Sajjad H. Maruf

Programmable, pattern-memorizing polymer surface.

However, all current SMP applications focus on harvesting the macroscopic scale deformation, i.e. employing the SMP as structural materials. An intriguing capability of all SMPs, which remains largely unexplored, is their ability to memorize and recover nanoscale patterns or structures. Here we demonstrate that SMPs can memorize and faithfully recover their lithographically fabricated, permanent or even temporary surface patterns. More signifi cantly, tunable multi-pattern memory capability can be achieved in Nafi on fi lms. Considering the prevalence of nanostructured surfaces in emerging nanotechnologies, such pattern-memorizing surfaces could potentially transform these technologies. During a typical shape memory cycle, an SMPs permanent shape is fi rst “programmed” into a temporary shape under mechanical loading at a temperature higher than the transition temperature (either glass transition temperature, T g , or melting temperature, T m ) of the SMP. At the permanent shape, the polymer chains between crosslinking points can be considered at the equilibrium state, or the lowest energy state. The mechanical loading during the programming deforms the chains into a higher energy state (with lower entropic freedom), forming the temporary shape. Without the mechanical constraints, the SMP sample will return to their permanent shape to minimize the system energy. However, this temporary shape can be “fi xed” as the temperature decreases below the T g (or T m ) of the SMP before releasing the mechanical loading and remains stable indefi nitely. The SMP softens and recovers its permanent shape when exposed to an environmental stimuli such as heat, [ 4 , 5 ] light, [ 1 ] or even solvent vapors. [ 6 ] During the recovery, strain or stress can be harvested under free or constrained conditions, respectively. [ 7 , 8 ] However, beyond such structural applications, the potential applications of SMP surfaces have yet to be explored. King et al. reported that AFM-indented holes on a SMP surface can be recovered via heating which enables the AFM-based data storage. [ 9 , 10 ] Recently, Burke et al. showed that micron scale patterns embossed on liquid crystalline elastomer can be erased

Surface patterning of polymeric membranes and its effect on antifouling characteristics

ABSTRACT Surface roughness of membranes is often perceived by many as a factor that promotes fouling during filtration, and thus is undesirable. Almost all liquid-based separation membranes display flat surfaces with an intrinsic surface roughness that is associated with the membrane manufacturing process. Recently, polymer ultrafiltration and thin film composite membranes containing regular, periodic surface patterns were fabricated using cost-effective lithographic methods. Here, we review the work to date on the fabrication and characterization of these patterned membranes with a focus on processing–structure–performance relationships. In addition, the antifouling performance of these membranes against model foulants including colloidal suspensions and protein solutions is also highlighted.