US 11,867,648 B2
Thermal fluid sensor with encapsulated fluid region
Syed Zeeshan Ali, Cambridgeshire (GB); Cerdin Ching Ching Lee, Cambridgeshire (GB); Ethan Gardner, Warwickshire (GB); Jonathan Owen Hardie, Cambridgeshire (GB); Jonathan Sean Callan, Cambridgeshire (GB); and Florin Udrea, Cambridgeshire (GB)
Assigned to Flusso Limited, Cambridge (GB)
Filed by Flusso Limited, Cambridgeshire (GB)
Filed on Jun. 22, 2021, as Appl. No. 17/354,327.
Prior Publication US 2022/0404300 A1, Dec. 22, 2022
Int. Cl. G01N 25/18 (2006.01); G01N 25/00 (2006.01); G01N 25/48 (2006.01); G01N 33/00 (2006.01)
CPC G01N 25/18 (2013.01) [G01N 25/00 (2013.01); G01N 25/48 (2013.01); G01N 25/4873 (2013.01); G01N 25/4893 (2013.01); G01N 33/0004 (2013.01); G01N 33/0027 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A fluid sensor for sensing a concentration or composition of a fluid, the fluid sensor comprising:
a semiconductor substrate comprising a first etched portion and a second etched portion;
a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises a first dielectric membrane located over the first etched portion of the semiconductor substrate, and a second dielectric membrane located over the second etched portion of the semiconductor substrate;
two temperature sensing elements on or within the first dielectric membrane and two temperature sensing elements on or within the second dielectric membrane; and
an output circuit configured to measure a differential signal between the two temperature sensing elements of the first dielectric membrane and the two temperature sensing elements of the second dielectric membrane;
wherein the first dielectric membrane is exposed to the fluid and the second dielectric membrane is isolated from the fluid; and
wherein one or both of the temperature sensing elements within the first and second dielectric membranes are configured to operate as heating elements.