Abstract
Digital microfluidics (DMF) devices enable precise manipulation of small liquid volumes in point-of-care testing. A printed circuit board (PCB) substrate is commonly utilized to build DMF devices. However, inkjet printing can be used to fabricate DMF circuits, providing a less expensive alternative to PCB-based DMF designs while enabling more rapid design iteration cycles. We demonstrate the cleanroom-free fabrication process of a low-cost inkjet-printed DMF circuit. We compare Kapton and polymethyl methacrylate (PMMA) as dielectric coatings by measuring the minimal droplet actuation voltage for a range of actuation frequencies. A minimum actuation voltage of 5.6 V was required for droplet movement with the PMMA layer thickness of 0.2 μm and a hydrophobic layer of 0.17 μm. Significant issues with PMMA dielectric breakdown were observed at actuation voltages above 10 V. In comparison, devices that utilized Kapton were found to be more robust, even at an actuation voltage up to 100 V.
Highlights
A minimum actuation voltage of 5.6 V was required for droplet movement with the polymethyl methacrylate (PMMA) layer thickness of 0.2 μm and a hydrophobic layer of 0.17 μm
Digital microfluidics (DMF) is an approach for manipulating small liquid volumes using electrostatic force; it allows for the precise control of individual droplet movement in microliter to nanoliter volumes in an array of electrodes [1]
This paper presents a methodology for the fabrication of a DMF circuit using an inkjet printer, followed by coating by dielectric and hydrophobic materials
Summary
Digital microfluidics (DMF) is an approach for manipulating small liquid volumes using electrostatic force; it allows for the precise control of individual droplet movement in microliter to nanoliter volumes in an array of electrodes [1]. Inkjet printing and other deposition methods have been utilized for microfluidic devices due to their low cost They are suitable for mass production, shortening the fabrication time and the design cycle [5,6]. The main advantages are their low cost, simple manufacturing process, and low thickness, which can translate to lower droplet actuation voltage Parametric characterization of these coatings is required to advance the fabrication of low-cost DMF devices. Other commercially available dielectric and hydrophobic coatings can be used; their parametrization is beyond the scope of this paper The stability of these materials under repeated exposure to high electric fields requires investigation. All fabrication steps were performed outside the cleanroom, enabling rapid, low-cost DMF chip fabrication
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