Laser Micromachining 3-D Free Standing Structure of MEMS Thermal Flow Sensor

A detailed study of the sensor structure, fabrication, and technical specification is essential for process design aimed at achieving miniaturization across various applications. This paper introduces a facile fabrication approach for creating a 3D free-standing structure of MEMS thermal flow sensors. Laser micromachining was used to pattern and separate the free-standing structure, which was then folded like origami to create a 3D shape. The sensor operates on the principle of thermal anemometry within a constant temperature electronic circuit to detect changes in flow rate within a tube. This proposed method simplifies the fabrication process through a single-step laser fabrication, successfully producing thin nichrome sensing elements as narrow as 45.1 μm with an electrical resistance up to 6 Ω and a temperature coefficient of resistance (TCR) of 390.39 ppm/°C. Thermal analysis via infrared thermography confirms that the free-standing design effectively reduced thermal mass. We detail the sensor's technical specifications, including time response and calibration curve, and demonstrate its sensitivity to airflow through the voltage responses. This highlights the sensor’s robust performance and its promising potential for various airflow measurement applications.