When it comes to cell-based ISFET applications, some cellular phenomena such as cellular respiration
and acidification have been monitored simultaneously. Lehmann et al. reported pH-dependency in
changes of the extracellular acidification and respiration rates under the same cell culture fluid [94].
Recently, Milgrewa et al. reported the fabrication of the sensor array chip based on pH-sensitive
ISFET for the direct extracellular imaging [95], which is composed of a 16 pixel by 16 pixel array of
ISFETs that have biopotential readout circuits for signal acquisition systems. As shown in Figure 6,
each pixel array has a floating gate structure which is passivated by a pH sensitive membrane.