Optimizing piezoelectric inkjet printing of silica sols for biosensor production

The inkjet printing of biocompatible silica sols has gained popularity, both for biosensor production and development of holographic devices. However, there still remain significant issues related to premature clogging of inkjet printheads when printing aqueous silica sols. To better understand the causes of clogging of piezoelectric inkjet nozzles, printing studies were coupled with studies of colloidal stability along with silica deposition on surfaces, both under normal flow and piezoelectrically driven oscillating flow through an inkjet cartridge. Our studies show that clogging most likely results from deposition of silica colloids onto the internal surfaces of the printhead, followed by displacement of micron-sized pieces of the deposited material upon piezoelectric deformation of the printhead surface, which then block the nozzles of the printhead. Based on this result, we formulated a low-pH sol derived from sodium silicate and evaluated its colloidal stability, binding to silica surfaces and resistance to clogging of inkjet nozzles under normal and voltage-driven oscillating flow. We show that silica sols with a pH of 3.1 provide optimal printing behavior while allowing reproducible printing of spatially controlled silica patterns on paper to produce enzyme-based biosensing devices.