This article explains the need for high-performance gas sensors, how they work, performance evaluation factors, and the latest technological advances to prevent accidents caused by hazardous gases in homes and industrial settings.
We may be exposed to various harmful gases in our daily lives. While humans can recognize the presence of hazardous gases through their sense of smell or respiratory system, it is difficult to determine the type of gas sensually, and even more difficult to detect minute concentrations. Because these hazardous gases can have devastating health effects, more sophisticated and accurate detection is needed. Therefore, using high-performance gas sensors that can detect the type of gas and its concentration is the best way to prevent accidents caused by hazardous gases.
A gas sensor is a generic term for a device that detects a specific gas and converts it into an appropriate electrical signal. Gas sensors are designed based on a variety of principles and technologies, and are categorized into different types depending on their intended use. Among the various types of gas sensors, resistive sensors using oxide semiconductor materials are widely used because of their fast detection speed, high stability, and easy miniaturization for portable devices. High stability in a sensor device means that the output of the sensor is nearly constant under the same conditions, even over repeated measurements over time.
Resistive gas sensors consist of an oxide semiconductor material, ranging in thickness from a few hundred nanometers (10-9 m) to a few micrometers (10-6 m), connected between two electrodes. As gas approaches the sensor, the amount of gas adsorbed by the oxide semiconductor material increases over time, until it reaches a steady state where the amount of adsorbed gas remains constant, resulting in a constant resistance value. During the steady state, oxidizing gases such as nitrogen dioxide adsorb electrons from the oxide semiconductor, increasing the resistance of the oxide semiconductor. On the other hand, a reducing gas such as carbon monoxide adsorbs electrons from the oxide semiconductor material while giving them away, reducing the resistance of the oxide semiconductor. This change in resistance is how the sensor works: it detects the gas and calculates its concentration.
The main factors that evaluate the performance of a resistive gas sensor are response sensitivity, response time, and recovery time. Response sensitivity is how sensitive a gas sensor’s resistance changes in the presence of a specific gas, and is derived from the steady-state resistance value (Rs), which is held constant, and the resistance value (Rair) measured in air without the specific gas. It is the difference in Rs divided by Rair, expressed as a percentage, and the higher the value, the more sensitive the gas sensor. Response time, a measure of how quickly a gas sensor detects and reacts to a particular gas, is also defined as the time it takes to reach 50% or 90% of the response sensitivity value. On the other hand, since the sensor is to be used repeatedly, the gas adsorbed in the steady state on the oxide semiconductor material must be desorbed and returned to its initial state as quickly as possible. Therefore, the recovery time, the time required for the adsorbed gas to desorb from the air, is also an important factor in evaluating the performance of a gas sensor.
Various research efforts are underway to improve the performance of gas sensors. Attempts are being made to improve sensitivity and response time through the development of new materials and modification of existing materials, and the development of ultra-small sensors using nanotechnology is also active. In particular, the miniaturization and low power consumption of sensors opens up the possibility of applying them to portable and wearable devices, which is expected to be used in various fields. In addition, systems that analyze and predict sensor data in real time by combining artificial intelligence and big data analysis technology are also being developed. These developments will contribute to minimizing the damage caused by harmful gases and providing a safer living environment in various fields such as air quality management, industrial safety, and environmental monitoring.
Gas sensors are used in a variety of applications, from domestic to industrial. For example, in residential areas, they can be used as carbon monoxide alarms or natural gas leak alarms to prevent fires or poisoning due to gas leaks. In factories and laboratories, they play an important role in detecting leaks of hazardous chemicals to ensure the safety of workers and reduce environmental pollution. The importance of gas sensors is growing every day, and continuous technological advancements and research are leading to more precise and reliable sensors.
In conclusion, gas sensors are becoming an essential safety device in the modern world. Protecting humans from various harmful gases, ensuring safety at industrial sites, and contributing to environmental protection, gas sensors will become increasingly important in the future. This will require continuous research, development, and commercialization efforts to create a safer and healthier living environment.
