Rapid Prototyping of Microfluidic Conductivity Detectors via Extrusion‐Based 3D Printing
Authors: Prabhu Siddharth , Strong Brandon , Jangid Aditya , Liu Bo , Martinez Nathaniel 
Published: June 2021

ObjectiveTo develop a cost‐effective, single‐step method of rapidly prototyping microfluidic conductivity detectors via extrusion‐based 3D printing for the purpose of biomolecule characterization.BackgroundLab‐on‐a‐chip (LOC) devices are commonly viewed as an ideal rapid diagnostic modality in clinical biotechnology due to various design characteristics, including: portability, robustness, independence from external power sources, cost‐effectiveness, and ability to be used in remote locations. However, such devices have not been brought into realization in quantities nearly great enough to meet the demands of global healthcare. A significant reason is due to the use of labor‐intensive, complex, multi‐step microfabrication techniques, including: photolithography, soft lithography, metal evaporation & sputtering, etching, and plasma bonding (many of which also require the use of a clean room). These time‐consuming fabrication methods lead to slow production of research prototypes, and subsequent testing. The newest generation of LOC devices integrate electronic components for the purposes of manipulation and detection, including multi‐electrode conductivity detectors, which have historically been utilized as an electrochemical detection method in chip and capillary electrophoresis. In this scenario, a pair of electrodes are used to apply an electromagnetic signal to the solution of interest and subsequently receive an attenuated signal based upon solution composition (i.e., analyte concentration). Here we propose utilizing dual‐extrusion 3D printing (widely used in engineering fields as a method of expediting design, development, and testing) as a method of rapid prototyping of microfluidic conductivity detectors. This could potentially convert a complex multi‐step process into a simple single‐step process.MethodsMicrofluidics devices were designed in SolidWorks 3D modeling software, and fabricated from polylactic acid (PLA) with inlaid conductive PLA electrodes. An Ultimaker 3 dual‐extrusion 3D printer was used for fabrication. Protein suspensions were added to device wells and a digital multimeter was used to confirm solution conductivity.ResultsMulti‐well, multi‐electrode devices were produced (Figure 1). Resolution was highly dependent upon print paths, temperature, and well geometries. A positive relationship was observed between protein concentration and solution conductivity, thus confirming detector functionality.DiscussionWhile rapid prototyping via 3D printing may not be suitable for all applications, it might be far more appropriate to test novel microfluidics prototypes via this method prior to pursuing higher‐order manufacturing techniques. Additionally, while alternative 3D printing technologies (i.e., stereolithography printers) can produce higher resolution devices, extrusion‐based 3D printing is the most economical, and also allows for the single‐step fabrication of devices with integrated electronic components. Here we have developed microfluidic conductivity detector prototypes, which can be used for the purposes of biomolecule detection, quantitation, and characterization (i.e., determination of DNA fragment length). We are also currently exploring printing more complex chip‐based microfluidic designs with integrated electronic components, including contactless conductivity detectors and multi‐layer PCB devices.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.