Physical virology seeks to define the principles of physics underlying viral infections, traditionally focusing on the fundamental processes governing virus assembly, maturation, and disassembly. A detailed understanding of virus structure and assembly has facilitated the development and analysis of virus-based materials for medical applications. In this Physical Virology review article, we discuss the recent developments in nanomedicine that help us to understand how physical properties affect the in vivo fate and clinical impact of (virus-based) nanoparticles. We summarize and discuss the design rules that need to be considered for the successful development and translation of virus-based nanomaterials from bench to bedside.

Variable angle of incidence spectroscopic ellipsometry (VASE) is commonly used for multilayer optical analysis, but in some cases this experiment (performed in reflection) does not provide sufficient information for the unique determination of the thicknesses and optical constants of the films in the given multilayer. We have found that augmenting the VASE data with data from other optical experiments greatly increases the amount of information which can be obtained for multilayers, particularly when they are deposited on transparent substrates. In this work, we describe a formalism which allows us to quantitatively characterize complex multilayer structures by using combined reflection and transmission ellipsometry, reflection ellipsometry with the sample flipped over, and intensity transmission measurements.To demonstrate the usefulness of this capability, the analysis of a complex graded, absorbing thin film structure (a Cr-based phase-shifting photomask blank), is presented.

The design ofan organic material satisfying all ofthe requirements for a single layer photolithography resist at 157 nm is a formidable challenge. All known resists used for optical lithography at 193 nm or longer wavelengths are too highly absorbing at 157 nm to be used at film thicknesses greater than -9O nm. Our goal has been to identify potential, new photoresist platforms that have good transparency at 157 nm (thickness normalized absorbance of2.5 rim' or less), acceptable plasma etch resistance, high Tg, and compatibility with conventional 0.26 N tetramethylammonium hydroxide developers. We have been investigating partially fluorinated resins and copolymers containing transparent acidic groups as potential 157 nm photoresist binders; a variety ofmaterials with promising initial sets ofproperties (transparency, etch resistance, solubility in aqueous TMAH) have been identified. Balancing these properties with imaging performance, however, remains a significant challenge.

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