Final Mems Nems (2)
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Transcript of Final Mems Nems (2)
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OUTLINE
NEMS SCHOOL OF BASIC SCIENCEIIT PATNA
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Introduction
Cantilever Technique
Nanocalorimeter
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INTRODUCTION
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Nano-Electro-Mechanical system (NEMS) is the integration of
mechanical elements, sensors, actuators and electronics on
a common silicon substrate.
The Nano mechanical components are fabricated using
compatible micromachining process.
NEMS is the enabling technology allowing the development of
smart products.
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Transducer
a device that converts a primary form of energy into a
corresponding signal with a different energy form
Primary Energy Forms: mechanical, thermal, electromagnetic, optical,
chemical, etc.
take form of a sensor or an actuator
Sensor
a device that detects/measures a signal or stimulus
acquires information from the real world
Actuator
a device that generates a signal or stimulus
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BENEFITS OF NANO MACHINES
Nano-Mechanical devices promise to revolutionize
measurements of extremely small displacements and forces.
Can built with the masses approaching a few attograms(10-18 gm)
and with the cross section of10nm.
A second important attribute Nano machines is that they
dissipate less energy.
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NEMS have an important impact on
1 Medicine and BioengineeringDNA and genetic code analysis and synthesis, drug delivery, diagnosticsand imaging.
2 Avionics and Aerospace
Nano- and microscale actuators and sensors, smart reconfigurablegeometry wings and blades. Navigational gyroscopes
3 In CommunicationDomain
Low insertion loss switches (High Frequency)
Mass Storage Devices; Nano nozzles
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The key elements in the detection of a mass are thevibrational frequency and the deflection of thecantilever
Deflection
Proportional to mass content
Resonance frequency
R =(k/m)1/2
K = spring constant
m= mass
Principle of Microcantilevers
Appl. Phys. Lett., Vol. 85, No. 13, 27 September 2004
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Readout Method
There are several methods available to
observe the deflection and resonance
frequency of the microcantilever
Optical method
Piezoresistive method
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Optical
Optical method requires the use of a low power
laser beam
If microcantilever does not deflect, then no
biomolecules have been absorbed
Laser beam hits a specific position on the position
sensitive detector (PSD)
Major weakness-high cost
*Karolyn M. Hansen, Hai-Feng Ji, Guanghua Wu, Ram Datar, Richard Cote, Arunava Majumdar, and Thomas Thundat
(2001) Cantilever-Based Optical Deflection Assay for Discrimination of DNA Single-Nucleotide Mismatches. Analytical
Chemistry 73 (7): 1567-1571
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Piezoresistive
These sensors measure the strain induced
resistance change
When the biomolecules are absorbed by the
material there is a volumetric change in the
sensing material
Volumetric change is measured by resistance
change in cantilever
Advantages-Low cost
*Viral detection using an embedded piezoresistive microcantilever sensor. Sensors and Actuators A: Physical 107 (3), 219-
224
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Cantilever Sensors
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In this receptor only allow specific analyte to get adsorbed
Rest remain out of contact
Since analyte increases the mass so there is shift in resonance frequency
As mass is added to the cantilever shifts the resonance frequency.
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Virus detection using NEMS
We have used a resonating mechanical cantilever to detectimmunospecific binding of viruses, captured from liquid.
Arrays of surface micromachined, antibody-coatedpolycrystalline silicon nanomechanical cantilever beams wereused to detect binding from various concentrations ofbaculoviruses in a buffer solution.
Because of their small mass, the 0.5 mm X 36 mm cantilevershave mass sensitivities on the order of 10-19g/Hz, enabling thedetection of a mass of about 3 X 10-15 gm.
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With these devices, we can detect the mass of single-virus particles boundto the cantilever. Resonant frequency shift resulting from the adsorbed
mass of the virus particles
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*Amit K. Gupta, Pradeep R. Nair, Demir Akin, Michael R. Ladisch, Steve Broyles,
Muhammad A. Alam, and Rashid Bashir (2006) Anomalous resonance in a
nanomechanical biosensor. PNAS 103 (36): 13362-13367
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Nanocalorimetry
# Calorimetry is the science of measuring the heat of chemical reactions
or physical changes. Calorimetry is performed with a calorimeter.
# The device consists of a substrate with an array ofmicromachined
nanocalorimeter sensors.
# Each nanocalorimeter consists of a silicon nitride membrane and a
tungsten heatingelement that also serves as a temperature gauge.
# The nanocalorimeter sensors are very sensitive, with a resolution of10 nJ/K, allowing thermal analysis of small quantities of material.
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# The small mass of the individual nanocalorimeters enablesmeasurements on samples as small as a few hundred
nanograms at heating rates up to 104K/s.
# Each nanocalorimetric sensor consists of a thin-film
thermistor sandwiched between two electrically insulating
ceramic layers that form a membrane supported by thesubstrate
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Layout of the nanocalorimeter cell
Photograph of the parallel nano-scanning calorimeter.
J. Mater. Res., Vol. 25, No. 11, Nov 2010
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The thermistor is fabricated from an electrically conductive
film and serves to both measure temperature and heat the
sample.
Samples to be measured are limited to the thermistor area
of each sensor, and may be deposited on either side of the
membrane.
The membrane design of the sensor thermally insulates the
sample from the surroundings and ensures that the thermal
mass of the sensor, i.e., the addendum, is very small.
A current passed through the heating element heats the sample and the
calorimetric cell The power dissipated in the thermistor is determined
experimentally from the current supplied to the thermistor and thepotential drop between the voltage probes.
The local temperature change is determined from a four-point thermistor
resistance measurement that has been calibrated to temperature
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Measurements are performed in vacuum to eliminate
convection losses and to provide a chemically inert testing
environment.
ceramic membrane consists ofsilicon nitride, selected
because it is a good electrical insulator and because it is made
easily into thin membranes. low thermal effusivity, which
reduces the heat loss into the membrane.
The thermistor is made oftungsten, because of its large
temperature coefficient of resistance and its small resistivity,
both of which are beneficial to measurement sensitivity
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Operating Principle
The power dissipated in the thermistor can be parsed into
stored power and power lost to the surroundings. At constant pressure, the stored power results in a
changeof the enthalpy of the sample and calorimeter
addendum. If we define a control volume (CV) that
comprises the sample and the calorimeter addendum
P is the total power dissipated in the thermistor,
H is the time rate of change of the enthalpy within the CV,
Q is the heat loss through the boundaries of the CV.
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. The rate of change of the enthalpy can be written as
where T is the temperature of the thermistor. Substituting Eq.
(2) into Eq. (1) and rearranging results in
where T is the heating rate of the thermistor. The left side of
Eq.3 can be directly calculated from measured quantities and
is defined as the calorimetric signal from the sensor.
If Q is known or if its contribution to Eq. (3) is negligible (e.g.,in the case of large heating rates), the change in enthalpy with
temperature, dH/dT, can be determined directly from the
calorimetric signal.
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J. Mater. Res., Vol. 25, No. 11, Nov 2010
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To reduce the effect of the calorimeter addendumand/or heat loss on the measurement, it is often
convenient to perform a reference measurement Equation (3) can then be rewritten to define the
differential calorimetric signal as
del represents the difference between a sensor with
a sample and a sensor that is either empty or
contains a reference sample.
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Application of Nanocalorimetry
Studying molecular interactions
It is also used to investigate the kinetics of phase transformations
and reactions.
Nanocalorimetry makes use of thin-film and micromachiningtechnologies to significantly reduce the addendum of the
calorimeter, enabling ultrasensitive calorimetric measurements
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Pros And Cons
Potential Positive Impacts
Reduction of disease.
Job opportunities in new fields.
Low-cost energy.
Cost reductions with improved efficiencies. Improved product and building materials.
Transportation improvements
Potential Negative Impacts
Material toxicity
Non-biodegradable materials.
Unanticipated consequences.
Job losses due to increased manufacturing efficiencies.
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CONCLUSION
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CONCLUSION NEMS are extensively used and now a days they play vital
role in our life.
Further technology development are going to improve their
synthesis and performance.
Many life saving robot are still to come.
R&D work is still on and lots of new ideas are still to beimplemented.
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REFERENCES
MEMS AND NEMS Systems, Devices, and Structures by Sergey
Edward Lyshevski
http://mems.sandia.gov
http://www.memsnet.org/mems/
http://gen.lib.rus.ec/
www.wikipedia.org
http://www.links999.net/robotics/robots/robots_introduction.html
Applied Physics Letters Volume 85, Number 13
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THANK YOU
Thank you