Wearable Flexible Perspiration Biosensors Using Laser-Induced Graphene and Polymeric Tape Microfluidics

Wearable biosensors promise real-time measurements ofchemicalsin human sweat, with the potential for dramatic improvements in medicaldiagnostics and athletic performance through continuous metaboliteand electrolyte monitoring. However, sweat sensing is still in itsinfancy, and questions remain about whether sweat can be used formedical purposes. Wearable sensors are focused on proof-of-conceptdesigns that are not scalable for multisubject trials, which couldelucidate the utility of sweat sensing for health monitoring. Moreover,many wearable sensors do not include the microfluidics necessary toprotect and channel consistent and clean sweat volumes to the sensorsurface or are not designed to be disposable to prevent sensor biofoulingand inaccuracies due to repeated use. Hence, there is a need to producelow-cost and single-use wearable sensors with integrated microfluidicsto ensure reliable sweat sensing. Herein, we demonstrate the convergenceof laser-induced graphene (LIG) based sensors with soft tape polymericmicrofluidics to quantify both sweat metabolites (glucose and lactate)and electrolytes (sodium) for potential hydration and fatigue monitoring.Distinct LIG-electrodes were functionalized with glucose oxidase andlactate oxidase for selective sensing of glucose and lactate acrossphysiological ranges found in sweat with sensitivities of 26.2 and2.47 x 10(-3) & mu;A mM(-1) cm(-2), detection limits of 8 and 220 & mu;M,and linear response ranges of 0-1 mM and 0-32 mM, respectively.LIG-electrodes functionalized with a sodium-ion-selective membranedisplayed Nernstian sensitivity of 58.8 mV decade(-1) and a linear response over the physiological range in sweat (10-100mM). The sensors were tested in a simulated sweating skin microfluidicsystem and on-body during cycling tests in a multisubject trial. Resultsdemonstrate the utility of LIG integrated with microfluidics for real-time,continuous measurements of biological analytes in sweat and help pavethe way for the development of personalized wearable diagnostic tools.