Selective Fluorination of the Surface of Polymeric Materials after Stereolithography 3D Printing

Abstract

With the microfluidics community embracing 3D resin printing as a rapid fabrication method, controlling surface chemistry has emerged as a new challenge. Fluorination of 3D-printed surfaces is highly desirable in many applications due to chemical inertness, low friction coefficients, antifouling properties, and the potential for selective hydrophobic patterning. Despite sporadic reports, silanization methods have not been optimized for covalent bonding with polymeric resins. As a case study, we tested the silanization of a commercially available (meth)­acrylate-based resin (BV-007A) with a fluoroalkyl trichlorosilane. Interestingly, plasma oxidation was unnecessary for silanization of this resin and indeed was ineffective. Solvent-based deposition in a fluorinated oil (FC-40) generated significantly higher contact angles than deposition in ethanol or gas-phase deposition, yielding hydrophobic surfaces with contact angle >110° under optimized conditions. Attenuated total reflectance-Fourier transform infrared spectroscopy indicated that the increase in the contact angle correlated with consumption of a carbonyl moiety, suggesting covalent bonding of silane without plasma oxidation. Consistent with a covalent bond, silanization was resistant to mechanical damage and hydrolysis in methanol and was stable over long-term storage. When tested on a suite of photocrosslinkable resins, this silanization protocol generated highly hydrophobic surfaces (contact angle > 110°) on three resins and moderate hydrophobicity (90–100°) on the remainder. Selective patterning of hydrophobic regions in an open 3D-printed microchannel was possible in combination with simple masking techniques. Thus, this facile fluorination strategy is expected to be applicable for resin-printed materials in a variety of contexts including micropatterning and multiphase microfluidics.

Rapid fabrication by digital light processing 3D printing of a SlipChip with movable ports for local delivery to ex vivo organ cultures

“…While the BV-007A resin yields parts that are moderately hydrophilic, we recently described a method for fluoroalkyl silanization for SLA resins [25]. Here, this method was applied to silanize the BV-007A, and we confirmed that silanization not only increased the three-phase contact angle of a 1x PBS droplet resting on the surface in air, but also when immersed in FC-40 oil (Figure 2c).…”

“…Parts printed in BV-007A were silanized using our recently described method [25]. The parts were submerged into a 10% v/v solution of tridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane (Gelest Inc., Morrisville PA, USA) in Fluorinert FC-40 (Sigma Aldrich, St. Louis, MO, USA) for 30 min at room temperature.…”

“…This additive method is quickly gaining popularity for fabricating small parts and microfluidic devices, because of the high feature resolution and reproducibility in parts and rapid fabrication speed compared to traditional soft-lithography [3,[22][23][24]. While 3D printing has not been reported previously for SlipChips, two of the four fabrication requirements are already met: We recently described a method for fluorination of a DLP-printed surface based on solvent-based deposition of a fluoroalkyl silane [25], and others have demonstrated transparent prints by using clear resins on a glass surface [26]. The latter process generated a smoother surface with less light scattering.…”

Applied tutorial for the design and fabrication of biomicrofluidic devices by resin 3D printing

“…[24][25][26] For commercial resins, strategies to diminish resin cytotoxicity have started to emerge recently, [27][28][29][30] along with solutions addressing print resolution, [31][32][33][34][35][36] imaging compatibility, 33,[37][38][39] and surface modification and bonding. 40,41 Sifting through the plethora of literature for best practices can be challenging for researchers who are new to this rapidly growing field.…”

Applied tutorial for the design and fabrication of biomicrofluidic devices by resin 3D printing

“…[25][26][27] For commercial resins, resolutions to diminish resin cytotoxicity have started to emerge recently, [28][29][30] along with solutions addressing print resolution, 26,[31][32][33] imaging compatibility, 25,32,34 and other surface modification and bonding. 35,36 Sifting through this literature for best practices can be challenging for researchers who are new to this rapidly growing field, who would especially benefit from more head-to-head comparisons and a systematic analysis of some of the factors that affect biomicrofluidic design in SL printing.…”