A thermoelectric wearable gas sensor is a device that detects the presence of specific gases in the environment by utilizing the thermoelectric effect. The thermoelectric effect is a phenomenon where a temperature gradient across a material leads to the generation of an electric voltage.
Here's how a thermoelectric wearable gas sensor typically works:
Gas Interaction: The sensor is designed to interact with specific gases of interest. This is often achieved through a gas-permeable membrane or a sensing material that reacts with the target gases. When the target gas comes into contact with the sensor, it causes a change in temperature near the sensing material.
Thermoelectric Module: The sensor consists of a thermoelectric module, which is usually made up of two different types of semiconductor materials connected in a circuit. These materials have different thermoelectric properties, meaning they respond differently to temperature changes.
P-Type Material: This material has an excess of positive charge carriers (holes). When heated, it generates a surplus of electrons.
N-Type Material: This material has an excess of negative charge carriers (electrons). When heated, it generates a deficit of electrons.
Temperature Gradient Generation: The gas interaction causes a localized temperature gradient across the thermoelectric module. The part of the module in contact with the sensing material becomes slightly warmer due to the gas reaction, while the other end remains relatively cooler.
Voltage Generation: The temperature gradient leads to the movement of charge carriers (electrons and holes) from the hot end (P-type) to the cold end (N-type) of the thermoelectric module. This migration of charge carriers generates a voltage difference between the two ends of the module. This voltage is proportional to the temperature difference and the material's thermoelectric properties.
Measurement and Analysis: The generated voltage is then measured using appropriate electronics and converted into a signal that can be analyzed by a microcontroller or other processing unit. The magnitude of the voltage is directly related to the gas concentration and the temperature difference caused by the gas interaction.
Calibration and Interpretation: The sensor's response is calibrated using known gas concentrations to establish a relationship between the measured voltage and the concentration of the target gas. This calibration allows the sensor's output to be converted into meaningful gas concentration units.
Output and Display: The final output is typically displayed on a screen, transmitted wirelessly to a device like a smartphone, or used to trigger alarms or other actions, depending on the application.
In summary, a thermoelectric wearable gas sensor utilizes the thermoelectric effect to detect specific gases. Gas interactions cause localized temperature differences, which in turn generate voltage differences across a thermoelectric module. The generated voltage is then measured, calibrated, and interpreted to determine the concentration of the target gas. This wearable sensor design is advantageous due to its portability and ability to operate without external power sources.