A. Rapid freezing of sample o Preservation of morphology o
B. Minimal freezing artifacts
C. Spray unit
D. Soft budget of $500
E. Incorporation of emersion tank (tank size ~5cm diameter)
Design Requirements Physical and Operational
Characteristics
A. Performance Requirements
1. Need to preserve the morphology in-vivo
2. Preserve cell structure
3. Minimal freezing artifacts; vitrification (glass like
solidification without the formation of crystals)
4. Extract the heat from the object as quickly as possible, because
the quality of the result is determined by the speed of cooling.
5. Temperature of cryogen cannot exceed 130 K or be below the freezing
point of the cryogen (85 K for propane)
6. Plunging velocity should be 3m/s for optimal freezing of sample.
B. Safety
1. Concerns with the cryogen used
2. Spray less than 50ml of cryogen (specifically for propane) in the
spray mechanism
3. Dependent upon the amounts of liquid nitrogen used a. Ventilation
of operational rooms b. Follow current handling guidelines
4. Transport and disposal of cryogens: prevent explosions a. Never
transport/store in a closed vessel b. Need a pressure release valve
5. Protective shield
C. Accuracy and Reliability
1. Minimal freezing artifacts
2. Rapid freezing time (less than 10 ms)
D. Operating Environment
1. This device is intended to be used in a laboratory setting
2. The room will be well ventilated
3. Will be operating in a standard pressure and temperature setting
4. Will be used by trained laboratory techs and other researchers.
E. Size
1. Emersion tank size around 5cm in diameter
2. Spray over 5mm square area
3. Thickness of specimen?
4. Overall size should be minimized (no exact dimension given by the
client)
F. Materials
1. Primary cryogens: liquid helium or liquid nitrogen
a. Used to cool secondary cryogens
b. Immediately envelop the specimen or any warmer object with a
thermally insulating layer of gas = Leidenfrost phenomenon; therefore
cannot use directly on the specimen.
2. Secondary cryogens: propane, ethane or halogenated hydrocarbons
3. Thermal insulation of primary cryogen
4. Spray component (mid-range pressure nozzle)
G. Aesthetics, Appearance, and Finish II. Production Characteristics
H. Quantity
1. One device is needed for professor Barry Ganetzky2. If the device
can be built for a fraction of the cost of the commercial units than it
could be marketable for other laboratories.
2. Target Product Cost; around $500 (soft number; the initial amount
that the client believes he can invest in the project; we want to stay
away form using department money so that the client can have the finished
product)
Miscellaneous
A. Standards and Specifications
B. Customer
1. This product is being designed for Professor Barry Ganetzky
2. Wants a variation of the commercially available freezing units, he
believes if the device can be built in house that the cost can be
drastically reduced.
C. Competition
1. The products on the market consist of the emersion tank component
and run around $10,000 per unit.
2. Commercial companies advertising this type of product
include: Leica Microsystems.