Kuva-alueen takareunan pikkautumisen laboratoriosimuloinnin jatkokehitys

The aim of this study was to improve a previously partially developed laboratory method of tail-edge pick simulation by increasing the sensitivity to the number of passes required to induce tail-edge pick and by adapting new flexographic polyester backing. The literature review introduces the offset printing method, and the edge pick phenomenon, its causes and solutions and describes how liquid-coating structure interactions, ink tack, coating strength and the stiffness and compressibility of multi-layered coated paper contribute to tail-edge pick. The number of successful passes without tail-edge pick was increased by investigating the effect of the following parameters on tail-edge pick: fountain solution type and amount, delay between wetting and printing, ink type and ink loading level, force and speed of printing, force and speed of passes and the delay between passes, and by developing an improved test setup based on these investigations. The ink loading level and force and speed of printing were found to be the most influential parameters. The number of successful passes was increased by increasing the ink loading level, reducing the speed and force of printing. The improved test method was used to test 11 commercially ranked papers. The number of successful passes was increased from a maximum of two to a maximum of eight, and the degree of tail-edge pick was decreased significantly when the results of the initial and improved test method were compared. A good correlation, having R2 = 0.92, was established between the improved tail-edge pick values and the commercial ranking when Paper 11 was excluded. This shows that this laboratory scale test method correlates well with the real printing trials, and can thus be used to simulate tail-edge pick effectively.Tämän työn tarkoituksena oli parantaa aiemmin kehitettyä kuva-alueen takareunan pikkautumisen (tail-edge picking) laboratoriosimulaatio menetelmää lisäämällä menetelmän herkkyyttä kuva-alueen takareunan pikkautumisen aiheuttamiseen tarvittavien toistojen lukumäärää koskien sekä ottamalla käyttöön uusi fleksograafinen polyesteritausta. Kirjallisuuskatsauksessa esitellään sekä offset painomenetelmä että kuva-alueen reunojen pikkautuminen, sen syyt sekä ratkaisuja ja kuvaillaan kuinka neste-päällyste vuorovaikutukset, painomusteen tahmeus, päällysteen lujuus, jäykkyys sekä kokoonpuristuvuus vaikuttavat painetun kuva-alueen takareunan pikkaantumiseen. Onnistuneiden toistojen lukumäärä ilman kuva-alueen takareunan pikkautumista korotettiin tutkimalla seuraavien parametrien vaikutusta pikkautumiseen: kostutusvesi ja sen määrä, kostutuksen ja painatuksen välinen viive, painomustetyyppi ja määrä, painamiseen käytetty puristusvoima ja nopeus, toistoihin käytetty puristusvoima ja nopeus sekä toistojen välinen viive, sekä kehittämällä paranneltu testiasetelma tutkimusten perusteella. Painomusteen määrällä sekä painamiseen käytetyllä puristusvoimalla ja nopeudella oli suurin vaikutus onnistuneiden toistojen lukumäärään. Toistojen lukumäärää korotettiin lisäämällä painomusteen määrää ja vähentämällä sekä painamiseen käytettyä puristusvoimaa että nopeutta. Parannettua testimetodia käytettiin 11 kaupallisesti luokitetun paperin testaamiseen. Onnistuneiden toistojen maksimi lukumäärää nousi kahdesta kahdeksaan, ja kuva-alueen takareunan pikkautuminen väheni selvästi kun uusia tuloksia verrattiin alkuperäisiin tuloksiin. Hyvä korrelaatio (R2 = 0.92) saatiin aikaiseksi tuloksien ja kaupallisen luokittelun välille, kun Paperi 11 jätettiin huomioimatta. Tämä osoittaa, että tämä laboratorio testimenetelmä korreloi hyvin todellisten painotutkimuksien kanssa, joten tätä metodia voidaan käyttää kuva-alueen reunan pikkautumisen simulointiin

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

A simple paper-based microfluidic device, fabricated on a highly porous coating consisting of functionalised calcium carbonate (FCC) pigment and a microfibrillated cellulose (MFC) and/or polyvinyl alcohol (PVOH) binder, was developed for glucose detection. Both the hydrophobic patterns, consisting of alkyl ketene dimer (AKD), and the enzyme ink, consisting of glucose oxidase (GOx), horseradish peroxidase (HRP) and an indicator containing 4-aminoantipyrine (4-AAP), and sodium 3,5-dichloro-2-hydroxy-benzenesulphonic acid (DHBS) were inkjet-printed. Multiple coating formulations were tested using two indicators, potassium iodide (KI) and 4-AAP/DHBS, to find the optimal formulation with regard to detection sensitivity and assay stability. Higher binder concentrations increased the enzyme activity, especially in the case of PVOH. Two coatings, containing either solely MFC or both MFC and PVOH were ultimately chosen for the glucose assay experiments. For the assays, a 42 nl volume of buffered enzyme solution, containing a total of 5.04 mU GOx and approximately 1.01 mU HRP, in combination with 4 mM 4-AAP and 8 mM DHBS, was printed, and a 1 µl glucose solution, made up over a range of concentrations, was applied onto the samples to evaluate the response. A good linearity was achieved between detection and glucose concentration between 0.1 and 0.6 mM with both coatings. The assays remained stable for four weeks when stored at − 20 °C. The results show that the functional coated substrates offer a viable alternative to cellulose-based substrates for microfluidic applications enabling the use of small reagent and sample volumes.Peer reviewe

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

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 custom-designed 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.Peer reviewe