In this landscape, advanced materials means the sensing layer itself is claimed as chemistry or structure — metal oxide semiconductor layers, two-dimensional materials such as graphene or transition metal dichalcogenides, or metal-organic framework (MOF) composites — rather than the sensor being treated as an undifferentiated black box in the claims. This distinction matters because a huge number of gas sensor patents claim packaging, circuitry or calibration methods without ever specifying the sensing material, and those records fall outside this corpus by design. If you are doing freedom-to-operate work, confirm which category your design falls into before relying on counts from either type of search.

The data shows filings rising from 6 in 2017 to 21 in 2019 before falling sharply, with only 2 records at the 2022 midpoint. The evidence here does not identify a specific cause, but the pattern is typical of a technology wave where an initial cluster of applicants stakes out claims around a new material class and then filing slows once the obvious claim territory is occupied. It is worth noting the 2025-2026 counts are also artificially low because of the roughly eighteen-month lag between filing and publication, so the true recent trend is likely higher than shown.

The corpus includes both established electronics companies and specialist materials and sensor firms, alongside a tightly linked group of individual co-inventors who file together repeatedly. Recent-year momentum data shows the named assignees tracked here — including a semiconductor major and a national research institute — all recorded zero filings in the latest year, suggesting the sector's filing activity is either dispersed across many smaller applicants or has shifted to publications not yet visible in this cut-off. Checking the assignee ranking table directly, rather than relying on any single company name, gives the fuller picture.

Relative to the dense claim coverage on metal oxide sensing layers — which anchor both of the top two most-cited records in this corpus — branches like 2D-material chemiresistive layers, MOF-based sensing composites and nanofiber sensing architectures carry comparatively few direct claims. That does not guarantee freedom to operate, since a thin count can also mean a technology is early rather than open, but it does mean these branches deserve a closer prior-art look before assuming they are blocked the way metal oxide claims are.

That application, filed by Apple and dated 2018-03-01, describes an environmental sensor combining a metal oxide sensing material heated by a shared heat source, with electrodes measuring resistance change to determine gas concentration, alongside an infrared light source and band-pass filter for detecting gases like carbon dioxide. Its notable feature is using the same heater as both the heat source for the metal oxide layer and the light source for the infrared detector, aimed at cutting power consumption in a consumer device context. It is one representative record among 83 in this corpus and should be read alongside the higher-cited structural patents rather than in isolation.