristics,which not only induce high tissue affinity but also allow the introduction of environmentally responsive nanoparticles to release specific smart properties.Herein,we reviewed novel smart hydrogels that can be applied in biomedicine and bioelectronics,and highlighted and discussed existing challenges in current technologies and research.

Polymer-based ?exible bioelectronics

Due to the mechanical mismatch between conventional rigid electronic devices and soft tissues at nature,a lot of interests have been attracted to develop flexible bioelectronics that work well both in vitro and in vivo. To this end, polymers that can be used for both key components and substrates are indispensable to achieve high performances such as high sensitivity and long-term stability for sensing applications.Here we will summarize the recent advances on the synthesis of a variety of polymers, the design of typical architectures and the integration of different functions for the flexible bioelectronic devices. The remaining challenges and promising directions are highlighted to provide inspirations for the future study on the emerging flexible bioelectronics at end.