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六、微感測器─機械感測器

MicrosensorsMechanical Microsensors

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Sensors 的分類

Smart Sensors: integrating sensor components and signal processing units

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感測器 (sensor) 和致動器 (actuator)

Sensor - a device that converts a non-electrical input quantity N into an electrical output signal E 。

Actuator- a device that converts an electrical signal E into a non-electrical quantity N 。

Six primary energy domainsElectrical EThermal TMechanical MeRadiation RMagnetic MBio(chemical) C

EE

E

E

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電性 (Electrical property) 及訊號 (Signal Type)

性質 :電阻 ,Resistance 　 R （歐姆 )電容 ,Capacitance 　 C( 法拉 )電感 ,Incutance 　 L( 亨利）

訊號 :電壓 ,Voltage V 　（伏特）電流 ,Current I 　（安培）電荷 ,Charge q 　（庫倫）

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壓阻式 ( 電阻變化率 )

A

lR

2A

ldA

A

dld

A

ldR

l

dl

h

dh

w

dw

hdhwdwAdA

wh

A

dA

l

dld

R

dR

///

A

電阻　電阻率

電阻變化率

單位應變的電阻變化率（計示因子 (Gauge factor)

/)21(

/G

)21(

dRdR

d

R

dR

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Gauge Factor( 計示因子 )

金屬之 G 約略為 (1+2v) ＝ 1.5-2.0 v=Poisson’s ratiou 一般約 0.25-0.5 （ 0.5 表示體積不因拉伸而變

化如橡皮 ,0.5 以上表示材料愈拉伸體積反而愈小）

半導體之 G 約略 80-150 主因在電阻率的變化

壓阻係數及正向應力

縱向及橫向應力及壓阻係數

)21(dV

V

gg

d

d

R

dR

ttll R

R

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電容式

較為靈敏 ,對溫度變化不甚敏感 ,電容量測技術發達( 可準確量測小到 0.16pF)

定義 C=Q/E 則一微伏 uV的最小的可量測電壓 , 只能汲取一個電子的電荷量 (1.6x10 -19C)

但電容變化不隨物理量成正比變化因電容與間隙成反比故線性度是主要問題

=Permittivity of material between plates( 介電常數 ) =8.86nF/m for vacuum or dry air

x

AC

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平行電容的能量及力量

Energy

Original energy

Final Energy

Mechanical work

Force

2

22

2

0

022

02

0

2

0

22

22

2

22

22

22

x

AV

A

Qf

A

dxQEEEfdx

A

dxxQ

C

QE

A

xQ

C

QE

CV

C

QE

f

ff

9

Microsensors

A vital organ of an artificial system The interface which can smell, taste, see and feel High reliability, low weight and volume, and low mas

s-production cost High accuracy, high safety for man and material, relia

ble results in real-time

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Major Applications – 1/2

Medical Applications 連續量測血液中的物理 / 化學參數如溫度、壓力、流量、 pH

值 呼吸系統中的氧、二氧化碳或麻醉劑 體內量測 (In situ measurement, integrated sensor, continuou

s record) 感測器需與生物共容，且長時間穩定，不需外加電源，無

毒，小尺寸。 ( 目前溫度、壓力 ) Environmental Protection( 化學的、生化的 )

偵測物質 ( 氣體、液體的固形量 ) ，如一氧化碳、氧化氮、重金屬等之濃度

大氣中的二氧化碳濃度 ( 氣候 ) 需常暴露於污水與垃圾等的侵害性大面積中，感測器晶片可於

現場同時進行資料的處理，減少訊號傳輸的必要性 ( 需大量，便宜 )

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Major Applications – 2/2

Food Processing: 化學與生物感測器以偵測污染與不純物 Automobile Applications

Distance, acceleration, pressure, vibration, temperature and chemical sensors

增加安全性與降低燃油消耗與污染 Microrobotics

Often equipped with distance, acceleration, force, torque, tactile, pressure and temperature sensors.

Materials: semiconductor materials, special metals, plastics, ceramics, glasses, enzymes and antibodies (protein compounds for biosensors)

Fabrication: Silicon technology, LIGA

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Pressure Sensors

The first developed and used by industry Must be

low cost, high resolution, accuracy, linearity and stability. Silicon-based pressure sensor: low cost, high sensitivity, and lo

w hysteresis Typical pressure sensor

Deflection Membrane structure is proportional to pressure Basic Categories:

Piezoresistive pressure sensor Capacitive pressure sensor Resonance pressure sensor Interferometer pressure sensor

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1. Piezoresistive Pressure Sensor

Bulk micromachining of a (100) silicon substrate Etch stop to produce membrane Piezoresistors integrated (doping) in the membrane Wheatstone bridge to measure the change of resistance

ttllR

R

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Wheatstone Bridge Connection

p-type resistors( 硼 ) are preferable since their piezoresistive coefficient is a maximum in (110) direction （電阻方向選擇的原因） whereas the n-type coefficient have a minimum in that direction （可精確控制電阻的尺寸與區間） .

Schematic representation of the basic position of four piezoresistors on a membrane.

membrane

<110>bV

R

RV

V

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Piezoresistance Coefficients

Piezoresistance Coefficients l and t for (100) silicon.

P-type n-type

Source: Fundamental of Microfabrication, p.202

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Schematic Illustration of Pressure Microsensor

Source: Fundamental of Microfabrication, p.203

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Membrane Stresses

Surface stress in the middle of the sides of the membrane: p: pressure a: membrane side length h: membrane thickness Stress is in proportional to pressure

2

2

max 31.0)(h

apx

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壓阻式微壓力計的感測轉換機制

藉由感測器結構與電路設計將壓力轉換成電壓訊號 矽薄膜：將壓力轉換為薄膜

應力 壓阻材料 (P+ doping silico

n) ：將薄膜應力轉換為電阻改變率

惠斯敦電橋：將電阻改變率轉換為電壓偏移量

SiliconMembrane

Pressure

P

P m

Piezo-resistor

MembraneStress

m

m R/R

WheastoneBridge

ResistantChange

R/R

R/R V

VoltageSignal

V

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2. Capacitive Pressure Sensor

Displaced mass changes the capacitance between two attached metal plates.

KOH anisotropic etching silicon substrate sandwiched between two Pyrex glasses through anodic bonding(8.4mmx6.2mm).

Integrated CMOS components including sensor, transformer, amplifier and temperature compensator

d

AC

2d

A

d

C

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電容式微壓力計的感測轉換機制

藉由感測器結構與電路設計將壓力轉換成電壓訊號 矽薄膜：將壓力轉換為薄膜位移量 平行電容結構：將薄膜位移量轉換

為電容改變量

SiliconMembrane

Pressure

P

P dm

ParallelCapacitor

Membranedeflection

dm

dm C

CircuitDesign

Capacitanceshift

C

VoltageSignal

Vo

inVCC

CV

)2(20

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Pressure resonance sensors

A silicon substrate A diaphram (d=1.2mm, t=3um) Three transducers (two resonators) Resonators (L=100um,t=0.5um) Range (up to 1000Pa) Accuracy(0.01Pa) Non-linearity(0.1%)

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Microoptical Systems

Optical Parameters Amplitude Phase shift Spectral

distribution Frequency Time

量測原理完全不同，不需電線故無電磁噪音，很多物 / 化參數可轉化成光學參數

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光晶片的波導

Mantle

受外界的效應

光導層有高折射指數

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Reflection and Refraction

Law of reflection ’1= 1

Law of refraction n1 sin1 = n2 sin 2

Refraction rate c: 光在空氣中的速度 vm: 光在介質中的速度

全反射 : 由高折射率介質到 低折射率介質 ( 折射角 =90 時之

臨界入射角 )

mm v

cn

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3. Mach-Zehnder Interferometer

Waveguide deformed Changes the properties of the light bea

m Use phase shift to measure pressure Integrate SiON waveguides, sensitive si

licon membranes, potodiodes, and CMOS amplifier.

0.3mmX5mm 膜 (4)200umx200um Sensitivity 14 V/mbar 1bar=1atm=760mmHg=760torr 1torr=1mmHg

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Interference of Waves

(a) Fully constructive interference, (b) Fully destructive interference, and (c) intermediate interference

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Interferometer

Superposition of two identical waves with a phase shift. y' (x, t) = y1 (x, t) + y2 (x, t)

= ym sin(kx-t)+ym sin (kx-t +)

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Wave Guide of Pressure Sensors

Consist of the light guiding layer (SiON) and a lower index of refraction (SiO2) to allow the passage of light

A 2 to 3 m thick silicon dioxide layer (index of refraction = 1.46) was applied to a (100) silicon wafer.

Deposit a 0.5 m thick light guiding layer made of SiON (index of refraction = 1.52).

A 0.6 m thick silicon dioxide layer was added and structured using a dry etching process.

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光干涉儀式微壓力計的感測轉換機制

藉由感測器結構與光路設計將壓力轉換成電流訊號 矽薄膜：將壓力轉換為薄膜

變形量 干涉儀：將薄膜變形轉換為

光路的相位差，因而改變干涉的光強度

光二極體：將光強度轉換為感應電流

SiliconMembrane

Pressure

P

P m

MZ Inter-ferometer

Membraneelongation

m

m

Photodiode

Phaseshift

Ain

t Aint I

CurrentSignal

I

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壓力計的優缺點

Capacitive: More sensitive, Less temperature-sensitive, more robust (l

ong term stability), No hysteresis Large piece of silicon for bulk micromachining (higher pro

duction cost), Electronically more complicated (needs integrated electronics)

Piezoresistive: Smaller structure than bulk capacitance, Simple circuit (no

need for integration) Strong temperature dependence, Piezocoefficient depend

s on the doping level Interferometer:

much higher sensitivity.

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4. Capacitive Force Sensor

A movable elastic structure transforms a force into a displacement.

A transformation unit consisting of the electrodes transforms the displacement into a measurable change of capacitance.

Better linearity and sensitivity (electrodes are placed on both sides, gap=10um).

Made by anisotropically etching (110) silicon

Pyrex substrate

20 nm resolution, 0.01 ~ 10 N

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Force Sensing Resistor

Resistance is inversely proportional to the pressure / force

Polymer foil with planar electrodes covered by semiconductor polymer

Applied force reduces the resistance due to current flows across the shunting polymer foil

Dynamic range affected by electrode pitch (low yield rate) and sensitivity affected by foil thickness

Major disadvantage: hysteresis (pressure changes)

Inexpensive, compact, robust and resistant to external influences

F=0 R=1MOhm5% deviation (10million times), 10g ~ 10Kg 400C

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Force Sensing Resistor 功能及用途

高分子膜加上平面電極，再加上一半導體高分子膜 當此裝置受一力時，電阻值會降低，即壓力與電阻成反比。 量測電阻值範圍 1 MOhm(百萬歐姆 )~2 KOhm ，力量感測約 10

g~10kg

http://www.steadlands.com

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Position and Speed Microsensors

Essential for automobiles, robots and medical instruments. Determine the exact position of an endeffector of a

microrobotics. Contact-free optical and magnetic methods are the most

significant ones: Magnetic sensor for angular displacement Inclination sensor Ultrasound distance sensors Capacitive rotational speed sensor Fiber optical swing angle sensor

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Magnetic Sensor for Angular Displacement

Use Hall effect to detect angular displacement

霍爾效應是指當固體導體有電流通過，且放置在一個磁場內，導體內的電荷載子受到洛倫茲力而偏向一邊，繼而產生電壓。電場

力會平衡洛倫茲力。

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Hall Effect

Magnetic Force (Lorenz Force) :the velocity of charge q : magnetic field

Hall Effect The separation of positive and nega

tive charges produces an electric field

The force due to (qE)and the force due to are in balance.

Hall potential difference V

V=Ed

BvqFB

v

B

E

E

B

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Block Diagram for Magnetic Sensor

Each Hall sensor covers one tooth and one notch of the rotor

Multiplexer scans all n Hall sensors creating a step function to represent the magnetic distribution

Rotation causes phase shift Accuracy of 0.028° (-10– 8

0C) Independent from the dista

nce (insentitive to vibrations)

Very stable

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Inclination Sensor

Consists of an LED and a semi-spherical glass cup mounted on a photodiode matrix array

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Principle of Inclination Sensor

The position of a small moving vehicle in a pipe system Speed should keep constant A topological study Accurate for small angle (10°)

5V

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Ultrasound Distance Sensors

Use the pulse-echo principle.(聲音訊號的行進時差 ) Membrane is brought to resonance with integrated heating resis

tors. Ultrasound transducer made from piezoceramics emits a pulse

sequence. Design using a single sensor membrane: “Blind spot" appears w

hen the detector is too close to an object . New design: two identical independent ultrasound membranes

One transmitter (熱電阻以電激發共鳴 )and one receiver, integrated on a silicon substrate.

Acoustic pressure response is detected by piezoresistors, integrated in the form of a Wheatstone bridge.

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Ultrasound Distance Sensors

Schematic design of a single sensor membrane and the measurement principle

Sensitivity 3 V/mPa, at a bridge voltage of 5V.

壓阻元件

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Capacitive Rotational Speed Sensor

Compact and inexpensive angular speed sensors in navigation and landing gear controllers

200um厚（ 110) 音叉共鳴器

置入磁場並加上交流電

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Lorenz Force (羅侖茲力 )

Lorenz Force (羅侖茲力) ：運動中帶電粒子的磁力 當帶電粒子 q 以一速度 v 垂直進入磁場 B 中，它會承受一

偏向力 FB ，稱為羅侖茲力。

當輸入電流為交流電，質塊因 Lorenz Force 而震盪

BvqFB

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Coriolis Force (柯氏力 )

柯氏力 (Coriolis Force) ：一質塊在某方向產生一個固定線動量，此方向稱作驅動方向，若有一垂直於驅動方向的旋轉角速度，將會有一作用力在同時垂直於驅動及旋轉的方向，此力稱為柯氏力，而柯氏力的大小與角速度成正比。

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電容式陀螺儀的感測轉換機制

藉由科氏力造成的質塊偏移，以電容方式轉換成電壓訊號 振動質塊與扭力彈簧：將角速度轉

化為科氏力 差動式電容轉換器：將質塊位移轉

換為電容變化量 電容電壓轉換器：將電容轉化為電

壓訊號

Seismic Mass

Angularvelocity

Fc

DifferentialCapacitanceConverter

Mass displacement

zC.V. convert

Capacitancechange

C

C V

VoltageSignal

V

HarmonicLorenz Force

z C

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電容式角速度感測器結構

Made of <110> silicon

[Hashimoto, in Micro System Technologies, 94]

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Fiber Optical Swing Angle Sensor

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Fiber Optical Swing Angle Sensor

Light is lead into a glass fiber via a polarization filter. A torque applied to the mechanical measuring section causes a

torsion in the glass fiber and changes the direction of the polarization of the light.

Change of the light intensity is detected by the second polarization filter and is then evaluated by a photodiode.

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M

K B

xi

xo

xM

Sensor Case

Transducer

Moving Part

Typical Model of Accelerometer

STRUCTURE OF ACCELEROMETER Mass-Spring-Damper substructure Displacement transducer Amplification circuit

SYSTEM MODEL Mechanical subsystem Gm

Electric subsystem Ge

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Mechanical Subsystem

MASS-SPRING-DAMPER SUBSTRUCTURE

NEWTON’S SECOND LAW

MECHANICAL TRANSFER FUNCTIONM

K B

xi

xo

xM

Sensor Case

Transducer

Moving Part

M

Knw

KM

B

2where

oooi KxxBxMxM

22

2

2)(

nn

nm

i

o

DDSD

x

x

K

MSm

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Cantilever Principles

DISPLACEMENT TRANSDUCER OF ACCELEROMETER Piezoresistive Capacitive Piezoelectric

M a ss

P ie z o re s is to r

B e a mS u b s tra te

M a ssB e a mS u b s tra te

E le c tro d e s

M a ss

P ie z o e le c tr ic film

B e a mS u b s tra te

(a) Piezoresistive Mode

(b) Capacitice Mode

(c) Piezoelectric Mode

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Cantilever Beam Spring

懸臂樑在自由端受負載之最大變形 ymax= PL3/(3EI)

虎克定律 P = Ky P = (3EI/L3)• ymax

懸臂樑的彈簧常數 K = (3EI) / L3 = (Ebh3) / (4L3)

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Capacitive Microaccelerometer

質塊位移造成電容的改變 : Permittivity, A: area, d: distance, V: voltage, Q: charge 0: Permittivity in vacuum, r: Dielectric constant

d

AC

V

QC

0 r

2d

A

d

C

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Piezoresistive Micro-accelerometers

在應變最大處鍍上壓阻（ Piezoresistive ）材料 加速度造成質塊位移而在懸樑上產生應變

ttllR

R

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Integrated Capacitive Accelerometer

Consists of independently fixed plates and a movable comb-like microstructure.

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Integrated Capacitive Accelerometer

Made from polysilicon by surface micromachining.

Initial Mass

Stationary polysilicon fingers

Displacement

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Integrated Capacitive Accelerometer

First commercialized MST device. Used in airbag system.

Sensor diameter about 9 mm. Signal pre-amplification, temperature

compensation and system self-test purposes were integrated

Accelerations up to 50 g can be measured with a sensitivity of 10 mV/g.

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Capacitive Cantilever Microsensor

Consist of a cantilever beam over an opposite electrode and a contact strip.

Threshold voltage applied to offset the forces caused by the acceleration.

The level of the threshold voltage is used to compute the acceleration

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Capacitive Cantilever Microsensor

A sawtooth voltage is applied in defined steps across the cantilever and the electrode.

Electrostatic force acting on the cantilever increases with the applied voltage until contact occurs.

For a cantilever length of 120-500 m, the microsensor sensitivity is in a range of 0.6-100 mV/g.

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Capacitive Cantilever Microsensor

Made of polysilicon by the dry etching process.

Microstructure height (polysilicon) = 2.2m.

The gap attained between the cantilever and the contact strip is 1.5 m.

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Piezoresistive Microsensor with Oil Damping

Oil damps the resonance of the suspended mass. The cantilever is 480 X 200 X 12 (m); the seismic mass weighs

2 (mg). Measurement range

20 ~ 50 g.

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Chemical Sensors ：偵測溶液中化學物質的溶度或存在

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Applications of Chemical Sensors

Detect the presence or concentration of a chemical substance in a solution.

For qualitative or quantitative measurements

About 60% are gas sensors. local measurement in a rea

l-time environment.

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Sensor Matrix

Instead of the global detection in conventional methods, chemical micro system can analyze the chemical distribution over a domain.

Oxygen profile using sensor matrix32 X 32 in 3cm X 3 cm.For medical measurement

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General Structure of a Chemical Sensor

The material characteristics of a sensitive layer are changed due to the presence of a selected substance

The transducer picks up the characteristics change of the sensitive layer by the following sensor principles

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Major sensor principles of a Chemical Sensor

IDT using the capacitive measurement by changing the dielectric properties of the sensitive layer

Pellistor sensors measuring temperature increase due to a chemical reaction

Optical sensors analyze the substance in direct contact with the waveguide, which changes its index of refraction

Acoustic (resonance and wave guide) sensors using the change of mass

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Interdigital Transducer (IDT) Sensor Principle

The capacitance of IDT (叉指式 ) deviates due to the change of the dielectric properties of the sensitive layer (eg. SnO2).

Good for measuring humidity, concentration of sulfur dioxide or ethanol （乙醇） .

68

Sensors Based on a Zigzag IDT Capacitance

The concentrations Of CO2 in a fluid is measured with AMO/PTMS (甲烷 ) whose dielectric properties is changed with the CO2.

Zigzag design has better capacitive properties.

NiCrAu capacitor,Zigzag width variesbetween 2.5~15 m.

AMO/PTMS thickness variesbetween 0.9~1.2 m.

69

(50nm n-doped) (a few nm, sputtered)

(Activate the metal oxide gas reaction)(1m, used as an electrical insulator)

Sensors Based on IDT Capacitance

Another interdigital transducer sensor for detecting CO, C02, N02 and water concentrations.

The sensitivity and selectivity of SnO2 can easily be enhanced by a catalyst.

70

Pellistor Sensor Principle

Determine concentration of gases.

Measure the increase of temperature due to a chemical reaction.

When a gas is burnt, energies are released, that causes a temperature increase specific to the gas on the catalytical surface.

High working temperatures of up to 700°C causes problems to silicon.

71

Bimetal Sensor

A chemical reaction is transformed into mechanical motions by using the bimetal effect.

Array of 400 m long silicon cantilevers made of (0.4 m Pt catalytic layer) / (0.4 m Al) / (1.5 m silicon).

The reaction heat causes the bimetal cantilevers to bend.

Displacement measured by a scanning force microscope with an optical laser detector.

Sensor resolution: 0.01 nm, (ie. 10-5°C)

72

Resonance Quartz Sensor Principle

The chemical reaction between the substance and the sensitive layer changes the sensor mass.

The mass change affects the resonant frequency of the standing acoustic wave in a mechanical structure such as a membrane,cantilever, or solid.

73

Principle of Standing Waves

If two sinusoidal waves of the same amplitude and wavelength travel in opposite directions along a stretched string, their interference with each other produces a standing wave.

74

Reflections at a Boundary

When the string is tied to a wall (a), the reflected pulse is inverted from the incident pulse.

When the string is tied to a ring (b), the pulse is not inverted by the reflection.

We can set up a standing wave in a stretched string by allowing a traveling wave to be reflected from the far end of the string.

75

Standing Waves and Resonance

Standing waves pattern on a string and on a membrane .

76

Waveguide Sensor Principle

The sensitive layer interacts with the analyzed substance and the wave transmission changes due to damping.

77

Acoustic Waves Transducers

Principle of Acoustic Wave Interdigital Transducer (IDT) over a piezoelectric layer. Using IDT as actuator and sensor. Sensitive layer, interacting with the chemical substance,

changes the phase or the resonance frequency of SAW.W

d

+VE -VE

IDT Actuator IDT Sensor

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BioSensors:在生物及營養研究上在分析微量元素上如重金屬毒物或過敏原 ; 手術現場

79

Sensing Principles

Similar principles as chemical sensors. The biologically sensitive elements such as enzymes, receptors a

nd antibodies are integrated with the sensor. In many molecular interactions, gases are either released or cons

umed, that can be detected by a chemical sensor. Major difficulties

Produce only short-lived sensors because the proteins are not very stable for a very long time.

Immobilization （固定） of the proteins. Biosensors are divided into metabolism sensors （代謝型） and

immuno-sensors （免疫型） .

80

Metabolism Sensors

Biosensitive enzymes （酵素） as biocatalysts （生物催化劑） to detect molecules in a substance and to catalyze a chemical reaction.

The analyzed substance is chemically transformed and the course of a reaction can be detected by a chemical sensor.

For instance, Phosphate （磷酸鹽） concentration can be determined from the amount of oxygen consumed.

(Enzyme)

81

Immuno-Sensors

To detect chemically inactive molecules in a substance. Immobilized antibody molecules ("lock") on the sensor surface

bond with an antigen molecule "key" in the substance.

82

Immuno-Acoustic Wave Sensor

免疫型聲波感測元件 病原菌濃度量測的應用 板波元件表面裝置生敏膜（抗體層） 生敏膜抗體與特定抗原結合改變傳遞平板質量，因而影響波

傳速度（訊號頻偏） 以頻偏量檢測生敏膜上的抗原數量

83

Single Channel Metabolism Sensors

Several thermal metabolism sensors can be installed in one sensor system.

Thermistors （熱量計） are made by doping and etching the quartz chip.

Tx-thermistor, Ex - enzyme reaction range.

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Single Channel Metabolism Sensors

The thermistors T0 and T1, are responsible for measuring the enzyme located in the reaction range E1.

The reaction between the enzymes Ei with the substances marked as Si generates heat that is registered by the thermister.

Si: substances to be measuredEX: urea （尿素脢） and penicillin-V （青黴素）

: Temperature difference across E1

: Temperature difference across E2

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Temperature Sensors在監視系統扮演重要角色如程序醫學及環保方面

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Fiber- Optical Thermometer

The multi-modal glass fiber is made of materials that have different temperature coefficients in the core and the mantle.

Temperature variation in the sensor surrounding changes the local index of refraction in the fiber, that results in an optical light attenuation.

Measure temperatures of up to 90°C with in accuracy of 0.1°C.

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Flow Sensors:在醫學及汽車上量測小量液體及氣體流動

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Two-mode Flow Sensor

Two modes: Elapsed time of the locally heated flow medium: A 5 Hz

signal was applied to the heater and the time was measured until the temperature rise is recorded by the 2nd sensor.

Thermal dilution: the heater supplies constant energy, and measure the temperature difference between the upstream and downstream sensors.

Sensitivity: 0.05~0.2 ml/min.

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Force-Measuring Flow Sensor

以壓阻原理量測物體在流體中所受的力，以計算流體流量 懸臂長 3mm寬 1mm厚 30m ，以表面與體型微細加工矽晶圓製

成。操作範圍 5~500 ml/min ，對水的敏感度為 4.3 V/V per l/min 。

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Thermal Flow Sensor

Consist of a circular silicon disc, an implanted heating resistor, a ring-like silicon dioxide layer (thermal insulation) around the disc, and a 3 um thick polyimide film as chip cover.

CMOS 二極體溫度計

CMOS 二極體量測上下游溫度差