Fabrication and high-speed characterization of SU-8 shrouded two-dimensional microimpellers

Abstract

In this study, the performance of shrouded two-dimensional microimpellers was measured for application to a micro centrifugal pump used in a portable fuel cell system. Two types of microimpellers were designed, and fabricated by a multi-layer photolithography process using an ultrathick photoresist (SU-8 3000). Microimpellers with a diameter of 10 mm were tested using an air spindle up to maximum rotation speeds determined by the destruction of the microimpellers, which are 350 000 rpm for a purely-radial-outlet blade impeller and 450 000 rpm for a backward blade impeller. The purely-radial-outlet blade impeller showed a higher pressure rise—2.8 kPa at 150 000 rpm, 5.1 kPa at 200 000 rpm and 12.5 kPa at 300 000 rpm. The measured performance satisfies the requirement of the micro centrifugal pump. However, the measured pressure rises are roughly half of the simulated values. The influence of the radial clearance and height difference between the impeller and the diffuser was investigated using an electromagnetic motor and impellers with a diameter of 16 mm. Against expectation, a better pumping performance was obtained with a larger tip clearance, and the height difference did not affect the pumping performance. These unexpected results suggest that the tip clearance and the clearance between the impeller shroud and the stationary housing act as a diffuser.

Fuel cells and their components based on microsystem technology

“…Nakajima et al reported a SU‐8‐based microcentrifugal turbo pump for miniature fuel‐cell applications. Pressure rise by a centrifugal turbo pump is primarily determined by the tip speed of an impeller, and thus very high speed rotation is necessary for a small impeller.…”

A versatile and flexible low-temperature full-wafer bonding process of monolithic 3D microfluidic structures in SU-8

“…Two types of this photoresist have been used, SU-8 3025 and SU-8 3050. Compared to the older SU-8 series the mechanical stress which emerges during the baking steps is drastically reduced by an adapted thermal expansion coefficient and a decreased volume shrinking [38,39]. This way, the adhesion force to the substrates is drastically improved, up to the double depending on the used substrate materials and enables the fabrication of connected large-area SU-8 structures.…”

Photosensitivity Characteristics of Novel Resists Consisting of a Photobase Generator and an Epoxy Resin

“…Especially, photopatterning materials composed of an epoxy resin and a photoacid generator (PAG) are used as high aspect ratio photoresists in the fabrication of MEMS devices [1][2][3]. However, there is a drawback that the acidic species from PAGs will induce the corrosion in next generation microchips.…”