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Risto Koivunen: Inkjet printed surface chemistry modification of porous coatings

This work explores inkjet printed surface modification of custom-designed pigment coatings intended as analytical device substrates.

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Risto Koivunen: Inkjet printed surface chemistry modification of porous coatings

Time & Location

29 Mar, 12:00 – 15:00 EEST

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About the Event

Abstract:

Printed microfluidic analytical devices can provide simple, mass producible assays, e.g. for medical diagnostics and environmental monitoring. Such devices typically consist of a permeable, porous base substrate, e.g. cellulosic paper, patterned hydrophobically to control flow of liquid samples. Reagents and/or catalysts within the substrate interact with sample, providing information of the contents, e.g. by colorimetric change or spectroscopically observable reaction products.

This work explores inkjet printed surface modification of custom-designed pigment coatings intended as analytical device substrates. Pigment coatings, consisting of fine particles attached with binder, are commonly used on commercial printing papers, but have not been significantly studied as an analytical platform. However, suitably designed coatings would provide thin wicking layers, requiring only tiny reagent and sample volumes, with adjustable surface chemistries. Inkjet printing provides a non-contact method to deposit reagents or surface chemistry modifiers.

The studied coatings consist of porous functionalised calcium carbonate (FCC) pigments and a variety of mainly organic binders. These coatings were printed with 2 custom-designed hydrophobising inks, controlling liquid flow within the hydrophilic coatings. Additionally, 5 polyelectrolyte inks were formulated to effect chromatographic separation of anionic and cationic compounds. Test patterns were developed for evaluating the effects of printing on coatings. Besides coating interactions, jettability studies were conducted on a series concentration of poly-diallyl dimethyl ammonium chloride (polyDADMAC) polyelectrolyte.

Hydrophobic patterning was successfully conducted with the hydrophobising agents, alkyl ketene dimer (AKD) and polystyrene, with a significant amount of agent required to cover the high area pore surfaces sufficiently. Printed polyelectrolyte increased chromatographic separation for oppositely charged molecules, whilst decreasing the separation of similarly charged molecules. This effect depended on both sample concentration and the amount of polyelectrolyte, though saturation effects were observable for the latter. PolyDADMAC inks up to 10 w/w% were jettable under steady conditions, though the printhead nozzles were increasingly affected by evaporation as polyelectrolyte concentration increased.

This work demonstrates that specialised pigment coatings can work as printed analytical platforms. Additional research is needed to provide more robust coatings and efficient printing. Inkjet deposited polyelectrolytes can adjust chromatographic separation on the coatings, and likely on other substrates, though possible re-dissolution and transport of non-adsorbed polyelectrolyte by elution needs to be considered.

Follow the remote defence: https://aalto.zoom.us/j/68609201115 

Opponent: Dr. Eric Moore, University College Cork (UCC), Tyndall Institute, Ireland

Supervisor: Professor Patrick Gane, Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems

Link to electronic thesis: Inkjet printed surface chemistry modification of porous coatings for application as microfluidic analytical platforms

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