Controlled Nucleation in Freeze Drying via Pressure Differential Ice Crystals

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Solution Overview

Problem

Current freeze-drying methods fail to control nucleation uniformly across multiple vials, leading to vial-to-vial variation in ice crystal structure and prolonged processing times due to random nucleation temperatures and inefficient ice fog distribution.

Innovation Solution

A method utilizing a pressure differential between a condenser chamber and the product chamber to generate and distribute larger ice crystals for controlled nucleation, achieved by forming condensed frost in the condenser and using gas turbulence to break it into larger ice crystals, which are then injected into the product chamber.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional ice fog method is used with cold gas introduction, then nucleation can be initiated, but nucleation time increases and product uniformity decreases

Engineering Contradiction:

Improvenucleation speedVSAvoidproduct uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention changes the temperature parameter of the ice fog from -196°C (liquid nitrogen chilled) to approximately -80°C (dry ice chilled), and controls the ice fog generation rate and distribution. This parameter optimization enables faster nucleation while maintaining product uniformity across all vials.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the mechanical nitrogen gas chilling apparatus with a simpler dry ice-based cooling system. This substitution reduces system complexity while achieving the desired nucleation control and product uniformity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If liquid nitrogen chilled gas is used to produce ice fog, then ice particles are generated, but system complexity and expense increase

Engineering Contradiction:

Improveice particle generationVSAvoidnitrogen gas chilling apparatus

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The invention uses dry ice (solid CO2) instead of liquid nitrogen as the cooling medium. Dry ice is cheaper, easier to handle, and does not require complex chilling apparatus. The dry ice sublimates to provide cold gas that generates ice fog, achieving the same nucleation initiation function with simpler equipment.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Temperature

If shelves are continually cooled during ice fog distribution, then cooling continues, but temperature difference between vials increases

Engineering Contradiction:

Improvecontinuous coolingVSAvoidvial-to-vial temperature uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The invention implements periodic control of the cooling process: cooling is paused or reduced during the ice fog distribution phase to maintain temperature uniformity across all vials, then resumed after nucleation is complete. This periodic action prevents temperature gradients from developing during the critical nucleation period.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach ensures rapid and uniform nucleation across all vials, reducing processing time and enhancing product uniformity by using larger, more effective ice crystals that maintain their structure during distribution, thus improving the freeze-drying process efficiency and product consistency.

Implementation Method 1

utilizing a pressure differential between a condenser chamber and a product chamber

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

using gas turbulence to break it into larger ice crystals

Methodology Applied

Scientific EffectGas turbulence: Turbulence

Implementation Method 3

The injected moisture freezes into tiny suspended ice crystals (ice fog) in the condenser chamber

Methodology Applied

Scientific EffectFreezing: Freezing

Implementation Method 4

forming condensed frost in the condenser

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 5

Ice crystals can themselves act as nucleating agents for ice formation in sub-cooled aqueous solutions

Methodology Applied

Scientific EffectNucleation: Nucleation

Implementation Method 6

lyophilization or freeze-drying process

Methodology Applied

Scientific EffectSublimation: Sublimation

Data Source

PatentEP2883012B1Controlled nucleation during freezing step of freeze drying cycle using pressure differential ice crystals distribution from condensed frost

Publication Date: 2018.01.31 MILLROCK TECHNOLOGY INC

Figure 1
Figure 2~3

AI summary

A method of controlling and enhancing the nucleation of product in a freeze dryer, wherein the product is maintained at a predetermined temperature and pressure in a chamber of the freeze dryer, and a predetermined volume of condensed frost is created on an inner surface of a condenser chamber separate from the product chamber and connected thereto by a vapor port. The condenser chamber has a predetermined pressure that is greater than that of the product chamber. The opening of the vapor port into the product chamber creates gas turbulence that breaks down the condensed frost into ice crystals that rapidly enter the product chamber for even distribution therein to create uniform and rapid nucleation of the product in different areas of the product chamber.