Filing is concentrated: the single leading assignee holds 325 of the 1,682 records in scope, and the five most active filers together hold 47.5% of the field. Past the top five, the count drops quickly — tenth place holds only 22 records — so the ranked 100 companies include a long tail of firms with narrow, specific filings rather than broad process portfolios. A freedom-to-operate search should prioritise the top handful of assignees first, then check the specific sub-area a new filing targets against the long tail.

Both terms appear as core search criteria in this corpus because they represent the two competing drying routes used to remove solvent from a silica wet gel without collapsing its porous structure. Supercritical drying uses high-pressure CO2 or similar fluids above their critical point and dominates the commercial literature, which is reflected in the size of the C01B and B01J IPC classes in this dataset. Ambient pressure drying avoids the pressure vessel entirely by relying on surface modification chemistry, and shows up as a distinct, comparatively thinner branch of filings worth checking separately for white space.

Filing volume peaked at 172 records in 2020 and eased to 94 by 2024, a 33% decline from the 2021 level of 141. That reads as a real cooling in new filing activity for the period that has fully published, but the 2025 and 2026 figures in any raw chart will look even lower purely because patent publication lags filing by roughly 18 months — those years are still filling in and should not be read as a continuing decline yet.