1. Sensors in microsystems
1.1 Distance variation
Distance sensors, Acceleration sensors, Vibration sensors, Pressure sensors
Accelerometer
Measurement effect
Capacitive effect
capacity changes with the distance between electrodes and surface Area → in practise we use differential capacitors
- we need electrodes and a seismic mass attach to a spring
- what are the process steps ? structuring and layer deponition
Piezoresistiv effect
Change of electrical resistivity under elongation or compression
Often start with a Si substrate, then structuring and deposition of layers
Deposit a layer and structurate it
Used in pressure sensors
Change in mechanical properties
Mechanical deflection
Change of resonant frequency
vibration sensor
the sensor vibrate at different frequencies depending on the cantilever mass (multiple trees of different mass)
detect amount of deposited mass
the resonant frequency changes
1.2 Change in electrical properties
Measure electrical impedance in function of electrical frequency
Impedance spectroscopy : impedance changes with impurities etc
Resistivity of thin film coating changes with absorbed species