Facile Fabrication of Microfluidic Chips for 3D Hydrodynamic Focusing and Wet Spinning of Polymeric Fibers

Abstract

Microfluidic wet spinning has gained increasing interest in recent years as an alternative to conventional wet spinning by offering higher control in fiber morphology and a gateway for the development of multi-material fibers. Conventionally, microfluidic chips used to create such fibers are fabricated by soft lithography, a method that requires both time and investment in necessary cleanroom facilities. Recently, additive manufacturing techniques were investigated for rapid and cost-efficient prototyping. However, these microfluidic devices are not yet matching the resolutions and tolerances offered by soft lithography. Herein, we report a facile and rapid method using selected arrays of hypodermic needles as templates within a silicone elastomer matrix. The produced microfluidic spinnerets display co-axially aligned circular channels. By simulation and flow experiments, we prove that these devices can maintain laminar flow conditions and achieve precise 3D hydrodynamic focusing. The devices were tested with a commercial polyurethane formulation to demonstrate that fibers with desired morphologies can be produced by varying the degree of hydrodynamic focusing. Thanks to the adaptability of this concept to different microfluidic spinneret designs—as well as to its transparency, ease of fabrication, and cost-efficient procedure—this device sets the ground for transferring microfluidic wet spinning towards industrial textile settings.

Effect of Flow Velocity on Laminar Flow in Microfluidic Chips

“…The diameter of the circular channel is set to 50 µm. Microfluidic laminar flow technology has emerged as a novel approach for gel fiber fabrication [21,22]. Nguyen et al [23] utilized polydimethylsiloxane (PDMS) microfluidic chips to produce tadpole-shaped alginate gel fibers, in which mesenchymal stem cells (MSCs) were implanted.…”

Microfluidic-assisted fiber production: Potentials, limitations, and prospects

“…Although the resolutions and tolerances of the microfluidic devices made by additive manufacturing techniques are lower than those made by soft lithography, these methods were recently investigated for rapid and cost-efficient prototyping. 103–105 Costa-Almeida et al 106 and Gursoy et al 103 presented a templating method based on PDMS elastomers combined with an array of disposable stainless-steel hypodermic needles that may be removed after the PDMS curing. Their devices can achieve precise three-dimensional (3D) hydrodynamic focusing with laminar flow conditions.…”

“…Their devices can achieve precise three-dimensional (3D) hydrodynamic focusing with laminar flow conditions. 103–106 Pham et al demonstrated a straightforward and cost-effective method based on the embedded template to fabricate PDMS microfluidic devices without requiring specialized facilities. As such, a diverged Y-shape template platform with three inlet ports and one outlet was fully covered by the PDMS pre-polymer.…”

“…Furthermore, microfluidic devices employed to fabricate such fibers are fabricated through soft lithography, which requires both time and investment in necessary cleanroom facilities initially, despite being a relatively inexpensive method after initial investment. 103–120 In addition, although the production speed is relatively low, this method is the desired route for the synthesis of advanced and functional fibers for specific purposes, where the throughput is not necessarily essential and microfluidics has the most impact, enabling the production of smaller amounts of higher-value materials. To expand on this, this section highlights the development of fibers having different geometries/shapes and made using various precursor materials through a variety of microfluidic technologies equipped with different solidification methods.…”

“…5(i) ], where the microfluidic spinnerets display coaxially aligned channels. 103 The developed setup exhibited the capability of operating under laminar flow regimes and achieving precise 3D hydrodynamic flow focusing. They exemplified the performance of the developed microfluidic setup by producing fibers with desired morphologies using commercial polyurethane by varying the degree of flow focusing.…”