Microfluidic Chip-Based Wearable Colorimetric Sensor for Simple and Facile Detection of Sweat Glucose

Abstract

This study reports a microfluidic chip-based wearable colorimetric sensor for detecting sweat glucose. The device consisted of five microfluidic channels branching out from the center and connected to the detection microchambers. The microchannels could route the sweat excreted from the epidermis to the microchambers, and each of them was integrated with a check valve to avoid the risk of the backflow of the chemical reagents from the microchamber. The microchambers contained the pre-embedded glucose oxidase (GOD)–peroxidase–o-dianisidine reagents for sensing the glucose in sweat. It was found that the color change caused by the enzymatic oxidation of o-dianisidine could show a more sensitive response to the glucose than that of the conventional GOD–peroxidase–KI system. This sensor could perform five parallel detections at one time. The obtained linear range for sweat glucose was 0.1–0.5 mM with a limit of detection of 0.03 mM. The sensor was also used to detect the glucose in sweat samples from a group of subjects engaged in both fasting and postprandial trials. The results showed that our wearable colorimetric sensor can reveal the subtle differences existing in the sweat glucose concentration after the fasting and the oral glucose uptake.

A Mediator‐Free Electroenzymatic Sensing Methodology to Mitigate Ionic and Electroactive Interferents' Effects for Reliable Wearable Metabolite and Nutrient Monitoring

“…The smartwatch was first coupled with the glucose sensor and utilized to monitor the sweat glucose change in three subjects before and after consumption of mixed meals (where standard iontophoresis protocol was performed 2 h before and 0.5 h after meal consumption in order to induce and subsequently analyze sweat). Figure e–g demonstrates the elevation of sweat glucose concentration level after meal consumption (in all three subjects), which is in agreement with a trend observed previously …”

“…Figure 5e-g demonstrates the elevation of sweat glucose concentration level after meal consumption (in all three subjects), which is in agreement with a trend observed previously. [3,55,56] Additionally, the smartwatch was coupled with the lactate sensor and used for continuous sweat lactate profile monitoring of a subject engaged in constant-load stationary cycling. As illustrated in Figure 5h (solid green), a decreasing profile of sweat lactate current responses were recorded, similar to that observed previously.…”

Applying Nanomaterials to Modern Biomedical Electrochemical Detection of Metabolites, Electrolytes, and Pathogens

“…Researchers aim to develop more technological tools to investigate the glucose concentration in alternative biofluids and examine the correlation of such glucose levels with blood glucose level [69,70]. Concentration ranges of glucose in alternative fluids are around 0.006-2 mM (sweat) [71][72][73], 3.9-6.6 (interstitial fluid) [74], 2.78-5.56 mM (urine) [75,76], and 0.03-1.39 mM (saliva) [64,65,77,78]. The use of nanomaterials is important to help the sensor to be able to operate under fluctuating conditions of real biological systems.…”

Tailoring Conducting Polymer Interface for Sensing and Biosensing

“…To realise continuous and accurate analytical operations, microfluidics can be built on the flexible and wearable bioelectronic devices to provide additional function to extract and capture sample at the device-tissue interface with minimised sample evaporation and external contamination 151 . For instance, in a skin-mountable device, an epidermal microfluidic system can collect the sweat from the skin surface and then transport biofluid sweat through the microchannels into separated microchambers for multianalysis including sweat volume, sweat rate, creatinine level, pH and glucose level etc 152,153 . Conformable PDMS is widely used for the fabrication of microfluidic systems via soft-lithography methods or laser cutting 154 .…”