A fluidic chip includes at least one nanochannel array, the nanochannel array including a surface having a nanofluidic area formed in the material of the surface; a microfluidic area on said surface; a gradient interface area having a gradual elevation of height linking the microfluidic area and the nanofluidic area; and a sample reservoir capable of receiving a fluid in fluid communication with the microfluidic area. In another embodiment, a fluidic chip includes at least one nanochannel array, the nanochannel array includes a surface having a nanofluidic area formed in the material of the surface; a microfluidic area on said surface; and a gradient interface area linking the microfluidic area and the nanofluidic area, where the gradient interface area comprises a plurality of gradient structures, and the lateral spacing distance between said gradient structures decreases towards said nanofluidic area; and a sample reservoir capable of receiving a fluid in fluid communication with the microfluidic area.