pH is of fundamental importance to contemporary issues in chemical oceanography such as ocean acidification and biogeochemical cycling, yet continues to be chronically undersampled in both space and time. This problem can only be overcome through the development of sensors capable of stable, long-term autonomous operation in situ. The approaching age of ocean observatories desperately needs such sensors for the various types of proposed platforms (e.g. moorings, profiling floats, gliders). The PI?s propose to evaluate the performance of the ion sensitive field effect transistor (ISFET) for measuring seawater pH. Initial tests at MBARI indicate that commercial ISFETs may now be capable of long-term operation in the surface ocean with minimal sensor drift. A side-by-side assessment of commercially available ISFETs will be carried out at MBARI. Off-the-shelf ISFETs will also be deployed on ocean moorings to test the effects of biofouling and to determine the necessary anti-biofouling measures. Concurrent to this, MBARI will work with existing chip technologies to build an ISFET sensor specifically intended for seawater pH measurements. In designing the customized ISFET, special attention will be given to pressure tolerance and type of reference electrode.
Broader Impacts:
pH value is among the most critical chemical parameters to our study in oceanography. At present time, there is no any other progress as successful as PI's work in obtaining long term pH measurement in seawater. Benefit of this development is almost no limitation to entire ocean science community. The improved ISFET pH sensor technology from this effort will certainly be valuable to our development towards other chemical sensors for gaining long term monitoring ability. In addition, the experience and knowledge gained through this sensor related development will also benefit wide ranges of the engineering community in dealing with long term monitoring of chemistry in aqueous system. Its hard to name anything more important than the carbon cycle in the ocean right now, and this sensor would be a great help in understanding its spatial and temporal variability. A successful sensor would have wide application in ocean observing system and in all sorts of autonomous vehicles as well as ship-based field programs. Their WATCH program will involve under-represented groups in the data analysis.
This award was fundamental in the development of the "SeaFET" and "SeapHOx" sensors, which have gained recognition within the oceanographic community as the first sensors to utilize the Honeywell DuraFET® ISFET pH sensor. The initial paper by Martz et al (2010) sparked a great deal of interest in the DuraFET for measuring pH of seawater and over the course of the award our group received several requests to replicate the SeaFET & SeapHOx design for use in a variety of moored and underway applications. As of Jan 2012, the Martz Lab has built 52 sensors for 13 different research groups. These sensors were funded externally by a variety of different sources while much of the development effort and several 1-2 day training sessions with collaborators, were funded through this award. By the completion of the award, four additional publications directly related to Martz et al. (2010) have come out (Yu et al., 2011; Kroeker et al., 2011; Hofmann et al., 2011; Matson et al., 2011), and a sixth publication (Martz et al. 2011) was the result of an REU supplement to this award. Kroeker et al., 2011 and Hofmann et al., 2011 were embargoed by high profile journals PNAS and PLoS One, respectively; and both received some media attention. Designs for the SeaFET were transferred to Satlantic Inc., where the sensor has been successfully commercialized.
