The Nakahara Effect and Its Influence On Solution-Based 3D Printed Films

Abstract

The Nakahara Effect and its Influence on Solution-Based 3D Printed Films Daryl Kwakye-Ackah Motivated by the Nakahara Effect, the influence of altering printing parameters on fragmentation mechanism(s) of directly written titanium dioxide(TiO 2) films is investigated. The Nakahara effect states that a long lasting memory can be introduced into a colloidal system prior to drying, affecting the type of crack pattern formed due to externally applied forces. TiO 2 has important applications due to its interesting semiconducting properties, tunable band gap, photocatalytic properties, biocompatibility, and relative abundance. This is the reason it is used in this project as a model printing ink system. In this research, two deposition methods (i.e. direct-ink writing and doctor-blading) were compared in order to study the Nakahara Effect. In particular, the focus was to investigate the effects of film thickness, drying process used and the concentration of primary TiO 2 particles in the aqueous ink on drying crack pattern formation. Crack patterns were observed during drying using an optical microscope, and crack lengths were measured using image analysis. Weibull statistics were used to study variability in crack patterns for the different deposition methods. The results suggest a distinction between the printed and doctor-bladed samples hence demonstrating the validity of the Nakahara Effect. They also provide new insights for the role of direct writing parameters for inducing distinct printing memory characteristics that may help to further understand and minimize crack formation during drying.