Researchers from the University of Michigan Mechanical Engineering Department have developed a technology that allows electrohydrodynamic ink jet printers to print on a wider range of surfaces with better droplet control. The technology enables the printing on both conductive and non-conductive surfaces, as well as those with irregularities and non-planar sections, which is important for fabrication of many biological sensor and electronics applications. Better droplet control is enabled by modifications in the electrodes and system alignment methods. This provides a printhead that does not use the substrate as a part of the electrical circuit, thus eliminating the errors caused by the surface of the substrate. Commercial off the shelf parts can be used with little modification to build this device. Experiments have shown the ability to carefully control feature size and position, as well as print on non-conductive surfaces, with dots as small as 1 micron in diameter on glass slides.
Electrohydrodynamic Jet Printing
There is a growing interest in using ink jet printing for a direct fabrication across a range of applications from electronics to biological sensors. An emerging technology of electrohydrodynamic (EHD) jet printing allows a wide range of substances to be printed onto a substrate. This direct additive fabrication allows for a lower material use and potentially faster and less costly production with greater design flexibility. EHD jet printing uses a voltage to overcome the surface tension of a droplet, thus releasing it to fall onto the substrate. The challenge is that many EHD jet printing devices use the substrate as part of the electronic circuit for overcoming the surface tension, which requires a conductive surface, and responds poorly to surface irregulars, substrate vibration, and existing deposited material on the substrate. The few designs that do not use the conductive surface still have poor control over the droplet, which causes lower precision and accuracy. With an equipment for inkjet printing of electronics market in 2011 of $13.6M, expected to reach $20.4M by 2015 (10.3% CAGR), and the application to a USA thin film solar cell manufacturing equipment market expected to reach $1.48B by 2015 (30.1% CAGR), there is a large market opportunity for an inkjet technology that print on a range of surfaces.
- Printed electronics
- Thin film solar cells
- Prints on a range of substrates
- Better droplet control
- Performance not affected by surface irregularities