Researchers have developed a hydrogel-based strain sensor that measures blood potassium from a single drop of serum in two minutes, enabling faster and less invasive monitoring for patients with kidney and heart conditions.
(Nanowerk Spotlight) Monitoring blood potassium levels has remained a persistent challenge in medical diagnostics, requiring specialized equipment, significant sample volumes, and considerable time to obtain accurate results. Clinical management of potassium-related conditions has been constrained by these limitations, forcing patients—particularly those with chronic kidney disease or heart failure—to undergo frequent, invasive blood draws and endure delayed results that complicate timely treatment adjustments.
Traditional methods such as flame atomic absorption spectroscopy offer precision but necessitate sophisticated laboratory infrastructure. Chemical-based approaches like ion-selective electrodes improve accessibility but remain vulnerable to interference from sample conditions. These diagnostic bottlenecks have real clinical consequences. For patients with hyperkalemia, where potassium concentrations exceed normal ranges, delays in detection can increase mortality risk. For those with hypokalemia, insufficient monitoring can precipitate serious cardiac events.
Advances in materials science have now created new possibilities for sensing technologies. Researchers from Sichuan University have developed a smart hydrogel strain sensor that can rapidly detect blood potassium concentration from just a single drop of serum. Their work, published in Advanced Functional Materials (“A Novel Smart Hydrogel Strain Sensor for Efficient and Quantitative Detection of Blood Potassium Concentration with a Drop of Serum”), introduces a sensing platform that integrates responsive polymer networks with electrical measurement systems, potentially transforming potassium monitoring.
The system combines a synthetic hydrogel with a resistance strain gauge to convert biochemical signals into mechanical deformation. The hydrogel contains crown ether units—specifically benzo-15-crown-5-acrylamide—that selectively recognize potassium ions. When potassium binds to these molecular recognition sites, it causes the hydrogel to contract, producing a measurable strain signal.
Schematic illustrations of the a) fabrication process and the b) sensing and detecting principle of the proposed smart hydrogel strain sensor for efficient and quantitative detection of blood potassium concentration with a drop of serum. (Image: Reprinted with permission by Wiley-VCH Verlag)
The researchers improved the sensor’s performance by rethinking how the hydrogel network is structured. Conventional chemical crosslinkers often create dense networks that slow ion transport and reduce responsiveness. Instead, the team used Laponite XLG nanosheets as physical crosslinkers, forming a loose, house-of-cards-like internal structure that facilitates rapid potassium diffusion while preserving mechanical stability.
To ensure reliable adhesion between the hydrogel and the strain gauge, the team developed a silanization modification technique. By chemically modifying the polyimide substrate, they enabled strong bonding between the hydrogel and the strain gauge, preventing delamination even under mechanical stress.
The resulting sensor demonstrates exceptional performance. It detects potassium concentration from a 16-microliter drop of serum—approximately a single drop of blood—within two minutes. Testing across potassium concentrations from 1 to 9 millimolar (mM) revealed a clear, linear relationship between potassium levels and strain signal, covering the clinically relevant range of 3.5 to 5.5 mM. The sensor maintained high specificity, showing negligible interference from other common blood ions, including sodium, calcium, and magnesium, even at concentrations typical in human serum.
The team also evaluated the sensor’s stability and reusability. Tests showed that the device could reliably perform repeated measurements over 12 detection cycles without degradation in performance. This robustness could support repeated use in clinical settings.
Temperature sensitivity, a known feature of the hydrogel material, was systematically addressed. The researchers calibrated the sensor across a temperature range of 25 to 40°C, providing clear reference ranges for interpreting potassium levels under varying environmental conditions.
Performance validation against atomic absorption spectroscopy confirmed the sensor’s accuracy and precision, with relative standard deviation values below 3.9% and relative errors less than 3.5% across tested samples.
Beyond its immediate application in potassium detection, the platform could be adapted to monitor other clinically relevant ions. By modifying the hydrogel’s recognition units, similar sensors could target alternative electrolytes or biomarkers.
This technology addresses a pressing clinical need for improved electrolyte monitoring. Hyperkalemia affects an estimated 6–7% of the global population and increases risks among chronic kidney disease patients, with 90% higher rates of adverse cardiovascular events and a 65% higher mortality rate. More accessible, rapid potassium testing could enable earlier intervention and more responsive treatment adjustments.
For patients requiring regular potassium monitoring, the simplified procedure could reduce the need for hospital visits and invasive blood draws. While further development is needed before clinical implementation, including packaging the sensor in user-friendly formats, this research establishes a strong foundation for a new generation of point-of-care electrolyte testing.
Get our Nanotechnology Spotlight updates to your inbox!
Thank you!
You have successfully joined our subscriber list.
Become a Spotlight guest author! Join our large and growing group of guest contributors. Have you just published a scientific paper or have other exciting developments to share with the nanotechnology community? Here is how to publish on nanowerk.com.
