Modeling of the return current in a light-addressable potentiometric sensor

Tatsuo Yoshinobu, Daisuke Sato, Yuanyuan Guo, Carl Frederik Werner, Ko Ichiro Miyamoto

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


A light-addressable potentiometric sensor (LAPS) is a chemical sensor with a field-effect structure based on semiconductor. Its response to the analyte concentration is read out in the form of a photocurrent generated by illuminating the semiconductor with a modulated light beam. As stated in its name, a LAPS is capable of spatially resolved measurement using a scanning light beam. Recently, it has been pointed out that a part of the signal current is lost by the return current due to capacitive coupling between the solution and the semiconductor, which may seriously affect the sensor performance such as the signal-to-noise ratio, the spatial resolution, and the sensitivity. In this study, a circuit model for the return current is proposed to study its dependence on various parameters such as the diameter of contact area, the modulation frequency, the specific conductivity of the solution, and the series resistance of the circuit. It is suggested that minimization of the series resistance of the circuit is of utmost importance in order to avoid the influence of the return current. The results of calculation based on this model are compared with experimental results, and its applicability and limitation are discussed.

Original languageEnglish
Article number4566
Issue number20
Publication statusPublished - 2019 Oct 2


  • Chemical imaging sensor
  • Field-effect sensor
  • LAPS
  • Light-addressable potentiometric sensor


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