As technology continues towards smaller, thinner and lighter devices, more stringent demands are placed on thin polymer films as diffusion barriers, dielectric coatings, electronic packaging and so on. Therefore, there is a growing need for testing platforms to rapidly determine the mechanical properties of thin polymer films and coatings. We introduce here an elegant, efficient measurement method that yields the elastic moduli of nanoscale polymer films in a rapid and quantitative manner without the need for expensive equipment or material-specific modelling. The technique exploits a buckling instability that occurs in bilayers consisting of a stiff, thin film coated onto a relatively soft, thick substrate. Using the spacing of these highly periodic wrinkles, we calculate the film's elastic modulus by applying well-established buckling mechanics. We successfully apply this new measurement platform to several systems displaying a wide range of thicknessess (nanometre to micrometre) and moduli (MPa to GPa).

In order to better understand the physical basis of the biological activity of nanoparticles (NPs) in nanomedicine applications and under conditions of environmental exposure, we performed an array of photophysical measurements to quantify the interaction of model gold NPs having a wide range of NP diameters with common blood proteins. In particular, absorbance, fluorescence quenching, circular dichroism, dynamic light scattering, and electron microscopy measurements were performed on surface-functionalized water-soluble gold NPs having a diameter range from 5 to 100 nm in the presence of common human blood proteins: albumin, fibrinogen, gamma-globulin, histone, and insulin. We find that the gold NPs strongly associate with these essential blood proteins where the binding constant, K, as well as the degree of cooperativity of particle--protein binding (Hill constant, n), depends on particle size and the native protein structure. We also find tentative evidence that the model proteins undergo conformational change upon association with the NPs and that the thickness of the adsorbed protein layer (bare NP diameter <50 nm) progressively increases with NP size, effects that have potential general importance for understanding NP aggregation in biological media and the interaction of NP with biological materials broadly.

Dewetting of polystyrene films on a silicon substrate is investigated as a function of film thickness h. We observe the nucleation of holes in the early stage of dewetting for relatively thick films ͑h. 100 Å͒, as observed previously, but the breakup of thinner films occurs through the growth of uniformly distributed surface undulations ("spinodal dewetting"). The average amplitude dh of these undulations increases exponentially up to the film rupture point where dh becomes comparable to h, as predicted by a capillary wave instability model. [S0031-9007(98)06787-8]

Neutron reflectivity measurements are made on a chemically end-grafted polymer brush swollen over

We utilize chemically patterned substrates with arrays of progressively narrower stripes (1-15 µm) to investigate the influence of pattern size on the morphology of ultrathin dewetting polystyrene films. The scale and orientation of the spinodal-like height fluctuations of the dewetting patterns are coupled to the imposed substrate chemical frequency, providing a powerful means of morphological control. Dewetting patterns are correlated to the substrate pattern period leading to the formation of droplet arrays. The measurements confirm recent numerical simulations by Kargupta and Sharma of the existence of upper and lower cutoff scales for pattern recognition of a dewetting fluid. For pattern dimensions less than the characteristic scale on nonpatterned substrates, the droplets become anisotropic as they coarsen to a scale comparable to the stripe width, and then undergo a morphological transition to circular droplets that cross multiple stripes. This leads to quantization of droplet size and contact angles, as indicated by theory.