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1、Micro Sensors華梵大學機電工程學系基礎課程名稱：微製造工程導論微微/奈米光機電高科技學程奈米光機電高科技學程SensorsTransfer the mechanical behavior ( such as deformation, stress, and acceleration ) to electrical signal.Sensing techniques can be characterized as static and dynamic approaches. Static method : stress and deformation + stress detecti
2、on piezoresistive strain gauges piezoelectric sensing. + deformation detection capacitance interferometer.Dynamic method : resonant frequency + resonant frequency.華梵大學機電工程學系Source：自強工業科學基金會 清華大學 方維倫 教授Stress detection piezoresistive strain gaugeStrain gauge a conductor or semi conductor that is fabr
3、icated on or bonded directly to the surface to be measured and that changes in dimension along with the surface.The gauge resistance is very proportional with the change in gauge dimension by two factors, + deformation of the shape of the gauge. + piezoresistivity effect.Piezoresistivity a material
4、property where the bulk resistivity , ,is influenced by the mechanical stresses applied to the material.華梵大學機電工程學系Source：自強工業科學基金會 清華大學 方維倫 教授Stress detection piezoresistive strain gaugeThe sensitivity is expressed by the Gauge factorGF = (1 + 2) + (d/)/ where, is Poissons ratio is residual strainTh
5、e strain gauge can also be used to measure the vibration frequency of a structures + the stress status of a structure ( at a certain face ) can vary from tension to compression during vibration, for example , a cantilever beam.華梵大學機電工程學系Source：自強工業科學基金會 清華大學 方維倫 教授Micro machined strain gauge has two
6、 advantages+Easy to define the pattern of the gauge.華梵大學機電工程學系+ High GF traditional conductor strain gauge the GF mainly determined by m, however, the GF is domainated by (d/) for a semiconductor strain gauge.Source：E,O. Doebelin, Measurement Systems, 1990Stress detection piezoelectric sensingPiezoe
7、lectricity the phenomenon in which an electrical voltage develops due to an externally applied stress.An opposite effect is also true the piezoelectric material will deform under an input voltage , therefore it can also be a material for actuator.Silicon is not a piezoelectric material, therefore an
8、 additional piezoelectric film has to be deposited onto the substrate when applying this technique.ZnO is the most common piezoelectric material used in microfabrication.華梵大學機電工程學系Source：自強工業科學基金會 清華大學 方維倫 教授Deformation detection - capacitanceThe basic parallel plate capacitor equation isC =A/dwhere
9、 is dielectric constant A is overlapping plate area d is distance between two platesThere are several ways to sense the deformation by the changing og capacitance, for example華梵大學機電工程學系Source：自強工業科學基金會 清華大學 方維倫 教授Why microsensors?The primary advantages of the micro sensor is the reducing of its size
10、 + lower weight + lower manufacturing cost + sensitivity + power consumption華梵大學機電工程學系Source：Semiconductor Sensors, edited by S.M. Sze, 1994 Micro machining processes batch fabrication , and IC processes compatible + lower cost + integration of the electrical and machanical parts + performance華梵大學機電工程學系Source：Honeywell
