Implantable Devices: Issues and Challenges

3D printed edible electronics: Components, fabrication approaches and applications

A recently minted field of 3D-printed edible electronics (EEs) represents a cutting-edge convergence of edible electronic devices and 3D printing technology. This review presents a comprehensive view of this emerging discipline, which has gathered significant scientific attention for its potential to create a safe, environmentally friendly, economical, and naturally degraded inside the human body. EEs have the potential to be used as medical and health devices to monitor physiological conditions and possibly treat diseases. These edible devices include different components, such as sensors, actuators, and other electronic elements, all made from edible ingredients such as sugars, proteins, polysaccharides, polymers, and others. Among the different fabrication approaches, 3D printing can provide reliable solutions to specific requirements. The concept of EEs has the potential to transform healthcare, providing more convenient, less invasive alternatives and personalized, customizable products for patients that beat traditional manufacturing methods. While the potential is enormous, there are critical challenges, notably ensuring the long-term stability, and regulatory and safety of these devices within the human body. Accordingly, a detailed understanding of the underlying concepts, fabrication approaches, design considerations, and action in the body/application range has been presented. As an evolving field, there is ample scope for research and multiple challenges must be addressed; these are elaborated towards the concluding sections of this article.

Antifouling Immunomodulatory Copolymer Architectures That Inhibit the Fibrosis of Implants

Immune reactions to medical implants often lead to encapsulation by fibrotic tissue and impaired device function. This process is thought to initiate by protein adsorption, which enables immune cells to attach and mount an inflammatory response. Previously, several antifibrotic materials have been either designed to reduce protein adsorption or discovered via high-throughput screens (HTS) to favorably regulate inflammation. The present work introduces antifouling immunomodulatory (AIM) copolymer coatings, which combine both strategies to effectively enhance implant protection. AIM copolymers synergistically integrate zwitterionic moieties to resist protein fouling, HTS-derived antifibrotics for immunomodulation, and silane monomers for grafting to diverse substrates including elastomers, ceramics, and metals. Interestingly, simply combining these monomers into conventional random or block copolymer architectures yielded no significant advantage over homopolymers. By contrast, an unusual polymer chain architecture - a zwitterionic block flanked by a mixed zwitterionic immunomodulatory segment - showed superior fibrosis resistance in both peritoneal and subcutaneous sites over one month in immunocompetent mice. This architecture also improved the performance of two different HTS-derived antifibrotic monomers, suggesting that tailoring AIM architectures may broadly complement immunomodulatory chemistries and provide a versatile approach to improving implant longevity.

Cuttlefish-Bone-Derived Hybrid Composite Scaffolds for Bone Tissue Engineering

Current investigations into the fabrication of innovative biomaterials that stimulate cartilage development result from increasing interest due to emerging bone defects. In particular, the investigation of biomaterials for musculoskeletal therapies extensively depends on the development of various hydroxyapatite (HA)/sodium alginate (SA) composites. Cuttlefish bone (CFB)-derived composite scaffolds for hard tissue regeneration have been effectively illustrated in this investigation using a hydrothermal technique. In this, the HA was prepared from the CFB source without altering its biological properties. The as-developed HA nanocomposites were investigated through XRD, FTIR, SEM, and EDX analyses to confirm their structural, functional, and morphological orientation. The higher the interfacial density of the HA/SA nanocomposites, the more the hardness of the scaffold increased with the higher applied load. Furthermore, the HA/SA nanocomposite revealed a remarkable antibacterial activity against the bacterial strains such as E. coli and S. aureus through the inhibition zones measured as 18 mm and 20 mm, respectively. The results demonstrated a minor decrease in cell viability compared with the untreated culture, with an observed percentage of cell viability at 97.2% for the HA/SA nanocomposites. Hence, the proposed HA/SA scaffold would be an excellent alternative for tissue engineering applications.

Recent advances in materials and manufacturing of implantable devices for continuous health monitoring

Implantable devices are vital in healthcare, enabling continuous monitoring, early disease detection, informed decision-making, enhanced outcomes, cost reduction, and chronic condition management. These devices provide real-time data, allowing proactive healthcare interventions, and contribute to overall improvements in patient care and quality of life. The success of implantable devices relies on the careful selection of materials and manufacturing methods. Recent materials research and manufacturing advancements have yielded implantable devices with enhanced biocompatibility, reliability, and functionality, benefiting human healthcare. This paper provides a comprehensive overview of the latest developments in implantable medical devices, emphasizing the importance of material selection and manufacturing methods, including biocompatibility, self-healing capabilities, corrosion resistance, mechanical properties, and conductivity. It explores various manufacturing techniques such as microfabrication, 3D printing, laser micromachining, electrospinning, screen printing, inkjet printing, and nanofabrication. The paper also discusses challenges and limitations in the field, including biocompatibility concerns, privacy and data security issues, and regulatory hurdles for implantable devices.

Increasing the stability of electrolyte-gated organic synaptic transistors for neuromorphic implants

Electrolyte-gated organic synaptic transistors (EGOSTs) can have versatile synaptic plasticity in a single device, so they are promising as components of neuromorphic implants that are intended for use in neuroprosthetic electronic nerves that are energy-efficient and have simple system structure. With the advancement in transistor properties of EGOSTs, the commercialization of neuromorphic implants for practical long-term use requires consistent operation, so they must be stable in vivo. This requirement demands strategies that maintain electronic and ionic transport in the devices while implanted in the human body, and that are mechanically, environmentally, and operationally stable. Here, we cover the structure, working mechanisms, and electrical responses of EGOSTs. We then focus on strategies to ensure their stability to maintain these characteristics and prevent adverse effects on biological tissues. We also highlight state-of-the-art neuromorphic implants that incorporate these strategies. We conclude by presenting a perspective on improvements that are needed in EGOSTs to develop practical, neuromorphic implants that are long-term useable.

Sustainability inspired fabrication of next generation neurostimulation and cardiac rhythm management electrodes via reactive hierarchical surface restructuring

Over the last two decades, platinum group metals (PGMs) and their alloys have dominated as the materials of choice for electrodes in long-term implantable neurostimulation and cardiac rhythm management devices due to their superior conductivity, mechanical and chemical stability, biocompatibility, corrosion resistance, radiopacity, and electrochemical performance. Despite these benefits, PGM manufacturing processes are extremely costly, complex, and challenging with potential health hazards. Additionally, the volatility in PGM prices and their high supply risk, combined with their scarce concentration of approximately 0.01 ppm in the earth's upper crust and limited mining geographical areas, underscores their classification as critical raw materials, thus, their effective recovery or substitution worldwide is of paramount importance. Since postmortem recovery from deceased patients and/or refining of PGMs that are used in the manufacturing of the electrodes and microelectrode arrays is extremely rare, challenging, and highly costly, therefore, substitution of PGM-based electrodes with other biocompatible materials that can yield electrochemical performance values equal or greater than PGMs is the only viable and sustainable solution to reduce and ultimately substitute the use of PGMs in long-term implantable neurostimulation and cardiac rhythm management devices. In this article, we demonstrate for the first time how the novel technique of "reactive hierarchical surface restructuring" can be utilized on titanium-that is widely used in many non-stimulation medical device and implant applications-to manufacture biocompatible, low-cost, sustainable, and high-performing neurostimulation and cardiac rhythm management electrodes. We have shown how the surface of titanium electrodes with extremely poor electrochemical performance undergoes compositional and topographical transformations that result in electrodes with outstanding electrochemical performance.

Hospital process performance and the adoption of medical devices: An organization-based view

Over the past two decades, there has been a growing scholarly interest in the adoption of technology in healthcare. While numerous studies have delved into the effects of specific technologies on the performance of different organizational units and medical specialties, the findings have often been divergent. Unlike the established literature, our approach focuses on the organization's perspective to analyze how technology impacts process performance in hospital settings. More precisely, we compiled a tailored dataset from 56 healthcare organizations in Italy and conducted a comprehensive analysis of panel data from 2016 to 2019, utilizing Ordinary Least Squares (OLS) regression as our main analytical tool. The data shows a clear relationship between an organization's use of medical devices and its overall process performance. Our research highlights the importance of achieving substantial improvements in process performance by strategically integrating new technologies and devices. Policymakers are encouraged to consider introducing incentives to drive hospitals to invest in innovative technologies. Furthermore, monitoring expenditures on new devices could serve as a valuable metric for assessing the extent of technology adoption within clinical practices.

Foreign Body Reaction to Ion-Beam-Treated Polyurethane Implant

All artificial materials used for implantation into an organism cause a foreign body reaction. This is an obstacle for a number of medical technologies. In this work, we investigated the effect of high-energy ion bombardment on polyurethane for medical purposes and the reaction of body tissues to its insertion into the mouse organism. An analysis of the cellular response and shell thickness near the implant showed a decrease in the foreign body reaction for implants treated with high-energy ions compared to untreated implants. The decrease in the reaction is associated with the activation of the polyurethane surface due to the formation on the surface layer of condensed aromatic clusters with unbonded valences on the carbon atoms at the edges of such clusters and the covalent attachment of the organism's own proteins to the activated surface of the implant. Thus, immune cells do not identify the implant surface coated with its own proteins as a foreign body. The deactivation of free valences at the edges of aromatic structures due to the storage of the treated implant before surgery reduces surface activity and partially restores the foreign body response. For the greatest effect in eliminating a foreign body reaction, it is recommended to perform the operation immediately after treating the implant with high-energy ions, with minimal contact of the treated surface with any materials.

An AlScN Piezoelectric Micromechanical Ultrasonic Transducer-Based Power-Harvesting Device for Wireless Power Transmission

Ultrasonic wireless power transfer technology (UWPT) represents a key technology employed for energizing implantable medical devices (IMDs). In recent years, aluminum nitride (AlN) has gained significant attention due to its biocompatibility and compatibility with complementary metal-oxide-semiconductor (CMOS) technology. In the meantime, the integration of scandium-doped aluminum nitride (Al90.4%Sc9.6%N) is an effective solution to address the sensitivity limitations of AlN material for both receiving and transmission capabilities. This study focuses on developing a miniaturized UWPT receiver device based on AlScN piezoelectric micro-electromechanical transducers (PMUTs). The proposed receiver features a PMUT array of 2.8 × 2.8 mm2 comprising 13 × 13 square elements. An acoustic matching gel is applied to address acoustic impedance mismatch when operating in liquid environments. Experimental evaluations in deionized water demonstrated that the power transfer efficiency (PTE) is up to 2.33%. The back-end signal processing circuitry includes voltage-doubling rectification, energy storage, and voltage regulation conversion sections, which effectively transform the generated AC signal into a stable 3.3 V DC voltage output and successfully light a commercial LED. This research extends the scope of wireless charging applications and paves the way for further device miniaturization by integrating all system components into a single chip in future implementations.

Brain-implanted conductors amplify radiofrequency fields in rodents: Advantages and risks

Over the past few decades, daily exposure to radiofrequency (RF) fields has been increasing due to the rapid development of wireless and medical imaging technologies. Under extreme circumstances, exposure to very strong RF energy can lead to heating of body tissue, even resulting in tissue injury. The presence of implanted devices, moreover, can amplify RF effects on surrounding tissue. Therefore, it is important to understand the interactions of RF fields with tissue in the presence of implants, in order to establish appropriate wireless safety protocols, and also to extend the benefits of medical imaging to increasing numbers of people with implanted medical devices. This study explored the neurological effects of RF exposure in rodents implanted with neuronal recording electrodes. We exposed freely moving and anesthetized rats and mice to 950 MHz RF energy while monitoring their brain activity, temperature, and behavior. We found that RF exposure could induce fast onset firing of single neurons without heat injury. In addition, brain implants enhanced the effect of RF stimulation resulting in reversible behavioral changes. Using an optical temperature measurement system, we found greater than tenfold increase in brain temperature in the vicinity of the implant. On the one hand, our results underline the importance of careful safety assessment for brain-implanted devices, but on the other hand, we also show that metal implants may be used for neurostimulation if brain temperature can be kept within safe limits.

Minimally invasive power sources for implantable electronics

As implantable medical electronics (IMEs) developed for healthcare monitoring and biomedical therapy are extensively explored and deployed clinically, the demand for non-invasive implantable biomedical electronics is rapidly surging. Current rigid and bulky implantable microelectronic power sources are prone to immune rejection and incision, or cannot provide enough energy for long-term use, which greatly limits the development of miniaturized implantable medical devices. Herein, a comprehensive review of the historical development of IMEs and the applicable miniaturized power sources along with their advantages and limitations is given. Despite recent advances in microfabrication techniques, biocompatible materials have facilitated the development of IMEs system toward non-invasive, ultra-flexible, bioresorbable, wireless and multifunctional, progress in the development of minimally invasive power sources in implantable systems has remained limited. Here three promising minimally invasive power sources summarized, including energy storage devices (biodegradable primary batteries, rechargeable batteries and supercapacitors), human body energy harvesters (nanogenerators and biofuel cells) and wireless power transfer (far-field radiofrequency radiation, near-field wireless power transfer, ultrasonic and photovoltaic power transfer). The energy storage and energy harvesting mechanism, configurational design, material selection, output power and in vivo applications are also discussed. It is expected to give a comprehensive understanding of the minimally invasive power sources driven IMEs system for painless health monitoring and biomedical therapy with long-term stable functions.

Biodegradable, Biocompatible, and Implantable Multifunctional Sensing Platform for Cardiac Monitoring

Cardiac monitoring after heart surgeries is crucial for health maintenance and detecting postoperative complications early. However, current methods like rigid implants have limitations, as they require performing second complex surgeries for removal, increasing infection and inflammation risks, thus prompting research for improved sensing monitoring technologies. Herein, we introduce a nanosensor platform that is biodegradable, biocompatible, and integrated with multifunctions, suitable for use as implants for cardiac monitoring. The device has two electrochemical biosensors for sensing lactic acid and pH as well as a pressure sensor and a chemiresistor array for detecting volatile organic compounds. Its biocompatibility with myocytes has been tested in vitro, and its biodegradability and sensing function have been proven with ex vivo experiments using a three-dimensional (3D)-printed heart model and 3D-printed cardiac tissue patches. Moreover, an artificial intelligence-based predictive model was designed to fuse sensor data for more precise health assessment, making it a suitable candidate for clinical use. This sensing platform promises impactful applications in the realm of cardiac patient care, laying the foundation for advanced life-saving developments.

Evaluation of a Machine Learning Algorithm to Classify Ultrasonic Transducer Misalignment and Deployment Using TinyML

The challenge for ultrasonic (US) power transfer systems, in implanted/wearable medical devices, is to determine when misalignment occurs (e.g., due to body motion) and apply directional correction accordingly. In this study, a number of machine learning algorithms were evaluated to classify US transducer misalignment, based on data signal transmissions between the transmitter and receiver. Over seven hundred US signals were acquired across a range of transducer misalignments. Signal envelopes and spectrograms were used to train and evaluate machine learning (ML) algorithms, classifying misalignment extent. The algorithms included an autoencoder, convolutional neural network (CNN) and neural network (NN). The best performing algorithm, was deployed onto a TinyML device for evaluation. Such systems exploit low power microcontrollers developed specifically around edge device applications, where algorithms were configured to run on low power, restricted memory systems. TensorFlow Lite and Edge Impulse, were used to deploy trained models onto the edge device, to classify signals according to transducer misalignment extent. TinyML deployment, demonstrated near real-time (<350 ms) signal classification achieving accuracies > 99%. This opens the possibility to apply such ML alignment algorithms to US arrays (capacitive micro-machined ultrasonic transducer (CMUT), piezoelectric micro-machined ultrasonic transducer (PMUT) devices) capable of beam-steering, significantly enhancing power delivery in implanted and body worn systems.

Comparative analysis of energy transfer mechanisms for neural implants

As neural implant technologies advance rapidly, a nuanced understanding of their powering mechanisms becomes indispensable, especially given the long-term biocompatibility risks like oxidative stress and inflammation, which can be aggravated by recurrent surgeries, including battery replacements. This review delves into a comprehensive analysis, starting with biocompatibility considerations for both energy storage units and transfer methods. The review focuses on four main mechanisms for powering neural implants: Electromagnetic, Acoustic, Optical, and Direct Connection to the Body. Among these, Electromagnetic Methods include techniques such as Near-Field Communication (RF). Acoustic methods using high-frequency ultrasound offer advantages in power transmission efficiency and multi-node interrogation capabilities. Optical methods, although still in early development, show promising energy transmission efficiencies using Near-Infrared (NIR) light while avoiding electromagnetic interference. Direct connections, while efficient, pose substantial safety risks, including infection and micromotion disturbances within neural tissue. The review employs key metrics such as specific absorption rate (SAR) and energy transfer efficiency for a nuanced evaluation of these methods. It also discusses recent innovations like the Sectored-Multi Ring Ultrasonic Transducer (S-MRUT), Stentrode, and Neural Dust. Ultimately, this review aims to help researchers, clinicians, and engineers better understand the challenges of and potentially create new solutions for powering neural implants.

Catheter-Free Urodynamics Testing: Current Insights and Clinical Potential

Lower urinary tract dysfunction not only interferes with the health-related quality of life of patients but may also lead to acute kidney injury and infections. To assess the bladder, urodynamic studies (UDS) have been implemented but the use of catheters leads to discomfort for the patient. Catheter-free long-term UDS would be useful and a potential solution could be ambulatory wireless devices that communicate via telemetry. Such sensors can detect pressure or volume. Numerous types of potential catheter-free sensors have been proposed for bladder monitoring. Despite substantial innovation in the manufacturing of implantable biomedical electronic systems, such sensors have remained at the laboratory stage due to a number of critical challenges. These challenges primarily concern hermeticity and biocompatibility, sensitivity and artifacts, drift, telemetry, and energy management. Having overcome these challenges, catheter-free ambulatory urodynamic monitoring could combine a synchronized intravesical pressure sensor with a volume analyzer but only the steps of cystometry and volume measurement are currently sufficiently reproducible to simulate UDS results. The measurement of volume by infrared optical sensors, in the form of abdominal patches, appears to be promising and studies are underway to market a telemetric ambulatory urodynamic monitoring system that includes an intravesical pressure sensor. There has been considerable progress in wearable and conformable electronics on many fronts, and continued collaboration between engineers and urologists could quickly overcome current challenges. In addition, to the diagnosis of UDS, such sensors could be useful in the development of a long-term closed-loop neuromodulation system. In this review, we explore the various types of catheter-free bladder sensors, inherent challenges and solutions to overcome these challenges, and the clinical potential of such long-term implantable sensors.

Dynamical flexible inference of nonlinear latent factors and structures in neural population activity

Modelling the spatiotemporal dynamics in the activity of neural populations while also enabling their flexible inference is hindered by the complexity and noisiness of neural observations. Here we show that the lower-dimensional nonlinear latent factors and latent structures can be computationally modelled in a manner that allows for flexible inference causally, non-causally and in the presence of missing neural observations. To enable flexible inference, we developed a neural network that separates the model into jointly trained manifold and dynamic latent factors such that nonlinearity is captured through the manifold factors and the dynamics can be modelled in tractable linear form on this nonlinear manifold. We show that the model, which we named 'DFINE' (for 'dynamical flexible inference for nonlinear embeddings') achieves flexible inference in simulations of nonlinear dynamics and across neural datasets representing a diversity of brain regions and behaviours. Compared with earlier neural-network models, DFINE enables flexible inference, better predicts neural activity and behaviour, and better captures the latent neural manifold structure. DFINE may advance the development of neurotechnology and investigations in neuroscience.

Neuromodulation and memory: exploring ethical ramifications in memory modification treatment via implantable neurotechnologies

Invasive implantable neurotechnologies capable of simultaneously altering and recording neural activity are no longer the exclusive province of science fiction but a looming reality that will revolutionize medical practice. These advancements, particularly in their memory-altering capabilities, herald a vast array of opportunities for addressing the complex landscape of neurodegenerative and psychiatric conditions linked to memory impairments. However, the panoply of ethical implications arising from such a novel neurotechnology remains relatively unexplored by the neuroethics literature. This study examines and contrasts the potential ethical implications of memory modification treatment via implantable neurotechnologies. The study contends that undesired side effects resulting from memory modulation can lead to significant identity harms, disrupting the coherence of self-narratives and impinging on our authenticity. To evince the practical impact of this moral argument, the study conducts a practical ethical assessment of how employing implantable neurotechnologies to modulate memory may jeopardize (i) our moral responsiveness to events and core system of values and (ii) the emotional component associated with the altered memory. From a first-person standpoint, changes to the way we reasonably feel and react to past events and future intentions may be deemed ethically problematic as these profound changes can yield significant moral disruptions and negatively impact our personal lives and interpersonal relationships. In addition, the study discusses further ethical conundrums from a third-person perspective as these disruptions can inhibit social activism against structural injustices, thereby hindering societal progress. Thus, taking into account this societal dimension is paramount when evaluating the ethical permissibility of memory modification procedures.

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.

Development of antibacterial neural stimulation electrodes via hierarchical surface restructuring and atomic layer deposition

Miniaturization and electrochemical performance enhancement of electrodes and microelectrode arrays in emerging long-term implantable neural stimulation devices improves specificity, functionality, and performance of these devices. However, surgical site and post-implantation infections are amongst the most devastating complications after surgical procedures and implantations. Additionally, with the increased use of antibiotics, the threat of antibiotic resistance is significant and is increasingly being recognized as a global problem. Therefore, the need for alternative strategies to eliminate post-implantation infections and reduce antibiotic use has led to the development of medical devices with antibacterial properties. In this work, we report on the development of electrochemically active antibacterial platinum-iridium electrodes targeted for use in neural stimulation and sensing applications. A two-step development process was used. Electrodes were first restructured using femtosecond laser hierarchical surface restructuring. In the second step of the process, atomic layer deposition was utilized to deposit conformal antibacterial copper oxide thin films on the hierarchical surface structure of the electrodes to impart antibacterial properties to the electrodes with minimal impact on electrochemical performance of the electrodes. Morphological, compositional, and structural properties of the electrodes were studied using multiple modalities of microscopy and spectroscopy. Antibacterial properties of the electrodes were also studied, particularly, the killing effect of the hierarchically restructured antibacterial electrodes on Escherichia coli and Staphylococcus aureus-two common types of bacteria responsible for implant infections.

Strengthening Privacy and Data Security in Biomedical Microelectromechanical Systems by IoT Communication Security and Protection in Smart Healthcare

Biomedical Microelectromechanical Systems (BioMEMS) serve as a crucial catalyst in enhancing IoT communication security and safeguarding smart healthcare systems. Situated at the nexus of advanced technology and healthcare, BioMEMS are instrumental in pioneering personalized diagnostics, monitoring, and therapeutic applications. Nonetheless, this integration brings forth a complex array of security and privacy challenges intrinsic to IoT communications within smart healthcare ecosystems, demanding comprehensive scrutiny. In this manuscript, we embark on an extensive analysis of the intricate security terrain associated with IoT communications in the realm of BioMEMS, addressing a spectrum of vulnerabilities that spans cyber threats, data manipulation, and interception of communications. The integration of real-world case studies serves to illuminate the direct repercussions of security breaches within smart healthcare systems, highlighting the imperative to safeguard both patient safety and the integrity of medical data. We delve into a suite of security solutions, encompassing rigorous authentication processes, data encryption, designs resistant to attacks, and continuous monitoring mechanisms, all tailored to fortify BioMEMS in the face of ever-evolving threats within smart healthcare environments. Furthermore, the paper underscores the vital role of ethical and regulatory considerations, emphasizing the need to uphold patient autonomy, ensure the confidentiality of data, and maintain equitable access to healthcare in the context of IoT communication security. Looking forward, we explore the impending landscape of BioMEMS security as it intertwines with emerging technologies such as AI-driven diagnostics, quantum computing, and genomic integration, anticipating potential challenges and strategizing for the future. In doing so, this paper highlights the paramount importance of adopting an integrated approach that seamlessly blends technological innovation, ethical foresight, and collaborative ingenuity, thereby steering BioMEMS towards a secure and resilient future within smart healthcare systems, in the ambit of IoT communication security and protection.

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices.

Histopathological changes in tissues surrounding vagal nerve stimulation generators: A retrospective analysis of revision surgeries

PURPOSE

Vagal nerve stimulation (VNS) is an effective treatment for patients with epilepsy, depression, and other neuropsychiatric conditions. Understanding the tissue changes associated with VNS devices is crucial for optimizing patient outcomes and device development. This study aimed to investigate the histopathological changes in the tissues surrounding the VNS generator and explore potential correlations with clinical factors and battery performance.

METHODS

A total of 23 patients who underwent VNS generator revision surgery owing to battery depletion were included. Tissue samples from the areas surrounding the VNS generator were obtained and analyzed for histopathological changes. Demographic and device-related variables were also recorded.

RESULTS

Capsule formation was observed in all patients. Acute inflammation were not detected in any case. Perivascular lymphocytic infiltration, foreign-body giant cell reaction (FBGCR), and calcification were observed in 8.7%, 26.1%, and 43.5% of patients, respectively. Crystalloid foreign body appearance was noted in 4 patients. The median output current of the generator was higher in patients with lymphocytic infiltration than in those without lymphocytic infiltration. The median off time was higher in patients with skin retraction than in those without skin retraction. Moreover, discomfort was associated with the presence of FBGCR.

CONCLUSION

Our study provides insights into the tissue changes associated with the VNS generator, with capsule formation being a common response. Crystalloid foreign body appearance was not reported previously. Further research is needed to understand the relationship between these tissue changes and VNS device performance, including the potential impact on battery life. These findings may contribute to VNS therapy optimization and device development.

Trends and Challenges in the Development of 3D-Printed Heart Valves and Other Cardiac Implants: A Review of Current Advances

This article provides a comprehensive review of the current trends and challenges in the development of 3D-printed heart valves and other cardiac implants. By providing personalized solutions and pushing the limits of regenerative medicine, 3D printing technology has revolutionized the field of cardiac healthcare. The use of several organic and synthetic polymers in 3D printing heart valves is explored in this article, with emphasis on both their benefits and drawbacks. In cardiac tissue engineering, stem cells are essential, and their potential to lessen immunological rejection and thrombogenic consequences is highlighted. In the clinical applications section, the article emphasizes the importance of 3D printing in preoperative planning. Surgery results are enhanced when surgeons can visualize and assess the size and placement of implants using patient-specific anatomical models. Customized implants that are designed to match the anatomy of a particular patient reduce the likelihood of complications and enhance postoperative results. The development of physiologically active cardiac implants, made possible by 3D bioprinting, shows promise by eliminating the need for artificial valves. In conclusion, this paper highlights cutting-edge research and the promise of 3D-printed cardiac implants to improve patient outcomes and revolutionize cardiac treatment.

Non-Directional Property of Human-Body Communication Channel for Implantable Device Application

In this paper, we present the properties of a communication channel used for implantable devices. The human-body communication (HBC) channel was proposed for data communication in implantable devices. The impulse response was measured using a channel-mimicking model, which mimics electrical losses caused by human body tissues. Furthermore, we compared two types of channel-mimicking models to evaluate their applicability depending on the measurement environment. The resultant impulse responses of the HBC channel showed that HBC does not cause severe changes in the channel properties even when the implantable device is rotated.

Implantable device with magnetically rotating disk for needle-free administrations of emergency drug

Prompt administration of first-aid drugs can save lives during medical emergencies such as anaphylaxis and hypoglycemia. However, this is often performed by needle self-injection, which is not easy for patients under emergency conditions. Therefore, we propose an implantable device capable of on-demand administration of first-aid drugs (i.e., the implantable device with a magnetically rotating disk [iMRD]), such as epinephrine and glucagon, via a noninvasive simple application of the magnet from the outside skin (i.e., the external magnet). The iMRD contained a disk embedded with a magnet, as well as multiple drug reservoirs that were sealed with a membrane, which was designed to rotate at a precise angle only when the external magnet was applied. During this rotation, the membrane on a designated single-drug reservoir was aligned and torn to expose the drug to the outside. When implanted in living animals, the iMRD, actuated by an external magnet, delivers epinephrine and glucagon, similar to conventional subcutaneous needle injections.

Zn Microbatteries Explore Ways for Integrations in Intelligent Systems

As intelligent microsystems develop, many revolutionary applications, such as the swallowing surgeon proposed by Richard Feynman, are about to evolve. Nonetheless, integrable energy storage satisfying the demand for autonomous operations has emerged as a major obstacle to the deployment of intelligent microsystems. A reason for the lagging development of integrable batteries is the challenge of miniaturization through microfabrication procedures. Lithium batteries, generated by the most successful battery chemistry, are not stable in the air, thus creating major manufacturing challenges. Other cations (Na⁺ , Mg²⁺ , Al³⁺ , K⁺ ) are still in the early stages of development. In contrast, the superior stability of zinc batteries in the air brings high compatibility to microfabrication protocols and has already demonstrated excellent practicability in full-sized devices. To obtain energy-dense and high-power zinc microbatteries within square-millimeter or smaller footprints, sandwich, pillar, and Swiss-roll configurations are developed. Thin interdigital and fiber microbatteries find their applications being integrated into wearable devices and electronic skin. It is foreseeable that zinc microbatteries will find their way into highly integrated microsystems unlocking their full potential for autonomous operation. This review summarizes the material development, configuration innovation, and application-oriented integration of zinc microbatteries.

NFC-Powered Implantable Device for On-Body Parameters Monitoring With Secure Data Exchange Link to a Medical Blockchain Type of Network

Implantable devices represent the future of remote medical monitoring and administration of both chemical and physical therapies to the patients. Although some of these devices are already in the market, the security mechanisms deployed inside them to withstand deliberate external influence are still decades away from the robust digital data security schemes employed in modern distributed networks these days. Medical data theft, spoofing, and disclosure pose serious threats that can ultimately lead to individual and social stigmas or even death. In this article, we present a small-form and batteryless implantable device with acquisition channels for biopotential (30-dB gain and 16-Hz bandwidth), arterial pulse oximetry, and temperature (0.12°C accuracy) recordings, suitable for cardiovascular, neuronal, and endocrine parameters assessment. The proposed device is powered by the near-field communication (NFC) interface with an external mobile phone, with a power consumption of 0.9 mW and achieving the full operation for distances close to 1 cm under the skin. In situ encryption of the acquired physiological signals is performed by a lightweight and short-term symmetric-key distribution scheme with data stream hopping, in order to ensure secure data transference over the air between the patient and trusted entities only, complemented by data storage, processing, and recovery through a medical blockchain type of network that involves the main stakeholders inside a medical community.

Ultrasoft and Biocompatible Magnetic-Hydrogel-Based Strain Sensors for Wireless Passive Biomechanical Monitoring

Implantable flexible mechanical sensors have exhibited great potential in health monitoring and disease diagnosis due to continuous and real-time monitoring capability. However, the wires and power supply required in current devices cause inconvenience and potential risks. Magnetic-based devices have demonstrated advantages in wireless and passive sensing, but the mismatched mechanical properties, poor biocompatibility, and insufficient sensitivity have limited their applications in biomechanical monitoring. Here, a wireless and passive flexible magnetic-based strain sensor based on a gelatin methacrylate/Fe₃O₄ magnetic hydrogel has been fabricated. The sensor exhibits ultrasoft mechanical properties, strong magnetic properties, and long-term stability in saline solution and can monitor strains down to 50 μm. A model of the sensing process is established to identify the optimal detection location and the relation between the relative magnetic permeability and the sensitivity of the sensors. Moreover, an in vitro tissue model is developed to investigate the potential of the sensor in detecting subtle biomechanical signals and avoiding interference with bioactivities. Furthermore, a real-time and high-throughput biomonitoring platform is built and implements passive wireless monitoring of the drug response and cultural status of the cardiomyocytes. This work demonstrates the potential of applying magnetic sensing for biomechanical monitoring and provides ideas for the design of wireless and passive implantable devices.

Ultrasonically actuated neural probes for reduced trauma and inflammation in mouse brain

Electrical neural recordings measured using direct electrical interfaces with neural tissue suffer from a short lifespan because the signal strength decreases over time. The inflammatory response to the inserted microprobe can create insulating tissue over the electrical interfaces, reducing the recorded signal below noise levels. One of the factors contributing to this inflammatory response is the tissue damage caused during probe insertion. Here, we explore the use of ultrasonic actuation of the neural probe during insertion to minimize tissue damage in mice. Silicon neural microprobes were designed and fabricated with integrated electrical recording sites and piezoelectric transducers. The microprobes were actuated at ultrasonic frequencies using integrated piezoelectric transducers. The microprobes were inserted into mouse brains under a glass window over the brain surface to image the tissue surrounding the probe using two-photon microscopy. The mechanical force required to penetrate the tissue was reduced by a factor of 2-3 when the microprobe was driven at ultrasonic frequencies. Tissue histology at the probe insertion site showed a reduced area of damage and decreased microglia counts with increasing ultrasonic actuation of the probes. Two-photon imaging of the microprobe over weeks demonstrated stabilization of the inflammatory response. Recording of electrical signals from neurons over time suggests that microprobes inserted using ultrasound have a higher signal-to-noise ratio over an extended time period.

In situ diagnosis and simultaneous treatment of cardiac diseases using a single-device platform

The in situ diagnosis of cardiac activities with simultaneous therapeutic electrical stimulation of the heart is key to preventing cardiac arrhythmia. Here, we present an unconventional single-device platform that enables in situ monitoring even in a wet condition and control of beating heart motions without interferences to the recording signal. This platform consists of the active-matrix array of pressure-sensitive transistors for detecting cardiac beatings, biocompatible, low-impedance electrodes for cardiac stimulations, and an alginate-based hydrogel adhesive for attaching this platform conformally to the epicardium. In contrast to conventional electrophysiological sensing using electrodes, the pressure-sensitive transistors measured mechanophysiological characteristics by monitoring the spatiotemporal distributions of cardiac pressures during heart beating motions. In vivo tests show mechanophysiological readings having good correlation with electrocardiography and negligible interference with the electrical artifacts caused during cardiac stimulations. This platform can therapeutically synchronize the rhythm of abnormal heartbeats through efficient pacing of cardiac arrhythmia.

Computational Analysis of a Multi-Layered Skin and Cardiac Pacemaker Model Based on Neural Network Approach

The presented study discusses the possible disturbing effects of the electromagnetic field of antennas used in mobile phones or WiFi technologies on the pacemaker in the patient's body. This study aims to obtain information on how the thickness of skin layers (such as the thickness of the hypodermis) can affect the activity of a pacemaker exposed to a high-frequency electromagnetic field. This study describes the computational mathematical analysis and modeling of the heart pacemaker inserted under the skin exposed to various electromagnetic field sources, such as a PIFA antenna and a tuned dipole antenna. The finite integration technique (FIT) for a pacemaker model was implemented within the commercially available CST Microwave simulation software studio. Likewise, the equations that describe the mathematical relationship between the subcutaneous layer thickness and electric field according to different exposures of a tuned dipole and a PIFA antenna are used and applied for training a neural network. The main output of this study is the creation of a mathematical model and a multilayer feedforward neural network, which can show the dependence of the thickness of the hypodermis on the size of the electromagnetic field, from the simulated data from CST Studio.

Implants with Sensing Capabilities

Because of the aging human population and increased numbers of surgical procedures being performed, there is a growing number of biomedical devices being implanted each year. Although the benefits of implants are significant, there are risks to having foreign materials in the body that may lead to complications that may remain undetectable until a time at which the damage done becomes irreversible. To address this challenge, advances in implantable sensors may enable early detection of even minor changes in the implants or the surrounding tissues and provide early cues for intervention. Therefore, integrating sensors with implants will enable real-time monitoring and lead to improvements in implant function. Sensor integration has been mostly applied to cardiovascular, neural, and orthopedic implants, and advances in combined implant-sensor devices have been significant, yet there are needs still to be addressed. Sensor-integrating implants are still in their infancy; however, some have already made it to the clinic. With an interdisciplinary approach, these sensor-integrating devices will become more efficient, providing clear paths to clinical translation in the future.

Femtosecond laser hierarchical surface restructuring for next generation neural interfacing electrodes and microelectrode arrays

Long-term implantable neural interfacing devices are able to diagnose, monitor, and treat many cardiac, neurological, retinal and hearing disorders through nerve stimulation, as well as sensing and recording electrical signals to and from neural tissue. To improve specificity, functionality, and performance of these devices, the electrodes and microelectrode arrays-that are the basis of most emerging devices-must be further miniaturized and must possess exceptional electrochemical performance and charge exchange characteristics with neural tissue. In this report, we show for the first time that the electrochemical performance of femtosecond-laser hierarchically-restructured electrodes can be tuned to yield unprecedented performance values that significantly exceed those reported in the literature, e.g. charge storage capacity and specific capacitance were shown to have improved by two orders of magnitude and over 700-fold, respectively, compared to un-restructured electrodes. Additionally, correlation amongst laser parameters, electrochemical performance and surface parameters of the electrodes was established, and while performance metrics exhibit a relatively consistent increasing behavior with laser parameters, surface parameters tend to follow a less predictable trend negating a direct relationship between these surface parameters and performance. To answer the question of what drives such performance and tunability, and whether the widely adopted reasoning of increased surface area and roughening of the electrodes are the key contributors to the observed increase in performance, cross-sectional analysis of the electrodes using focused ion beam shows, for the first time, the existence of subsurface features that may have contributed to the observed electrochemical performance enhancements. This report is the first time that such performance enhancement and tunability are reported for femtosecond-laser hierarchically-restructured electrodes for neural interfacing applications.

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.

PELP: Accounting for Missing Data in Neural Time Series by Periodic Estimation of Lost Packets

Recent advances in wireless data transmission technology have the potential to revolutionize clinical neuroscience. Today sensing-capable electrical stimulators, known as "bidirectional devices", are used to acquire chronic brain activity from humans in natural environments. However, with wireless transmission come potential failures in data transmission, and not all available devices correctly account for missing data or provide precise timing for when data losses occur. Our inability to precisely reconstruct time-domain neural signals makes it difficult to apply subsequent neural signal processing techniques and analyses. Here, our goal was to accurately reconstruct time-domain neural signals impacted by data loss during wireless transmission. Towards this end, we developed a method termed Periodic Estimation of Lost Packets (PELP). PELP leverages the highly periodic nature of stimulation artifacts to precisely determine when data losses occur. Using simulated stimulation waveforms added to human EEG data, we show that PELP is robust to a range of stimulation waveforms and noise characteristics. Then, we applied PELP to local field potential (LFP) recordings collected using an implantable, bidirectional DBS platform operating at various telemetry bandwidths. By effectively accounting for the timing of missing data, PELP enables the analysis of neural time series data collected via wireless transmission-a prerequisite for better understanding the brain-behavior relationships underlying neurological and psychiatric disorders.

Full-duplex enabled wireless power transfer system via textile for miniaturized IMD

Full-duplex (FD) enabled wireless power transfer (WPT) system via textile for miniaturized IMD is presented. By utilizing the battery-free near-field communication (NFC) method, the system realizes wireless power and data transmission without a bulky battery or energy harvester which can diminish the physical size of implantable medical device (IMD). Moreover, using textile as a medium of power transmission, the system overcomes the drawback and extends the limited effective range of the NFC method. In addition, as realizing simultaneous bidirectional data transmission over a single data channel, IMD has been further miniaturized. The proposed system including an external transmitter and the minimized IMD receiver supports 200 kbps and 50 kbps data rates for FSK downlink and LSK uplink telemetries at the same time with bit error rate (BER) of < \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$8{ } \times { }10^{ - 5}$$\end{document}8×10-5 and < \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4{ } \times { }10^{ - 5}$$\end{document}4×10-5, respectively. The measured power transfer efficiency (PTE) and DC-to-DC power delivered to load (PDL) are 5.77% and 64 mW at 0.5/60 cm of vertical/horizontal distance.

Piezoelectric ultrasound energy-harvesting device for deep brain stimulation and analgesia applications

Supplying wireless power is a challenging technical problem of great importance for implantable biomedical devices. Here, we introduce a novel implantable piezoelectric ultrasound energy-harvesting device based on Sm-doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (Sm-PMN-PT) single crystal. The output power density of this device can reach up to 1.1 W/cm² in vitro, which is 18 times higher than the previous record (60 mW/cm²). After being implanted in the rat brain, under 1-MHz ultrasound with a safe intensity of 212 mW/cm², the as-developed device can produce an instantaneous effective output power of 280 μW, which can immediately activate the periaqueductal gray brain area. The rat electrophysiological experiments under anesthesia and behavioral experiments demonstrate that our wireless-powered device is well qualified for deep brain stimulation and analgesia applications. These encouraging results provide new insights into the development of implantable devices in the future.

Inkjet-Printed Phospholipid Bilayers on Titanium Oxide Surfaces: Towards Functional Membrane Biointerfaces

Functional biointerfaces hold broad significance for designing cell-responsive medical implants and sensor devices. Solid-supported phospholipid bilayers are a promising class of biological materials to build bioinspired thin-film coatings, as they can facilitate interactions with cell membranes. However, it remains challenging to fabricate lipid bilayers on medically relevant materials such as titanium oxide surfaces. There are also limitations in existing bilayer printing capabilities since most approaches are restricted to either deposition alone or to fixed microarray patterning. By combining advances in lipid surface chemistry and on-demand inkjet printing, we demonstrate the direct deposition and patterning of covalently tethered lipid bilayer membranes on titanium oxide surfaces, in ambient conditions and without any surface pretreatment process. The deposition conditions were evaluated by quartz crystal microbalance-dissipation (QCM-D) measurements, with corresponding resonance frequency (Δf) and energy dissipation (ΔD) shifts of around −25 Hz and <1 × 10−6, respectively, that indicated successful bilayer printing. The resulting printed phospholipid bilayers are stable in air and do not collapse following dehydration; through rehydration, the bilayers regain their functional properties, such as lateral mobility (>1 µm2/s diffusion coefficient), according to fluorescence recovery after photobleaching (FRAP) measurements. By taking advantage of the lipid bilayer patterned architectures and the unique features of titanium oxide’s photoactivity, we further show how patterned cell culture arrays can be fabricated. Looking forward, this work presents new capabilities to achieve stable lipid bilayer patterns that can potentially be translated into implantable biomedical devices.

Soft Bioelectronics Based on Nanomaterials

Recent advances in nanostructured materials and unconventional device designs have transformed the bioelectronics from a rigid and bulky form into a soft and ultrathin form and brought enormous advantages to the bioelectronics. For example, mechanical deformability of the soft bioelectronics and thus its conformal contact onto soft curved organs such as brain, heart, and skin have allowed researchers to measure high-quality biosignals, deliver real-time feedback treatments, and lower long-term side-effects in vivo. Here, we review various materials, fabrication methods, and device strategies for flexible and stretchable electronics, especially focusing on soft biointegrated electronics using nanomaterials and their composites. First, we summarize top-down material processing and bottom-up synthesis methods of various nanomaterials. Next, we discuss state-of-the-art technologies for intrinsically stretchable nanocomposites composed of nanostructured materials incorporated in elastomers or hydrogels. We also briefly discuss unconventional device design strategies for soft bioelectronics. Then individual device components for soft bioelectronics, such as biosensing, data storage, display, therapeutic stimulation, and power supply devices, are introduced. Afterward, representative application examples of the soft bioelectronics are described. A brief summary with a discussion on remaining challenges concludes the review.

Microstructural, electrical and biological activity in [Formula: see text] ceramic composites designed for tissue engineering applications

The article investigates electrically active ceramic composite of [Formula: see text] (HAP) and [Formula: see text] (BST) for biomedical applications. The study is a systematic blend of the materials science aspect of composites with a special focus on the dielectric and biological properties and their relationships. The article emphasized primarily extracting the dielectric constant ([Formula: see text] of the specimens (that lay in the range of 3-65) and related them to microstructural properties like the grain size and at.% of BST. A broad outlook on the importance of [Formula: see text] in determining the suitability of bioceramics for clinical applications is presented. Bioactivity analysis of the specimens led to probing the surface charges (that were negative), and it was found crucial to the growth of dense apatite layers. Furthermore, the cytocompatibility of the specimens displayed cell viability above 100% for Day 1, which increased substantially for Day 3. To reveal other biological properties of the composites, protein adsorption studies using bovine serum albumin (BSA) and fetal bovine serum (FBS) was carried out. Electrostatic interactions govern the adsorption, and the mathematical dependence on surface charges is linear. The protein adsorption is also linearly correlated with the [Formula: see text], intrinsic to the biomaterials. We delve deeper into protein-biomaterials interactions by considering the evolution of the secondary structure of BSA adsorbed into the specimens. Based on the investigations, 20 at.% HAP-80 at.% BST (20H-80B) was established as a suitable composite comprising the desired features of HAP and BST. Such explorations of electrical and biological properties are interesting for modulating the behavior of bioceramic composites. The results project the suitability of 20H-80B for designing electrically active smart scaffolds for the proposed biomedical applications and are expected to incite further clinical trials.

How do packet losses affect measures of averaged neural signalsƒ

Recent advances in implanted device development have enabled chronic streaming of neural data to external devices allowing for long timescale, naturalistic recordings. However, characteristic data losses occur during wireless transmission. Estimates for the duration of these losses are typically uncertain reducing signal quality and impeding analyses. To characterize the effect of these losses on recovery of averaged neural signals, we simulated neural time series data for a typical event-related potential (ERP) experiment. We investigated how the signal duration and the degree of timing uncertainty affected the offset of the ERP, its duration in time, its amplitude, and the ability to resolve small differences corresponding to different task conditions. Simulations showed that long timescale signals were generally robust to the effects of packet losses apart from timing offsets while short timescale signals were significantly delocalized and attenuated. These results provide clarity on the types of signals that can be resolved using these datasets and provide clarity on the restrictions imposed by data losses on typical analyses.

Functionalized Elastomers for Intrinsically Soft and Biointegrated Electronics

Elastomers are suitable materials for constructing a conformal interface with soft and curvilinear biological tissue due to their intrinsically deformable mechanical properties. Intrinsically soft electronic devices whose mechanical properties are comparable to human tissue can be fabricated using suitably functionalized elastomers. This article reviews recent progress in functionalized elastomers and their application to intrinsically soft and biointegrated electronics. Elastomers can be functionalized by adding appropriate fillers, either nanoscale materials or polymers. Conducting or semiconducting elastomers synthesized and/or processed with these materials can be applied to the fabrication of soft biointegrated electronic devices. For facile integration of soft electronics with the human body, additional functionalization strategies can be employed to improve adhesive or autonomous healing properties. Recently, device components for intrinsically soft and biointegrated electronics, including sensors, stimulators, power supply devices, displays, and transistors, have been developed. Herein, representative examples of these fully elastomeric device components are discussed. Finally, the remaining challenges and future outlooks for the field are presented.

Wireless Power Transfer and Telemetry for Implantable Bioelectronics

Implantable bioelectronic devices are becoming useful and prospective solutions for various diseases owing to their ability to monitor or manipulate body functions. However, conventional implantable devices (e.g., pacemaker and neurostimulator) are still bulky and rigid, which is mostly due to the energy storage component. In addition to mechanical mismatch between the bulky and rigid implantable device and the soft human tissue, another significant drawback is that the entire device should be surgically replaced once the initially stored energy is exhausted. Besides, retrieving physiological information across a closed epidermis is a tricky procedure. However, wireless interfaces for power and data transfer utilizing radio frequency (RF) microwave offer a promising solution for resolving such issues. While the RF interfacing devices for power and data transfer are extensively investigated and developed using conventional electronics, their application to implantable bioelectronics is still a challenge owing to the constraints and requirements of in vivo environments, such as mechanical softness, small module size, tissue attenuation, and biocompatibility. This work elucidates the recent advances in RF-based power transfer and telemetry for implantable bioelectronics to tackle such challenges.

In vivo biocompatibility of diamond-like carbon films containing TiO2 nanoparticles for biomedical applications

Hybrid diamond-like carbon (DLC) with incorporated titanium dioxide (TiO₂) nanoparticle coatings have low friction coefficient, high wear resistance, high hardness, biocompatibility, and high chemical stability. They could be employed to modify biomedical alloys surfaces for numerous applications in biomedical engineering. Here we investigate for the first time the in vivo inflammatory process of DLC coatings with incorporated TiO₂ nanoparticles. TiO₂-DLC films were grown on AISI 316 stainless-steel substrates using plasma-enhanced chemical vapor deposition. The coated substrates were implanted in CF1 mice peritoneum. The in vivo cytotoxicity and biocompatibility of the samples were analyzed from macrophage lavage. Analysis in the first weeks after implantation could be helpful to evaluate the acute cytotoxicity generated after a possible inflammatory process. The in vivo results showed no inflammatory process. A significant increase in nitric oxide production on the uncoated substrates was confirmed through cytometry, and the coated substrates demonstrated biocompatibility. The presence of TiO₂ nanoparticles enhanced the wound healing activity, due to their astringent and antimicrobial properties. DLC and TiO₂-DLC coatings were considered biocompatible, and the presence of TiO₂ nanoparticles reduced the inflammatory reactions, increasing DLC biocompatibility.

Bioinspired, Nanostructure-Amplified, Subcutaneous Light Harvesting to Power Implantable Biomedical Electronics

Implantable biomedical electronics hold immense promise for in vivo personalized healthy monitoring and even precise therapeutic intervention. Tremendous miniaturization of indwelling modules enables implanted biomedical devices to perform multiple functions with ultralow power consumption but exacerbates the technical challenges of supplying effective power to the devices in vivo. In this Perspective, we summarize new developments in transmitting near-infrared light from sunlight or a light-emitting diode into subcutaneously implanted photovoltaic cells, in which the light utilization efficiency can be amplified with the aid of nanostructured rear reflectors. Considering the many natural examples of nanostructure-induced structural coloration displayed by submarine animals, we wish to open up new prospects of bioinspired, nanostructure-amplified, subcutaneous light harvesting to power implanted biomedical electronics.