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Hussain et al. Soft Sci. 2025, 5, 21 https://dx.doi.org/10.20517/ss.2025.02 Page 15 of 19

Figure 10, the Δλ values remained nearly identical to those of a freshly prepared patch. These results
PBG
highlight the sensor’s durability and reliability, indicating that it can maintain its functionality after storage
for at least two weeks and be reused multiple times without a loss in performance. This reusability opens
exciting possibilities for its application in continuous, long-term sweat monitoring, making it a highly
efficient tool for wearable diagnostics.

On-body sweat analysis
To evaluate the real-time performance of the soft, wearable multiplex biosensor for sweat analysis, the
device was affixed to the forearm of a healthy volunteer with no prior medical history of glycemia (elevated
glucose), uremia (high urea), or hyperlactatemia (high lactate). The volunteer’s skin was thoroughly
cleansed with water and dried before the biosensor was securely attached using medical-grade adhesive. The
patch adhered firmly to the skin throughout the exercise without causing any irritation, ensuring comfort
during the testing period. As shown in Figure 6A, both the lactate and urea sensors were blue, while the
glucose sensor appeared green prior to exercise. The sensor’s sleek design not only enabled seamless
adhesion to the skin but also enhanced the aesthetic appeal, offering a stylish integration into wearable
technology. Before exercise, the λ for the CLCN-IPN urease , CLCN-IPN , and CLCN-IPN sensors was
Gox
Lox
PBG
measured at 430, 432, and 502 nm, respectively, as depicted in Figure 6B. The sweat-collecting chamber,
2
with a diameter of 7 mm, effectively covered an area of 38.4 mm , corresponding to approximately 153
active sweat pores. After 30 min of exercise, the biosensor patch was fully saturated with sweat, as shown in
Figure 6C, resulting in a color shift to mint green across all sensors, indicating sweat absorption. Two hours
post-exercise, the Δλ was analyzed, with shifts of 31, 34, and 16 nm observed for the urea, lactate, and
PBG
glucose sensors, respectively, as shown in Figure 6D. Using standard curves [Supplementary Figures 5D, 6D,
and 7C], the C , lactate, and glucose in sweat were quantified at 12.83, 13.1, and 0.39 mM, respectively.
urea
These values are within the normal physiological range, confirming the healthy status of the volunteer. This
on-body analysis demonstrates the robustness and practicality of the wearable multiplex biosensor for non-
invasive monitoring of critical sweat biomarkers such as glucose, urea, and lactate. The real-time
colorimetric response, coupled with the biosensor’s seamless integration into wearable applications,
underscores its potential for continuous health monitoring. The device not only offers a cutting-edge
solution for real-time sweat analysis but also integrates user-friendly design, making it an ideal candidate for
healthcare, fitness, and personal wellness applications.

CONCLUSION
In this study, we introduced a multiplexed sensing technology integrated into a flexible, wearable
microfluidic PDMS device, offering excellent reliability and reproducibility for non-invasive human sweat
analysis. The soft wearable patch was engineered to collect sweat from the human epidermis, directing it to
each photonic sensor while excess sweat is drained away. The photonic CLCN-IPN flexible film,
immobilized with glucose oxidase, LOx, and urease enzymes, enabled selective and enzyme-based detection
of glucose, lactate, and urea in sweat. Optical photonic sensing provided a significant advantage by allowing
naked-eye visualization of quantitative results through color changes in the film, eliminating the need for
complex instrumentation. This technology is not only non-invasive and battery-free but also easy to use in
both outdoor and indoor environments, making it highly adaptable for real-world applications. As a proof
of concept, the fabricated wearable biosensor array was successfully demonstrated for real-time sweat
sensing on a healthy human subject. The combination of optical photonic technology and flexible design
marks an important step forward in the development of accessible, user-friendly wearable biosensors. Such
an approach has the potential to inspire scalable production of multi-modal sensors for personalized
healthcare and pre-diagnosis. Furthermore, this platform can be expanded to incorporate additional
biosensors, allowing for the detection of a wider array of analytes.