A thermoelectric wearable body temperature sensor operates on the principle of the Seebeck effect, which is the conversion of temperature differences into electric voltage. This technology enables the sensor to monitor the wearer's body temperature by measuring the temperature difference between the skin and the ambient environment.
Here's how it works:
Thermoelectric Material: The sensor contains a thermoelectric material, typically made of semiconductor materials like bismuth telluride, that exhibits the Seebeck effect. This material has two different types of conductors, often referred to as the "hot" and "cold" junctions. The hot junction is placed in contact with the wearer's skin, while the cold junction is exposed to the surrounding air.
Temperature Gradient: When there's a temperature difference between the hot and cold junctions, due to the difference between the wearer's body temperature and the ambient temperature, a voltage is generated across the junctions of the thermoelectric material. This voltage is directly proportional to the temperature difference according to the Seebeck coefficient of the material.
Thermocouple Effect: The voltage generated is essentially a result of the "thermocouple effect." A thermocouple is a pair of different metals connected at two points. When there's a temperature difference between the junctions of the metals, a voltage is generated due to the varying electron energy levels in the metals. In the case of a thermoelectric material, this voltage is generated within a single material.
Measurement and Conversion: The generated voltage is then measured by integrated electronics within the wearable sensor. This voltage is usually very small and needs to be amplified and converted to a readable signal. The electronics perform amplification and analog-to-digital conversion to provide a digital temperature reading that can be displayed or transmitted to a connected device, such as a smartphone or a smartwatch.
Calibration and Accuracy: To ensure accurate temperature readings, the sensor needs to be calibrated to account for variations in the Seebeck coefficient of the thermoelectric material, electronic noise, and other factors. This calibration process helps provide reliable and consistent temperature measurements.
Wearable Form Factor: The sensor is designed to be integrated into a wearable device, such as a patch, band, or clothing, making it comfortable for the wearer to keep it in contact with their skin. This allows continuous monitoring of body temperature without the need for invasive methods like thermometers.
Thermoelectric wearable body temperature sensors have gained popularity due to their non-invasive nature, convenience, and potential use in various applications, including healthcare, sports, and personal wellness monitoring. They can provide real-time temperature data that can be valuable for detecting fever, monitoring thermal comfort, and tracking trends in body temperature over time.