Scanning-laser-beam semiconductor pH-imaging sensor

Motoi Nakao, Tatsuo Yoshinobu, Hiroshi Iwasaki

Research output: Contribution to journalArticlepeer-review

105 Citations (Scopus)


We have constructed a two-dimensional (2-D) pH-imaging sensor that enables us to observe th H+ distribution produced by living cells. The pH-sensing principle is similar to that of thelight-addressable potentiometric sensor. The electrolyte-insulator-semiconductor (EIS) structure (electrolyteSi3N4SiO2Si) is illuminated by a focused (∼1 μm) and modulated (1-10 kHz) He-Ne laser bean from the backside of the semiconductor, and the a.c. photocurrent flowing through the EIS structure is measured. By scanning the laser beam, 2-D pH images can be obtained. By using this sensor, pH distributions of colonies of yeast (Saccharomyces cerevisiae) have been observed. The spatial resolution of this sensor could be improved by thinning the Si wafer.

Original languageEnglish
Pages (from-to)119-123
Number of pages5
JournalSensors and Actuators B: Chemical
Issue number2-3
Publication statusPublished - 1994 Jun


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