BioMEMS

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BioMEMS
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BioMEMS

• MEMS is being applied to biomedical applications
  and has become a new field of research unto
  itself.
• The interface between biology and microtechnology
  encompasses many diverse areas and levels of
  biological complexity.
• Include DNA arrays (genes), immmunoassays
  (proteins), miniaturized lab-on-a-chips (genes,
  proteins, and sensors), and finally the
  integration of live cells (bacterial and
  mammalian) with semiconductor materials and
  components.

Immmunoassays ????
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Definition of BioMEMS
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Microfluidics Applications
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Market

• Several market studies are available for BioMEMS,
  biochips, lab-on-chips, µTAS Definitions are
  varying, however, they all predict a rapidly
  growing and high market for microtechnologies in
  life sciences.
• For instance, NEXUS is predicting that the market
  for In Vitro Diagnostics (IVD) will grow from US
  1,9 billion in 2000 to US 9.9 billion in 2005.

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Biosensors

• A biosensor is an analytical device which
  converts a biological response into an
  electrical signal
• Biosensors are devices that can detect and/or
  quantify
• molecules of interest. 
• Sensing occurs when there is an interaction
  between the
• target molecule and a biological macromolecule
• (e.g. enzyme, antibody, receptor or DNA
  strand). 

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Biosensor application

• Some of the most intense application in biosensor
  are diverse as blood glucose monitoring,
  explosive detection, food quality determination,
  genetic screening, and environmental monitoring. 
  

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The components of biosensor

• (1) The sensitive biological element.
• (biological material tissue,
  micro-organisms, organelles, cell receptors,
  enzymes, antibodies, nucleic acids etc ).
• (2) The transducer in between.
• (3) The detector element.

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Biosensor types

• Immunosensor - Immunosensors transduce
  antigen-antibody interactions directly into
  physical signals.

(Left) Antibodies labelled with microperoxidase
MP11 for generation of the electrochemical
signal via electrocatalytic reduction of H2O2
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Optical- immunosensor
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Enzyme biosensor

• Enzyme was used to demonstrate the selectivity of
  analytes.
• The transduced signal varies with the rate of
  reaction of analyte with certain enzyme.

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• Advantages
• more specific than cell based sensors
• faster responds due to shorter diffusion paths
  (no cell walls)
• Disadvantages
• more expensive to produce due to the additional
  problem of isolating the enzyme
• enzymes are often unstable when isolated
• many enzymes need cofactors for the detection of
  substances

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E1 Urease E2 Penicillinase
An enzyme sensor used to detect the
concentration of urea and penicillin-V
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DNA microarrays (Gene chip)

• A rapid method to read out from the gene strand.
• Microarray technology now allows us to exam many
  genes at once and determine which are expressed
  in a particular cell type.
• DNA molecules representing many genes are placed
  in discrete spots on a microscope slide. This is
  called a microarray.
• The RNA molecules are then "labeled" by attaching
  a fluorescent dye that allows us to see them
  under a microscope, and added to the DNA dots on
  the microarray.

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The DNA molecular
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(left) The intensity and color of each spot
encode information on a specific gene from the
tested sample
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Lab-on-a-chip (Microfluidic)

• Is a term for devices that integrate (multiple)
  laboratory functions on a single chip of only
  millimeters to a few square centimeters in size.
• Capable of handling extremely small fluid volumes
  down to less than pico liters.
• Lab-on-a-chip devices are a subset of MEMS
  devices and often indicated by "Micro Total
  Analysis Systems" (µTAS) as well.

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• Advantages of LOCs
• Low fluid volumes consumption and less sample
  fluid is used for diagnostics
• (2) Higher analysis and control speed of the chip
  and better efficiency.
• (3) Better process control because of a faster
  response of the system.
• (4) Large integration of functionality and small
  volumes.
• (5) Massive parallelization due to compactness,
  which allows high-throughput
• analysis.
• (6) Lower fabrication costs, allowing
  cost-effective disposable chips.
• (7) Safer platform for chemical, radioactive or
  biological studies.
• Disadvantages of LOCs
• (1) Novel technology and therefore not fully
  developed yet.
• (2) Physical effects like capillary forces and
  chemical effects of channel surfaces
• become more dominant and make LOC systems
  behave differently
• and sometimes more complex than
  conventional lab equipment
• (3) Detection principles may not always scale
  down in a positive way,
• leading to low signal to noise ratios.

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(upper) This "Lab-on-a Chip" electrophoresis
device allows mixtures of DNA or proteins to be
separated at 1 of the time required by
conventional capillary electrophoresis while
using much less sample.
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Microfludic design

• Viscosity of fluids -

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If m is constant, the fluid is called newtonian
fluid.
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• For newtonian fluid,

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Reynolds Number

• The Reynolds Number is defined as
• If 10lt Relt100 compressive fluid
• Re lt 1000 incompressive fluid

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Continuity equation

• For incompressive fluid

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Example 1
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Bernoulli equation

• Bernoulli equation is the equation of motion to
  calculate the pressure needed to drive the force
  in the micro-channel.

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Example 2
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Surface tension

• Surface tension is due to the cohesion force in
  between the fluid molecular.