Responsive microgel-based inks for inkjet printing

Abstract

Inkjet printing is a technology that has been widely studied and implemented. The liquids that are used for inkjet printing can vary. There is the traditional ink which can be found in almost every household printer. But it is also possible to use inkjet printing to deposit drugs, proteins and nanoparticles on substrates. Inkjet printing has the ability to precisely deposit picoliters of liquid onto the substrate. Thus, reducing cost and waste when the material being used is expensive and/or of limited quantity. This project works with a LP50 PIXDRO inkjet printer. Another interest that gained traction in the scientific community are the stimuli-responsive microgels. These microgels are able to change their dimensions depending on the external stimuli and if this stimuli is removed from the microgel, it changes back to its original shape, thus it is a reversible process. This project uses a suspension of the stimuli-responsive microgel; poly(N-isopropylacrylamide)-coacrylic acid (pNIPAm). This microgel is responsive to temperature and pH. To deposit the pNIPAm suspension on the substrate, inkjet technology will be used. The printability of the pNIPAm will be determined by characterizing the physical and rheological properties. Such as the density, surface tension, viscosity and particle size of the pNIPAm beads. These properties will be compared to the ideal liquid requirements given by the print cartridge that will be used, a Fuijifilm Dimatix. To influence the surface tension three surfactants will be tested. These surfactants are Triton X-114 (TRT), Sodium dodecyl sulphate (SDS) and Hexadecyltrimethylammonium bromide (CTAB). Based on the results the and comparison to the requirements the surfactant Triton X-114 is chosen because it lowers the surface tension the most. While it has minimal to no affect on the pNIPAm particles. The next phase of the project is testing the printability of the pNIPAm. This is done by adjusting the waveform on the LP50 PIXDRO inkjet printer. As a result it is indeed possible to deposit pNIPAm on a substrate with an inkjet printer. After this step a SEM is used to investigate if the printed pNIPAm particles will form a monolithic layer. This monolithic layer is important when it comes to having a functional etalon. The pNIPAm particles form indeed a monolithic layer on the substrate. The last step is to see if there is a peak shift in the wavelength when the temperature is increased. The microgel based etalons that used an inkjet printer to deposit the micrgol show a peak shift. Therefore, it can be concluded that it is possible to use an inkjet printer to deposit pNIPAm on a substrate and that the pNIPAm particles behave according to literature. All the results of this project show that using an inkjet printer is a viable alternative for fabricating microgel based etalons.