Researchers have developed a soft and nonirritating microfluidic sensor for the real-time measurement of lactate concentration in sweat. This wearable device will help monitor the state of the body during intense physical exercise or work. Chemical biomarkers in bodily fluids such as blood, saliva, and sweat are challenging to quantify with wearable sensors.
The team first focused on the sensing mechanism that they would employ in the sensor. Most lactate biosensors are made by immobilizing lactate oxidase (an enzyme) and an appropriate mediator on an electrode. A chemical reaction involving lactate oxidase, the mediator, and free lactate results in the generation of a measurable current between electrodes — current that is roughly proportional to the concentration of lactate.
The scientists employed a method called electron beam-induced graft polymerization, by which functional molecules were bonded to a carbon-based material that can spontaneously bind to the enzyme. They turned the material into a liquid ink that can be used to print electrodes.
The team then designed an appropriate system for collecting sweat and delivering it to the sensor. They achieved this with a microfluidic sweat collection system made out of polydimethylsiloxane (PDMS); it comprised multiple small inlets, an outlet, and a chamber for the sensor in between. The detection limits of the sensor and its operating range for lactate concentrations was confirmed to be suitable for investigating the lactate threshold.
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