Presentation - Analysis - Atomic Force Microscopy

7/23/2019 Presentation - Analysis - Atomic Force Microscopy

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ATOMIC

FORCEMICROSCOPY

MR. PRATIP K. CHASKAR (M.

PHARM.)ASST. PROFESSOR, VES COLLEGE OF

PHARMACY

https://sites.gg!e."#/$/%es.$".i&/p'$tip "h$s$'/



SYLLA*S

Atomic ForceMicroscopy

Principle

InstrumentationSample preparationPharmaceuticalapplications



PARTS1. Laser – defected o

cantilever2. Mirror – relects laser

!eam tophotodetector

". Photodetector –photodiode – measuredierences in li#htintensity $ converts tovolta#e

%. Ampli&er'. (e#ister). Sample*. Pro!e – tip that scans

sample



MO+ES• (epulsive orce -contact – At short pro!e/sample

distances0

the orces are repulsive

• Measures repulsion !eteen tip and sample• Force o tip a#ainst sample remains constant• Feed!ac re#ulation eeps cantilever defection

constant• 3olta#e re4uired indicates hei#ht o sample• Pro!lems – e5cessive tracin# orces

applied !y pro!e to

sample



MO+ESC&t$"t Me• ,ontact mode operates in the repulsive re#ime

o the van der 6aals curve• 7ip attached to cantilever ith lo sprin#

constant -loer than eective sprin# constant!indin# the atoms o the sample to#ether.

• In am!ient conditionsthere is also a capillaryorcethin

e5erted !ythe ater

layerpresent -2/'8 nmthic



MO+ES-&C&t$"t Me• Attractive orce -non/

contact

– At

lar#e

pro!e/

sampledistances0 the orces areattractive

• Measures attractive orces !eteen tip andsample

• 7ip doesn9t touch sample• 3an der 6aals orces !eteen tip and sample

detected• Pro!lems / ,an9t use ith samples in fuid• :sed to analy;e semiconductors

9



MO+ES-&C&t$"t Me• :ses attractive orces to interact surace ith tip• =perates ithin the van der 6aal radii o the

atoms• =scillates cantilever near its resonant re4uency

->288 ?;

to improve sensitivity

• Advanta#es overcontact@

nolateral

orces0non/

or

no

destructivecontamination tosample0 etc.



ORKI-G• 7he cantilever is

desi#ned ith avery lo sprin#constant -easy to!end so it is verysensitive to orce.• 7helaserrefecto

is ocusedto thecantileverand onto the sensor

•

7he position o the!eam in the sensormeasures thedefection o thecantilever and inturn the orce



ORKI-G

closesurace

pro5imity tothe

• 7he orce is

detected !y thedelection o asprin#0 usually acantilever -divin#

!oard

• Forces !eteen thepro!e

van der Waals force curve

and thesample.

tipand

thesample

are

sensed to control the

distanc !eteen ti



ORKI-G• 7ip !rou#ht ithin

nanometers o the sample

-van der 6aals

• (adius o tip limits theaccuracy o analysis

resolution

• Stier cantileversprotect a#ainst sample

dama#e !ecause theydelect less in responseto a small orce

• 7his means a moresensitive detectionoscillatio



ORKI-G• 7he tip passes !ac and

orth in a strai#ht lineacross the sample -thinold typeriter or ,(7

• In the typical ima#in#mode0 the tip/sample orce

is held constant !yadBustin# the verticalposition o the tip-eed!ac• A topo#raphic ima#e is!uilt up !y the computer!y recordin# the verticalposition as the tip israstered across the sample.

Scanning Tip



A+VA-TAGES• Easy sample preparation

• Accurate height information

• Works in vacuum, air and liquids

• Provides a true three-dimensional surface profile.

• Samples do not require any special treatments (e.g. coatings, etc

•



+ISA+VA-TAGES• !imited vertical " magnification range

•

#ata not independent of tip• $ip or sample can %e damaged

• &an image an area of mm ' mm ith a depth of

feof millimetres.• &an only image a ma'imum height of fe micrometres

and a ma'imum scanning area of )*+ ' )*+ micrometres.

• At high resolution, the quality of an image is limited %y the radius

of curvature of the pro%e tip.

• equire several minutes for a typical scan

• mages can %e affected %y hysteresis of the

pieoelectric



CeneralApplications• /aterials nvestigated0 $hin and thick film coatings,

ceramics, composites, glasses, synthetic and %iologicalmem%ranes, metals, polymers, and semiconductors.

•

1sed to study phenomena of0 A%rasion, adhesion,cleaning, corrosion, etching, friction, lu%ricating, plating,and polishing.

• A2/ can image surface of material in atomic resolution and

also measure force at the nano-3eton scale.



Applicatio

ns• Study 1nfolding 4f Proteins

• magining 4f 5iomolecules

• 2orce /easurements n eal Solvent Environments

• Anti%ody-Antigen 5inding Studies

• !igand-eceptor 5inding Studies

• 5inding 2orces 4f &omplimentary #3A Strands

• Study Surface 2rictional 2orces• on &hannel !ocaliation



Applications

$he A2/ is useful for o%taining three-dimensional topographic information ofinsulating and conducting structures ith lateral resolution don to ).* nmand vertical resolution don to +.+* nm.

$hese samples include clusters of atoms and molecules, individualmacromolecules, and %iologic al species (cells, #3A, proteins.

1nlike the preparation of samples for S$/ imaging, there is minimal samplepreparation involved for A2/ imaging.

Similar to S$/ operation, the A2/ can operate in gas, am%ient, and fluid

environments and can measure physical properties including elasticity,

adhesion, hardness, friction and chemical functionality.

A concise applications listing is given %elo.

13$ 6 !E&$1E 7 )7



/etals0 tooling studies, roughness measurements,corrosion studies...

Solid poder catalysts0 aggregate structural determination,Polymers0 determination of morphology and surface properties,kinetic studies, aging phenomena, surface treatment

modifications,adhesion force measurement and indentation,

5iological samples, %iomaterials0 macromolecules association and

conformation studies, adsorption kinetic of molecules on polymer

surfaces,3ano- and microparticle structures, !angmuir-5lodgett. 2ilmstudies...

13$ 6 !E&$1E 7 )8

Presentation - Analysis - Atomic Force Microscopy

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