Inkjet Printing of Self-Supporting and Self-Contained Structured Objects Onto Liquid Surfaces

Some applications in miniaturized fabrication like valves or force sensors require self-supporting structures. These may be generated on top of a solid substrate and separated from it afterwards, but this separation is an additional manufacturing step and may stress the structure. Therefore, it may be of advantage to create the desired objects directly on top of a liquid. Here, it is shown that self-supporting and self-contained structures including lines of defined width, full tone squares and delicate structures with non-uniform line width, edges and openings can be prepared by inkjet printing of a photo-curable ink onto a water surface followed by irradiation with ultraviolet light and lift-off. To make this feasible, convection, spreading, and dewetting of the ink from the water surface has to be suppressed by controlling the timing of the irradiation, the mobility of the water surface and the long and short range interactions between the printed ink and the water substrate. These tasks may be achieved via addition of soluble amphiphiles or via spreading of water insoluble amphiphiles or hydrophobized particles onto the water surface prior to printing. Best results are obtained by printing the desired structures onto a water surface that bears a monolayer of hydrophobized particles.