Fabrication of digital microfluidic devices on flexible paper-based and rigid substrates via screen printing

Abstract

In this work, a new fabrication method is presented for digital microfluidic (DMF) devices in which the electrodes are generated using the screen printing technique. This method is applicable to both rigid and flexible substrates. The proposed screen printing approach, as a batch printing technique, is advantageous to the widely reported DMF fabrication methods in terms of fabrication time, cost and capability of mass production. Screen printing provides an effective means for printing different types of conductive materials on a variety of substrates. Specifically, screen printing of conductive silver and carbon based inks is performed on paper, glass and wax paper. As a result, the fabricated DMF devices are characterized by being flexible, disposable and incinerable. Hence, the main advantage of screen printing carbon based inks on paper substrates is more pronounced for point-of-care applications that require a large number of low cost DMF chips, and laboratory setups that lack sophisticated microfabrication facilities. The resolution of the printed DMF electrodes generated by this technique is examined for proof of concept using manual screen printing, but higher resolution screens and automated machines are available off-the-shelf, if needed. Another contribution of this research is the improved actuation techniques that facilitate droplet transport in electrode configurations with relatively large electrode spacing to alleviate the disadvantage of lower resolution screens. Thus, we were able to reduce the cost of fabrication significantly without compromising the DMF performance. The paper-based devices have already shown to be effective in continuous microfluidics domain, so the investigation of their applicability in DMF systems is worthwhile. With this in mind, successful integration of a paper-based microchannel with paper-based digital microfluidic chip is demonstrated in this work.

Micro- and Nanofluidics for Bionanoparticle Analysis

“…Nozzle clogging Screen printing [65,66] Carbon; silver Rapid and low cost; can print high viscosity ink Requires a mask; produces thick electrodes Spraying [67] Graphite Simple and low cost…”

“…Depends on the quality of a commercial tape Wrapping [65,69] Paraffin film; plastic wrap/silicon oil…”

Ultra-Portable Smartphone Controlled Integrated Digital Microfluidic System in a 3D-Printed Modular Assembly

“…Electrowetting on a dielectric (EWOD) is one the actuation techniques used to manipulate the droplets in both open and closed DMF devices [29]. DMF chips can be fabricated by several methods such as photolithography [30], inkjet printing, and rapid prototyping on paper substrates [31][32][33]. Open and closed DMF systems may each offer some advantages and disadvantages for different applications.…”

An inkjet printed, roll-coated digital microfluidic device for inexpensive, miniaturized diagnostic assays

“…[26][27][28][29] While DMF has proven to be a useful technology, one of its leading challenges is fabrication -devices are typically manufactured on glass substrates with slow and expensive photolithography, wet-etching, vapour deposition, and spincoating techniques (often requiring a clean room facility). 16 There have been various efforts at forming DMF devices using cleanroom-free methods over the years, [30][31][32][33] but the performance of devices generated using these techniques was limited, and the techniques themselves were typically not scalable for mass manufacturing. In a critical breakthrough, two groups recently reported methods for forming devices by inkjet printing 34,35 (IJP).…”