Engineering of Removing Sacrificial Materials in 3D-Printed Microfluidics

Pengju Yin, Bo Hu, Langlang Yi, Chun Xiao, Xu Cao, Lei Zhao, Hongyan Shi, Pengju Yin, Bo Hu, Langlang Yi, Chun Xiao, Xu Cao, Lei Zhao, Hongyan Shi

Abstract

Three-dimensional (3D) printing will create a revolution in the field of microfluidics due to fabricating truly three-dimensional channels in a single step. During the 3D-printing process, sacrificial materials are usually needed to fulfill channels inside and support the printed chip outside. Removing sacrificial materials after printing is obviously crucial for applying these 3D printed chips to microfluidics. However, there are few standard methods to address this issue. In this paper, engineering techniques of removing outer and inner sacrificial materials were studied. Meanwhile, quantification methods of removal efficiency for outer and inner sacrificial materials were proposed, respectively. For outer sacrificial materials, a hot bath in vegetable oil can remove 89.9% ± 0.1% of sacrificial materials, which is better than mechanics removal, hot oven heating, and an ethanol bath. For inner sacrificial materials, injecting 70 °C vegetable oil for 720 min is an optimized approach because of the uniformly high transmittance (93.8% ± 6.8%) and no obvious deformation. For the industrialization of microfluidics, the cost-effective removing time is around 10 min, which considers the balance between time cost and chip transmittance. The optimized approach and quantification methods presented in this paper show general engineering sacrificial materials removal techniques, which promote removing sacrificial materials from 3D-printed microfluidics chips and take 3D printing a step further in microfluidic applications.

Keywords: 3D printing; microfluidics; quantification; removing efficiency; sacrificial materials.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Design and fabrication of three-dimensional (3D)-printed microfluidic chips. (a) A microfluidic chip with a serpentine channel. (b) A 3D chip model designed by SolidWorks. (c) Schematic of the polyjet 3D printer with three main parts, including the photopolymer inkjet system, the positioning system, and the forming platform. (d) 3D printed chips with build materials and sacrificial materials.
Figure 2
Figure 2
Four approaches to removing outer sacrificial materials. (a) Mechanical removing, (b) Removing outer sacrificial materials in a hot oven, (c) 95% hot ethanol, (d) hot vegetable oil, and (e) Mass reductions with the four approaches. The scale bar is 1 cm.
Figure 3
Figure 3
Inner sacrificial materials removal with three removers. (a–d) Inject air into the heating chip and take pictures at the (a) inlet, (b) front part, (c) rear part, and (d) outlet under the microscope. (e–h) Inject ethanol into a hot bath with the chip and take pictures at the (e) inlet, (f) front part, (g) rear part, and (h) outlet under the microscope. (i–l) Inject vegetable oil into a hot bath with the chip and take pictures at the (i) inlet, (j) front part, (k) rear part, and (l) outlet under the microscope. (m–p) Transmittance results at the (m) inlet, (n) front part, (o) rear part, and (p) outlet after processing by air, ethanol, and vegetable oil. The scale bar is 1 mm.
Figure 4
Figure 4
Transmittance of the chips after removing inner sacrificial materials with different removers. The transmittances of four parts are calculated: the inlet of the chips, the front part of the chips, the rear part of the chips, and the outlet of the chips. The average transmittance of the four parts represents the transmittance of the chips.
Figure 5
Figure 5
Removing inner sacrificial materials with different temperatures. (a) The microchannel transmittances of different parts in the chip and the average after processing with 60, 70, and 80 °C hot vegetable oil. (b–d) Chip deformation after processing at (b) 60 °C, (c) 70 °C, and (d) 80 °C. The scale bars are 1 cm.
Figure 6
Figure 6
Microchannel transmittances of chips under optimized conditions as time goes on (1, 3, 10, 20, 40, 120, 360, and 720 min).
Figure 7
Figure 7
Removing inner sacrificial materials of 3D-printed microfluidic chips. Chips with a (a) rectangle, (b) circle, (c) half-circle, and (d) triangle cross-section, respectively. (e) The microchannel transmittances of different chips after processing with the optimized engineering technique. The scale bars of full images and enlarged images are 1 cm and 200 μm, respectively.

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