Microfluidic laminate-based phantom for diffusion tensor-magnetic resonance imaging

Abstract

This paper reports fabrication of a magnetic resonance imaging (MRI) phantom created by stacking of multiple thin polydimethylsiloxane (PDMS) layers. PDMS is spin-coated on SU-8 molds to obtain the desired layer thickness and imprints of the microchannel patterns that define the phantom geometry. This paper also identifies the unique challenges related to the fabrication and assembly of multiple thin layers and reports for the first time assembly of a large number of thin laminates of this nature. Use of photolithography techniques allows us to create a wide range of phantom geometries. The target dimensions of the phantoms reported here are two distinct stacks of 30 thin PDMS layers each of 10 µm thickness with either (i) curved 5 µm × 5 µm microchannels with 8.7 µm spacing, or (ii) straight 5 µm × 5 µm microchannels with 3.6 µm spacing. SEM scans of the assembled phantoms show open microchannels and a monolithic cross section with no visible interface between PDMS layers. Based on the results of diffusion tensor magnetic resonance imaging scanning, the anisotropic diffusion of water molecules due to the physical restriction of the microchannels was detected, which means that the phantom can be used to calibrate and optimize MRI instrumentation.