Wearable and Battery-Free Health-Monitoring Devices With Optical Power Transfer

Wireless epidermal wearable devices attract interests and expectations as a tool for personalized, low-cost health monitoring technology. The concept of the wireless attachable personal health monitoring devices has been more widely considered by combining them with biosensors. To bring the most advantage out of the structure of the epidermal attachable device, a battery-free approach was introduced to reduce the volume and extend the lifetime of the device. In this work, an energy harvesting technology and noninvasive sensor were applied with the attachable battery-free devices as a wireless power system and painless measuring system. A glucose sensor was used as an example to develop the wireless wearable device for diabetes-monitoring. The device consists of two functional parts: an optical power transfer and an electrochemical sensing part. The operation starts when the optical power transfer part accumulates power from series-connected photovoltaic cells and intermittently supplies the power to the electrochemical sensing part. In the electrochemical sensing part, an amperometric method was used for controlling the oxidation voltage and measuring a faraday current from the noninvasive sensor and current as brightness and duration of light pulses from a light-emitting diode (LED). The experiment results show that the device works as expected for a variety of glucose concentrations.