Porous silicon (psi) has emerged as a potential drug delivery vehicle/carrier because of its high surface area to volume ratio, convenient surface chemistry, biocompatibility, and very low toxicity. psi based drug delivery systems were prepared by tuning its morphological characteristics (i.e. porosity, pore size, etc.). in this study, psi single layers were prepared in order to study the effect of current density and etching time on psi morphology. the results showed a higher porosity and larger pore size at high current density. etching rate was also found to be more at higher current density. thickness of psi layer was increased with increase in etching time. the present work also reports design and fabrication of psi based one-dimensional (1d) photonic crystal. distributed bragg reflector (dbr) is a 1d photonic crystal composed of the multilayer stack of high and low refractive index layers. design of psi dbr is a complex one and requires appropriate control in optical parameters of its constituent layers. in order to design dbr, two psi single layer samples were fabricated using current density of 10 and 50 ma/cm2. reflective interferometric fourier transform spectroscopy (rifts) method was employed to determine optical constants of psi single layers. dbr simulation was carried out based on transfer matrix method. dbr was then fabricated using optical parameters obtained from rifts method. reflection bandwidth of prepared dbr was found to be 216 nm, which is comparable to the simulated value of 203 nm. psi based sustained drug delivery system of acyclovir was prepared and the effect of different surface chemistries of psi on drug loading and release behaviour was studied. psi films were fractured by ultrasonication to prepare micro- and nanoparticles. psi native particles were thermally oxidized (topsi) and thermally hydrosilylated using undecylenic acid (unpsi). psi particles with three different surface chemistries were then loaded with acyclovir by physical adsorption and covalent attachment. in vitro acyclovir release experiments in phosphate buffered saline showed sustained release behaviour from both micro- and nanoparticles and order of release was found to be native psi > topsi > unpsi. drug release kinetics study using korsmeyer-peppas model suggested a combination of both drug diffusion and silicon scaffold erosion based drug release mechanisms. the drug release study was also carried out using porous films still attached to the si wafer. native psi films were stabilized by partial and complete thermal oxidation. acyclovir was then loaded into the three types of psi films by immersing in drug loading solution. in vitro drug release studies showed slower release (up to 8 hours), and immediate release (up to 3 hours) from native and thermally oxidized psi, respectively. drug release kinetics studies of thermally oxidized psi suggested diffusion sustained drug release whereas native psi indicated a combination of both diffusion of acyclovir and erosion of the silicon scaffold as drug release mechanisms. in addition, the ability of psi dbr microparticles for sustained and observable delivery of the acyclovir was demonstrated. the hydrogen-terminated native surface of dbr microparticles was modified by thermal oxidation and thermal hydrosilylation. particles were loaded with acyclovir and drug release experiments were conducted in phosphate buffered saline. drug loading and surface chemistry of particles were characterized by scanning electron microscopy and fourier transform infrared spectroscopy. drug release profiles from psi dbr particles show sustained release behaviour from all three studied surface chemistries. the change in color of microparticles was observed as the drug released from the psi matrix. therefore, psi micro- and nanoparticles allowed the dual advantage of drug delivery and drug release monitoring in real- time.