Paper Title
EHD Direct Printing of Protein - DNA Solutions for Paper-based Biosensors

Abstract
Paper one of humanity’s oldest technological achievements has been retrofitted into high-tech devices. Foldable electronics, microfluidic devices and biosensors are few of the new areas of application. Not only, is paper common, cheap and biodegradable, it is also the model platform for our current printing technology. These characteristics make it the perfect candidate for the development of low-cost biosensors in the form of lateral flow assays, able to revolutionize point-of-care diagnostics. We developed an EHD printing device that can jet-print lines directly on cellulose or nitrocellulose paper with no prior treatment. The advantage of our method is that the size of the printed features are several times smaller than the emitter capillary size preventing clogging. The “inks” are water-based protein solutions without any other polymer addition. We tackled the challenge of stabilizing a cone-jet for a water-based solution, using a laminar co-axial gas co-flow around the EHD emitter. In addition, for the final lateral flow assembly we used a novel modular DNA-binding protein that can be modified to detect different DNA targets and produce a colorimetric signal directly on the lateral assay strip. In this work we successfully demonstrate detection of the Human Papilloma Virus (HPV) DNA target Keywords - EHD Jetting, bioprinting, DNA Binding Proteins, Co-flow, biosensors.