PDMS lab-on-a-chip fabrication using 3D printed templates

Abstract

The fabrication of conventional PDMS on glass lab-on-a-chip (LOC) devices, using templates printed with a commercial (2299 US$) micro-stereo lithography 3D printer, is demonstrated. Printed templates replace clean room and photolithographic fabrication resources and deliver resolutions of 50 μm, and up to 10 μm in localized hindrances, whereas the templates are smooth enough to allow direct transfer and proper sealing to glass substrates. 3D printed templates accommodate multiple thicknesses, from 50 μm up to several mm within the same template, with no additional processing cost or effort. This capability is exploited to integrate silicone tubing easily, to improve micromixer performance and to produce multilevel fluidics with simple access to independent functional surfaces, which is illustrated by time-resolved glucose detection. The templates are reusable, can be fabricated in under 20 min, with an average cost of 0.48 US$, which promotes broader access to established LOC configurations with minimal fabrication requirements, relieves LOC fabrication from design skills and provides a versatile LOC development platform.

A planar surface acoustic wave micropump for closed-loop microfluidics

“…Microfluidic channels were cast from PDMS (1:10 base to cross-linker), which was degassed at a pressure of 5 mBar for 20 min. Prior to casting PDMS over the mold, the resin surface was passivated by depositing a fluorocarbon film in a reactive-ion etcher [27][28][29] (low pressure CHF 3 for 120 s at an RF power of 45 W). PDMS was next cast onto the passivated molds and baked at 70 C for 1 h. The cured material was then peeled from the mold and sonicated for 20 min in acetone to dissolve the embedded ABS tube and thereby produce a fully 3D fluidic channel of dimensions w ¼ 500 lm, t ¼ 100 lm, and h ¼ 1:3 mm [ Fig.…”

Rapid assembly of multilayer microfluidic structures via 3D-printed transfer molding and bonding

“…Although some PTM devices can interface directly, whether, by punching holes (in a manner, similar to standard soft lithography processes) 36 , molding open wells 33,47 , and adding connectors during the curing process 34,37,48 , other PTM devices can interface indirectly by attaching to 3D-printed components that do have the desired interfaces 39 . Similar to soft lithography, PTM devices are sealed with glass or other 3D-printed components to provide enclosed channels after molding (including, through plasma bonding 33 , mechanical pressure 39 , or tape 39 ).…”

“…This work advances 3D PTM techniques from single-sided microfluidics 33,34,37 to multilayer microfluidic manufacturing, using the ease of 3D printing to create multiple molds with alignment structures to shape multiple layers of PDMS structures and quickly assemble them in the final step. First, we discuss details specific to the ProJet™ 3000 3D printer, including resolution and surface treatments.…”

“…27-32. Although direct 3D printing is a rapid process for prototyping, for making multiple copies of microfluidic devices, 3D-printed transfer molding (PTM), in which polymer is poured into a 3D-printed mold, remains faster, cheaper, and more reliable. First pioneered by McDonald et al 33 using fused deposition modeling techniques, the technique has since been used with stereolithography 34 and multijet printing 23 as well as with wax printers 35 and office-quality laser printers 36,37 . Although PTM does not allow the geometric flexibility of fully 3D-printed microfluidics, it possesses the following three notable advantages: (i) each mold can be used for multiple microfluidic devices, reducing 3D printing times and costs, (ii) many 3D printers exhibit lower resolution for features requiring support materials, and (iii) the process is compatible with conventional microfluidic fabrication materials, most notably PDMS 34,35,[37][38][39] .…”

“…First pioneered by McDonald et al 33 using fused deposition modeling techniques, the technique has since been used with stereolithography 34 and multijet printing 23 as well as with wax printers 35 and office-quality laser printers 36,37 . Although PTM does not allow the geometric flexibility of fully 3D-printed microfluidics, it possesses the following three notable advantages: (i) each mold can be used for multiple microfluidic devices, reducing 3D printing times and costs, (ii) many 3D printers exhibit lower resolution for features requiring support materials, and (iii) the process is compatible with conventional microfluidic fabrication materials, most notably PDMS 34,35,[37][38][39] . Because PDMS can be used to transfer patterns with high fidelity, the resolution and surface finish of the mold define the resulting quality of the resulting PDMS structure 38,40 , provided the mold features reasonable aspect ratios 23 .…”