Surface Engineering Using Layer-by-Layer Assembly of Polymers and Nanoparticles

An electrostatic layer-by-layer deposition scheme has been used successfully to produce conformal ultra thin films on a variety of three-dimensional objects, including colloidal particles, membrane pores and nanofluidic channels as well as on conventional flat substrates. Various charged macromolecules and/or nanoparticles have been employed; in some cases suitable post-treatment of the films provides enhanced functionality. There is potential for applications of these films in areas such as structural color, antireflection, self-decontamination, antifogging, non-wetting and water gathering. 

Optical Thin Films for Eyewear Applications

The central function of ophthalmic lenses is to provide a good quality of vision relying on high precision optical surfaces and sophisticated materials. Modern spectacle lenses are consumer products designed through fast growing complexity in the recent years. In order to serve a large variety of visual needs, a key challenge is to combine strong product customization along with mass production. The progressive replacement of mineral lenses by specialized optical polymers has paved the way to the addition of multifunctional coatings in order to improve wearers comfort as well as spectacle aesthetics.
We will explain what kind of complex coating system has been able to combine different features like light absorption, variable optical transmission, scratch resistance, impact resistance, antireflective and easy-to-clean lens surfaces, etc.. Optical thin films and vacuum surface processing play today a major role to achieve some of these functions along with nanotechnology.
The optimization of many different materials properties is necessary in regard to the composite and multilayer lens structure. In addition to the tight control of optical and cosmetic performance, more and more emphasis is being placed on mechanical and physicochemical properties of layers.

Finally, as a conclusion we will comment on current challenges and future opportunities of ophthalmic coatings.

Magnetic Multilayer Thin Film Rings for Magnetoelectronic Devices

Patterned magnetic nanostructures are interesting, both as model structures for the study of the fundamentals of magnetic behavior, and for applications in data storage. Rings are particularly interesting because they can adopt a variety of stable and metastable magnetic states characterized by different numbers of domain walls. In this seminar we will describe the behavior of thin film magnetic rings with micron and submicron diameters made from single layer magnetic films, multilayer films and exchange biased stacks. We will show how the direction of circulation of the magnetization around the ring can be controlled, how the rings can be electrically contacted to show magnetoresistance values exceeding 100%; and we will describe how these structures may be used in multi-bit memory cells and logic devices.

Heat Assisted Magnetic Recording

The tremendous increase in magnetic areal density has been largely responsible for the proliferation of hard disk drive recording into new applications and markets. The superparamagnetic limit imposes a signal-to-noise ratio, thermal stability, and writability tradeoff that limits the ability to continue to scale traditional magnetic recording technology to higher storage densities. Heat Assisted Magnetic Recording (HAMR) offers a new degree of freedom with elevated writing temperature that holds the promise of extending the areal density of magnetic data storage. By temporarily heating the media during the recording process, the media coercivity can be lowered below the available applied magnetic write field, allowing higher media anisotropy and therefore smaller thermally stable grains. The heated region is then rapidly cooled in the presence of the applied head field where transition is recorded. In this talk, I will present recent updates of HAMR.

Supra-molecular Nano-Materials and Lithography

It is know that specific molecules can spontaneously arrange on various surfaces forming two-dimensional poly-crystalline self-assembled monolayers (SAMs). SAMs composed of more than one type of molecule (mixed-SAMs) are used to simultaneously impart multiple properties. Scanning tunneling microscopy studies have shown that, in mixed SAMs, molecules phase-separate in domains of random shape and size.
It will be shown that mixed SAMs formed on nanoparticle surfaces spontaneously phase-separate into ribbon-like domains (called ‘ripples’) whose width is comparable to the size of a small molecule. The reasons that lead to this fine nano-structuring will be presented. I Rippled nanoparticles show new properties solely due to their unique surface morphology. For example, the particles’ solubility (defined as the saturation concentration) depends critically on the ratio between the dimensions of the phases and that of the solvent molecules. More in general we will show that the whole surface energy landscape depends on the size of the ripples. Unexpected consequences on cell/nanoparticles interactions will be presented.

MAD (Multi-Agent Delivery) Nanolayers - New Approaches to Thin Film Drug Delivery

The ability to develop multifunctional release coatings, and to tune the release profiles of drugs on a near continuous level provides a disruptive technology that can create numerous pathways to new medical applications, ranging from stents and medical sutures to hip and bone implants.  We have recently demonstrated the construction of multilayers for which one of the polyions is a degradable polycation; in such systems, once the film is constructed, it undergoes hydrolytic degradation at biological conditions to release the corresponding polyanionic species originally bound in the LBL film.  Depending on the nature of the anionic macromolecular drug system to be delivered, interdiffusion and its impact on the film composition can impact delivery behavior, yielding complex but tunable delivery behavior.  The tuning of the release profile to obtain the simultaneous or timed sequential release of two separate model drugs at different times will be addressed, as well as the extended delivery of biologic drugs.   New explorations include the use of unique redox active nanoscale systems as systematically deconstructible polymers in multilayers with potential uses as an electrochemical means of drug delivery. New methods of obtaining controlled release in response to electrochemical stimuli from thin films will also be addressed.