A wearable antenna sensor based on ePDA/SiO2 nanowalls for the detection of lactic acid in sweat

Lactic acid (LA) concentration in sweat is closely related to the human metabolic system. A novel wearable antenna sensor based on electropolymerization dopamine (ePDA) film is proposed to achieve non-invasive and real-time monitoring of LA concentration in sweat. The antenna sensor adopts polydimethylsiloxane (PDMS) as a flexible substrate and operates at the 2.45 GHz industrial, scientific, and medical (ISM) frequency band. The Cu patch was immersed in a dopamine solution doped with SiO2 nanoparticles. The electropolymerization formed ePDA/SiO2 nanowalls films can interact with LA through hydrogen bonding, resulting in the resonant frequency shifts of the antenna sensor. The LA concentration in human sweat can be obtained by remotely reading the resonant frequency of the worn antenna sensor. Experiments demonstrate that the sensitivity of the antenna sensor to LA is 150 KHz/mM with a wide detection range of 0–20 mM. Furthermore, the antenna sensor shows omnidirectional radiation characteristics. This proves that the antenna sensor can detect LA concentration and transmit the data in a wireless and real-time manner. In addition, the antenna sensor exhibits good biocompatibility, flexibility, selectivity, long-term stability, and dynamic stability. In conclusion, the proposed antenna sensor is a good candidate for wireless wearable LA monitoring in sweat.