Polymers are widely used in micro-systems for biological detection and sensing and to provide easier alternatives for fabrication of Biomedical Micro-devices (BMMDs). The most widely used polymeric system amenable to micro-fabrication is silicone rubber, particularly poly(dimethylsiloxane) (PDMS). The principal advantage that silicone rubber offers is its ability to get replicated with high aspect ratios by micro-molding. In addition to PDMS, other polymer systems, like resists or epoxies, find extensive use in micro-fabrication providing many aspects such as good interlayer bonding, selective patterning, modified physical properties like variable electrical or optical properties, etc. Most polymer systems are amenable to rapid changes in their surface energies as they are exposed to gas plasmas or UV radiation. Such changes can sometimes be reversible and the exposed surfaces can regain their original configuration with time called hydrophobic recovery. In general, polymer surfaces after such external stimuli become constitutionally highly dynamic and this makes them well suited to prominent applications in fabrication of BMMDs. Our group has extensively worked in the area of polymer surface modification by external stimuli and its characterization and in this paper we have attempted to review some of the group's work. (C) Koninklijke Brill NV, Leiden, 2010