Xurography as a Rapid Fabrication Alternative for Point-of-Care Devices: Assessment of Passive Micromixers

Abstract

Despite the copious amount of research on the design and operation of micromixers, there are few works regarding manufacture technology aimed at implementation beyond academic environments. This work evaluates the viability of xurography as a rapid fabrication tool for the development of ultra-low cost microfluidic technology for extreme Point-of-Care (POC) micromixing devices. By eschewing photolithographic processes and the bulkiness of pumping and enclosure systems for rapid fabrication and passively driven operation, xurography is introduced as a manufacturing alternative for asymmetric split and recombine (ASAR) micromixers. A T-micromixer design was used as a reference to assess the effects of different cutting conditions and materials on the geometric features of the resulting microdevices. Inspection by stereographic and confocal microscopy showed that it is possible to manufacture devices with less than 8% absolute dimensional error. Implementation of the manufacturing methodology in modified circular shape- based SAR microdevices (balanced and unbalanced configurations) showed that, despite the precision limitations of the xurographic process, it is possible to implement this methodology to produce functional micromixing devices. Mixing efficiency was evaluated numerically and experimentally at the outlet of the microdevices with performances up to 40%. Overall, the assessment encourages further research of xurography for the development of POC micromixers.

Keywords: ASAR; Point-of-Care; SAR; in-plane; lamination; low-cost; microfluidics; micromixer; rapid fabrication; splitting and recombination; xurography.

Figure 1

Rapid fabrication methodology based on xurography patterning and lamination; (a) Layer 1 patterning and adhesion to substrate; (b) Layer 2 patterning and alignment; (c) Layer 3 patterning, alignment, and final assembly; (d) Exploded view of a sample microdevice.

Figure 2

Schematic diagram; (a) T-micromixer (45° angle) shaped pattern cutting references (see Table 2 for details); (b) Balanced split and recombine (w₂/w₁ = 1) micromixer (SAR); (c) Unbalanced (asymmetric) split and recombine micromixer (w₂/w₁ = 2) (ASAR).

Figure 3

Rapid fabrication of T-micromixer (45°); (a) Cutting plotter holder and tool; (b) Photos of w_nom = 200 μm device (left) and w_nom = 750 μm (right); (c) 3D mapping of a w_nom = 200 μm device (cases I to IV); (d) 3D mapping through confocal microscopy at an inlet of a w_nom = 750 μm device (cases V to VIII); (e) T-micromixer sealing test; (f) Detail of laminar flow performance on a T-micromixer device.

Figure 4

Average dimensional deviation error (%) for a w_nom = 750 μm microchannel T-micromixer design with three replicates (see Table 3 for details, red represents overcutting and blue undercutting; (a) Setup I; (b) Setup II; (c) Setup III; (d) Setup IV.

Figure 5

Average dimensional deviation error (%) for w_nom = 200 μm microchannel T-micromixer design with three replicates (see Table 3 for details, red represents overcutting and blue undercutting); (a) Setup V; (b) Setup VI; (c) Setup VII; (d) Setup VIII.

Figure 6

Absolute average dimensional error E_t (%) for several setups (see Table 2 for details).

Figure 7

Absolute average dimensional error E_t (%) for standalone and portable setups (Table 4).

Figure 8

Mixing performance numerical analysis for a device with Re ≈ 0.7; (a) SAR micromixer (w₂/w₁ = 1); (b) ASAR micromixer (w₂/w₁ = 2); (c) Cross-sectional numerical mixing efficiency (M_n) for (balanced SAR) and unbalanced micromixers (ASAR).

Figure 9

Passive micromixing in a xurography rapid fabricated microdevice for red (upper inlet) and clear blue (down inlet). The microchannels walls are conformed by the dark blue vinyl processed by xurography and lamination process; (a) SAR micromixer (w₂/w₁ = 1); (b) ASAR micromixer (w₂/w₁ = 2); (c) Windows delimited for evaluation of the experimental mixing efficiency (M_s); (d) Experimental mixing efficiency (M_s) at the output region of the circular based SAR and ASAR micromixers manufactured with xurography and lamination.