Candyfluidics: The Art of Fabricating Micro- and Nano-fluidic Geometries using Surface-deposited Sugar Scaffolds

The adoption of miniaturization technologies, such as micro and nanofluidic systems, as a strategy for democratized healthcare in developing countries was proposed decades ago. However, regions in most need of cost-effective global health technological solutions such as sub-Saharan Africa, contribute less than 1\% of the global research output in the microfluidics field. This dearth of research output from the region may be attributed to economic and technical barriers to rapid prototyping with state-of-the-art tools such as 3D printing and micromilling. As a more accessible, low-cost, and low-resource alternative, we introduce candyfluidics, an innovative method for fabricating micro- and nano-fluidic structures using sugar and screen-printing, which are respectively abundant materials and technology in the region. Exemplified through the creation of flow-focusing chips, we provide detailed procedure for creating microfluidic architectures from surface-deposited candy mixture. The resulting flow-focusing chips were validated by generating water-in-oil droplets with volumes ranging from 0.2 to 1.22 nL under pressure-driven flows. Furthermore, the chips were used to demonstrate digital droplet loop-mediated isothermal amplification for the detection of dengue virus type 1 nucleic acids at femtomolar concentration ($\sim 85$ copies/ $\mu$L). The Candyfluidics fabrication process takes less than 30 minutes and enables the parallel production of multiple chips, offering a rapid and scalable approach to manufacturing microfluidic devices for point-of-need applications.