Soft printing of droplets digitized by electrowetting

This paper describes a new way of printing, enabled by electric control and geometric utilization of surface tension. The printing is performed by contact between liquid droplets and a solid printing surface (e.g. a glass plate), with neither solid-solid contact nor droplet ejection. The droplets are formed prior to the printing by electrowetting-on-dielectric (EWOD) so that the droplet volume is not affected by the printing surface or environment. Micromachining processes have been developed to accommodate active liquid digitization and passive droplet transfer in the testing device. Successful printings of water and diluted DNA solution droplets (/spl sim/100 nl) were demonstrated. Incorporated with EWOD, this printing mechanism is capable of programming the sizes and positions of printed spots using multiple nozzles and various droplet volumes.