Digital inkjet printing is developing quickly today because inkjet printing processes consume less energy and water and produce less waste discharge than traditional dyeing and other printing technologies. Inkjet printing provides more versatility and flexibility in terms of printing patterns and colors. Natural pigments are gaining more attention today as a preferred choice of pigment for printing as it can reduce the toxic waste from the production of synthetic pigments. In addition, natural pigment is more compatible with human bodies in general.
The author developed a printable and eco-friendly ink of a biological pigment extracted from fungus. The main research includes:
1. An aqueous-based ink from the biological pigment was developed. First by selecting a suitable surfactant to aid the dispersion of biological pigment in water. Serious foaming issue was observed for this ink. The cause of foam formation in this ink was identified and eliminated to produce enable its printability.
2. Acetone and ethanol-based inks without surfactants were also developed from the biological pigment.
3. The factors affecting the stability and printability of these inks were also investigated. In particular, key factors affecting stable droplet formation were identified and then adjusted to make a printable ink.
4. Research on the factors that affect the ink droplet placement after the ink drop on the fabrics. First is to analyze the wettability of ink droplet on fabric surface. Second is to analyze the capillary behaviors among the space between fibers and to see its relationship with the ink penetration in fabrics. The color of the printed fabrics was characterized by the color meter. It was found the color depends on the pigment crystal size and types of fabrics.
5. The effect of pigment crystal size on color was carried by printing pigment on glass substrate. Well defined nanowires of biological pigments were formed on glass by inkjet printing of acetone-based ink. The size of the wires increases with increasing the number of printing cycles. The pigment particle size and color relationship for biological pigments on glass was analyzed. It was found the hue has a dependence on the size. However, this study also suggests the size effect alone cannot fully explain the color variations shown on fabrics. Further study on the pigment substrate interaction is needed.
In summary, stable and inkjet printable inks were successfully formulated from biological pigment derived from wood fungus, Scytalidium cuboideum. Fabrics with inkjet printing biological pigments were successfully fabricated and analyzed by a color meter. The results suggest that the color depends on the pigment crystal size and substrate pigment interaction. To understand the size effect, inkjet printing biological pigments on glass substrates were prepared and analyzed. Well defined nanowires were formed from inkjet printing of acetone-based inks. The analysis on these samples indicated that the color of the pigment change it hue from red to orange when the particle size of the pigment increases within a certain range.