Laser-based direct-write technique for enabling newer functionalities in paper-based devices

Abstract

The demand for low-cost diagnostic devices that are user-friendly and deliver results rapidly to the patients is a universally accepted goal that has led to extensive development of paper-based microfuidic devices (µPADs). Despite the progress in the field of µPADs, there are still some important requirements yet to be addressed to improve their performance and enable their widespread use as a commercial product. In this thesis, we focus on the use of a laser-based direct-write (LDW) technique for enabling newer functionalities in paper-based devices for improved sensitivity of diagnostic tests as well as the quantitative detection of either a single or multiple analytes. The LDW method we are using for paper patterning is based on the local deposition of a photo-polymer on top of a porous substrate followed by the exposure with a laser light source to create solid polymeric structures. In our first demonstration, we are using the LDW method to create in-line filters on a porous nitrocellulose membrane that are capable of separating particles based on their size. These in-line filters act as barriers to delay the flow of samples and increase the sensitivity for the detection of an analyte. The LDW method is later used to create porous flow-through filters on cellulose paper that again have the ability for the size-exclusive separation of particles. When these flow-through filters are combined with a lateral flow assay they can act as a diagnostic tool for the detection of a single analyte over a wide concentration range. Additionally, the LDW can be extended for the fabrication of platforms that are able to detect multiple analytes within the same device. For that, we report the fabrication of multilayer 3D-µPADs used for the simultaneous detection of three analytes spiked in artificial urine as well as the pH of the tested sample. Finally, we report the use of light-activated materials (hydrogels) on paper-based devices to create optically triggered gates that are able to control the flow of samples, and therefore provide an alternative pathway to increase the sensitivity for the detection of analytes. Adding these newer functionalities to paper-based devices is highly desirable, as this will allow their extensive use as a diagnostic sensor at the point-of-care.

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Identifiers

ORCID for Panagiotis Galanis: orcid.org/0000-0002-2028-5803

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