Note: Development of a microfabricated sensor to measure thermal conductivity of picoliter scale liquid samples.

This paper presents a thermal analysis device, which can measure thermal conductivity of picoliter scale liquid sample. We employ the three omega method with a microfabricated AC thermal sensor with nanometer width heater. The liquid sample is confined by a micro-well structure fabricated on the sensor surface.

Monitoring protein denaturation using thermal conductivity probe.

We propose a method for probing denaturation of proteins by measuring the thermal conductivity of the solution. We use the three-omega method with a microfabricated ac thermal sensor to measure the thermal conductivity of lysozyme, β-lactoglobulin, and bovine serum albumin protein solutions over a range of temperature and pH. Results suggest that conformation transformation of the protein during denaturation changes the thermal network in protein solutions and thus changes the thermal conductivity for all the tested proteins.

Micro-droplet detection and characterization using thermal responses.

We suggest a novel method to detect droplets and determine the protein content of droplets in microfluidic system using the 3ω method, which is a powerful tool to easily detect thermal response changes with a simple device. By measuring the thermal response of droplets and a carrying flow in real time, water droplets in an oleic acid carrying flow can be detected, and the concentration of bovine serum albumin in droplets can be estimated. This method is expected to increase the practicality and power of droplet-based microfluidic systems.

Note: Three-omega method to measure thermal properties of subnanoliter liquid samples.

There are growing needs to measure the thermal properties of small-volume liquid samples in various fields of bioengineering and microfluidics. Accordingly, there have been efforts toward miniaturization of the sensing device without substantially sacrificing the sensitivity. The minimum sample volume required for quantitative thermal analysis is currently in the 10 nl scale.