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Biosensors > quiz 4 > Flashcards

quiz 4 Flashcards

1
Q

Acoustic wave bio sensors are based on what physical property

A

Mass change (advantageous because it does not involve labels)

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2
Q

Two types of acoustic waves

A

Bulk (BAW) & surface (SAW)

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3
Q

What is the most common BAW sensor

A

TSM resonator
- made up for an AT(Bulk) and BT(surface) cut

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4
Q

What is the Pieozoeletric effect

A

Create eletric polarization when under mechanical stress

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5
Q

thickness shear deformation crystal

A

when dc voltage is applied ossilation
- when AC
- ossilation is perpendicular

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6
Q

when does a standing wave occur

A

when frequency is twice the crystal thickness

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7
Q

Two challeneges for QCM

A
  • gas bubbles
  • must be reusable
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8
Q

two QCM operation modes

A

Flow through- constant flow rate till equilibrium

Flow injection- less reliable quick bursts of sample

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9
Q

how can you increase mass sensitvity

A

use a thinner device but then it is harder to manufacture and easier to break

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10
Q

4 ways to describe Biosensors

A
  • Type of Cut( AT, BT, ST)
  • Material
  • Location of the transducer
  • Type of transducer
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11
Q

Basic principle of a SLAW device

A
  • St cut
  • uses two electrodes (IDTs) on one surface for detection
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12
Q

4 SLAW devices

A

SAW, FPW, SH-APM, STW

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13
Q

SAW

A
  • not very good for liquids
  • partical motion in longitudinal and sheer
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14
Q

STW

A
  • most suitable for liquids
  • high frequency results in small penetration making is better at sensing small particles
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15
Q

What is the physical property for micro-cantilever biosensors

A

induced stress

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16
Q

micro-calnlivever biosensors also called MEMS basic properties

A
  • responds by undergoing deformation
  • sensitive to temp and humidity
  • four shapes (rectangular, V, U, and T shaped)
17
Q

Chemical sensing in micro-cantivlever biosensors

A
  • bends down if compressive
  • bends up if tensile
18
Q

Static deformation transduction

A

caused be analyte interaction with the surface layer
- energy comes from binding energy, repulsive, or attractive, forces

19
Q

3 types of mirco cantilevers

A
  • statice: no stress= horizontal
  • Dynamic: countiuously vibrates at a F0 changes when analytie is introduced F0’
  • bridge: higher sensitivity
20
Q

What causes the resonance freq to increase in resonance mode transdcution

A

a decrease in length and an increase in thickness

21
Q

Challeneges with microcantilevers

A

affected by thermal drift & interactions with enviornment
- nonspecific binding and physcial adsorption (fixed by reference sensor and arrays)

22
Q

optical measurement of deflection and pro/con

A

similar to afm
Pro:
- simultaneous measurments
- vertical deflection of 0.1
Con:
- requires frequent optical alignment and calibration
- issues with light adsorption/ scattering
-individual light source is needed for each cantilever

23
Q

eletrical measurement

A

utilizies piezoeletric effect-change in resistance under mechanical strain
- resistance is proportional to length
Pro:
- sensitivity increase with decrease in thickness
- no alignment needed
- read-out can be on the same chip
- resistor can be used a a heating element
Con:
- liquid samples can cause short circuiting

24
Q

Affinity sensors

A
  • high qualituy factor due to operation in a high vacuum
  • response can be amplified using sandwich technique
  • good for label-free sensors
25
Q

thermistor

A

ceramic semiconductor made up of oxides of transition metals

26
Q

IDTs

A

generation and detection of sound waves in SLAW devices

27
Q

Thermocouples/ therompiles

A

thermocouple- generates voltage based on temperature difference between two points
thermopiles- thermocouples in series ( have a higher sensitivity)

28
Q

Enzymatic sensors

A

enzymes are used to boost if substrate is not thermally effecient( challenge is to avoid thermal dissipation)

29
Q

optical transduction

A

achieved by measuring the light power absorbed or emitted at a specific wavelength

30
Q

electromagnetic radation characterizations

A

characterized by intensity, direction of propogation, frequency/ wavelength, & polarization

31
Q

passive optical fiber

A

serves only to convey light (detection)

32
Q

active optical fiber

A

involved and transduction and detection

33
Q

fiber optic sensor arrays

A

allow for a high res image

34
Q

optical immunosensors

A
  • both competitive and sandwich format
  • flouresence is the preferd transduction method
35
Q

intrinsic optical immunosensor

A
  • flow through cell
  • competitive assay
  • reduces flourescence intensity
  • evanescent wave

Biosensors (4 decks)

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