In this paper, we review the approaches developed in our laboratory for polymer-based micro/nanofabrication. For fabrication of microscale features, UV-LIGA (UV-lithography, electroplating, and molding) technology was applied for low-cost mass production. For fabrication of sub-micron or nanoscale features, a novel nano-manufacturing protocol is being developed. The protocol applies a novel nano-lithography imprinting process on an ultra-precision motion-control station. It is capable of economically producing well-defined pores or channels at the nanometer scale on thin polymer layers. The formed thin layers can be used as nano-filters for chemical or bio-separation. They can also be integrated into miniaturized devices for cell immunoprotection or tissue growth. For bonding of polymer-based microfluidic platforms, a novel resin-gas injection-assisted technique has been developed that achieves both bonding and surface modification. This new approach can easily seal microfluidic devices with micron and sub-micron sized channels without blocking the flow path. It can also be used to modify the channel shape, size, and surface characteristics (e.g., hydrophilicity, degree of protein adsorption). By applying the masking technique, local modification of the channel surface can be achieved through cascade resin-gas injection.