The central engineering challenge is deceptively simple to state. A battery must store and deliver meaningful energy, yet every component—anode, cathode, electrolyte, separator, current collector and packaging—must remain stable during operation and then degrade predictably into products the body can metabolize or excrete. Conventional lithium-ion chemistry fails this test on nearly every count: lithium is reactive, the organic electrolytes are toxic, and the metal casings persist indefinitely. Designing around those constraints requires rethinking the battery from first principles, choosing electrode materials from the palette of biologically tolerated elements and finding ionic chemistries that function in aqueous, physiological environments.

Among the most promising strategies reported in recent work are metal–air and metal-based cells built around magnesium, zinc, iron, molybdenum and tungsten. Zinc, in particular, has attracted attention because it is an essential trace nutrient, electrochemically well behaved in neutral aqueous media, and yields benign zinc ions and hydroxide species upon discharge. Magnesium offers a higher theoretical voltage and specific capacity and is already widely used in biodegradable orthopedic implants, giving clinicians a long safety track record to draw upon. Pairing these metals with cathodes made from oxides, phosphates or even bio-derived molecules such as iodine and quinones allows researchers to assemble complete cells whose every element participates in the body’s normal biochemistry.

Electrolytes present a subtler problem. The medium through which ions shuttle must conduct well, resist premature self-discharge, and dissolve cleanly afterward. Teams have explored hydrogels cross-linked from natural polymers, salt-loaded chitosan membranes, phosphate-buffered solutions held within biodegradable pouches, and solid polymer electrolytes based on polyethylene glycol and polylactic acid. The encapsulation strategy matters as much as the chemistry: a transient battery is only as transient as its slowest-dissolving layer. Researchers have therefore developed multilayer packaging from polyanhydrides, polycaprolactone and silk fibroin, tuning film thickness and crystallinity so that the operational lifetime can be programmed from days to months, much as drug-eluting stents control their release kinetics.

Power output has long been the Achilles heel of resorbable energy storage, since aqueous chemistries deliver lower cell voltages than lithium systems. The field has responded with clever circuit-level solutions. Stacking individual cells in series within a single package boosts voltage to the levels needed by microcontrollers, radios and sensors, while parallel arrays extend operating time. Reports of transient batteries generating on the order of one to a few volts, sufficient to power cardiac pacemakers in large animal models and to drive wireless transmission from implantable sensors, have shifted the conversation from feasibility to engineering refinement. Energy densities approaching levels useful for clinical devices have been demonstrated in packages small enough to fit within the capsule formats familiar from swallowable diagnostics.

The ingestible application is arguably the most immediate. Electronic capsules that sample the gastrointestinal tract, deliver drugs on schedule, or monitor pH, temperature and pressure currently contain rigid, persistent hardware. A power source that dissolves after a defined period means the device can be designed to break apart and pass or absorb without intervention, reducing the risk of retained foreign bodies and simplifying regulatory pathways. Transient batteries have been engineered to survive the acidic environment of the stomach, activate in the intestine, and maintain output long enough to complete a diagnostic or therapeutic mission before their hydrogel electrolytes swell, weaken and finally dissolve into the surrounding fluid.

Implanted applications raise the stakes in different ways. Temporary pacemakers intended to support patients after cardiac surgery, biodegradable sensors for monitoring wound healing, and stimulators for nerve regeneration all require power for days to weeks and none of the encumbrance of permanent hardware. In animal studies, resorbable battery packs have successfully paced hearts at clinically relevant rates and then degraded over weeks with no significant inflammatory response, the degradation products appearing at concentrations well within physiological tolerance. Surgeons and cardiologists watching these demonstrations see a path to devices that avoid the extraction procedures, infections and device erosion complications that complicate conventional implants.

Safety evaluation is where laboratory promise meets biological reality, and the field has been accumulating the necessary evidence. Biocompatibility testing of the constituent materials—zinc, magnesium, molybdenum, tungsten, silk, chitosan, PLGA and related polymers—shows degradation products that are cleared renally or metabolized into water and carbon dioxide. Histological examination of implantation sites typically reveals a mild, transient foreign-body response that resolves as the materials disappear. The critical design parameter is the balance of dissolution rates: the battery must not release its stored electrochemical charge or its degradation products faster than tissue clearance mechanisms can handle, a constraint that drives careful control of surface area, porosity and protective coatings.

Manufacturing and integration remain open questions on the road to commercialization. Many laboratory devices are assembled by hand from foils, films and gels; scaling to consistent, sterile, high-volume production demands reel-to-reel deposition, laser micromachining and packaging methods borrowed from flexible electronics. Integration with ultrathin silicon sensors, biodegradable antennas and dissolvable interconnects is advancing rapidly, driven by parallel progress in transient semiconductor research. As these threads converge, researchers envision complete diagnostic and therapeutic systems—power, electronics, antenna and all—that are implanted or swallowed, perform their function, and vanish, leaving nothing behind but a small, harmless chemical trace.

For patients, the implications extend beyond convenience. Eliminating extraction surgeries removes anesthesia risks, costs and anxiety; for pediatric and elderly populations especially, any procedure avoided is meaningful. For health systems, self-erasing devices could reduce long-term follow-up burdens. The research community is candid that clinical adoption will require years of validation, standardization of degradation timelines and regulatory frameworks adapted to hardware that is designed to fail safely. But the trajectory is clear: energy storage is joining the broader movement toward medical technology that respects the body’s own temporality, delivering function precisely when it is needed and then, quietly and completely, disappearing.

Subject of Research: Development of biodegradable, transient power sources for ingestible and implantable bioelectronics

Article Title: Bioresorbable batteries for transient ingestible bioelectronics

Article References: Say, M. G., Erus, A., Morgan, L., Cai, Y., Moon, I., Park, Y.-G., DeBruyn, B., Kang, Z., Parvataneni, K., Akouissi, O., Girand, O., You, S. S., Pettinari, A., Guevara, A., Laidlaw, B., Schmidt, K., Fabian, N., Hayward, A., & Traverso, G. (2026). Bioresorbable batteries for transient ingestible bioelectronics. Nature Chemical Engineering. https://doi.org/10.1038/s44286-026-00443-7

Image Credits: AI Generated

DOI: 10.1038/s44286-026-00443-7

Keywords: bioresorbable batteries, transient electronics, ingestible devices, biodegradable implants, zinc battery, magnesium anode, hydrogel electrolyte, biocompatibility, implantable sensors, transient pacemaker, biomedical engineering, dissolvable electronics

β-TCP is a calcium phosphate ceramic whose chemistry places it unusually close to the mineral phase of natural bone. Bone itself is a composite built from collagen fibers reinforced with poorly crystalline, calcium-phosphate-rich mineral, and the apatite that forms in and around β-TCP implants as the material degrades echoes that native chemistry. The authors highlight three properties that have made β-TCP a central figure in orthopedic biomaterials: excellent biocompatibility, controlled biodegradability, and mechanical behavior that can be matched to bone tissue. Unlike inert implant materials that remain permanently in the body, β-TCP is designed to disappear gradually, dissolving and being resorbed by bone-resorbing cells while new bone grows into the space it vacates. This resorbability is what transforms the implant from a static filler into an active participant in remodeling, the lifelong biological process by which bone is continuously broken down and rebuilt.

The review identifies a clear gap in the existing literature as its starting point. Previous overviews of β-TCP, the authors note, have concentrated mainly on comparing biological performance and discussing application prospects, leaving the synthesis and preparation methods, the curing and osteogenic mechanisms, and the performance-optimization strategies insufficiently integrated. A clinician or materials engineer searching for guidance has therefore had to consult fragmented sources to answer questions that are really one connected question: how do choices made in the laboratory or factory cascade through material structure, physicochemical behavior, and cellular response to determine whether a bone defect heals? The new review is organized to answer that question end to end, beginning with the characteristics and structural foundations of β-TCP and moving systematically through synthesis, curing behavior, property regulation, biological mechanism, and clinical application.

Synthesis sits at the foundation of that chain. The way β-TCP crystals are created determines their phase purity, crystallinity, grain size, and elemental composition, and each of those parameters feeds forward into degradation rate and biological response. Established routes described in the literature include solid-state reactions, in which calcium-deficient or mixed calcium phosphate precursors are calcined at high temperature to form the β phase, and wet-chemical precipitation, in which calcium and phosphate ions are combined in solution under controlled pH and temperature before being heat-treated. Sol-gel processing offers molecular-level mixing and fine, homogeneous powders, while hydrothermal and other solution-based methods can tailor crystal morphology directly. The review also surveys emerging pathways that reflect the modern push toward materials engineered at ever finer scales, including routes designed to produce the highly porous, interconnected architectures that bone tissue requires for vascular ingrowth and cell migration.

A distinctive feature of the review is its treatment of curing behavior, which connects β-TCP to the clinically important class of self-setting calcium phosphate bone cements. These cements are formed as powders that react with an aqueous liquid at physiological temperature, hardening in situ inside a defect and conforming to its irregular shape. For surgeons, this injectable or moldable character solves a persistent problem with prefabricated ceramic blocks, which are difficult to fit precisely into complex defects. The review analyzes the setting reactions and the factors that govern them, since setting time, cohesion in the presence of blood and body fluids, and the mechanical integrity of the hardened cement all determine whether a cement can survive the surgical window and the early loading period that follow implantation.

The physicochemical side of the review maps the regulatory mechanisms through which processing controls performance. Porosity, for example, exists on multiple scales: micrometer-scale pores provide surfaces and spaces for cell attachment and fluid transport, while larger, interconnected channels allow blood vessels and bone tissue to infiltrate. Grain size and sintering conditions set the balance between mechanical strength and dissolution rate, because denser, coarser ceramics tend to be stronger but slower to resorb, whereas more soluble, finer structures degrade faster but may lack support capacity. Phase composition matters as well, since residual secondary phases such as hydroxyapatite or calcium pyrophosphate can shift both resorption behavior and local chemistry. By systematically linking each of these controllable parameters to its biological consequence, the review provides the kind of design map that researchers developing next-generation implants have lacked.

On the biological side, the review connects material properties to the cellular machinery of osteogenesis. When β-TCP contacts physiological fluid, partial dissolution releases calcium and phosphate ions into the local environment, elevating supersaturation and favoring the deposition of carbonate-containing apatite on the implant surface. That biologically formed mineral layer supports the adhesion and spreading of bone-forming cells and can permit direct bonding between implant and host bone. Osteoclasts, the body’s bone-resorbing cells, also recognize and break down β-TCP, creating the degradation-and-replacement dynamic that distinguishes truly regenerative implants from permanent ones. The review discusses the signaling pathways and growth-factor environments implicated in these responses, and its indexed research subjects include bone remodeling and transforming growth factor beta, signaling molecules central to how bone-forming and bone-resorbing cells coordinate during healing.

The application section of the review confronts the realities that currently limit β-TCP’s reach. In non-load-bearing and moderately loaded sites, such as defect filling in spinal surgery and the repair of cavitary bone losses, β-TCP-based materials including granules, blocks, and cements are already established clinical tools. The challenges are equally well known: β-TCP ceramics are comparatively brittle and their standalone mechanical strength is generally insufficient for major load-bearing reconstruction, and matching the degradation rate of the implant to the pace of new bone formation remains an unresolved balancing act, since an implant that resorbs too quickly leaves a structural deficit while one that resorbs too slowly crowds out regenerating tissue. The authors frame these challenges not as disqualifications but as engineering targets that synthesis and fabrication strategy can attack.

Toward that end, the review proposes novel approaches to material design and fabrication that map the field’s future directions. These include composite strategies in which β-TCP is combined with reinforcing phases or polymers to improve toughness and controllability, advanced fabrication methods capable of producing patient-specific, architecturally optimized scaffolds, and refinement of the ion-release behavior and surface chemistry that cells actually sense. The overarching vision is a material whose dissolution, resorption, and replacement by bone proceed at matched rates from the first day of implantation to the last. The authors close by positioning high-performance β-TCP bone repair materials as a realistic near-term goal rather than a distant aspiration, arguing that the field already possesses the mechanistic understanding assembled in this review and now needs to translate it systematically into materials that move orthopedic surgery from mechanical repair toward biological regeneration.

Subject of Research: β-tricalcium phosphate (β-TCP) as a resorbable biomaterial for bone defect repair and regeneration

Article Title: From mechanical repair to biological regeneration: a review on β-TCP for bone repair

Article References: From mechanical repair to biological regeneration: a review on β-TCP for bone repair. (n.d.). https://doi.org/10.1007/s42114-026-02080-3

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02080-3

Keywords: β-TCP, calcium phosphate, bone repair, bone regeneration, bioceramics, bone cement, osteogenesis, biodegradable implants, orthopedic biomaterials, bone defect, tissue engineering, biocompatibility

The research team fabricated a series of hybrid-reinforced composites using powder metallurgy, embedding varying amounts of short carbon fibers and graphite particles into an AZ91 magnesium alloy matrix. This processing route, which blends elemental and alloy powders before compaction and sintering, allowed the researchers to tune the reinforcement content systematically, producing composites with carbon fiber fractions ranging from 5 to 15 percent alongside a fixed 5 percent graphite particle loading. By holding the graphite fraction constant while stepping up the fiber content, the team could isolate the contribution of each reinforcement and, crucially, probe how the two interact when present together.

The central discovery rests on a well-known electrochemical phenomenon: the microgalvanic couple. Magnesium sits at the base of the galvanic series, making it exquisitely vulnerable to accelerated attack whenever it is electrically coupled to a nobler phase. Both carbon fibers and graphite particles are far more noble than the surrounding magnesium alloy, so each embedded carbon reinforcement acts as a microscopic cathode, drawing anodic current from the matrix and driving localized metal dissolution. The study confirms that both reinforcements lower the composite’s self-corrosion potential through this mechanism, but they are far from equal partners in the process.

Under identical content, carbon fibers proved dramatically more effective at accelerating dissolution than graphite particles. The mass loss rate of fiber-reinforced material increased by approximately 200 percent compared with the baseline, while graphite particles delivered an increase of roughly 110 percent. The researchers attribute this superiority to the fiber geometry and interfacial characteristics, which create a denser network of galvanic contact sites and sustain stronger anodic polarization across the matrix. For designers of soluble tools, this finding is a practical one: if dissolution speed is the goal, the form of the carbon matters as much as its quantity.

Perhaps the most significant result is the demonstration of synergy between the two reinforcements. With graphite particles fixed at 5 percent, increasing the carbon fiber content from 5 to 15 percent raised the mass loss rate of the composites from 17.67 to 24.56 milligrams per square centimeter per hour. Electrochemical measurements tracked this acceleration in detail: the self-corrosion current density climbed from 3.73 times ten to the minus fifth to 1.25 times ten to the minus fourth amperes per square centimeter, while the charge-transfer resistance—a direct measure of how strongly the interface resists the corrosion reaction—fell from 727 to 213 ohm square centimeters. Lower resistance means electrons flow more freely through the dissolution reaction, and the numbers show the composite interface becoming progressively easier to drive.

The optimal formulation identified in the study combines 15 percent carbon fiber with 5 percent graphite particle, achieving a dissolution rate about 390 percent higher than that of the unreinforced matrix. That is not merely an incremental improvement; it represents the difference between a material that lingers for its entire service life and one that can be removed from a wellbore or absorbed by tissue on an engineer’s timetable. Importantly, this speed-up was achieved without the composite dissolving so violently that structural integrity collapses prematurely, a balance that has frustrated earlier attempts to design soluble magnesium matrix materials.

Beyond raw rates, the study documents a striking morphological transformation. Unreinforced magnesium alloys typically corrode through large, deep, localized pits that concentrate stress and weaken the remaining structure unpredictably. In the hybrid composites, the corrosion morphology evolved into homogeneously distributed micro-pits spread evenly across the surface. The team traced this shift to the dense, uniform array of galvanic sites created by the fibers and particles, which recruit the entire surface into the anodic reaction rather than allowing dissolution to concentrate at a few weak points. For dissolvable frac plugs and biodegradable implants alike, uniform dissolution translates directly into predictable performance and safer failure modes.

The analysis of dissolution products adds a final mechanistic layer. In these composites, the corrosion products form discrete, cluster-like deposits rather than the continuous passive film that normally protects magnesium and throttles its degradation. Because the film never becomes continuous, it cannot suppress the underlying electrochemical activity, and dissolution persists at high rates for extended periods. The authors characterize the overall process as one of rapid initial dissolution followed by a later dynamic equilibrium, an evolution they attribute to the gradual surface accumulation of insoluble products and their local shielding effect, which slows but never fully arrests the reaction. This two-stage kinetic profile gives engineers a quantifiable window of predictable behavior after deployment.

Methodologically, the study is notable for combining gravimetric mass-loss testing, corrosion morphology imaging, product analysis, and a full electrochemical workup of potential, current density, and impedance into a single coherent picture of the dissolution mechanism. The work was supported by the National Natural Science Foundation of China under grant 51905426 and by the Scientific Research Program of the Shaanxi Provincial Education Department under grant 23JK0606. The corresponding authors are Lu-yan Ju and Jia Xie, both of the Mechanical Engineering College at Xi’an Shiyou University.

The implications stretch across several industries. In petroleum engineering, soluble magnesium components are used to seal and then clear wellbores without mechanical intervention, and a fourfold dissolution acceleration could shorten waiting times and cut operating costs. In biomedicine, biodegradable magnesium implants must corrode slowly enough to support healing yet fast enough to vanish within months, and the ability to tune dissolution rate precisely through reinforcement content and type offers exactly that dial. More broadly, the study reframes carbon reinforcements not merely as strengthening phases in magnesium composites but as electrochemical actuators, whose galvanic coupling can be deliberately engineered to control how, where, and how fast a structural material disappears. As soluble materials move from laboratory curiosity to commercial deployment, the design principles laid out here—favoring fibers over particles, exploiting hybrid synergy, and engineering the passive film away—are likely to shape the next generation of materials built to vanish on demand.

Subject of Research: Dissolution mechanism of carbon fiber and graphite particle hybrid-reinforced soluble magnesium matrix composites

Article Title: Study on the dissolution mechanism of Cf/GP-reinforced soluble magnesium matrix composites

Article References: Ju, L.-Y., AI, K., Zhang, Z.-Y., XI, J.-H., Xie, J., & LI, Q.-S. (2026). Study on the dissolution mechanism of Cf/GP-reinforced soluble magnesium matrix composites. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13705-9

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13705-9

Keywords: magnesium matrix composites, carbon fibers, graphite particles, microgalvanic corrosion, soluble materials, powder metallurgy, AZ91 alloy, anodic dissolution, charge-transfer resistance, biodegradable implants, dissolution rate, passive film