Supercritical Drying – Aerogels

What…

is supercritical CO₂ Sterilisation?

Supercritical CO₂ drying removes liquid from a gel without allowing the structure to collapse. The wet gel is first exchanged into a solvent compatible with CO₂, then brought above the critical point of CO₂ (31 °C and 74 bar). In this state, CO₂ behaves as a dense fluid with gas-like diffusivity and liquid-like solvating power, enabling it to dissolve and replace the pore liquid before being vented as a gas.

Why…

use supercritical CO₂ Sterilisation?

With supercritical CO₂ there is no liquid–vapour boundary, meaning no surface tension acts on the internal pore network during drying. Traditional evaporation forces the liquid through a phase boundary, generating capillary stresses that shrink or fracture the gel. By remaining entirely above the critical point and then depressurising from the supercritical state, those stresses are eliminated, allowing the gel to retain its high surface area, porosity, and delicate 3D structure.

How…

to use supercritical CO₂ for Sterilisation

Successful drying requires precise control of pressure, temperature, and depressurisation rate. The gel is loaded into a high-pressure vessel, solvent-exchanged, and then brought above 74 bar and 31 °C to enter the supercritical region. Fresh CO₂ is circulated to extract the solvent, and once fully exchanged, the system is depressurised slowly and uniformly to prevent density gradients or rapid cooling. Controlled venting ensures the structure remains intact, producing a stable aerogel with minimal shrinkage.

Key System Features