Rapid fabrication of electrohydrodynamic micro-/nanostructures with high aspect ratio using a leaky dielectric photoresist

A leaky dielectric photoresist was designed and prepared for rapid fabrication of high-aspect-ratio micro-/nanostructures via electrohydrodynamic patterning (EHDP). The rheological behavior and electrical properties of the photoresists were systematically investigated, since the structure formation in EHDP essentially originates from the flow and deformation of the polymeric film actuated by an applied electric field. It is found that the photoresists exhibit the suitable rheological behavior with a low viscosity of 2.4-157.7 mPa s, controllable electrical conductivity of 5.0 × 10− 6 − 7.2 × 10− 4 S m− 1, as well as high homogeneity, minor surface tension of about 30 mN·m− 1, favorable wettability and film-forming property on substrate and an extremely large reduction in the contact angle (down to 1.64°) of electrowetting on dielectric (EWOD). The EHDP results have shown that a higher electrical conductivity of the photoresists can lead to a higher filling height, a smaller characteristic wavelength and a shorter patterning time, while a lower viscosity can also lead to a shorter patterning time, which is accordance with the theoretical prediction. In addition, the patterning time of the photoresists cannot be too short because the following rapid ripening and coalescence of the formed microstructure will damage the high fidelity of the final pillar arrays.

The electrohydrodynamic microstructures with either higher aspect ratio or smaller feature size can be fabricated instantaneously at ambient temperature via fine modulating the rheological behavior and the electrical conductivity of a designed UV-curable leaky dielectric fluid.158