Surface modification is of essential importance in bioengineering. Polymer thin coatings offer various functionalities and biocompatibility to the interface of biomaterials and biosystems. While conventional solution-based polymer coating techniques are fully capable of providing uniform thin coatings on flat surfaces, they have limitations in coating nano- and micro-structured substrates. Vapor-based polymer coatings have also been investigated mainly by plasma-assisted processes, which encounter difficulties in retaining the delicate functional groups and controlling stoichiometric chemistry. We employed initiated chemical vapor deposition (iCVD) to conformally coat micro- and nano-structured materials with different biofunctional polymer films. The introduction of the initiator allows complete retention of the monomer functionality, while the vapor-based approach permits the excellent preservation of the original morphology of the substrates.

Using iCVD technique, we achieved successful surface modification in three different applications of bioengineering. In CHAPTER II, we demonstrate the creation of durable antibacterial coatings on textile and catheter. Bacterial killing efficacy of more than 99% was achieved on both substrates. The bactericidal effect was durable against continuous washing for up to 10 hours. CHAPTER III, IV, and V presented another important application of iCVD functionalization of vertically aligned carbon nanotubes, which is difficult to achieve using conventional methods. We demonstrated both non-covalent and covalent functionalization of aligned carbon nanotubes with different chemistry. The epoxy chemistry enabled significantly enhanced mechanical properties and wetting stability to the multi-walled carbon nanotube arrays. The covalent functionalization tuned electronic properties of the single walled carbon nanotube arrays. Hydrogel chemistry offered pH-responsiveness and substantially improved wettability to the low-site-density carbon nanotube arrays. In CHAPTER VI, we presented thermo-responsive hydrogel coatings on nanoporous membranes to fabricate smart nanovalves. The tunable transportation of biomolecules through the nanovalves was successfully triggered by the adjustment of temperatures.