In one aspect, a microfluidic device includes a substrate with a top surface and a raised channel architecture in which at least one channel is formed and defined across a top surface of the substrate and between raised side walls such that a floor of the channel is coplanar with the top surface. The device has a cover positioned over the substrate in alignment with the substrate and including a seal portion that is sealingly received between the raised side walls so as to seal the at least one channel. In addition, the device includes a column packing material disposed within the at least one channel between the raised side walls prior to sealing the at least one channel by merely only inserting the seal portion of the cover within the at least one channel between the raised side walls.