Laser ablation and injection moulding as techniques for producing micro channels compatible with Small Angle X-Ray Scattering

Abstract

Microfluidic mixing is an important means for in-situ sample preparation and handling while Small Angle X-Ray Scattering (SAXS) is a proven tool for characterising (macro-)molecular structures. In combination those two techniques enable investigations of fast reactions with high time resolution (<1 ms). The goal of combining a micro mixer with SAXS, however, puts constraints on the materials and production methods used in the device fabrication. The measurement channel of the mixer needs good x-ray transparency and a low scattering background. While both depend on the material used, the requirement for low scattering especially limits the techniques suitable for producing the mixer, as the fabrication process can induce molecular orientations and stresses that can adversely influence the scattering signal. Not only is it important to find a production method that results in a device with low background scattering, but it also has to be versatile enough to produce appropriate mixer designs. Here we discuss two methods -laser ablation of polycarbonate and injection moulding of Topas -which were found suitable for our needs, provided care is taken in aligning the mixing/reaction channel, where the actual measurements will be carried out. We find injection moulding to be the better of the two methods.

Microfluidic Nanomaterial Synthesis and In Situ SAXS, WAXS, or SANS Characterization: Manipulation of Size Characteristics and Online Elucidation of Dynamic Structural Transitions

“…In addition to the high reproducibility and possible implantation of automation steps, microfluidics offers unique opportunities for online chemical and biological analyses, rheological characterization, and structural screening and analysis [ 5 , 8 , 9 , 21 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. These opportunities include short measurement times, a high precision of liquid modulation and control of timing and flow parameters, and use of minimal input sample volumes (particularly important for minimizing the consumption of expensive materials) [ 4 , 7 , 12 , 16 , 31 , 32 , 38 ].…”

From CAD to microfluidic chip within one day: rapid prototyping of lab-on-chip cartridges using generic polymer parts

“…During the last years, a plurality of rapid prototyping techniques has been applied to, or developed for the fabrication of microfluidic systems: 3D-printing [8][9][10][11][12][13][14], laser micromachining [6,[15][16][17][18][19], micromilling [6,20], replication from a master [6,[21][22][23][24] or casting from a mold [25], thermoforming [26][27][28][29][30], hot embossing [6,23,30,31], soft lithography [32,33], photolithography [34,35], and tonermediated lithography [36]. A wide range of different materials were addressed by such RP techniques, in particular polymers like polydimethylsiloxane (PDMS) [8,21,25,28,33,34], poly(methyl methacrylate) (PMMA) [16,30,31], polycarbonate (PC) [19,30] or cyclic o...…”

3D Micromachined Polyimide Mixing Devices for in Situ X-ray Imaging of Solution-Based Block Copolymer Phase Transitions

“…To seal microstructured Kapton with plain Kapton windows, the silane coupling approach can be applied . Although Kapton is not malleable like common microfluidic device materials such as poly­(di­methyl­siloxane) (PDMS) or COC, it can be rapidly microstructured using pulsed laser ablation. , This reproducible top-down method follows the “rapid prototyping” scheme known from soft lithography as it allows one to design a structure, fabricate it, test it, and rapidly create the next refined iteration to obtain incrementally improved devices on the path toward highly optimized device geometries …”

“…23 Although Kapton is not malleable like common microfluidic device materials such as poly(dimethylsiloxane) 24 (PDMS) or COC, 25 it can be rapidly microstructured using pulsed laser ablation. 26,27 This reproducible top-down method follows the "rapid prototyping" scheme known from soft lithography 28 as it allows one to design a structure, fabricate it, test it, and rapidly create the next refined iteration to obtain incrementally improved devices on the path toward highly optimized device geometries. 29 While there have been examples for rapid-mixing continuous-flow devices for time-resolved X-ray studies, most of these devices only use lateral (or two-dimensional (2D)) flowfocusing from the side channels, which can easily lead to agglomerations of the sample at the channel walls.…”