Multi-Storey Gas Sensor With Pulsed UV for Selectivity
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Solution Overview
Problem
Current micro-sensors, particularly semi-conducting metal-oxide gas sensors, face challenges in achieving high accuracy and selectivity for gas detection and composition analysis due to low selectivity and lengthy recovery times, necessitating improved measurement techniques and architectures.
Innovation Solution
A multi-storey gas sensor architecture is introduced, where gas samples pass through stacked sensing elements with selectively-activatable layers, allowing for varied operating conditions and pulsed UV radiation to enhance data points and accuracy, including the use of micro-hotplate structures for rapid heating and cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-storey gas sensors are used, then the device structure is simple, but the measurement precision and selectivity are insufficient
Solution Approach 1:
The sensor is divided into multiple storeys, each containing a sensing element with a sensing layer. Gas passes through each storey sequentially, allowing multiple measurements to be taken under different conditions (with/without UV illumination, with/without heater activation). This segmentation enables richer data collection for improved gas discrimination while maintaining a modular structure that can be manufactured using standard integrated circuit techniques.
Solution Approach 2:
The patent transitions from a single-storey (one-dimensional) sensor structure to a multi-storey (three-dimensional) stacked architecture. This dimensional change allows gas to be analyzed multiple times as it passes through different storeys, with each storey providing additional measurement opportunities under varied operating conditions, thereby enhancing measurement precision without significantly increasing planar footprint.
2Loss of time
If heating is applied to clean the sensing layer, then the recovery time is reduced, but the energy consumption increases
Solution Approach 1:
The heater is activated periodically only during the cleaning phase between measurements, rather than continuously. The control unit activates the heater to heat the sensing layer to a temperature sufficient for desorption of adsorbed particles, then deactivates it once cleaning is complete. This periodic activation reduces overall energy consumption while maintaining rapid recovery capability between measurements.
Solution Approach 2:
The sensing layer is deliberately allowed to accumulate adsorbed particles during the measurement phase, which is then discarded through thermal cleaning. The heater provides the energy needed to desorb and remove the accumulated particles, restoring the sensing layer to its initial state. This cycle of accumulation and removal optimizes the balance between measurement sensitivity and recovery speed.
3Measurement precision
If ultraviolet light is applied continuously, then the gas discrimination capability is improved, but the energy consumption increases
Solution Approach 1:
The UV light source is activated in pulses during the measurement phase rather than continuously. The control unit activates the UV source for specific time intervals to enhance the sensor response to target gases, then deactivates it. This pulsed operation maintains the gas discrimination capability provided by UV illumination while significantly reducing the average power consumption compared to continuous operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the accuracy and selectivity of gas detection by generating a rich set of measurements, enabling better discrimination of gases and reducing measurement times, thus overcoming the limitations of conventional single-storey sensors.
Implementation Method 1
gas particles G may become adsorbed on the surface of the sensing layer 2
Implementation Method 2
oxidation-reduction reactions may occur, leading to a change in the impedance of the sensing layer 2
Implementation Method 3
it is necessary to heat the sensing layer 2 to a relatively high temperature (notably 250°C or above) for useful adsorption phenomena to be observed
Implementation Method 4
the heater 6 is activated to heat the active layer to a high temperature, above the usual operating temperature, so as to cause de-sorption of adsorbed particles
Implementation Method 5
A chemoresistor type gas sensor uses pulsed ultraviolet light to illuminate a gas sample during analysis
Data Source
Figure 1~2(c)
Figure 3~4
Figure 5
AI summary
A gas sensor of chemoresistor type comprises a gas-sensitive layer (52/75/85), and a source of ultraviolet light operable to expose the gas-sensitive layer (52/75/85) to pulses of ultraviolet light. The gas sensor comprises a setting unit configured to control a duty ratio or duration, of the ultraviolet light pulses applied by the source of ultraviolet light, in dependence on a target gas species to be adsorbed on the gas-sensitive layer. An analysis unit may measure the transient response of the sensing layer at onset of application of ultraviolet light.