MOSFET Pressure Sensor with Mobile Gate for Fingerprint Recognition
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Solution Overview
Problem
Existing microelectronic pressure sensors for surface profiling, such as fingerprint recognition, are sensitive to electrical conductivity and chemical pollution, and require complex measurement devices, making them unreliable in noisy electrostatic environments.
Innovation Solution
A microelectronic pressure sensor using a MOSFET transistor with a mobile gate and a silicone gel or membrane that captures surface pressure, allowing for independent measurement of surface profiles regardless of conductivity or electrostatic interference, with adjustable speed and spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive measurement is used for fingerprint sensing, then the sensor can capture surface profiles, but the measurement becomes sensitive to electrical conductivity and chemical pollution
Solution Approach 1:
The patent replaces the electrical capacitive measurement system with a mechanical measurement system. A movable probe physically contacts the fingerprint surface and transfers mechanical displacement to a detection point on the sensor substrate, converting electrical sensing into mechanical sensing that is immune to electrostatic interference and chemical pollution.
2Measurement precision
If complex measurement devices are used to measure capacitor values, then surface profiles can be measured, but the device complexity increases
Solution Approach 1:
The complex electrical measurement circuitry for measuring capacitor values is replaced with a simple mechanical displacement detection system. The movable probe's physical displacement directly translates to a detection point position that can be read by simple position sensing circuitry, eliminating the need for complex capacitance measurement devices.
Solution Approach 2:
The patent creates a mechanical copy of the fingerprint surface profile through the movable probe array. Each probe physically replicates the surface topology at its contact point, and the collection of these mechanical copies provides the complete fingerprint pattern without requiring complex electrical measurements.
3Device complexity
If the sensor surface is made planar for capacitive measurement, then the measurement structure is simple, but the sensor cannot capture rugosity information effectively
Solution Approach 1:
The patent introduces dynamic elements to the otherwise simple planar sensor structure. Movable probes can physically follow the surface rugosity, and a movable detection point can dynamically position itself to read the profile, adding the necessary complexity to capture rugosity information while maintaining a relatively simple overall sensor structure.
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
The sensor effectively captures and recognizes surface profiles, including fingerprints, with improved reliability and accuracy in noisy environments, and can be integrated into various display systems for touch-sensitive applications.
Implementation Method 1
a silicone gel which is mechanically in contact with the latter and able to transform any pressure applied on a surface exterior of said gel into a movement of said gate by means of said mechanical contact
Implementation Method 2
means for measuring the position of said gate
Data Source
AI summary
A microelectronic pressure sensor comprises a MOSFET transistor adapted with a mobile gate and a cavity between the mobile gate and a substrate. The sensor includes a gate actuator configured to move mobile gate in response to a pressure being exercised. A fingerprint recognition system includes a matrix of such sensors.