A new microfluidic sensor measures lactate concentration during exercise

Researchers at the Tokyo University of Science have created a new wearable microfluidic sensor that can measure lactate concentration in sweat in real-time. Lactate is a compound present in sweat that's an important biomarker used to quantify exercise. Available wearable sensors are typically rigid devices that can cause skin irritation.

The wearable sensor developed by the researchers is soft and non-irritating, making it ideal for real-time measurement of lactate concentration and sweat. Lactate is produced during the breakdown of glucose in the absence of oxygen and tissues. It is a biomarker present in blood and sweat, reflecting the intensity of physical exercise and muscle oxygenation.

Lactate buildup can cause pain and fatigue and is released in the bloodstream to be eliminated through sweat. To develop the sensor, the team focused on the sensing mechanism they would deploy inside the sensor. While most lactate biosensors use immobilizing lactate oxidase and an appropriate mediator on the electrode, the system developed by the researchers took a different path. The scientists use a method called electron beam-induced graft polymerization.

In that process, functional molecules are bonded to a carbon-based material that can spontaneously bind to the enzyme. The material was turned into a liquid ink used to print electrodes, which is an important aspect for potential future commercialization of the product. Researchers on the project say the fabrication of their sensor is compatible with screenprinting for mass production.

To collect sweat and deliver it to the sensor, the team used a microfluidic sweat collection system made of polydimethylsiloxane. That method was chosen because it's soft and nonirritating, allowing it to contact the skin directly. Monitoring the lactate threshold can help optimize athletic training and exercise routines for people in rehabilitation.