Sublimation is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-01-24. Numbers and descriptions here follow the published literature rather than marketing material.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
| Property | Value | Notes |
|---|---|---|
| Primary phase change | Sublimation | Ice changes directly to vapor under reduced pressure |
| Typical chamber pressure | 0.01–0.5 mbar (1–50 Pa) | Below the triple point of water; product-specific |
| Typical product temperature during primary drying | −40 °C to −10 °C | Kept below collapse temperature |
| Typical residual moisture | 0.5–3% w/w | Target range varies by formulation and use |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilization is the US spelling |
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
As a matter of fact, Millennials and Generation Z have given life to nostalgia as an industry in the late 2010s and early 2020s, a trend that coincides with the resurgence of some cultural phenomena of the late 1990s and early 2000s (Y2K), such the television series Friends (1994–2004), something that is well-received among young people despite its age. Nostalgia has also contributed to the anticipation and subsequent commercial success of the summer film Barbie (2023) based on a well-known doll of the same name, even though it was intended for adults rather than children. Millennials and Generation Z on average begin using cosmetics in their mid-teens, or a few years earlier than the Baby Boomers and Generation X.
=== Stages of healing === The graft is carefully spread on the bare area to be covered. It is held in place by a few small stitches or surgical staples. The healing process for skin grafts typically occurs in three stages: plasmatic imbibition, capillary inosculation, and neovascularization. During the first 24 hours, the graft is initially nourished by a process called plasmatic imbibition in which the graft "drinks plasma" (i.e., absorbs nutrients from the underlying recipient bed). Between 2 and 3 days, new blood vessels begin growing from the recipient area into the transplanted skin in a process called capillary inosculation. Between 4 and 7 days, neovascularization occurs in which new blood vessels form between the graft and the recipient tissues.
The following table is based on the ISSCAAP classification (International Standard Statistical Classification of Aquatic Animals and Plants) used by the FAO to collect and compile fishery statistics. The production figures have been extracted from the FAO FishStat database, and include both capture from wild fisheries and aquaculture production.
== Co-culture composition and conditions == Based on the desired product of the SCOBY, different species of bacteria and yeast are used. Such cultures generally include aerobic, gram negative AAB species such as Acetobacter, Gluconobacter and Komagataeibacter, aerobic, gram positive LAB such as Lactobacillus, as well as various yeasts such as Saccharomyces and Zygosaccharomyces. Strains are pre-screened for viability under compatible conditions, increased yield of desired product, and indisposition to compete; once chosen, various culture conditions are modified for optimal growth and productivity. For kombucha SCOBYs, the first step is yeast fermentation of sugars such as glucose from black or green tea into ethanol and carbon dioxide. Zygosaccharomyces is reported to be involved in 84.1% of all kombucha SCOBY fermentation processes due to its improved stability in high sugar and halophilic conditions, while Saccharomyces is predominantly used for its efficient fermentation rates and resistance to high temperature and alcohol content. Different variations of yeast can also be added as either a supplemental means to introduce different flavors and aromas or ensure reaction completion by utilizing different niches. While these niches vary yeast to yeast, certain fermentation conditions remain consistent. Such conditions include but are not limited to high substrate concentration, sufficient oxygen levels, temperatures of 20–30 °C (68–86 °F), and a pH between 4–4.5.
Sources: en.wikipedia.org
CR665 (H-D-Phe-D-Phe-D-Nle-D-Arg-NH-4-Picolyl), also known by the previous developmental code names FE-200665 and JNJ-38488502, is an all D-amino acid peptide that acts as a peripherally restricted κ-opioid receptor agonist. The selectivity for FE 200665 is 1/16,900/84,600 for the human κ, μ, and δ opioid receptors, respectively. The dose of FE 200665 required to produce motor impairment (measure of CNS penetration) was 548 times higher than the dose required for antinociceptive activity. It is being developed for use by Cara Therapeutics under the code name CR665. A small, blinded study was done in healthy humans to determine the analgesic effects. CR665 was dosed at 0.36 mg/kg I.V., and was compared to 15 mg oxycodone orally. CR665 had analgesic effects on visceral pain, but produced a hyperalgesic response in a skin pinch test.
=== Federal funding === Canada's National Research Council (NRC) provided Providence Therapeutics with CAD$5 million for the launch of January 2021 first phase of PTX-COVID19-B clinical trials. As part of the federal government's "next generation manufacturing supercluster" program, Providence and Northern mRNA had also been "cleared to access up to $5 million" towards the manufacturing start up process, according to a federal government spokesperson. The CBC report in late April 2021 also stated that "it could be eligible for a slice of $113 million in additional funding from the National Research Council of Canada Industrial Research Assistance Program". The federal government had provided funding to some other companies in Canada that were also working to develop a COVID-19 vaccine. Sorenson as Providence Therapeutics CEO posted an open letter to Prime Minister Justin Trudeau, in which he requested $CDN 150 million upfront to be used to pay for clinical trial and material costs. On April 29, 2021, Sorenson appeared before the House of Commons standing committee on international trade, to ask the Minister of Procurement, Anita Anand, to consider PTX-COVID19-B as an alternative to Moderna and Pfizer for the "2022 booster vaccines". Sorenson said that the NRC had approached Providence Therapeutics in 2020 after the company had announced their Phase I trial PTX-COVID19-B. Sorenson told the Standing Committee that, "We've had really good dialogue ever since phase I started. That process has gone on.
== Patents == Compositions and methods for inducing apoptosis. J. Kopeček, J. Yang, T.-W. Chu. (2019) US 10,251,906 B2. Compositions and methods for using albumin-based nanomedicines. J. Kopeček, J. Yang. US 10,925,973 (Feb. 23, 2021) Polymeric drug delivery conjugates and methods of making and using thereof. H. Pan, J. Yang, P. Kopečková, K. Luo, J. Kopeček (2016) US 9,289,510 B2 Hydrogels of water-soluble polymers crosslinked by protein domains. J. Kopeček, R. Stewart, K. Caldwell, C. Wang, C-H. Ho (2007) US 7,179,487 Synthetic polymeric drugs. J. Kopeček, P. Rejmanová, J. Strohalm, K. Ulbrich, B. Říhová, V. Chytrý, J.B. Lloyd, R. Duncan (1991) US 5,037,883 Copolymers based on N-substituted acrylamides, N-substituted methacrylamides and N,N-disubstituted acrylamides and the method of their manufacturing. J. Kopeček, K. Ulbrich, J. Vacík, J. Strohalm, V. Chytrý, J. Drobník, J. Kálal (1977) US 4,062,831 Device for connecting or joining the ends of interrupted tubular organs in surgical operations without stitching. D. Lím, L. Šprincl, J. Kopeček (1973) US 3,774,615 Increasing permeability of reverse osmosis membranes. J. Kopeček, S. Sourirajan (1970) US 3,536,612
== Prevalence == A number of studies have examined the prevalence of link rot within the World Wide Web, in academic literature that uses URLs to cite web content, and within digital libraries. In a 2023 study of the Million Dollar Homepage external links, it was found that 27% of the links resulted in a site loading with no redirects, 45% of links have been redirected, and 28% returned various error messages. A 2002 study suggested that link rot within digital libraries is considerably slower than on the web. The article found that about 3% of the objects were no longer accessible after one year, equating to a half-life of nearly 23 years. A 2003 study found that on the Web, about one link out of every 200 broke each week, suggesting a half-life of 138 weeks. This rate was largely confirmed by a 2016–2017 study of links in Yahoo! Directory (which had stopped updating in 2014 after 21 years of development) that found the half-life of the directory's links to be two years. A 2004 study showed that subsets of Web links (such as those targeting specific file types or those hosted by academic institutions) could have dramatically different half-lives. The URLs selected for publication appear to have greater longevity than the average URL. A 2015 study by Weblock analyzed more than 180,000 links from references in the full-text corpora of three major open access publishers and found a half-life of about 14 years, generally confirming a 2005 study that found that half of the URLs cited in D-Lib Magazine articles were active 10 years after publication.
== Histology == Gastric chief cells are epithelial cells which are found within the gastric unit or gastric gland, and form the base of the gastric unit. The gastric chief cell has an extensive network of lamellar rough endoplasmic reticulum organized around the nucleus. The gastric chief cell also contains many large secretory vesicles filled with digestive enzymes in the apical cytoplasm.
Sources: en.wikipedia.org
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.
The process has three main stages: freezing, primary drying, and secondary drying. Freezing sets the ice structure, primary drying removes free ice, and secondary drying removes bound water. Each stage uses specific temperature, pressure, and time settings.
No, it is a drying method rather than a sterilization method. Removing water can limit microbial growth, but it does not reliably kill microorganisms. Sterility must come from separate steps such as filtration, heat treatment, or aseptic processing.
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.