Biocompatible/Biodegradable Electrowetting on Dielectric Microfluidic Chips with Fluorinated CTA/PLGA

Abstract

One of the major hurdles in the development of biocompatible/biodegradable EWOD (Electrowetting-on-dielectric) devices is the biocompatibility of the dielectric and hydrophobic layers. In this study, we address this problem by using reactive ion etching (RIE) to prepare a super-hydrophobic film combining fluorinated cellulose triacetate (CTA) and poly (lactic-co-glycolic acid) (PLGA). The contact angle (CA) of water droplets on the proposed material is about 160°. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) characterizations indicate that a slight increase in the surface roughness and the formation of CFx (C-F or CF2) bonds are responsible for the super-hydrophobic nature of the film. Alternating Current (AC) static electrowetting and droplet transportation experiments evidence that contact angle hysteresis and contact line pinning are greatly reduced by impregnating the CTA/PLGA film with silicon oil. Therefore, this improved film could provide a biocompatible alternative to the typical Teflon® or Cytop® films as a dielectric and hydrophobic layer.

Lab-based operando x-ray photoelectron spectroscopy for probing low-volatile liquids and their interfaces across a variety of electrosystems

“…74 This process had been investigated using a number of electrochemical, spectroscopic, and microscopic tools, 75 but the use of XPS was sparse. [76][77][78] Within the last three years, we have reintroduced XPS as a powerful analytical arsenal for probing electrical potential developments of liquids and their interfaces with dielectric substrates to extract novel information about them, under in situ and in operando conditions. [37][38][39][40] In order to probe impedance type properties of the samples under investigation, it is necessary to impose a varying frequency (AC) actuation for which the natural choice is a sine-wave.…”

X-ray Photoelectron Spectroscopy with Electrical Modulation Can Be Used to Probe Electrical Properties of Liquids and Their Interfaces at Different Stages

“…Electrowetting is a long and heavily investigated phenomenon utilized in a wide span of scientifically and technologically important areas such as microfluidics, liquid lenses and displays, and biochemical separation and analytical sciences. − Electrowetting refers to controlling the wettability of liquids via the application of electrical forces in either the dc or ac form . The process has been investigated using a multitude of electrochemical, spectroscopic, and microscopic tools, but the use of XPS is not extensive. − Our findings have reintroduced XPS as a powerful analytical arsenal for mapping the electrical voltage developments on and around liquid drops and at their interfaces to probe the effects of various electrochemical processes, in situ and in operando, similar to recent NMR studies utilized to investigate battery development, relevant to energy generation and storage. , …”

Materials and Manufacturing Methods for EWOD Devices: Current Status and Sustainability Challenges

“…Zhang et al used a combination of cellulose triacetate (CTA) and poly(lactic-co-glycolic acid) (PLGA) at 7% and 2% respectively and achieved a 2 μm dielectric layer by spin coating at 5000 rpm for 5 min. [89] This CTA/PLGA combination doubles SU-8 or PDMS dielectric constant 6 F m −1 and the driving voltage of the device was reduced to 60 V.…”

“…Therefore, thicker layers cause a lower capacitance in spin-coated dielectric layer devices, resulting in less efficient devices. [92] Authors have tested alternatives to decrease the thickness, Clement SU-8 3 4 μm 0-350 V DC Ciou et al [78] SU-8 3 15 μm 0-100 V DC Wang et al [79] Si 3 N 4 7.2 35 μm 70 V DC Torabina et al [80] AZ 1500 photoresist 4.03 5 μm 14,8 V DC Li et al [81] SU-8 3 500 nm 220 V AC Chao et al [82] Cyanoethyl pullulan 18 6 μm 100 V DC Yu et al [83] PDMS 2.35 2 μm 160-360 V DC Bansal et al [84] PDMS 2.35 500 nm 275 V DC Jain et al [56] Ion gel 12 N/A 0-80 V DC Narasimhan et al [21] SU-8 3 4 μm 0-350 V DC Ciou et al [85] SU-8 3 15 μm 0-100 V DC Wang et al [86] PDMS 2.35 8 μm 0-250 V DC Li et al [87] SU-8 3 10 μm 200 V AC Nahar et al [17] Cellulose triacetate/PLGA 6 1.8 μm 110 V DC Kojima et al [82] PDMS 2.35 N/A 1500-5000 V DC Chen et al [88] Cellulose triacetate/PLGA 3 6 μm 40-100 V DC Zhand et al [89] Ion gel 3 5 μm 150 V AC Clement et al [53] SU-8 3.8 2 μm 1 3 0 V A C Y i e t l . [77] SU-8 3 2.5 μm 0-100 V DC Chae et al [73] SU-8 3 2 μm 10-100 V DC Chen et al [76] SU-8 3 N/A 100 V DC Huang et al [90] HN-008N 3 500 nm 175 V DC Yang et al [91] PDMS + graphene oxide 3.2 15 μm 100 V DC Basu et al [66] et al used the same ionic gel and reduced the thickness of the dielectric layer to 500 nm using dip-coating techniques.…”