Researchers at Penn State University, USA, developed a new wearable sensor to monitor glucose levels in sweat over multiple weeks. [Image: Kate Myers / Penn State]
With the growing incidence of diabetes worldwide, the need for a noninvasive method of measuring glucose is more relevant than ever. While countless attempts have been made, there is still no commercially viable, noninvasive glucose monitor available on the market.
Now, researchers at Penn State University, USA, are hoping their wearable electrochemical sweat biosensor will provide a low-cost, highly sensitive platform for continuous glucose detection (Adv. Funct. Mater., doi: 10.1002/adfm.202306117). The device integrates a laser-induced graphene (LIG) nanocomposite electrode with a microfluidic network for sweat sampling.
Laser-induced graphene
Electrochemical biosensors that use sweat for the detection of biomarkers face a number of significant challenges to achieving commercial viability. Human sweat varies in salinity, pH and temperature depending on the circumstances of the individual, which can affect biosensor read-out. Also, the concentration of biomarkers in sweat is generally lower than those found in blood or interstitial fluids.
Study author Farnaz Lorestani and her colleagues decided to investigate LIG—a 3D porous carbon-based nanomaterial fabricated by direct laser writing—as a material for the biosensor’s electrode. Since its discovery in 2014, LIG has emerged as a promising technology that greatly reduces production costs compared with traditional, wet chemistry–based processing methods.
“Nevertheless, the sensitivity and stability of the porous laser-induced graphene are limited, posing challenges for accurately detecting trace biomarker concentrations in sweat or other biofluids,” said Lorestani, an associate research fellow at Penn State. “Consequently, we have embarked on a journey to tackle these issues and develop a highly sensitive, selective, cost-effective and durable flexible sensing platform for continuous and precise health care monitoring.”
Next-generation biosensors
The sensor was able to maintain more than 91% sensitivity over 21 days in ambient conditions.
The device includes three major components: a LIG-based electrochemical dual glucose and pH sensor with three electrodes, a LIG-based temperature sensor and a stretchable microfluidic network for sweat sampling. The researchers created a 3D network of conductive nanomaterials on a porous graphene electrode using a simple plasma and laser treatment.
“This forms a 3D network of conductive materials, offering improved sensitivity and greater stability by facilitating electron transfer for non-enzymatic detection of glucose and the other biomarkers,” Lorestani explained. “When combined with a flexible porous graphene-based pH and temperature sensor, this wearable device can calibrate glucose measurements based on temperature and pH readings as both of them affect glucose sensor performance.”
After first calibrating the sensor in artificial sweat, the researchers validated it against a commercial glucometer during on-body measurements up to two hours after a meal. The sensor was able to maintain more than 91% sensitivity over 21 days in ambient conditions.
“This robust flexible sensing platform based on highly sensitive and stable nanomaterials could lead to the creation of the next generation of advanced sensors and devices for continuous, noninvasive monitoring of multiple biomarkers and physiological signals,” Lorestani said.
