Implantable Biomedical Devices Research Articles

Designing of intelligent PID controller for cardiac pacemaker using artificial bee colony algorithm

ABSTRACT For real-time patient heart rate management, most widely used biomedical implantable devices in the cardiovascular system is the cardiac pacemaker (CP). A key factor in keeping the patient alive is the development of novel heart pacing techniques which can reduce the risk of cardiac arrhythmia. The present work is inspired to achieve this goal. To achieve an accurate, controlled, and regulated heart rate, a pacemaker with an intelligent proportional integral derivative (PID) controller is considered. The proposed PID controller is an integration of the traditional PID controller with appropriate tuning, that uses a swarm intelligence-based artificial bee colony (ABC) algorithm for handling the bio-electrical signals. To ensure the efficacy of the proposed controller experiments are conducted. MATLAB/Simulink software is used to test and simulate the suggested model and to adjust the controller gains. The simulation is performed in the time and frequency domain. The resulting pulse rate from the ABC-PID controller has a rise time (0.0985 s), settling time (0.3293 s), maximum overshoot (0.111367%), and MSE (0.0040565). External disturbances of various duty cycles are also introduced in the proposed CP control system. The proposed ABC-PID controller for implanted pacemakers reduces the risk of heart rate over-run.

Electrografted mixed organic monolayers as antibacterial coatings for implantable biomedical devices

Bacterial infections associated with the implantation of biomedical devices belong to one of the leading causes of their failure. Accordingly, novel methods of surface modifications are highly required to prevent bacterial adhesion and limit the use of antibiotics. Electrochemical grafting of organic moieties is a well-known method of surface modification at the nanoscale level, allowing for the modulation of surface wettability, roughness, and the ability to enhance/reduce cellular adhesion, among others. In this work, the presence of an organic coating formed through the electrografting of a mixture of diazonium salts is proposed to tailor interactions between the surface and a living matter. Through the application of diazonium compounds possessing different functional groups, it is possible to alter electrochemical and surface properties, as well as cell survivability and anti-adhesive activity towards bacteria. It is shown that the presence of organic layers results in 4.5-fold increase in the wettability of the surface and 1.5-fold increase in roughness, leading to the 84% decrease in bacterial adhesion without affecting surface's biocompatibility. In this way, mixed organic monolayers formed through the electroreduction of a mixture of diazonium salts can serve as antibacterial coatings suitable for implantable biomedical devices.

The potential of organic piezoelectric materials for next-generation implantable biomedical devices

Piezoelectricity or piezoelectric effect is a phenomenon by which mechanical energy is converted into electrical energy and vice versa. Piezoelectric effect has been observed in several organic materials. Therefore, in past few years organic piezoelectric materials have received significant research interests in biomedical applications and specifically for fabrication of implantable biomedical devices because of their high piezoelectric performance, excellent biocompatibility and biodegradability, superior mechanical properties, and cheap fabrication process. This article provides a comprehensive review of the recent research progress on organic piezoelectric materials. It extensively covers the piezoelectric properties and preparation methods of different organic piezoelectric materials including amino acids, peptides, proteins, polysaccharides, and polymers (such as PVDF, PLLA, PHB), as well as their representative implantable biomedical device applications namely biosensing, tissue regeneration, and drug delivery. Finally, the article discusses the challenges and future directions of this research field.

Interfacial Polarization Locked Flexible β-Phase Glycine/Nb2 CTx Piezoelectric Nanofibers.

Biomolecular piezoelectric materials show great potential in the field of wearable and implantable biomedical devices. Here, a self-assemble approach is developed to fabricating flexible β-glycine piezoelectric nanofibers with interfacial polarization locked aligned crystal domains induced by Nb2 CTx nanosheets. Acted as an effective nucleating agent, Nb2 CTx nanosheets can induce glycine to crystallize from edges toward flat surfaces on its 2D crystal plane and form a distinctive eutectic structure within the nanoconfined space. The interfacial polarization locking formed between O atom on glycine and Nb atom on Nb2 CTx is essential to align the β-glycine crystal domains with (001) crystal plane intensity extremely improved. This β-phase glycine/Nb2 CTx nanofibers (Gly-Nb2 C-NFs) exhibit fabulous mechanical flexibility with Young's modulus of 10 MPa, and an enhanced piezoelectric coefficient of 5.0 pCN-1 or piezoelectric voltage coefficient of 129×10-3 VmN-1 . The interface polarization locking greatly improves the thermostability of β-glycine before melting (≈210°C). A piezoelectric sensor based on this Gly-Nb2 C-NFs is used for micro-vibration sensing in vivo in mice and exhibits excellent sensing ability. This strategy provides an effective approach for the regular crystallization modulation for glycine crystals, opening a new avenue toward the design of piezoelectric biomolecular materials induced by 2D materials.

Human-friendly flexible solid-state biodegradable supercapacitor based on Ti3C2Tx MXene film without adhesive structure

With the rapid development of biomedical technology, biodegradable and implantable energy storage devices for biosensor and bioelectronics applications have attracted the great attention of scientists. However, the limited energy density, poor biocompatibility, and excessive space occupation of existing biodegradable energy storage devices pose major challenges to their application in the biomedical field. To address these challenges, in this work, flexible Ti3C2Tx film with an adhesive-free structure construction is proposed as electrode material for the flexible solid-state biodegradable supercapacitor (FSBSC). The morphology and structure of MXene films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A 0.9% NaCl saline, similar human body fluids was used as the electrolyte solution to construct symmetrical FSBSC (Ti3C2Tx//NaCl-PVA//Ti3C2Tx-FSBSC) Poly(vinyl alcohol) (PVA). The Ti3C2Tx//NaCl-PVA//Ti3C2Tx-FSBSC exhibits a high capacitance of 112 F/g at 1 A/g, excellent rate capability (73.2% at 20 A/g), long lifetime (81.6% after 10,000 cycles), and high specific energy/power (62.3 Wh/kg at 1000.8 W/kg). The charge storage mechanism was analyzed using ex situ XRD, TEM, and density function theory (DFT). DFT results show that the Ti3C2Tx (Tx = O)) electrode possesses metallic properties. The calculated adsorption energies (Eads) and smaller diffusion barriers of Na+ ions further proved the outstanding performance of the Ti3C2Tx electrode. Moreover, the apparatus is entirely biodegradable, thereby paving a promising path for the progression of bioelectronics and biomedical energy storage technologies.

Fibrous capsule-resistant, controllably degradable and functionalizable zwitterion-albumin hybrid hydrogels.

Foreign body response (FBR) represents an immune-mediated cascade reaction capable of inducing the rejection of foreign implants, thereby compromising their in vivo performance. Pure zwitterionic hydrogels have demonstrated the ability to resist long-term FBR, owing to their outstanding antifouling capabilities. However, achieving such a robust anti-FBR effect necessitates stringent requirements concerning the purity of zwitterionic materials, which constrains their broader functional applications. Herein, we present a biocompatible, controllably degradable, and functionalizable zwitterion-albumin hybrid hydrogel. The zwitterionic hydrogel crosslinked with serum albumin exhibits controllable degradation and excels in preventing the adsorption of various proteins and adhesion of cells and bacteria. Moreover, the hydrogel significantly alleviates the host's FBR compared with PEG hydrogels and particularly outperforms PEG-based cross-linker crosslinked zwitterionic hydrogels in reducing collagen encapsulation when subcutaneously implanted into mice. The zwitterion-albumin hybrid hydrogel shows potential as a functionalizable anti-FBR material in the context of implantable materials and biomedical devices.

In vivo flexible energy harvesting on porcine heart via highly-piezoelectric PIN–PMN–PT single crystal

One of the main challenges with implantable biomedical devices is the replacement surgeries of depleted batteries for elderly patients. This not only poses medical risks but also results in financial burdens. Consequently, there is a growing need for self-powered in vivo electronics that can convert the biomechanical movements of organs into usable electric energy. Notably, a previously reported in vivo flexible energy harvester generated relatively low current output from a living porcine heart, restricting its ability to operate self-powered electronic devices. In this study, a high current output implantable flexible energy harvester was demonstrated by adopting a highly-piezoelectric single crystal Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) film. The in vivo flexible energy harvester generated a short-circuit output current of 20 µA (corresponding to a current density of 3.08 µA/mm3) from the contraction and relaxation of a porcine heart. This recorded in vivo output current density was attributed to its outstanding piezoelectric charge coefficient of the single crystal PIN-PMN-PT, optimized Ni stressor assisted exfoliation as well as the implementation of a metal-insulator-metal (MIM) structure. Moreover, the flexible energy harvester was also demonstrated as a self-powered cardiac sensor to monitor irregular heartbeats by observing heart rate variations due to drug administration in a porcine heart. Additionally, output performance evaluation was conducted with the chest closed to further assess the feasibility of practical in vivo harvesting. Finally, the single crystal harvester exhibited biocompatibility, showing no signs of cytotoxicity based on cell viability assessments and histological characterizations. These results underscore the potential of the flexible PIN-PMN-PT energy harvesting device as a sustainable power source for self-powered in vivo biomedical electronics.

Piezoelectric nanogenerators for self-powered wearable and implantable bioelectronic devices.

One of the recent innovations in the field of personalized healthcare is the piezoelectric nanogenerators (PENGs) for various clinical applications, including self-powered sensors, drug delivery, tissue regeneration etc. Such innovations are perceived to potentially address some of the unmet clinical needs, e.g., limited life-span of implantable biomedical devices (e.g., pacemaker) and replacement related complications. To this end, the generation of green energy from biomechanical sources for wearable and implantable bioelectronic devices gained considerable attention in the scientific community. In this perspective, this article provides a comprehensive state-of-the-art review on the recent developments in the processing, applications and associated concerns of piezoelectric materials (synthetic/biological) for personalized healthcare applications. In particular, this review briefly discusses the concepts of piezoelectric energy harvesting, piezoelectric materials (ceramics, polymers, nature-inspired), and the various applications of piezoelectric nanogenerators, such as, self-powered sensors, self-powered pacemakers, deep brain stimulators etc. Important distinction has been made in terms of the potential clinical applications of PENGs, either as wearable or implantable bioelectronic devices. While discussing the potential applications as implantable devices, the biocompatibility of the several hybrid devices using large animal models is summarized. This review closes with the futuristic vision of integrating data science approaches in developmental pipeline of PENGs as well as clinical translation of the next generation PENGs. STATEMENT OF SIGNIFICANCE: Piezoelectric nanogenerators (PENGs) hold great promise for transforming personalized healthcare through self-powered sensors, drug delivery systems, and tissue regeneration. The limited battery life of implantable devices like pacemakers presents a significant challenge, leading to complications from repititive surgeries. To address such a critical issue, researchers are focusing on generating green energy from biomechanical sources to power wearable and implantable bioelectronic devices. This comprehensive review critically examines the latest advancements in synthetic and nature-inspired piezoelectric materials for PENGs in personalized healthcare. Moreover, it discusses the potential of piezoelectric materials and data science approaches to enhance the efficiency and reliability of personalized healthcare devices for clinical applications.

Recent advancements in piezoelectric energy harvesting for implantable medical devices

Biomedical implantable devices like deep brain stimulators, implantable cardioverter-defibrillators and cardiac pacemakers are essential for treating the human heart and brain-related diseases. In the past few decades, a considerable amount of research has focused on improving bio-implant technologies. Conventional bio implant devices consist of an external generator like a battery to power the system, which requires replacement after a particular time. Therefore, in recent years, self-powered implants with various energy harvesting techniques have been proposed to avoid frequent surgery for battery replacement and to miniaturise the implant systems. However, the research communities have yet to explore all the limitations and possibilities of improvement on such energy-scavenging technologies, especially when the application is in vivo. Several aspects of recent developments in energy harvesting technologies feasible for biomedical implantable devices are reported systematically. A detailed review of piezoelectric energy harvester mechanism and miniaturisation, electric output and power management and biocompatibility of an energy harvester for implantable medical devices in vitro and in vivo environments. Furthermore, the piezoelectric energy harvester’s durability, packaging material, connection and evaluation criteria are discussed.

Large-area, stretchable, ordered silver nanowires electrode by superwetting-induced transfer of ionic liquid@silver nanowires complex

Stretchable transparent electrodes (STEs) are widely used in electronic skin, implantable biomedical devices and wearable devices, which need to meet metal-like conductivity and high transparency while being prepared in a large area. Silver nanowires are the most widely used material to construct conductive networks because of their excellent optoelectrical properties. However, the silver nanowires-based networks prepared by conventional large-area preparation processes are generally composed of disordered silver nanowires, which suffer both high junction resistance and high diffuse reflection. Herein, a large-area, stretchable, ordered silver nanowires electrode is prepared by superwetting-induced transfer of a self-assembled complex composed of ionic liquid (1-ethyl-3-methylimidazolium (bis-trifluoromethane sulfonyl) imide) and silver nanowires onto stretchable substrates. Then, electroless-welding is used to further reduce the junction resistance between silver nanowires. The generated STE shows a low sheet resistance of 26–46 Ω sq−1 and a high transmittance of 84 %–88 % at 550 nm. The STE is successfully applied for transparent heating devices, exhibiting high heating performance and tensile stability. This study provides a new method for the preparation of large-area high-performance STE for the next generation of stretchable devices.

A Survey of the Thermal Analysis of Implanted Antennas for Wireless Biomedical Devices.

Wireless implantable biomedical devices (IBDs) are emerging technologies used to enhance patient treatment and monitoring. The performance of wireless IBDs mainly relies on their antennas. Concerns have emerged regarding the potential of wireless IBDs to unintentionally cause tissue heating, leading to potential harm to surrounding tissue. The previous literature examined temperature estimations and specific absorption rates (SAR) related to IBDs, mainly within the context of thermal therapy applications. Often, these studies consider system parameters such as frequency, input power, and treatment duration without isolating their individual impacts. This paper provides an extensive literature review, focusing on key antenna design parameters affecting heat distribution in IBDs. These parameters encompass antenna design, treatment settings, testing conditions, and thermal modeling. The research highlights that input power has the most significant impact on localized temperature, with operating frequency ranked as the second most influential factor. While emphasizing the importance of understanding tissue heating and optimizing antennas for improved power transfer, these studies also illuminate existing knowledge gaps. Excessive tissue heat can lead to harmful effects such as vaporization, carbonization, and irreversible tissue changes. To ensure patient safety and reduce expenses linked to clinical trials, employing simulation-driven approaches for IBD antenna design and optimization is essential.

A multiband SSr diode RF rectifier with an improved frequency ratio for biomedical wireless applications

This paper described a four-band implantable RF rectifier with simplified circuit complexity. Each RF-rectifier cell is sequentially matched to the four operational frequencies to accomplish the proposed design. The proposed RF rectifier can harvest RF signals at 1.830, 2.100, and white space Wi-Fi bands between 2.38 to 2.68 GHz, respectively. At 2.100 GHz, the proposed RF harvester achieved a maximum (radio frequency direct current) RF-to-DC power conversion efficiency (PCE) of 73.00% and an output DC voltage V_{DC} of 1.61 V for an RF power of 2 dBm. The outdoor performance of the rectenna shows a V_{DC} of 0.440 V and drives a low-power bq25504-674 evaluation module (EVM) at 1.362 V. The dimension of the RF-rectifier on the FR-4 PCB board is 0.27lambda _{g}times 0.29lambda _{g}. The RF-rectifier demonstrates the capacity to effectively utilize the frequency domain by employing multi-band operation and exhibiting a good impedance bandwidth through a sequential matching technique. Thus, by effectively controlling the rectenna’s ambient performance, the proposed design holds the potential for powering a range of low-power biomedical implantable devices. (BIDs).

Flexing the Spectrum: Advancements and Prospects of Flexible Electrochromic Materials.

The application potential of flexible electrochromic materials for wearable devices, smart textiles, flexible displays, electronic paper, and implantable biomedical devices is enormous. These materials offer the advantages of conformability and mechanical robustness, making them highly desirable for these applications. In this review, we comprehensively examine the field of flexible electrochromic materials, covering topics such as synthesis methods, structure design, electrochromic mechanisms, and current applications. We also address the challenges associated with achieving flexibility in electrochromic materials and discuss strategies to overcome them. By shedding light on these challenges and proposing solutions, we aim to advance the development of flexible electrochromic materials. We also highlight recent advances in the field and present promising directions for future research. We intend to stimulate further innovation and development in this rapidly evolving field and encourage researchers to explore new opportunities and applications for flexible electrochromic materials. Through this review, readers can gain a comprehensive understanding of the synthesis, design, mechanisms, and applications of flexible electrochromic materials. It serves as a valuable resource for researchers and industry professionals looking to harness the potential of these materials for various technological applications.

Lubricant skin on diverse biomaterials with complex shapes via polydopamine-mediated surface functionalization for biomedical applications.

Implantable biomedical devices require an anti-biofouling, mechanically robust, low friction surface for a prolonged lifespan and improved performance. However, there exist no methods that could provide uniform and effective coatings for medical devices with complex shapes and materials to prevent immune-related side effects and thrombosis when they encounter biological tissues. Here, we report a lubricant skin (L-skin), a coating method based on the application of thin layers of bio-adhesive and lubricant-swellable perfluoropolymer that impart anti-biofouling, frictionless, robust, and heat-mediated self-healing properties. We demonstrate biocompatible, mechanically robust, and sterilization-safe L-skin in applications of bioprinting, microfluidics, catheter, and long and narrow medical tubing. We envision that diverse applications of L-skin improve device longevity, as well as anti-biofouling attributes in biomedical devices with complex shapes and material compositions.

Hybrid Energy Harvesting for Self-powered Implantable Biomedical Devices

Hybrid Energy Harvesting for Self-powered Implantable Biomedical Devices

Omni-Directional Ultrasonic Powering via Platonic Solid Receiver for mm-Scale Implantable Devices

Despite the recent advancements in implantable microdevices, providing sufficient electrical power to deeply seated microsystems has remained challenging due to the small dimension of the system, limiting the total storable energy. Ultrasound powering, where a portion of the externally induced ultrasonic wave is converted to electrical power by a small receiver, has been explored as an attractive source of power, especially for deeply seated implantable microdevices. While all other components have been advanced and miniaturized, the ultrasonic receiver is still a slab of bulk piezoelectric materials, e.g., diced PZT (lead zirconate titanate). Such a rectangular or disc shape is not an ideal form factor for wireless ultrasonic power transfer due to many challenges, particularly angular sensitivity with respect to an incoming ultrasonic wave. In this paper, we present the first demonstration of omnidirectional ultrasonic powering enabled by the high geometrical symmetry of three-dimensional polyhedral shapes. Based on our 3D printing technique of lead-free piezoelectric barium titanate ceramic, we designed highly symmetric, miniaturized, regular polyhedra, known as Platonic solids (i.e., cube, octahedron, dodecahedron), as well as a sphere. For each geometry, we investigate the effect of axial and radial piezoelectric poling, output power levels, efficiency, and angular sensitivity while the surface areas are the same. Across all the geometric shapes, radially poled Platonic solid receivers produce at least 1 order of magnitude larger electrical power density compared to diced PZT. Further, we observed that the higher the order of Platonic solid, the more excellent power transfer efficiency and omnidirectionality. The 3D printability of the Platonic solid also allows for customizable packaging, which we implemented as an implantable light source. Overall, the proposed ultrasonic powering scheme warrants a revolutionary solution for implantable biomedical devices.

Controlling C2C12 Cytotoxicity on Liquid Metal Embedded Elastomer (LMEE).

Liquid metal embedded elastomers (LMEEs) are highly stretchable composites comprising microscopic droplets of eutectic gallium-indium (EGaIn) liquid metal embedded in a soft rubber matrix. They have a unique combination of mechanical, electrical, and thermal properties that make them attractive for potential applications in flexible electronics, thermal management, wearable computing, and soft robotics. However, the use of LMEEs in direct contact with human tissue or organs requires an understanding of their biocompatibility and cell cytotoxicity. In this study, the cytotoxicity of C2C12 cells in contact with LMEE composites composed of EGaIn droplets embedded with a polydimethylsiloxane (PDMS) matrix is investigated. In particular, the influence of EGaIn volume ratio and shear mixing time during synthesis on cell proliferation and viability is examined. The special case of electrically-conductive LMEE composites in which a percolating network of EGaIn droplets is created through "mechanical sintering" is also examined. This study in C2C12 cytotoxicity represents a first step in determining whether LMEE is safe for use in implantable biomedical devices and biohybrid systems.

Polydopamine/graphene oxide coatings loaded with tetracycline and green Ag nanoparticles for effective prevention of biofilms

Bacterial adhesion and biofilm formation are significant challenges for medical devices and implants. Surface modification to alter the surface properties of biomedical device surfaces to prevent the biofilm formation is an important driving force for the development of anti-biofilm coatings. Here, a simple and feasible method to fabricate antibacterial coatings that combines the adhesion properties of polydopamine (PDA) and the high drug loading capacity of graphene oxide (GO). Tetracycline and green-synthesized silver nanoparticles were successfully assembled onto the coating surface, endowing the coating an anti-biofilm effect and exhibit strong inhibitory effect on S. aureus and E. coli biofilms by a factor of more than 1000 (3 log10 units). Kirby-Bauer diffusion test, colony forming unit (CFU) counts, biofilm topography studies and live/dead staining were used to evaluate the antibacterial activity of the coatings. This study is proposed that PDA/GO coatings loaded with antibiotics or silver nanoparticles can be used as a potential approach to prevent infection associated with implantable biomedical devices.

Incorporating Tantalum Oxide Nanoparticles into Implantable Polymeric Biomedical Devices for Radiological Monitoring.

Longitudinal radiological monitoring of biomedical devices is increasingly important, driven by the risk of device failure following implantation. Polymeric devices are poorly visualized with clinical imaging, hampering efforts to use diagnostic imaging to predict failure and enable intervention. Introducing nanoparticle contrast agents into polymers is a potential method for creating radiopaque materials that can be monitored via computed tomography. However, the properties of composites may be altered with nanoparticle addition, jeopardizing device functionality. Thus, the material and biomechanical responses of model nanoparticle-doped biomedical devices (phantoms), created from 0-40 wt% tantalum oxide (TaOx ) nanoparticles in polycaprolactone and poly(lactide-co-glycolide) 85:15 and 50:50, representing non, slow, and fast degrading systems, respectively, are investigated. Phantoms degrade over 20 weeks in vitro in simulated physiological environments: healthy tissue (pH 7.4), inflammation (pH 6.5), and lysosomal conditions (pH 5.5), while radiopacity, structural stability, mechanical strength, and mass loss are monitored. The polymer matrix determines overall degradation kinetics, which increases with lower pH and higher TaOx content. Importantly, all radiopaque phantoms could be monitored for a full 20 weeks. Phantoms implanted in vivo and serially imaged demonstrate similar results. An optimal range of 5-20 wt% TaOx nanoparticles balances radiopacity requirements with implant properties, facilitating next-generation biomedical devices.

Combustion-Synthesized KNiPO4: A Non-toxic, Robust, Intercalating Battery-Type Pseudocapacitive Electrode for Hybrid Supercapacitors as a Large-Scale Energy Storage Solution

Polyanionic-type electrode material made of (PO4)n− polyhedral covalently bonded with Ni–O linkage is envisaged as a novel electrode material for intercalative battery-type hybrid supercapacitors. Highly porous, flake-type KNiPO4 showed robust electrochemical performances as a result of its open framework structure and active participation of the Ni2+/3+ redox couple that results in superior pseudocapacitive intercalating charge storage in the aqueous KOH electrolyte. The KNiPO4 electrode shows the specific charge storage equivalent to 168.5 mAh/g (capacitance of 935 F/g) at 1 A/g current rate in the potential window of 0.65 V in the aqueous 2 M KOH electrolyte. KNiPO4 electrodes exhibit excellent long-term cycle stability at 10 A/g for 5000 cycles with 87% of the initial capacity retention of the electrode and coulombic efficiency (η = td/tc) equivalent to 95.1% after 5000 cycles. Further, in full cell hybrid supercapacitor (HSC) mode in which porous KNiPO4 acted as the positive electrode and activated carbon (AC) functioned as the negative electrode, in the voltage window of 1.6 V, the highest energy density equivalent to 200 Wh/kg and power density equivalent to ∼819 W/kg were obtained at 1 A/g current rate. At a higher current rate (10 A/g), the hybrid supercapacitor attains a very high power density equivalent to 7981 W/kg with a retention of energy density close to 75 Wh/kg with superior cyclic stability. Coulombic efficiency of the full cell [asymmetric supercapacitor (ASC) mode] has lost only 3.4% with excellent capacity retention (92.3%) of its initial value after 2200 cycles. The robust performance and long cycle life of the electrode in full cells confirm the applicability of the material to power implantable biomedical devices. Further, high power performance coupled with superior cyclic stability coupled with strong electrochemical energy storage properties of the KNiPO4 electrode makes it suitable for bulk, grid-level charge storage applications.