From Eye to Insight

MaterialResearch

Life ScienceResearch

MedicalResearch

IndustrialManufacturing

NaturalResources

White Paper

COMPARING HIGH PRESSURE FREEZING PRINCIPLES

related instruments: EM ICE

2

COMPARING HIGH PRESSURE FREEZING PRINCIPLES

The EM ICE is the only High Pressure Freezer on the market using a pneumatic freezing principle and no alcohol in the pressure chamber.All other suppliers are using a hydraulic freezing principle and alcohol in the pressure chamber. This white paper offers a short comparison of the two principles and shows the advantages of the pneumatic freezing principle of the EM ICE.

Hydraulic freezing principle1. Unpressurized LN2 is waiting in tube2. Pressure chamber is filled with alcohol3. For pressurization:

> The hydraulically driven piston pushes LN2 towards the chamber to replace the alcohol > The alcohol flow is blocked by the exit nozzle and the full pressure of 2100 bar builds up before pressurized LN2 comes in contact

with the sample4. Cooling by LN2 only after the alcohol has been pushed out

Advantages > Small piston diameters > Timing of pressure / temperature can be influenced by alcohol volume > Less abrupt pressurization

Disadvantages > High system pressure (320 bar) with large pressurized gas volume for pressure stability imposes regular safety inspection > Regular change of hydraulic fluid necessary > Cooling rate influenced by the turbulence at the ethanol/LN2 interface > Sample may be exposed to ethanol before freezing > Alcohol residues after freezing

Pneumatic freezing principle1. LN2 gets compressed by a pneumatically driven piston in front of a valve2. Samples sits dry in pressure chamber3. For pressurization:4. By opening the valve, a pressure wave rushes into the chamber, compressing the air surrounding the sample. The air is warming up,

preventing the sample from cooling down while pressure is established5. The pressure wave is stopped by the exit nozzle causing pressurization of the chamber6. Cooling starts immediately in the wake of pressurization7. Pressurized LN2 volume is calculated to keep the pressure up to around 360 ms

Advantages > Maximum 10 bar system pressure and no hydraulic oil > Fastest pressure increases in pressure chamber > Sample is cooled immediately after pressurization (minimum pressure induced artefacts) > No effect of alcohol on sample > No alcohol residues on sample and carriers > No alcohol exhaust fumes > Well defined light and electrical stimulation timing

Disadvantages > Abrupt pressurization is a challenge for carrier stability > Pressure and cooling synchronisation is a given no shift possible

LNT White Paper - COMPARING HIGH PRESSURE FREEZING PRINCIPLES 3

Illustration of pneumatic freezing principle of the EM ICE1. Liquid nitrogen gets pressurized in front of needle valve2. Sample inside cartridge moves into pressure chamber.3. Sample sits in pressure chamber. Light or electrical stimulation happens now if programmed.4. Needle valve opens. Pressurized LN2 hade in pressure chamber and freezes sample. LN2 leaves pressure chamber via outlet nozzle.5. Pressure chamber is empty.6. Sample cartridge moves out of pressure chamber. 7. Sample cartridge is clipped. Sample arm removes. Sample cartridge is released and falls in LN2 sample Dewar.

1

2

3

4

5

6

7

© 2

018

by L

eica

Mic

rosy

stem

s Gm

bH.

Subj

ect t

o m

odifi

catio

ns. L

EICA

and

the

Leic

a Lo

go a

re re

gist

ered

trad

emar

ks o

f Lei

ca M

icro

syst

ems

IR G

mbH

.

Leica Mikrosysteme GmbH | Vienna, AustriaT +43 1 486 8050-0 | F +43 1 486 8050-30

www.leica-microsystems.com

CONNECT WITH US!