The present invention provides biochips that include: (a) a plurality of cards, each card having a plurality of card apertures extending therethrough, each respective card aperture having one or more cross sectional areas; and (b) a plurality of gaskets, at least one gasket residing intermediate two neighboring cards, each gasket having a plurality of gasket apertures extending therethrough. At least some of the gasket apertures have an area that is greater than that of at least one adjacent card aperture. Different sets of the gasket apertures and card apertures define a plurality of fluidic flow channels. Also provided herein are methods of making and using biochips.