A Novel 3-D-Printed Passive Microfluidic Temperature Sensor for Medical Applications

The electrical response of a novel passive 3-D-printed temperature sensor could significantly broaden its scope of applications and enhance the integration of microelectro-mechanical system (MEMS) microfluidic-based laboratory-on-a-chip (LOC) technologies. This article introduces an innovative temperature sensor based on the microfluidic technology which is well-suited for medical applications. The sensor’s design and optimization were conducted using multiphysics modeling and finite element method (FEM) simulations, implemented through FreeFEM++ software. Samples were produced using stereolithographic 3-D printing. A metal carrier was constructed to secure the chips during tank heating and the flow visualization with a microscope. X-ray microtomography tests were performed on chips to compare real parts with CAD models. Filling tests were conducted to position the liquid within the microfluidic channel. Furthermore, several types of liquids were tested, and contact angle (CA) measurements were employed to characterize the microfluidic chip’s structural material (DS3000) and various liquids, aiding in discerning the dielectric liquid were applied also. Among the liquids tested, water emerged as the most promising for this type of temperature sensor. Volume expansion calculations for different temperature values were performed, revealing a measured linear thermal expansion exceeding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu $ </tex-math></inline-formula>m/°C within the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~^{\circ }$ </tex-math></inline-formula>C–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$55~^{\circ }$ </tex-math></inline-formula>C. This study paves the way for microfluidic devices capable of measuring low flow rates using a temperature effect, thereby providing access to 16 an electrical response.