Inkjet Printed Polyelectrolytes for Microfluidic Paper-based Analytical Devices

Paper-based microfluidic devices can provide practical
analytics platforms for applications such as point-of-care
medical diagnostics. So far immobilisation or separation of
analytes on such devices has received limited attention. This
study introduces inkjet printed polyelectrolyte patterns as
possible platforms for immobilisation of cationic and anionic
compounds through surface charge interaction. Both cationic
(polydiallyldimethylammonium chloride) and anionic (sodium
polyacrylate) polyelectrolytes were inkjet printed on a custom
designed porous pigment coating, having fine particle internal
pore structure to ensure high surface contact between the
analytical sample and modified pore walls. Printed
polyelectrolyte patterns were themselves largely invisible,
including under UV light. In a proof of principle test, a
controllable degree of separation of anionic Uranine and
Tartrazine dyes from aqueous solution passing through a printed
cationic polyelectrolyte region could be observed. However,
weakly cationic Rhodamine B could not be captured on anionic
regions.