Pillar of Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore.
SUTD-MIT International Design Centre, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore.
Biosensors (Basel). 2021 Mar 17;11(3):84. doi: 10.3390/bios11030084.
This paper describes the use of fused deposition modeling (FDM) printing to fabricate paper-based analytical devices (PAD) with three-dimensional (3D) features, which is termed as 3D-PAD. Material depositions followed by heat reflow is a standard approach for the fabrication of PAD. Such devices are primarily two-dimensional (2D) and can hold only a limited amount of liquid samples in the device. This constraint can pose problems when the sample consists of organic solvents that have low interfacial energies with the hydrophobic barriers. To overcome this limitation, we developed a method to fabricate PAD integrated with 3D features (vertical walls as an example) by FDM 3D printing. 3D-PADs were fabricated using two types of thermoplastics. One thermoplastic had a low melting point that formed hydrophobic barriers upon penetration, and another thermoplastic had a high melting point that maintained 3D features on the filter paper without reflowing. We used polycaprolactone (PCL) for the former, and polylactic acid (PLA) for the latter. Both PCL and PLA were printed with FDM without gaps at the interface, and the resulting paper-based devices possessed hydrophobic barriers consisting of PCL seamlessly integrated with vertical features consisting of PLA. We validated the capability of 3D-PAD to hold 30 μL of solvents (ethanol, isopropyl alcohol, and acetone), all of which would not be retained on conventional PADs fabricated with solid wax printers. To highlight the importance of containing an increased amount of liquid samples, a colorimetric assay for the formation of dimethylglyoxime (DMG)-Ni (II) was demonstrated using two volumes (10 μL and 30 μL) of solvent-based dimethylglyoxime (DMG). FDM printing of 3D-PAD enabled the facile construction of 3D structures integrated with PAD, which would find applications in paper-based chemical and biological assays requiring organic solvents.
本文描述了使用熔融沉积成型（FDM）打印技术制造具有三维（3D）特征的纸质分析器件（PAD）的方法，我们称之为 3D-PAD。材料的沉积和热回流是制造 PAD 的标准方法。这种器件主要是二维（2D）的，只能在器件中容纳有限量的液体样品。当样品由与疏水性屏障具有低界面能的有机溶剂组成时，这种限制会带来问题。为了克服这一限制，我们开发了一种使用 FDM 3D 打印制造与 3D 特征（以垂直壁为例）集成的 PAD 的方法。3D-PAD 是使用两种热塑性塑料制造的。一种热塑性塑料具有低熔点，在渗透时形成疏水性屏障，另一种热塑性塑料具有高熔点，在不回流的情况下保持滤纸的 3D 特征。我们使用聚己内酯（PCL）作为前者，聚乳酸（PLA）作为后者。PCL 和 PLA 都可以通过 FDM 无界面间隙打印，得到的纸质器件具有由无缝集成的 PCL 形成的疏水性屏障，以及由 PLA 形成的垂直特征。我们验证了 3D-PAD 容纳 30 μL 溶剂（乙醇、异丙醇和丙酮）的能力，所有这些溶剂都不会保留在使用固体蜡打印机制造的常规 PAD 上。为了突出包含更多液体样品的重要性，我们使用两种体积（10 μL 和 30 μL）的溶剂基二甲基乙二肟（DMG）演示了二甲基乙二肟（DMG）-Ni（II）形成的比色测定法。3D-PAD 的 FDM 打印实现了与 PAD 集成的 3D 结构的轻松构建，这将在需要有机溶剂的基于纸张的化学和生物测定中得到应用。
