Gap Freezing for Uniform Lyophilization Cake Crystallization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lyophilization of materials, such as sugars, often results in the formation of solute layers on the top of the frozen solution, which can inhibit solvent sublimation due to rapid bottom-up freezing, leading to the formation of amorphous solids that prevent gas flow and require higher drying temperatures or longer times.
Innovation Solution
A method and apparatus that utilize a thermal insulator to separate the sample container from the heat sink, allowing for simultaneous freezing from the top and bottom surfaces, preventing solute concentration and promoting uniform sublimation, including a lyophilization device with heat sinks and a tray system that maintains a fixed distance for thermal insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the solution is frozen using conventional direct contact with heat sink, then freezing efficiency is improved, but solute concentration layers form on top surface inhibiting sublimation
Solution Approach 1:
A thermally insulating support is introduced as an intermediary between the heat sink and the sample container. This mediator modifies the thermal field distribution, enabling simultaneous freezing from both top and bottom surfaces while preventing solute concentration layer formation on the top surface that would otherwise inhibit sublimation.
Solution Approach 2:
The freezing process is segmented into dual-directional freezing (top and bottom surfaces simultaneously) rather than conventional single-directional freezing. This segmentation is achieved by positioning the sample container on a thermally insulating support above the heat sink, allowing independent thermal control from both surfaces and preventing harmful solute layer accumulation.
2Stability of the object's composition
If thermal insulator is added between heat sink and container, then uniform freezing from top and bottom is achieved, but device complexity increases
Solution Approach 1:
The thermally insulating support serves multiple functions simultaneously: it provides mechanical support for the sample container, acts as a thermal insulator to enable uniform freezing from both surfaces, and facilitates the gap freezing configuration. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
3Reliability
If solute layers form on top surface, then sublimation is inhibited, but higher drying temperatures and longer times are required
Solution Approach 1:
The uniform freezing structure is established during the freezing stage before sublimation begins. By preventing solute concentration layer formation on the top surface during freezing, the structure is pre-prepared to allow efficient sublimation without the need for higher temperatures or extended drying times, thus maintaining high sublimation efficiency and reducing processing time.
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 prevents the formation of impermeable solute layers, enabling efficient solvent sublimation and resulting in lyophilized cakes with larger, consistent pore sizes, improving the freeze-drying process by maintaining uniform temperature profiles and reducing drying time.
Implementation Method 1
providing a thermal insulator between the container and the heat sink
Implementation Method 2
a heat sink with a heat sink surface in thermal communication with a refrigerant
Implementation Method 3
the frozen solvent is removed by sublimation under reduced pressure
Implementation Method 4
Optimization of nucleation and crystallization for lyophilization using gap freezing
Data Source
AI summary
This application discloses devices, articles, and methods useful for producing lyophilized cakes of solutes. The devices and articles provide for a method of freezing liquid solutions of the solute by the top and the bottom of the solution simultaneously. The as frozen solution then provides a lyophilized cake of the solutes with large and uniform pores.