A team of biomedical engineers at Anna University in Chennai has unveiled a new electrode material that can detect glucose in artificial sweat with remarkable sensitivity, offering a possible route toward needle-free diabetes monitoring. Writing in the Journal of Materials Science, Kirubha Perumal and Sreeja B. S. describe a multi-walled carbon nanotube and cobalt oxide nanocomposite, abbreviated MWCNT/Co3O4, that was grown through a straightforward hydrothermal process and then deposited onto a simple graphite electrode. The work addresses one of the most persistent challenges in wearable health technology: how to measure glucose accurately and continuously without relying on fragile biological enzymes or invasive finger-prick blood sampling.
The appeal of sweat as a diagnostic fluid has grown steadily over the past decade. Sweat contains glucose at concentrations that correlate with blood glucose, and it can be harvested passively through a wearable patch during exercise or induced perspiration. The difficulty lies in sensitivity. Glucose levels in sweat are far lower than in blood, so any sensor intended for this matrix must detect minute quantities of the sugar against a background of salts, lactate, urea and other interfering compounds. Conventional enzymatic sensors, which use glucose oxidase to catalyze the reaction, suffer from well-known weaknesses: enzymes degrade with heat, humidity and time, losing activity within days and making long-term wearable use impractical.
Non-enzymatic sensing sidesteps this fragility by letting an inorganic catalyst do the electrochemical work directly. Cobalt oxide, specifically the spinel phase Co3O4, has emerged as a strong candidate because its cobalt ions readily shuttle between oxidation states, mediating the oxidation of glucose at the electrode surface. The catch is that bare cobalt oxide is a relatively poor electrical conductor, which limits how efficiently the electrons generated by glucose oxidation can be collected. This is precisely where the carbon nanotubes enter the picture. Multi-walled carbon nanotubes form a highly conductive, three-dimensional scaffold with enormous surface area, and when cobalt oxide nanoparticles are dispersed uniformly across this network, the two materials complement each other: the oxide supplies catalytic sites while the nanotubes provide an electron highway.
The synthesis reported by the Chennai team is deliberately simple. A hydrothermal route, in which precursor materials react in water inside a sealed vessel at elevated temperature and pressure, was used to grow the nanocomposite. Hydrothermal methods are attractive because they produce crystalline nanoparticles at relatively low cost and without exotic reagents, and the resulting particles can be tuned in size and distribution through reaction conditions. The researchers then modified a graphite electrode with the nanocomposite, creating a working sensor surface. Graphite is inexpensive, widely available and mechanically robust, which matters for any device intended to be mass-produced as a disposable or wearable component.
Characterization formed a substantial part of the study, and the authors deployed an unusually complete analytical arsenal. X-ray diffraction confirmed the crystalline structure of the cobalt oxide spinel phase, while Fourier-transform infrared spectroscopy verified the chemical bonds and functional groups present in the composite. Field-emission scanning electron microscopy revealed the morphology of the material, showing cobalt oxide nanoparticles distributed across the nanotube network, and energy-dispersive spectroscopy confirmed the elemental composition. Brunauer-Emmett-Teller measurements quantified the surface area, a critical parameter for sensing because more accessible surface means more catalytic sites in contact with the analyte. Finally, X-ray photoelectron spectroscopy probed the surface chemistry and oxidation states of the cobalt, confirming that the active species needed for glucose electrocatalysis were present at the interface where sensing actually occurs.
Electrochemical testing was carried out in 0.1 molar phosphate buffer solution at pH 7.4, a standard electrolyte that mimics physiological neutrality. The team used a battery of electroanalytical techniques, each probing a different aspect of sensor behavior. Cyclic voltammetry mapped the redox activity of the electrode as the potential was swept back and forth. Differential pulse voltammetry and linear sweep voltammetry provided higher-resolution measurements of the glucose oxidation signal. Square-wave voltammetry added another sensitive detection mode, while electrochemical impedance spectroscopy measured how readily electrons moved across the electrode-electrolyte interface, a direct indicator of charge-transfer efficiency. Chronoamperometry, in which the current is monitored at a fixed potential over time, served as the workhorse for quantitative detection, since the current step produced when glucose is added scales with its concentration.
The performance figures are striking. The sensor achieved a sensitivity of 18.47 milliamperes per millimolar per square centimeter, a high value for a non-enzymatic system, with a detection limit of 0.1 millimolar. That detection limit is relevant to the glucose concentrations expected in sweat, which typically sit well below blood levels. Equally important for real-world deployment, the electrode demonstrated strong stability, repeatability and reproducibility. After thirty days of storage, the sensor retained more than 96 percent of its original response, a figure that speaks directly to the durability problem that plagues enzymatic alternatives. Reproducibility across multiple electrodes suggests the hydrothermal synthesis is controllable enough to yield consistent devices, a prerequisite for any commercial translation.
Perhaps the most consequential test came when the researchers moved from buffer solution to artificial sweat, a synthetic formulation designed to reproduce the salt content and pH of human perspiration. Real sweat is a hostile medium for electrochemistry: chloride ions, lactic acid, urea and ascorbic acid can all generate signals that masquerade as glucose or poison the catalyst. The MWCNT/Co3O4 electrode recovered 94 percent of the expected glucose signal in this matrix, demonstrating that the composite can function under conditions that approximate the physiological environment a wearable patch would actually encounter. While artificial sweat is not identical to the genuine article, and human trials remain a necessary next step, the recovery result provides meaningful evidence that the sensing chemistry survives outside the pristine laboratory beaker.
The broader context makes the result timely. Diabetes affects hundreds of millions of people worldwide, and the burden of daily finger-stick testing drives much of the noncompliance that leads to poor outcomes. Continuous glucose monitors based on subcutaneous sensors have transformed care for many patients, but they remain invasive, expensive and require regular replacement. A truly noninvasive alternative that reads glucose from sweat could lower the barrier to frequent monitoring dramatically, particularly in resource-limited settings. Non-enzymatic electrodes are especially well suited to this vision because they tolerate temperature swings, long storage and repeated use, all of which are unavoidable in a consumer wearable. The literature on cobalt oxide and carbon nanotube composites for glucose sensing is already substantial, and the present work builds on that foundation while pushing sensitivity and stability figures forward with an unusually accessible fabrication route.
Challenges remain before a sweat-based patch built on this chemistry reaches the clinic or the drugstore. Sweat glucose correlates with blood glucose but the relationship is dynamic and influenced by sweating rate, skin conditions and individual physiology, so calibration strategies and on-body validation will be essential. The researchers tested their electrode on graphite in artificial sweat rather than in a fully integrated flexible device on human subjects, and scaling from a laboratory electrode to a manufacturable, skin-conformal sensor involves additional engineering in fluid handling, electronics and data interpretation. Nevertheless, the combination of a low-cost hydrothermal synthesis, an inexpensive graphite substrate, enzyme-free operation, high sensitivity and thirty-day stability makes the MWCNT/Co3O4 nanocomposite a credible candidate platform for the next generation of noninvasive glucose monitors. As the field of wearable diagnostics accelerates, studies like this one show how careful materials engineering at the nanoscale can translate into practical devices that patients may one day simply wear, sweat into, and read.
Subject of Research: Non-enzymatic electrochemical glucose sensing using an MWCNT/Co3O4 nanocomposite for sweat-based monitoring
Article Title: Facile hydrothermal synthesis of MWCNT/Co3O4 nanocomposite for sweat-based non-enzymatic glucose sensing in artificial sweat
Article References: Perumal, K., & B. S., S. (2026). Facile hydrothermal synthesis of MWCNT/Co3O4 nanocomposite for sweat-based non-enzymatic glucose sensing in artificial sweat. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13873-8
Image Credits: AI Generated
DOI: 10.1007/s10853-026-13873-8
Keywords: glucose sensing, non-enzymatic sensor, MWCNT, cobalt oxide, Co3O4, nanocomposite, hydrothermal synthesis, sweat, wearable biosensor, electrochemistry, noninvasive monitoring, diabetes
News Source: Sylvia Mullen. (October 7, 2026). Carbon Nanotube and Cobalt Oxide Nanocomposite Detects Glucose in Sweat Without Enzymes. Scienmag.
