Measurement of pH in fluidic chip using a terahertz chemical microscope

Toshihiko Kiwa, Shohei Oka, Yuji Minami, Iwao Kawayama, Masayoshi Tonouchi, Keiji Tsukada

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


A terahertz chemical microscope (TCM) has been developed to visualize the chemical concentration of solutions in fluidic chips. Chemical potential-terahertz transducers were newly developed and applied to the bottom surfaces of the flow channels. When femtosecond laser pulses hit the transducers, terahertz waves are radiated from them. Since the amplitude of terahertz waves can be related to the chemical potential on the surface of the device, the distribution of chemical reactions on the surface can be visualized by scanning the laser on the device. Here, we report the demonstration of mapping of pH values using TCM with a spatial resolution of less than 1 mm. The pH distribution of the flow channels filled with 0.01 M NaOH and HC1 was successfully visualized. In addition, the neutralization process was monitored.

Original languageEnglish
Pages (from-to)221-224
Number of pages4
JournalIEEJ Transactions on Sensors and Micromachines
Issue number7
Publication statusPublished - Sept 25 2009


  • Chemical potential
  • Femtosecond laser
  • Fluidic chip
  • PH detection
  • Terahertz

ASJC Scopus subject areas

  • Mechanical Engineering
  • Electrical and Electronic Engineering


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