Oxide Surfaces with Tunable Stiffness

Abstract

An important challenge of modern materials science and nanoscience is to develop ways to alter the mechanical properties of an interface in a controlled fashion. Doing this while preserving the bulk properties of a material and maintaining a fixed chemical composition and reactivity of the interface is particularly attractive. In this work, the creation of substrates with tunable stiffness has been achieved by coating a soft polymer with an adherent, crack-free oxide overlayer whose thickness is varied from 8 to 70 nm. Specifically, amorphous titania with controlled, variable, thickness was deposited on polydimethylsiloxane (PDMS), and the surface mechanical properties were characterized using atomic force microscope (AFM)-based nanoindentation. The force/deformation curves can be quantitatively reproduced using a finite element analysis (FEA) modeling protocol. The FEA modeling facilitates predictability and enables the design of surfaces with independently customized chemical and mechanical properties.

A nanolayer coating on polydimethylsiloxane surfaces enables a mechanistic study of bacterial adhesion influenced by material surface physicochemistry

“…Surface topography and force curve measurement were performed with cantilever PointProbe® Plus Non-Contact / Soft Tapping Mode -Au Coating (PPP-NCST-Au, Nanosensor, Switzerland). Young's modulus was analysed based on elastic deformation of all samples from AFM-force spectroscopy by AtomicJ converting raw deflection vs sample displacements plots into force vs deformation plots according to the probe signal sensitivity (nm/V) and spring constant (N/m) [52][53][54] .…”

Considering the degradation effects of amino-functional plasma polymer coatings for biomedical application

“…Electrospun scaffolds for tissue engineering and porous membranes for drug delivery were thus functionalized using plasma polymerization with the aim to maintain their submicrometer 3D architecture and their mechanical properties. Ultrathin plasma polymer layers (b10 nm) were deposited, since thicker coatings were found to affect substrate stiffness and degradability [3,4]. While CO 2 /C 2 H 4 gas discharges have already been proven to support cell growth on electrospun poly(ε-caprolactone) (PCL) scaffolds used for tissue engineering [5], we now investigate the ability of NH 3 /C 2 H 4 gas discharges for the same purpose.…”

A nanometric cushion for enhancing scratch and wear resistance of hard films

“…We note that the yield pressure, which is proportional to R 2 [ H 3 / E 2 ] where R is the contact radius, H hardness and E reduced modulus, has an even stronger dependence on the hardness to modulus ratio. This ratio is enhanced for the titania on PDMS film since the effective E is significantly reduced relative to pure titania, as discussed in [37], whereas H remains high as dictated by the properties of the titania film. The negligible effect on H is due to the fact that the contact area of the indenter in the titania film itself at a given load is not increased here (relative to that for pure titania).…”

“…We refer to this as a “cushioning effect”. Taking the Young's modulus as a measure of the substrate compliance, this quantity varies from 170 GPa for Si [ 39 ], to 2.5 GPa for kapton [ 40 ] to 20 MPa for PDMS which has undergone plasma activation [ 37 ].…”

“…Finite element analysis (FEA) provides insights into the mechanism of friction reduction. Finally, we show the value of AFM-based methods for measuring nanoscale mechanical properties of thin hard films – a system that is otherwise difficult to characterize [ 37 ].…”