Biomems 1 Intro

8/13/2019 Biomems 1 Intro

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Dr. Marc Madou

BIOMEMS

Class I. Introduction: From MEMS to BIOMEMS/

Definitions

Winter 2011

Aequorea victoria


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Content

From MEMS to BIOMEMS

BIOMEMS and analytical chemistry

Definition of sensors

Sensitivity

Cross-sensitivity and crosstalk

Signal-to-noise-ratio and drift

Resolution

Span or range and bandwidth

Dynamic range, gain and dynamic error

Selectivity Hysteresis

Accuracy

Calibration


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From MEMS to BIOMEMS

Miniaturization engineering is a more appropriate name than MEMS(NEMS), but the name MEMS (NEMS) is more popular. It involves agood understanding of scaling laws, different manufacturing methodsand materials.Initially it involved mostly Si and mechanical sensors(e.g., pressure, acceleration, etc). Miniaturization engineering or

MEMS applied to biotechnology is called BIOMEMS. In BIOMEMSthe number of materials involved is much larger, modularity is often amust (not integration as in ICs !), costs often need to be less thanwhats possible with Si and batch processes are not always the answer (continuous manufacturing need !).


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From MEMS

to BIOMEMS

Silicon Valley Micromachining

1972 Foxboro/ICT

1972 Sensym/National Semiconductor (sold to Hawker Siddley in 1988)

1975 Endevco

1975 IBM Micromachining

1976 Cognition (sold to Rosemount in 1978)

1980 Lawrence Livermore Lab

1981 Microsensor Technology (sold to Tylan in 1986)

1982 Transensory Devices (sold to ICSensors in 1987)

1982 ICSensors (sold to EG&G in 1994)

1985 NovaSensor (sold to Lucas in 1990)

1986 Captor (sold to Dresser in 1991)

1988 Redwood Microstructures

1988 TiNi Alloys

1989 Teknekron Sensor Development Corporation (dissolved in 1993)

1990 Microflow

1991 Sentir

1992 Silicon Microstructures 1992 Rohm Micromachining

1993 Silicon Micromachines

1993 Fluid IC

1993 Next Sensors

1994 Berkeley Microstructures

1994 Piedmont Microactuators

1995 Caliper

1995 Cepheid


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BIOMEMS as part of analytical chemistry

BIOMEMS may often be seen as a type of analytical

technique used in many research areas :

Chemistry

Biochemistry

Biology

Geology

Oceanography, etc. Analytical techniques which are also used in many

industrial areas :

Forensic science (e.g. O.J.s DNA)

Clinical diagnostics (e.g.glucose in blood)

Product development (e.g. new drug)

Quality control (e.g.pH of swimming pool)

Both instruments and sensors (see next

viewgraph for definition) are used in

BIOMEMS both will be discussed in

this course- the distinction between the

two is rather vague (e.g. size,

complexity, parts of an instrument

might be called a sensor, etc.)


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Sensitivity

A sensor detects information input,Iin, and then transduces or convertsit to a more convenient form, Iouti.eIout= F(Iin). So sensitivity is theamount of change in a sensors

output in response to a change at asensors input over the sensorsentire range. NOT THE SAME ASLOWER LIMIT OF DETECTION!

Very often sensitivity approximatesa constant; that is, the output is alinear function of the input

Sensitivity may mathematically beexpressed as

Sensitivity 35,000 Ohms/K @ 4.2 K

http://www.sci-inst.com/sensors/grt.htm

=dI

out

dIin

Germanium

Resistance

Thermometers


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Cross-sensitivity and crosstalk

Cross-sensitivity: The influence of

one measurand on the sensitivity of

the sensor for another measurand

(e.g., OH-influences F-detection)

Crosstalk: Electromagnetic noise

transmitted between leads or

circuits in close proximity to each

other


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Signal-to-noise-ratio-S/N and drift

S/N: The ratio of the output signal with

an input signal to the output signal with

no input signal

Drift: Gradual departure of the

instrument output from the calibrated

output. An undesirable change of theoutput signal.

Noise is normally measured "peak-to-peak": i.e., the distance from the top of one such

small peak to the bottom of the next, is measured vertically. Sometimes, noise is averaged

over a specified period of time. The practical significance of noise is the factor whichlimits detector sensitivity. A practical limit for this is a 2 x signal-to-noise ratio.


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Resolution

The smallest increment of change in the

measured value that can be determined

from the instruments readout scale.


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Span or range (also called bandwidth)

Span or range: The difference

between the highest and lowest

scale values of an instrument

Bandwidth: The range of scale

values over which the measurement

system can operate within aspecified error range ( also used as

another word for span)


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Dynamic range, gain and dynamic error

Dynamic range: The ratio of thelargest to the smallest value of a

range, often expressed in

decibels (dB),

Gain:The ratio of the amplitude

of an output to input signal. Dynamic error: The error that

occurs when the output does not

precisely follow the transient

response of the measured

quantity.


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Selectivity

Selectivity: The ability of a sensor to

measure only one parameter, in the

case of a chemical sensor, to measure

only one chemical species

Because of the lack of perfect

selectivity arrays are oftenimplemented (e.g., electronic nose and

tongue)

The electronic nose

The sensitivity of certain gas sensors to different gases

depends on the choice of catalytic sensor material and the

operating temperature. By combining several different gas

sensors into a sensor array, complex gas mixtures can be

analysed. Although the selectivity of the sensors is limited,

qualitative and quantitative gas analysis can be performed

using pattern-recognition techniques. The combination of

multiple gas sensors and signal analysis using pattern-

recognition techniques is the concept behind the electronic

nose and tongue. These instruments have been successfully

used in a number of applications, e.g., the quality estimation

of ground meat, the identification of different paper qualities,

the classification of grains with respect to microbial quality,and the screening of irradiated tomatoes.


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Hysteresis

The difference in the output when a

specific input value is approached

first with an increaseing and then

with a decreasing input.

Piezoelectric ceramics display hysteretic behavior. Suppose we start at zero applied

voltage, gradually increase the voltage to some finite value,and then decrease the

voltage back to zero. If we plot the extension of the ceramic as a function of the

applied voltage, the descending curve does not retrace the ascending curve - it follows

a different path.


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Accuracy

The degree of correctness with which a

measuring system yields the true

value of a measured quantity (e.g.

bulls eye) --see calibration

http://ull.chemistry.uakron.

edu/analytical/animations/


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Precision

The difference between the instruments

reported values during repeated

measurements of the same quantity.

Typically determined by statistical analysis

of repeated measurements

http://ull.chemistry.uakron.

edu/analytical/animations/


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Accuracy, precision and standard

deviation

A measurement can be precise but may

not not be accurate

The standard deviation (s) is a statistical

measure of the precisionin a series of

repetitive measurements (also often

given as with N the number of data,xiis each individual measurement, and

is the mean of all measurements. The

value xiis called the residual for

each measurement

X

X


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Calibration: standard curve

A process of adapting asensor output to a know

physical or chemical quantity

to improve sensor output

accuracy i.e. remove bias

A working or standard curve

is obtained by measuring thesignal from a series of

standards of known

concentration. The working

curves are then used to

determine the concentration

of an unknown sample, or tocalibrate the linearity of an

analytical instrument-for

relatively simple solutions


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What is Next?

Biomems 1 Intro

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Transcript of Biomems 1 Intro