10:30-11:00

Self Surface Replenishing hydrophobic networks

During the last decade, extensive research has been carried out on coatings with easy-to-clean/self-cleaning, anti-bacteria or anti-fouling properties1, 2, which was largely driven by an industrial demand but also by an academic interest. These properties are strongly related to the coatings surface chemistry. While the challenge to make such functional surfaces has already produced a considerable number of new materials and methods3, attention is now on robust and durable manufacturing. Moreover, since coatings damage can never be totally avoided, introducing self-repairing mechanisms into such functional coatings is one way to extend their service life-time4.

A recently investigated mechanism is the self-replenishing of polymer network surfaces through the self-segregation of chemical groups to the damage loci, using surface-energy as driving force5. Tethering of of the low-surface energy groups by a polymeric spacer to the network prevents excessive segregation and forms a reservoir of low-surface energy groups in the bulk of the crosslinked film. The self-replenishing process was shown to occur at room temperature (inside a ~ 5 nm “fresh” toplayer), after a previous top layer (5-100 μm thick) of a crosslinked polyurethane film (T_g ~ - 20 °C) was intentionally removed.

Currently we are aiming to understand and control the self-replenishing behaviour on model low-surface-energy crosslinked polymeric networks through a dual approach: experimental and modelling (Dissipative Particles Dynamics, DPD). In the phase-mixed polyurethane networks, a number of structural variables were varied (e.g. T_g, M_n of the polymer precursors and tethers, crosslink density, concentration of the low-surface-energy groups) to investigate their influence on the network’s self-replenishing capability. Alternatively, in phase-demixed PDMS-modified networks based on Styrene-Maleic Anhydride6 latices some of these variables were checked for comparison, in addition to the influence of the (nano)scale of the phase separation. In parallel experimental / simulations efforts we investigated the self-replenishing mechanism (e.g. kinetics and extent of recovery), the distribution of low-surface-energy groups through the polymer network and also the interactions between the self-replenishing surface and surrounding media.

The combination of these two approaches has revealed interesting insights into the distribution of the dangling chains through the polymer films, the (re)constitution of the network’s surfaces and the film-structure/self-replenishing-response relationships.

Speaker

Prof. Dr. Rolf van Benthem, DSM Ahead Materials Sciences R&D/Eindhoven University of Technology, Netherlands

Chair

Dr. Chiaki Yoshikawa, MANA Scientist, MANA, NIMS

11:10-11:45

Towards an Atomically Precise H Lithography Process

The vision of Zyvex is to develop techniques for Atomically Precise Manufacturing; that is, the building of atomically precise structures, which could be used in applications such as P-in-Si qubits in quantum computing, or for precise electrode structures for tunnelling FETs. Removal of H atoms from a Si(001) surface by an STM tip, to write simple patterns such as dots, lines and rectangles, a technique known as H depassivation lithography, has been demonstrated by many different groups over the past two decades. However, for a practical atomically precise manufacturing process with larger and more complex patterning, required for applications such as P-in-Si quantum computers, a more efficient process is necessary.

In our vector writing approach, the tip is moved directly to the area to be patterned, with a positioning precision of around 1 Å. Patterns are written as a series of adjacent lines, such that H is removed from the whole area. The tip can follow several different paths within the pattern, e.g. a series of separate lines, a serpentine pattern, a spiral, or a continuous outline of a larger area. We have used this approach to write 3 nm square boxes with a line edge precision, which ranges between 0.01 – 0.1 nm.

Speaker

Dr. James Owen, Zyvex Labs LLC, USA

Chair

Dr. Tomonobu Nakayama, MANA PI, MANA, NIMS