Printing-Free Nucleic Acid Microarrays Using AC Electric Fields

Nucleic acid microarrays are widely used in many biological and medical applications. One of the critical steps in the nucleic acid microarray is the placement of nucleic acid molecules using molecular printing in designated spots on the substrate to produce molecular patterns. Molecular printing involves loading molecules onto a printer head and then mechanically moving the head to deposit them in the designed areas on the substrate. This study focuses on eliminating bulky mechanical and moving components in printing technologies, thereby enabling scalable molecular printing. We have employed low-frequency electric fields (0-10 MHz, 0-10 Vpp) to produce highly localized high-electric-field regions within a glass substrate patterned with two-dimensional (2D) gold electrodes. The experiments were conducted using short single- and double-stranded DNA molecules, and the DNA molecules were concentrated in high-electric-field regions. We have also studied the critical factors, such as dielectrophoresis, AC electroosmosis, and capillary flow, that affect DNA patterning. Our results show that electric-field-based molecular patterning is scalable and can be applied broadly to pattern a broad range of molecules, including DNA, mRNA, and proteins.