Fabrication and Characterization of a Metal-Based Micro-Heat Exchanger by Electrodeposition Technique

Abstract

The investigation of a small-scale, MEMS-based heat exchanger is reported in this work. The Exchanger is based on capillary action and is designed for use in low-temperature thermal energy scavenging applications. The device is a microfabricated design, employing unique nickel channels for capillary effect. Fabrication of the nickel channels is based on processes that pattern and develop SU-8 negative photoresist on the substrate. Electroplating is then used to form metal channels between the bounding SU-8 structures. The removal of the SU-8 leaves only the metallic channels behind. Channels are fabricated to heights of 115 μm using these methods. The operation of this micro heat exchanger (MHE) is compared to other exchangers fabricated with SU-8 channels. Working fluid mass transfer rate from the heated MHE is utilized as a basic metric of operation. The mass transfer rate recorded from the nickel-based MHE is 2.51 mg/s. By contrast, an MHE fabricated with 150 μm tall SU-8 channels is shown to evaporate up to 3.01 mg/s. This translates into an effective thermal power consumption rate of 1.92 kW/m2 and 2.28 kW/m2 for the nickel and SU-8 based MHE respectively. Investigations of working fluid contact angle with the electroplated nickel surface are also presented. The surface is found to be a porous structure stemming from the electroplating process.