Double ChemFET for the In-Line Monitoring of Silver Dosing in Potable Water Systems



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51st International Conference on Environmental Systems


With NASA Advanced Exploration Systems (AES) Life Support Systems (LSS) baselining ionic silver (Ag+) as the biocide of choice, development in silver monitoring technologies becomes necessary to monitor and control Ag+ release. Ion-selctive field effect transistors (ISFETs) and chemically-sensitive field effect transistors (ChemFETs) are capable of selective detection of Ag+ with reversible and low detection limit responses. However, one major hurdle to ChemFET technologies is the requirement of a reference electrode, which can leak its fill solution into the potable water system and is prone to drift requiring frequent calibration. To circumvent this issue, a double chemically-sensitive field effect transistor (dChemFET) was proposed. The dChemFET uses a second ChemFET to selectively monitor the counter ion and serves in place of the reference electrode. This work reports on the development of the dChemFET, starting with the development of the Ag+ and NO3- ion selective memberanes (ISMs) to be used in the ChemFETs. The Ag+ ISM has a detection range of 50-100000 ppb. The counter ion ISM, NO3- ISM, has shown a detection range of 50-500 ppb. However, both ISMs face significant challenges in terms of drift that obstruct its application for long-term monitoring, but it can serve as a starting point for demonstrating the dChemFET proof of concept.


John Abdou, KBR, US
Lance Delzeit, NASA, US
Jing Li, NASA, US
Ami Hannon, KBR, US
ICES303: Physio-Chemical Life Support- Water Recovery & Management Systems- Technology and Process Development
The 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.


silver, silver ion, biocide, monitoring, field effect transistor, ChemFET, chemically-sensitive field effect transistor