In situ thermal diagnostics of the micro-PCR system using liquid crystals

Jermim Noh, Su Whan Sung, Min Ku Jeon, Soo Ho Kim, Luke P. Lee, Seong Ihl Woo

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


A simple, reliable liquid crystal (LC) thermometry of a polymerase chain reaction (PCR) chip that has a microchamber inside the chip and a film heater and a film sensor patterned on the surface is firstly introduced. The silicon-based PCR chip is made by MEMS technology. A non-linear feedback proportional-integral control scheme adjusts the power input of the Pt heater to control the surface temperature of the micro-PCR chip measured by the Pt sensor with an accuracy of less than ±0.1 °C at steady state. We use the LC thermometry to analyze the temperature distribution in the microchamber of the micro-PCR chip. The reflected colors of LC's inside the microchamber are captured through a charge-coupled device (CCD) camera, subsequently analyzed using a hue-based color analysis system. Two LC's of which individual working range is near the typical PCR temperature of 55 °C and 72 °C are calibrated in a constant temperature bath with a resolution of less than ±0.3 °C. While the average microchamber temperature near the annealing temperature is similar to the surface temperature, it is lower than the surface temperature by ca. 1 °C in the range of the extension temperature. Also, the temperature variations along the center of the microchamber, are less than 1.5 ± 0.5 °C and 3 ± 0.3 °C in the range of the annealing and the extension temperature, respectively.

Original languageEnglish
Pages (from-to)196-202
Number of pages7
JournalSensors and Actuators, A: Physical
Issue number2
StatePublished - 26 Aug 2005

Bibliographical note

Funding Information:
This research was funded by “Center for Ultramicrochemical Process Systems (CUPS)” sponsored by KOSEF (2002–2003).


  • Hue
  • Liquid crystals
  • Microfabrication
  • PCR chip
  • Temperature uniformity


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