Pillar array structure with uniform and high aspect ratio nanometer gaps

An apparatus comprising:

• an inlet configured to receive a fluid;
• an outlet configured to exit the fluid;
• and
• a nanopillar array connected to the inlet and the outlet, the nanopillar array configured to allow the fluid to flow from the inlet to the outlet;
• wherein the nanopillar array includes nanopillars arranged to separate entities by size;
• wherein the nanopillars are arranged to have a gap separating one nanopillar from another nanopillar;
• wherein the gap is constructed to be in a nanoscale range;
• wherein the nanopillar array comprises an oxide layer applied on the nanopillars, the oxide layer causing the gap to be uniform along a vertical axis of the one nanopillar and the another nanopillar;
• and
• wherein the oxide layer causes unevenness in a diameter of the nanopillars to be uniform, resulting in the gap being uniform along the vertical axis of the one nanopillar and the another nanopillar.