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Microwave heating

A bit of theory

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Theory of microwave heatingTheory of microwave heating

c

HH

Microwaves are electromagnetic radiations

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Microwaves are not ionising radiation

Microwaves energy is largely below the energy necessary to break the bonds of common organic molecules

H-OH 5,2CH3-CH3 3,8

Hydrogen bond (water) 0,21

Chemical bond energy (eV)

Microwaves radiation (2.450 MHz) quantum energy (eV)0,0016

EnergyEnergy

Theory of microwave heatingTheory of microwave heating

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Wavelengths range from 1mm to 1m

Frequency allowed for commercial, medical and

scientific applications:

2,450 MHz (12.2 cm wavelength)

Heating is caused by

- Dipole rotation

- Ionic migration

Theory of microwave heatingTheory of microwave heating

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Dipole rotationDipole rotation

--

+

Ele

ctr

ic F

ield

Ele

ctr

ic F

ield

t=0ns

H HH H

OO

Loss of energy in form of heat

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--

+

Ele

ctr

ic F

ield

Ele

ctr

ic F

ield

t=0ns

ClCl--

Ionic migrationIonic migration

Loss of energy in form of heat

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The three parameters of the microwaves:

Dielectric constant e’ (polarizing level of a molecule in an electromagnetic field)

Dielectric loss e” (efficiency of the microwave conversion in heat)

Tangent loss (material capability of absorbing microwaves = e”/e’)

MicrowaveMicrowave Theory energyTheory energy

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Interaction MicrowaveInteraction Microwave//MaterialsMaterials

Material Temperature (°C) Loss tangent (x10-4)Water 25 1570Fused quartz 25 0,6Ceramic F-66 25 5,5Porcelain No 4462 25 11Phosphate glass 25 46Borosilicate glass 25 10,6Corning glass No 0080 25 126Plexiglass 27 57Nylon 6-6 25 128Polyethylene 25 3,1Polystyrene 25 3,3Teflon PFA 25 1,5

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Microwave Theory PenetrationMicrowave Theory Penetration

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Interaction of materialsInteraction of materials with microwaveswith microwaves

METALS

WATER

PTFE, PP, TPX

Reflective

Absorptive

Transparent to Microwaves

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Metals

Water, alcohols

PTFE, PP, Cassette, WAX, Glass

• Transparent to Microwaves

Absorptive

Reflective

Interaction of materialsInteraction of materials with microwaveswith microwaves

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It’s a kind of low power energy

carried by micro-waves

Internal direct heating is our advantage

It’s a physical effect,

neither chemical nor magical

Microwave heating: where’s the Microwave heating: where’s the magic?magic?

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Reality

• Microwaves cook my samples

• Rapid processing = poor morphology

• Antigens will be lost forever

• Molecular studies are not possible

• Day processing is useless

Microwaves create physical heat like conventionals do but internally the tissues. Better homogenity & efficiency.

Today’s technology makes 12-14hours a useless waste of time. Quality is guaranteed priority.

Diagnostic equivalence is validated by studies showing optimal antigen reactivity.

Microwave do not affect DNA, RNA and proteins’ quality at all.

Day processing = same day diagnosis = patient centric care

Perception

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Conventional HeatingConventional Heating

The temperature of the outside surface of the vessel is in excess of the boiling point of the solution

Container is heated first thenthen the solution.

CONDUCTIVE HEATING

SOLUTIONCONVECTIVE CURRENTS

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Microwave heatingMicrowave heating

Shorter ReactionTimes

Solution is heated firstfirst

MICROWAVE HEATING

SOLUTION

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Microwave effectMicrowave effect

This is an experimental proofThis is an experimental proof

Fresh sample of animal’s muscle were sectioned in two mirror blocks

(Fig.1 A-B), approximately 8cm3 each (20x20x20mm)

A B

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Place a beaker containing 100ml ethanol on an electronic controlled hotplate. Set the temperature at 70°C.When temperature is reached immersethe specimen A in this solution for 5minutes.

Place a beaker containing 100mlEthanol in an laboratory RHS typemicrowave tissue processor. Set the temperature at 70°C. When thetemperature is reached immerse the specimen B in this solution for 5minutes.

Microwave effectMicrowave effect

Hot Plate

HeatingMicrowave

HeatingA

A B

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Microwave effectMicrowave effect

After 5 minutes samples were removed from respective solution

A B

…and immediately bisected

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Microwave effectMicrowave effectA B

RESISTANCE HEATING MICROWAVE HEATING

Slight hardening in the outer part only

no sign of alcohol penetration and dehydration in the internal area.

The specimen was still soft

Complete hardening in the total area

the MW stimulated enhanced diffusion of alcohol into the inner area

complete dehydration/hardening is indicated by the color change

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Thank you