The corpus of 921 families is led by a small group of water-treatment specialists and equipment integrators with the deepest historical filing counts, though several of them show zero filings in the most recent tracked year. Japan-origin and US-origin assignees dominate the receiving-office split, with 209 and 216 records respectively, ahead of China, Taiwan and Europe. Because the most recent year is always undercounted due to publication lag, current rankings should be treated as a snapshot through the 2022-2023 filing years rather than a live leaderboard.

Yes, based on the trend data: filings ran at 72-73 per year through 2017-2018 and had fallen to 40 by the 2022 midpoint, a clear decline rather than growth. That does not mean the technology is losing commercial relevance — UPW systems remain essential fab infrastructure — it more likely reflects that the core purification architecture (ion exchange, reverse osmosis, ultrafiltration, polishing loop) was heavily claimed in earlier years and incremental novelty has become harder to find. Readers should also discount the very last one or two years for publication lag before concluding the slowdown is real.

US20260234029A1, filed by Nomura Micro Science, covers a secondary pure water device that runs a water supply pump, ion exchanger and ultrafiltration membrane in sequence, with an acoustic particle counter combined with either an optical particle counter or a TOC meter placed upstream or downstream of the UF stage. The base purification train it describes is standard and not novel on its own. The part worth checking against any new design is the specific sensor-combination-and-placement claim; a design that measures particles or TOC at a different point in the loop, or with a different sensor combination, likely sits outside its claim scope.

The IPC composition shows C02F water-treatment claims in 825 of 921 records versus only 67 in G01N (analysis and testing) and 86 in B08B (cleaning), which suggests the measurement and cleaning-integration layers are comparatively under-claimed relative to the core treatment chemistry. Inline colloidal particle counting, sensor placement relative to membrane stages, and resistivity feedback control in the polishing loop all look thinner than the base purification claims. A first claim in these areas would likely combine a specific sensor type, its placement point in the loop, and the control action it triggers, rather than claiming a purification method broadly.

The United States and Japan are the two largest receiving offices in this dataset, with 216 and 209 records respectively, followed by China at 138, EPO at 84, Taiwan at 72 and WIPO/PCT filings at 64. A search or clearance exercise that skips US and Japan will miss the majority of the foundational and most-cited prior art in this field. Taiwan's presence, while smaller in volume, is still worth checking given its concentration of semiconductor fabrication capacity.