Eyeglasses based wireless electrolyte and metabolite sensor platform

Abstract

The demand for wearable sensors has grown rapidly in recent years, with increasing attention being given to epidermal chemical sensing. Here, we present the first example of a fully integrated eyeglasses wireless multiplexed chemical sensing platform capable of real-time monitoring of sweat electrolytes and metabolites. The new concept has been realized by integrating an amperometric lactate biosensor and a potentiometric potassium ion-selective electrode into the two nose-bridge pads of the glasses and interfacing them with a wireless electronic backbone placed on the glasses' arms. Simultaneous real-time monitoring of sweat lactate and potassium levels with no apparent cross-talk is demonstrated along with wireless signal transduction. The electrochemical sensors were screen-printed on polyethylene terephthalate (PET) stickers and placed on each side of the glasses' nose pads in order to monitor sweat metabolites and electrolytes. The electronic backbone on the arms of the glasses' frame offers control of the amperometric and potentiometric transducers and enables Bluetooth wireless data transmission to the host device. The new eyeglasses system offers an interchangeable-sensor feature in connection with a variety of different nose-bridge amperometric and potentiometric sensor stickers. For example, the lactate bridge-pad sensor was replaced with a glucose one to offer convenient monitoring of sweat glucose. Such a fully integrated wireless "Lab-on-a-Glass" multiplexed biosensor platform can be readily expanded for the simultaneous monitoring of additional sweat electrolytes and metabolites.

Fig. 1

A) Photograph of interchangeable sticker printed sensors. B) Photograph of the eyeglasses biosensor system integrated with wireless circuit board along the arms. C) Nose pad electrochemical sensors with schematic of potassium sensor (left) and lactate sensor (right), along with the corresponding recognition and transduction events. D) Schematic of screen printing process steps and electrode modification for the lactate sensor (left) and potassium sensor (right).

Fig. 2

A) Chronoamperometric response for 0, 2, 4, 6, 8, 10, 12 and 14 mM lactate along with the corresponding calibration plot. Standard deviation n=3. B) Selectivity study: Response to (a) 84 μM creatinine, (b) 10 μM ascorbic acid, (c) 0.17 mM glucose, (d) 59 μM uric acid, and (e) 4 mM lactate. C) Response of the potassium sensor using 0.1, 1, 10 and 100 mM KCl, along with the corresponding calibration plot. D) Hysteresis curve (carry-over study) for the potentiometric sensor using varying potassium concentrations.

Fig. 3

A) MAG biosensor device with both potentiometric (Pot.) and amperometric (Amp.) PCBs boards. B) Setup for in-vitro measurements using the wearable MAG biosensor device. C) Response of the potassium sensor to 0.01, 0.1, 1 and 10 mM KCl in DI water. D) Response of the lactate biosensor to increasing lactate concentration from 0 to 10 mM, with 2 mM increments in PBS (pH 7). E) Response of the glucose sensor to increasing glucose concentration from 0 to 2 mM with 0.2 mM steps in PBS (pH 7). Insets C, D and E: corresponding calibration plots for potassium, lactate and glucose sensors, respectively.

Fig. 4

Wireless measurements using the PCBs boards. A) Simultaneous sweat potassium (a,a′) and lactate (b,b′) signals recorded during cycling exercise of two different volunteers via wireless using the MAG device.. B) Female volunteer cycling a stationary bike using the wireless MAG device C) Simultaneous measurements of sweat glucose response for glucose sensor (a,a′) and control (no-enzyme) sensor (b, b′), obtained with two different volunteers, during exercise using the MAG device.