Enzymatic biofuel cells (EBFCs), which harness endogenous biofuels such as glucose to generate electricity, offer an alternative for sustainable energy harvesting within the body. The growing demand for reliable self-powered systems has led to an increased interest in long-term implantable medical devices. Glucose biofuel cells (GBFCs) present a promising energy source by utilizing the natural glucose found in bodily fluids. However, developing small and flexible electrodes remains a significant challenge. This study introduces a novel, flexible bioelectrode made from embroidered silver thread (Ag) that can be safely implanted in a living, freely moving rat. This Ag thread embroidered over cotton cloth later this electrode employs specific enzymes as anode catalysts, laccase as cathode catalysts, a destructively stimulating supervising polymer, a redox-active compound suitable for biological systems, and gold nanostructures to enhance electron transfer. In vitro testing of this embroidery-inspired enzymatic biofuel cell achieved a power density of 132.5 μW/cm2. In vivo, we have performed with a wistar rat, and the performance improved to 292 μW/cm2, which can be useful for portable and wearable electronics applications. These results demonstrate that subdermal-implanted microsystems can be powered in a biocompatible and cost-effective manner.

Whole-cell bioelectronic sensors are particularly well-suited for environmental and health monitoring as they can be integrated into compact electronic devices for field deployment over extended periods. However, current engineering strategies lack modularity, are limited to a few microbial chassis and depend on specialized instruments for signal detection. We present the electroactive co-culture sensing system (e-COSENS), a plug-and-play system for whole-cell bioelectronic sensor development. Here a 'sender' bacterium produces electron mediators in response to analytes and a 'receiver' bacterium utilizes the electron mediators to generate electrical signals via extracellular electron transfer. Modularly swapping the sender bacterium and its associated genetic sensing elements achieved bioelectronic sensing of metals, small molecules and peptides in distinct environments, such as urban waterways, milk, saliva and microbial communities. We designed a centimeter-sized bioelectronic device for portable signal readout using a household digital multimeter. The e-COSENS system simplifies the whole-cell bioelectronic sensor design and expands the potential of bioelectronic sensor applications.

We report a scalable, moisture-powered in-planta sensor platform for the continuous monitoring of plant hydration and growth. The system integrates two components: a leaf-mounted tattoo sensor for estimating vapor pressure deficit (VPD) and a kirigami-inspired strain sensor for tracking radial stem growth. Uniquely, the tattoo sensor serves a dual function: measuring temperature and humidity beneath the leaf surface while simultaneously harvesting power from ambient moisture via a vanadium pentoxide (V2O5) nanosheet membrane. This moist-electric-generator (MEG) configuration enables energy-autonomous operation, delivering a power density of 0.1114 μW/cm2. The V2O5-based sensor exhibits high sensitivity to humidity (4.2 mV/% RH) and temperature (1.02%/°C), enabling accurate VPD estimation for over 10 days until leaf senescence. The eutectogel-based kirigami strain sensor, wrapped around the stem, offers a gauge factor of 1.5 and immunity to unrelated mechanical disturbances, allowing for continuous growth tracking for more than 20 days. Both sensors are fabricated via cleanroom-free, roll-to-roll compatible methods, underscoring their potential for large-scale agricultural deployment to monitor abiotic stress and improve crop management.

Existing flexible electronics are typically planar and visually conspicuous. In this work, the authors present a new paradigm: free-form three-dimensional integrated circuits (ICs) built primarily on a single textile thread, offering exceptional flexibility and discrete integration. Millimeter-scale transistors are assembled easily as daisy chains on a thread and utilize deep eutectic solvent gels or eutectogels as nonvolatile dielectrics for gating organic electrochemical transistors. The eutectogels provide stable transistor performance without the need for encapsulation and make the Organic Eutectogel-Gated Electrochemical Transistor (OEGET) a promising candidate for flexible electronics. Complex analog ICs, such as single-stage and multistage amplifiers, can be realized on a single thread that can easily fold and bend out of the plane of stretching for true three-dimensional flexibility. An all-thread-based device that uses a thread-based strain sensor and a thread-based integrated circuit for eye motion and respiration monitoring is also presented.

Reliable and continuous access to interstitial fluid (ISF) remains a major challenge for wearable and tissue-embedded biosensing systems. Conventional microneedle-based methods, while widely adopted, often exhibit variable sampling efficiency across different skin types and are prone to performance fluctuations during motion. Herein, we introduce a tissue-embedded thread-based open capillary microfluidics-based sampling that enables minimally invasive, pump-free, and reliable continuous monitoring of small molecules from ISF. The system employs open capillary-driven microfluidic channels in textile threads, which facilitate the partial separation of small molecules from complex biological matrices, mimicking a microdialysis process. The continuous sampling is achieved through evaporation-driven capillary pressure, eliminating the need for an external pump. The experimental results confirm the numerical simulation of diffusion-controlled and capillary-driven transport of analytes in ISF. The performance of the developed platform was validated in phantom skin (agarose gel) and porcine skin models, confirming stable, long-duration sampling and continuous biomarker detection in tissue fluid. For practical applications, the developed platform was validated for real-time measurement of glucose and pH utilizing flexible electrochemical sensors. The sensor exhibited sensitivities of 0.027 µA/glu (mg/dL) and −56.25 mV/pH change, respectively. These findings establish thread-based dialysis-like open capillary microfluidics sampling as a promising approach for reliable, tissue-embedded monitoring of biomarkers in ISF for tissue-embedded biosensing applications.

The current standard of care (SOC) for battlefield burn wound management is dry sterile gauze. While this does provide exudate management and some barrier function by limiting exposure to the environment, it does little to treat the burn injury or improve healing outcomes. In this study, we developed a therapeutic microneedle patch (MNP) comprised of a hydrogel for point of injury (POI) burn wound stabilization. The hydrogel microneedles were loaded with agents that can mitigate the impediments to wound healing, including ibuprofen (IBU) to manage inflammation, deferoxamine (DFO) to support neovascularization, and infection prevention in the form of azithromycin (AZ). Hydrogel MNPs were fabricated and characterized for size, shape, and release kinetics of loaded agents. Loaded therapeutic hydrogel microneedle patches (THMNPs) were confirmed as noncytotoxic in vitro prior to in vivo testing in a porcine model of deep partial-thickness contact burn injury. In vivo studies employed therapies within a battlefield-relevant timeline and compared THMNPs to unloaded MNPs as well as two forms of military SOC, dry sterile gauze and Silverlon antimicrobial dressing. Animal studies were taken out to 28 days to observe relevant wound healing outcomes, including reductions in burn progression, re-epithelialization, and inflammation. THMNPs were ultimately found to be applicable for battlefield burn wound care in the tested model.

Monitoring cortisol levels is essential for understanding the body's response to stress. Traditional cortisol testing is confined to centralized labs, and current portable platforms are based on slow and complex assays. Here, we introduce a portable, disposable, non-invasive, and sensitive electrochemical sensor strip created using electropolymerized molecularly imprinted polymers (eMIPs) on laser engraved graphene (LEG) electrodes for rapid, simple, and reliable salivary cortisol detection. Herein, the characteristics of LEGs generated on a polyimide (PI) film with different laser processing parameters are also studied and optimized. The sensor quantifies salivary cortisol by selectively binding onto the cortisol-imprinted electropolymerized polypyrrole-Prussian blue (eMIP-PPy/PB) film on LEG electrodes. The PB redox probes embedded in the eMIP produce direct electrical signals upon cortisol binding, allowing sensitive and label-free amperometric detection. The developed cort-eMIP/LEG sensor strip displays an outstanding dynamic range (0.10 to 10 000 pg mL-1), a remarkable limit of detection (0.08 pg mL-1), and a strong correlation coefficient (R2) of 0.9983 (n = 4) for cortisol detection in human saliva. A rapid 3-minute analysis can more effectively measure cortisol levels in real-time than traditional methods. This sensor's performance was evaluated in human samples and validated two-way using enzyme-linked immunosorbent assays (ELISAs) and a third-party provider, Salimetrics, on 12 student volunteers exposed to varying stress levels. Results show an excellent correlation (r = 0.9948) between the developed sensors and standardized tests. The cort-eMIP/LEG cortisol sensor strip offers a simple, accessible, sample-to-answer diagnostic platform for stress monitoring.

Biopolymer-supported deep eutectic solvent (DES)-based gels, also known as eutectogels, have emerged as promising alternatives to hydrogels and ionic-liquid-based gels for multiple applications in stretchable electronics and sensors due to many key advantages including their high ionic conductivity, tensile toughness, easy handling, simple synthesis, low cost, biocompatibility, and ultralow volatility. Particularly, gelatin-supported 1,2-propanediol (PD)-based eutectogels containing water have shown promise due to their hydrogel-like properties. They have low modulus values and biofriendly components, making them "skin-like" materials. They are optically transparent, which makes them ideal as user-friendly visual devices. Incorporation of color-tunable micropatterned opal structures into these novel gelatin-supported eutectogels enables the preparation of user-friendly, mechanically resilient, and stimuli-responsive materials for many applications via a simple color change. In this work, we utilize a simple and robust evaporative deposition-stamping technique to prepare eutectogels containing opal micropatterns to overcome limitations in existing fabrication techniques such as photolithography and soft lithography that suffer from costly equipment, harsh radical polymerization, and multistep processing and/or reliance on external forces. First, uniform and color-tunable opal micropatterns are formed via simple evaporative deposition. Scanning electron microscopy (SEM) images show the formation of a uniform hexagonal packing throughout the opal micropatterns. Next, the opal micropatterns are successfully transferred into gelatin-supported PD eutectogels via a simple hand-stamping technique to form opal eutectogels having uniform opal micropatterns due to the eutectogels' adhesive and mechanically resilient nature without the need for costly equipment. Photographs and dark-field optical micrographs, in combination with wavelength spectra measurements, illustrate the reliable nature of our simple evaporation-stamping method. Finally, sandwich eutectogels that fully encapsulate the opal micropatterns were produced by simply adding a secondary eutectogel layer to the top, yielding a reversible optical response to mechanical stimuli. We envision that this simple, reliable, and robust evaporation-stamping technique can be readily extended to manufacture biocompatible and user-friendly visual monitoring devices.

Chronic wounds present significant therapeutic challenges due to prolonged inflammation and bacterial infections, impeding healing. Conventional medicinal dressings typically deliver a single drug with a fixed release profile and lack responsiveness to variations in wound size, nature, or severity. This study introduces an innovative microneedle (MN) patch designed with different microneedle geometries and capable of dual‐drug delivery to address irregular wounds and complex therapeutic requirements. Utilizing CO₂ laser lithography, microneedle molds are fabricated with diverse geometries by precisely controlling laser parameters such as speed, power, and focus, achieving needle heights ranging from 162 ± 30 µm to 1570 ± 40 µm. The patch facilitates simultaneous delivery of simvastatin (SIM) for anti‐inflammatory and tetracycline hydrochloride (TH) for antibacterial properties, targeting different skin depths. In vitro diffusion studies confirm geometry‐dependent drug release profiles, with SIM achieving controlled release over three days and TH exhibiting sustained release over four days. Biocompatibility assays confirmed safety and enhanced fibroblast migration is noted in wound‐healing studies. Antimicrobial testing reveals a 99.9% reduction in bacterial viability. This cost‐effective and scalable approach enables precise, localized delivery and customization of MN arrays to match various wound geometries, offering a versatile platform for personalized medicine and improved chronic wound management.

This study presents a simple and inexpensive distance-based paper analytical device (dPAD) for plasma separation from whole blood samples and its application in monitoring albumin protein and glucose levels using colorimetric and fluorescent distance methods. The developed dPAD consists of a sample zone, a separation zone with hydrophobic wax-patterned lines, a pretreatment zone, and a straight zone channel pre-deposited with chemical reagents for both albumin protein and glucose quantification. Plasma separation relies on the capillarity-driven different flow velocities of blood cells and plasma with varying hydrophilicity in the paper channel. Remarkably, the blood cells are trapped in the separation channel of the device, while plasma can be separated and subsequently flow with a buffer solution to the detection zone by capillary force. Target analyte in plasma content then reacts with its specific reagents, resulting in the change in the color or fluorescent distance signal. Our sensor exhibited remarkable accuracy and precision for the detection of albumin protein and glucose in whole blood samples with an acceptable recovery range between 99.94 and 101.65% and the highest relative standard deviation (RSD) of 4.49%. Furthermore, the results indicated no significant differences between our method and conventional methods for albumin protein and glucose determination in whole blood samples. Additionally, to the best of our knowledge, this method is the first time for the development of the fluorescent dPAD sensor for glucose monitoring. It is also the first demonstration to use a dPAD sensor for the direct detection of both albumin protein and glucose levels in whole blood. Hence, despite its simplicity, the concept offers a more cost-effective and accessible method for plasma separation from whole blood and subsequent albumin protein or and glucose detection. Moreover, it can be extended for further advancements in POC analytical sensing.

Accurate measurement of stress marker cortisol and neurotransmitter dopamine is essential for understanding the physiological effects of chronic stress, enabling early therapeutic interventions to prevent adverse health consequences. Herein, we introduce the first fully integrated wearable device comprising a microneedle (MN) patch and distance-based paper analytical device (dPAD) for minimally invasive dermal interstitial fluid (ISF) sampling and simultaneous cortisol and dopamine sensing. The MN patch employs a swellable hydrogel matrix for efficient ISF extraction, whereas the simple dPAD sensor can simultaneously detect cortisol and dopamine through colorimetric reactions. Quantitative analysis was achieved through simple measurement of the colored distance proportional to the analyte concentration using a ruler. The device demonstrates high sensitivity, with detection limits of 0.25 μg mL-1 for cortisol and 1.0 ng mL-1 for dopamine, along with excellent selectivity for both analytes. It also exhibited high accuracy and precision, with recovery rates of 98.5-100.7% for cortisol and 98.8-102.2% for dopamine. These results show that the developed sensor device is user-friendly, simplifies the analysis process, reduces costs, and eliminates the need for complex instrumentation, making it a promising tool for point-of-care (POC) testing for stress and its relative disorders, with potential applications in diagnosing other biomarkers.

A flexible piezotronic sensor using MXene/Te heterostructure was developed for selective, ultrasensitive acetone detection at room temperature. It shows strain enhanced response and outperforms GC-MS in cost, speed, and real world VOC analysis.

We present an innovative, self-powered tattoo sensor crafted from a vermiculite clay nanosheet membrane layered with graphene. Sweat is a critical indicator of hydration status, helping the body regulate temperature, and can also signal potential health issues, including dehydration and electrolyte imbalances. Therefore, it is important to continuously monitor sweat levels as a surrogate for hydration level. In this study, we have developed a wearable tattoo sensor, paired with a semi-custom circuit, that monitors sweat humidity changes as they relate to an individual's hydration status. Notably, no external power source is required where the sensor serves as a sweat moisture-based energy generator. The developed moist energy generator from sweat has a power density of 7.16 nW/cm2. By measuring real-time output from this energy harvester, this sensor has the potential to provide an indication of hydration levels, that may enable early intervention to prevent life-threatening conditions from dehydration.

This paper introduces an innovative platform for head motion tracking using soft gels of eutectic solvents, namely eutectogels. Eutectogels are flexible, conformal, and inconspicuous for on-skin strain sensing applications. The experimental results show that the eutectogel strain sensor exhibits a gauge factor of approximately 1.34 at 1 kHz. A multiplexed impedance readout with wireless connectivity was implemented and tested at a range of 10 – 12 meters in a lab setting. To evaluate the sensor response to deformation, yaw, pitch, and roll movements were performed to the head's maximum range of motion. The sensors showed significant changes in impedance with yaw/roll resulting in asymmetric changes (10 % – 15 %) and pitch inducing a larger change (15 % – 20 %) due to greater neck flexion. The proposed eutectogel strain sensors can also be used to monitor other body motions with applications in the assessment of gait and mobility impairments, cognitive function decline, or human-machine interface.

Timely monitoring of inflammation following transplant surgery is essential to prevent complications such as ischemia or death. Centralized testing often leads to delays. Point-of-care immunoassays offer some promise. However, they lack the form factor and the performance needed for localized monitoring of inflammation. This work demonstrates a novel dual-mode microcatheter platform for in situ quantification of inflammatory biomarkers, such as interleukin- 6 (IL-6). By combining an electrochemical approach, namely differential pulse voltammetry (DPV), and an optical approach, namely localized surface plasmon resonance (LSPR), the platform enables reliable, on-demand, precise monitoring of inflammation. The novelty of the approach is using surgical sutures for electrochemical sensing and its co-integration with an optical fiber for LSPR sensing in a miniaturized and flexible microcatheter platform. This platform can locally probe the surgical or wound site for inflammation monitoring, providing high precision and reliability. The dual-mode approach enhances detection accuracy, precision, and dynamic range. The dual-mode microcatheter sensor exhibited a broad dynamic range from 0.1 to 1000 pg/mL for IL-6 measurement with a limit of detection (LOD) of 0.076 pg/mL for the electrochemical approach and 0.10 pg/mL for the optical LSPR approach. Furthermore, the performance of the dual-mode sensing microcatheter was successfully evaluated in buffer, artificial serum, skin-gel, and human serum samples with co-interferents in the clinical range.

Electroactive microbes can serve as living components in bioelectronic devices, where their unique ability to transfer electrons enables applications in sensing, energy conversion, and synthesis, but they remain challenging to engineer because the bioelectrochemical systems (BESs) used for characterization are low throughput. Here, we present a bioelectrochemical crossbar architecture screening platform (BiCASP) that uses stacked and orthogonally arrayed electrodes to enable individual sample selection for characterization in arrayed formats. This device reports on the current generated by electroactive bacteria on the minute timescale, decreasing the time for data acquisition by several orders of magnitude compared to conventional BESs. This device increases the throughput of screening engineered biological components in cells, identifying mutants of the membrane protein wire MtrA in Shewanella oneidensis that retain the ability to support extracellular electron transfer (EET). BiCASP may be integrated with bioelectronics that need directed evolution of electroactive proteins.

Effective point-of-care (POC) methods for detecting metabolic disorders, such as hyperammonemia, are crucial. Urinary ammonia is an underexplored but physiologically relevant biomarker for such conditions and can be conveniently monitored noninvasively. Conventional detection methods, while reliable, are time-consuming and costly. We propose a green, low-cost microfluidic distance-based thread analytical device (dTAD) that incorporates curcumin for urinary ammonia quantification. Through a simple immersion technique, curcumin was deposited on the surface of cellulose-based threads, resulting in a user-friendly device that correlates ammonia titers to a naked-eye colorimetric distance-based measurement. Curcumin undergoes a color change from yellow to red in the presence of ammonia and demonstrates strong selectivity with major interferants in urine. Moreover, this sensor exhibits a linear range of 20.0-80.0 mmol L-1 (R2 = 0.994) with a limit of detection (LOD) of 5.0 mmol L-1. The LOD was theoretically predicted using the mass balance volatilization of ammonia along the thread channel in conjunction with Darcy’s law. The thread-based device offers significant advantages in terms of simplicity, affordability, versatility, and future scalability. With a total analysis time of 3.0 min, a cost of less than $0.20 per sensor, and a recovery range of 91%-102% in human control urine samples, the device meets the demands of REASSURED (Real-time connectivity, Ease of specimen collection, Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable) POC diagnostics for the developing world. To the best of our knowledge, this is the first application of a distance-based thread device that quantifies ammonia in biofluid samples.

On-demand dental-floss-based point-of-care platform is developed for the noninvasive and real-time quantification of salivary cortisol utilizing redox-molecule embedded molecularly imprinted polymer structures and thread microfluidics. Herein, we explore the high-surface-area graphene-based electrode substrate for electrochemically synthesizing selective cortisol MIPs and integrate it with thread microfluidics to build a highly sensitive cortisol-sensing platform for stress monitoring. This platform uses flossing to collect and transport saliva to a flexible electrochemical sensor via capillary microfluidics, where cortisol, a stress biomarker, is measured. This strategy allowed us to detect cortisol as low as 0.048 pg mL-1 in real-time with a detection range of 0.10-10,000 pg mL-1 (R2 = 0.9916). The saliva-sensing dental floss provides results within 11-12 min. The thread-based microfluidic design minimizes interference and ensures consistent repeatability when testing both artificial and actual human saliva samples, yielding 98.64-102.4% recoveries with a relative standard deviation of 5.01%, demonstrating high accuracy and precision. For the human saliva sample (as part of the stress study), the platform showed a high correlation (r = 0.9910) against conventional ELISA assays. Combined with a wireless readout, this saliva floss offers a convenient way to monitor daily stress levels. It can be extended to detect other critical salivary biomarkers with high sensitivity and selectivity in complex environments.