A wearable chemical-electrophysiological hybrid biosensing system for real-time health and fitness monitoring

Abstract

Flexible, wearable sensing devices can yield important information about the underlying physiology of a human subject for applications in real-time health and fitness monitoring. Despite significant progress in the fabrication of flexible biosensors that naturally comply with the epidermis, most designs measure only a small number of physical or electrophysiological parameters, and neglect the rich chemical information available from biomarkers. Here, we introduce a skin-worn wearable hybrid sensing system that offers simultaneous real-time monitoring of a biochemical (lactate) and an electrophysiological signal (electrocardiogram), for more comprehensive fitness monitoring than from physical or electrophysiological sensors alone. The two sensing modalities, comprising a three-electrode amperometric lactate biosensor and a bipolar electrocardiogram sensor, are co-fabricated on a flexible substrate and mounted on the skin. Human experiments reveal that physiochemistry and electrophysiology can be measured simultaneously with negligible cross-talk, enabling a new class of hybrid sensing devices.

Figure 1. Fabrication and function of the Chem–Phys hybrid sensor patch.

(a) Schematic showing the screen-printing process. (b) Image of the Chem–Phys printing stencil. (c) An array of printed Chem–Phys flexible patches. (d) Image of a Chem–Phys patch along with the wireless electronics. (e) Schematic showing the LOx-based lactate biosensor along with the enzymatic and detection reactions. (f) Block diagram of the wireless readout circuit.

Figure 2. In-vitro characterization of Chem–Phys hybrid patch.

(a) Amperometric response to increasing lactate concentration from 0 to 28 with 2 mM additions in phosphate buffer (pH 7.0). Applied voltage=−0.1 V versus Ag/AgCl. (b) Electrocardiogram signals using 3M Red Dot electrodes (top), and printed electrocardiogram sensor (bottom).

Figure 3. On-body test configuration.

(a) A photograph of Chem–Phys hybrid patch. (b) Location of the Chem–Phys patch for mounting on the human body—the fourth intercostal space of the chest. (c) Cycling resistance profile for on-body tests. (d) Effect of amperometric measurement on the electrocardiogram signal before cycling (no sweat state) and during cycling (sweating state).

Figure 4. Real-time on-body evaluation of the Chem–Phys hybrid patch showing the lactate levels and heart rate for three human subjects.

(a–c) The corresponding blue plots represent the real-time lactate concentration profiles for each subject, while, the red plots depict the heart rate data obtained by the electrocardiogram electrodes of the Chem–Phys patch. The black plots correspond to the heart rate data recorded by the Basis Peak heart rate monitor. Typical real-time electrocardiogram data obtained before, during and after the cycling bout for each subject is also shown. (d) Additional heart rate data from subject #1. (e) Response of the control amperometric sensor (without LOx enzyme) for subject #1.