Printed chemical sensors

Namen magistrskega dela je priprava kemijskih senzorjev, natisnjenih s tehniko sitotiska. Pripravljene so bile tiskovne forme za večplastni tisk prepletenih kondenzatorjev, ki so bile na podlagi rezultatov meritev dopolnjene in izboljšane. Analiziranih je bilo sedem potencialnih tiskovnih materialov na osnovi različnih polimernih materialov. Na podlagi rezultatov dimenzijske stabilnosti pri visokih temperaturah in diferenčne dinamične kalorimetrije se je določilo optimalne parametre sušenja odtisov in materiale, ki so primerni za tisk električnih oblik. Uporabljene so bile tržno dostopne funkcionalne tiskarske barve, prevodna barva s srebrovimi delci in dve dielektrični tiskarski barvi. S sitom gostote mrežice 120 linij/cm so bile uspešno natisnjene prevodne strukture dimenzije 300 mikronov. Na tiskovni material s prevodno plastjo indij-kositrovega oksida pa je bil uspešno natisnjen dvoplasten nanos dielektrične tiskarske barve in na njo še plast prevodne tiskarske barve. Na podlagi izbire elektrod se je uspešno izmerilo kapacitivnost ploščatega kondenzatorja in prepletenega kondenzatorja. Rezultati meritev kapacitivnosti niso bili odvisni od energije UV-sevanja pri sušenju dielektrične plasti, pač pa sta na kapacitivnost vplivala geometrija in površina kondenzatorja. Ploščati kondenzatorji z dielektrikom med pozitivno in negativno elektrodo in večjo površino so imeli višjo kapacitivnost od prepletenih kondenzatorjev. Dokazano je bilo, da se faktor disipacije kondenzatorja niža z uporabo višje energije UV-sevanja pri sušenju dielektrične plasti. Rezultati meritev odziva senzorjev na spremembe relativne zračne vlage so pokazali, da se senzorji odzivajo enakomerno in ponovljivo. Sprememba kapacitivnosti senzorja se viša z višanjem relativne zračne vlage v prostoru, kar pomeni, da so senzorji zadovoljivo odzivni.The purpose of master\u27s thesis “Printed chemical sensors” is preparation of screen printed chemical sensors. Printing forms for multi-layered prints of interdigitated capacitors were prepared and improved on the basis of measurement results. The feasibility of seven print substrates based on polymer materials was analysed. Suitable substrates were chosen for further study and optimal drying parameters were specified after thorough testing of materials’ dimensional stability at high temperatures and results of differential scanning calorimetry were obtained. Commercially available printing inks were applied, including one silver-based conductive ink and two dielectric inks. Conductive structures with resolution of up to 300 microns were printed with a screen density of 120 lines/cm. Two-layered elements of dielectric printing ink and an additional layer of conductive ink were successfully applied onto a printing substrate coated with a conductive indium tin oxide layer. Capacitance of a parallel-plate and interdigitated capacitor was determined by the help of position of electrodes. The results confirm that the change of UV energy applied for curing of the dielectric ink has no significant influence on the capacitance of printed sensors, but is a factor of capacitor function and surface area. Capacitance was greater when measured as a parallel-plate capacitor with dielectric layer between two electrodes and larger surface area than interdigitated capacitor printed on the same sample. Factor of dissipation diminishes with higher UV energy applied for curing of the dielectric ink. Sensor response to changes in relative humidity is even and can be reproduced. Change of capacity of sensor is higher with increase in relative humidity, thus the prepared sensors are properly responsive