Microfluidic devices for synchrotron-based hard X-ray spectroscopy

The microfluidic devices used in this publication (link here) were designed and fabricated by Customized Microfluidics in collaboration with MAX IV. Here, the microfluidic device was capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions so that samples could be analysed without damage.

The figure below shows a chip with 3 channels dry-etched in a 525um silicon wafer, bonded on both sides with glass via anodic bonding. Side-mounted glass capillaries are interfacing the channels with an external pump.

Instead of PDMS, a material commonly used in microfluidics, this chip allows to handle harsh solutions for spectroscopic analysis. Triplicate channels on one chip provide flexibility in often time-sensitive beam time experiments.

A second device, also in collaboration with MAX IV, is shown below, where a three-layer polyimide chip (outer dimensions 75mm x 25mm) is held on a custom-made holder. Laser cut channels are closed on both sides with polyimide adhesive layers. The chip design allows to focus a solution of interest, injected in the middle inlet (left side of the chip), via hydrodynamic focusing provided by the outer sheath buffers.

This fabrication technique can bring a high degree of freedom to the channel design and configurations (e.g. three inlets with one outlet or three outlets). Polyimide was chosen as it shows high compatibility with X-ray analysis. Customized Microfluidics also designed and fabricated chip holders that are compatible with beam line apparatus.