Direct inkjet printing of micro-scale silver electrodes on polydimethylsiloxane (PDMS) microchip

Abstract

Recently, direct inkjet printing of conductive solutions has received much attention in the microfluidics and lab-on-a-chip community because of its low-cost and mask-free deposition of electrodes on various substrates. However, the investigation of micro-scale direct inkjet printing on the polydimethylsiloxane (PDMS) substrate has not been completed. Here we present a direct inkjet printing technique to produce narrow (40-90 µm) silver microelectrodes on PDMS. Extensive experimental characterization studies on the pattern uniformity and electrical properties of the printed silver lines are presented. The effect of major printing parameters such as drop spacing, sintering temperature and duration, platen temperature, and nozzle temperature have been thoroughly investigated. We also investigated multiple layer printing as well as the effects of thermal expansion and mechanical bending. In order to demonstrate the utility of the inkjet-printed silver microelectrode, we fabricated both quadruple and castellated electrodes, and conducted dielectrophoretic manipulation of microbeads. The results clearly show that the printed silver electrodes can be used for electrokinetic applications in PDMS microchip devices. We believe that the direct inkjet printing of silver ink on PDMS presented here can provide a very convenient way of creating microelectrodes on PDMS devices for a variety of applications in the MEMS, microfluidics, and lab-on-a-chip communities.

Experimental Characterization of Inkjet-Printed Stretchable Circuits for Wearable Sensor Applications

“…Next, the mold with the liquid PDMS is degassed in a vacuum chamber for 30 min. Finally, the PDMS substrate is cured at 70 °C for 2 h in a convection oven [34,35]. …”

“…In particular, the wettability of the substrate can affect the size and stability of the printed lines. Hence, it is critical to chemically or physically treat the PDMS surface prior to the inkjet printing of NP ink [34,35]. In order to improve PDMS hydrophilicity, a plasma barrel etcher is used for PDMS surface treatment (ZEPTO Diener, Ebhausen, Germany).…”

“…There are several printing parameters which affect the conductivity, resistivity, and durability, as well as the dimensions of the printed patterns, such as drop spacing DS, cartridge/nozzle temperature, platen (substrate holder) temperature, number of printed layers, and sintering temperature [9,34]. In order to obtain uniform and continuous lines on PDMS, the printing process parameters need to be optimized.…”

Switchable disposable passive RFID vapour sensors from inkjet printed electronic components integrated with PDMS as a stimulus responsive material

“…Whilst the inkjet printing of silver colloidal solutions has been well reported, [20][21][22][23] the deposition of material onto PDMS from solution is a considerable challenge due to its intrinsic hydrophobic nature which can be improved by rendering the surface more hydrophilic through the use of oxygen, argon and air plasma along with UV-ozone. [24][25][26][27] UV-ozone treatment was seen to improve the printing of silver inks onto highly stretched Sylgard-184 PDMS. 26 while air plasma treatments were used to a similar effect in order to create silver patterns on Sylgard-184 coated glass slides.…”

“…26 while air plasma treatments were used to a similar effect in order to create silver patterns on Sylgard-184 coated glass slides. 27 This work will demonstrate that, using inkjet technology, the loop for an RFID tag can be printed from conductive ink. This not only indicates a step towards developing an entirely printed tag, but results in a system where the tag can be used repeatedly whilst maintaining a clear RFID response to vapour environments.…”