Investigating chromatographic interactions in porous pigment coatings between inkjettable polyelectrolytes and model colorant solutions

Abstract

Printed, self-contained sensor designs based on capillary transport and microfluidic principles form a major part of current research in printed functionality. Previous work into such designs has mainly focused on cellulosic papers as base substrates. In this study, novel findings are presented employing alternative customdesigned functional pigment coated substrates, locally functionalised by inkjet printed polyelectrolytes, to separate or transport anionic or cationic molecules by surface chemistry tailoring. Both anionised and cationised coatings are tested and found to transport similarly charged model colorants successfully, while separating those of opposite charge, with the extent of separation depending on colorant concentration. Furthermore, surface chemistry reversal by cationic (polyethyleneimine, polyDADMAC) and anionic (carboxymethyl cellulose) polyelectrolyte inks is demonstrated as a complementary method for analyte separation or concentration. However, the deposition of the polyelectrolyte ink itself was found to affect the cationised coating by solubilising and re-depositing coating components, while the printed polyethyleneimine was found to be partially dissolved and transported by water elution, suggesting limited adsorption under tested conditions.

Chromatographic Effects in Inkjet Printing

“…Figure f shows the extracted retardation factor R f as a function of c 0 . The results qualitatively resemble those obtained by Koivunen et al using the imbibition of tartrazine and safranine solutions from infinite reservoirs into porous layers that are comprised of calcium carbonate microparticles and polymeric binders …”

Fully inkjet-printed glucose assay fabricated on highly porous pigment coating

“…Furthermore, we have shown that our coatings are biocompatible and that they offer enhanced sensitivity compared to filter paper (Jutila et al 2019). We have also shown that the properties of the coating can be altered either completely (Jutila et al 2019) or locally (Koivunen et al 2017(Koivunen et al , 2019 with polyelectrolytes, affecting the transfer and separation of positively or negatively charged molecules on the coating, which may be useful for some microfluidic applications.…”

“…Hydrophobising ink consisted of 10 w/w% commercial AKD FennoWax 1865 (Kemira, Helsinki, Finland) dissolved in p-xylene. Jetting settings were as described previously by the authors for a similar, though colourant containing, ink in contemporary work (Koivunen et al 2019). The hydrophobising ink in the present case contains no colourant, resulting in almost invisible printed patterns for minimum background interference in the colorimetric analysis.…”

“…While in previous studies we have employed hydrophobising inks with a variety of colourants (Jutila et al 2018;Koivunen et al 2016Koivunen et al , 2019, in the present work a colourantfree hydrophobising ink was prepared to produce patterns that would have minimal effect on the coating background signal in colorimetric analysis. AKD in dry form is white, and, thus, when applied on the white pigment coatings, the printed pattern was only faintly visible to the naked eye, though still allowing for manual application of the glucose samples to the sample insertion zone.…”

“…However, copy paper and commercial coated papers as such do not offer as fast wicking as the specialised cellulose-based substrates, making them unfavourable for microfluidic applications (Zhong et al 2012). In the past, paper-based glucose assays have been successfully fabricated on both copy paper and commercial coated paper, although the assays were based on circular reaction arrays instead of lateral flow (Määttänen et al 2011), thus limiting additional opportunities for subsequent component analysis, including, for example, chromatographic separation or analyte reaction (Koivunen et al 2019).…”