Microscale thermometry: A review

Recent advancements in microelectromechanical systems (MEMS) have required state-of-the-art techniques that provide accurate information of physical parameters such as fluid velocities and temperatures, at small scales, to fully characterize fluid flows in these devices. Especially it is difficult to measure temperature fields at microscale using conventional methods due to the limitation of spatial resolution in these techniques. In this paper, we present a comprehensive review of various advanced microscale thermometry techniques for measurements of bulk fluid or wall surface temperature fields. Differing from earlier publications, this review particularly focuses on categorizing the thermometry techniques based on how they measure temperature information at the microscale, i.e., either contact or noncontact methods. The paper presents details of measurement principles for each thermometry technique and includes a broad range of their applications. For the contact-based thermometry, the most recent fabrication and measurement results with micro-thermocouples are introduced, followed by discussions for scanning temperature probes and atomic force microscope (AFM) temperature probes. On the other hand, noncontact-based thermometry techniques are broadly summarized, including optical thermometry, liquid crystal thermometry, infrared thermometry, and Raman spectroscopy. Strengths and weaknesses of each technique compared to other approaches, with information of spatial, temporal, and temperature resolutions are introduced and discussed. This review will provide a general guideline for readers regarding the advantages and disadvantages of the most recent microscale thermometry techniques considering key requirements such as tool availability, system limitations, and temperature resolution. (C) 2015 Elsevier B.V. All rights reserved.