ABSTRACT
Conventionally, pH is measured on the assumption that a solution is a uniform concentration. If the distribution of biochemical pheno-mena can be obtained as a visible image in real time, the local variations in these will lead to a better understanding. 32 × 32 pH image sensors were successfully fabricated by using the CCD/CMOS image sensor technique, and real-time imaging of a chemical reaction and pH distribution was carried out. The technique of this pH sensor is based on the principle of a charge-coupled device (CCD). Two-dimensional sensor comprising a 32 × 32 pixel array is integrated in a chip, whose size is 8.0 mm × 7.4 mm, and the size of the sensing area is 4.16 mm × 4.16 mm. The
pH variations by a chemical reaction are observed by 200 m/sec step (i.e. 5 frames per sec). Since the CCD device can sense lights, the pH image sensor also detects the photon. The two-dimensional optical distribution and pH distribution, in real time, have been obtained with the same sensor. In the device, a photo sensor and a pH sensor are fused in the same pixel, enabling the optical and pH signals to be detected simultaneously in the same sensing area.By modifying a potassium ion selective membrane consisting of a plasticized poly(vinyl chloride) (PVC) with bis(benzo-15-crown-5) on the semiconductor devices, a potassium ion image sensor was realized. The potential response linearly increased with its logarithmic concentration from 10-2 M to 10-5 M, and the selectivity coefficient for sodium ion was 10-2.7.The ion image sensor is expected to have applications in various fields, such as biochemistry and environmental and medical sciences to observe various reactions. 26.1 IntroductionMost familiar ion sensor using semiconductors is an ion-sensitive field effect transistor (ISFET). The ISFET-based biosensor can be assembled a very appropriate configuration for the in situ monitoring of various chemical processes, in vivo medical diagnosis, and several other fields.1
