With the sensor fabrication optimized, the sensor showed linear responses from 100 to 500 µM with a high R-sqr value at 0.99. The device showed a high sensitivity of about 0.5 per 100 µM lactate and a low detection limit at 23 µM at S/N=3. The sensor was then exposed to artificial sweat samples spiked with lactate at 300 mM. Results have shown an excellent recovery rate at 99.8% for a batch of 6 devices. This result indicated the great potential of such inkjet printer device to achieve active monitoring of lactate in sweat. The sensor needed further research on its selectivity when incubated with nontarget as well as stability tests.