Recalling some of the progress that has been made in understanding the mechanical properties of materials over the past 50 years or so reveals the importance of remembering and applying old lessons when addressing new opportunities in materials research. Often, the classical lessons of the past are especially useful as a guide for thinking about new problems. Such an approach to new problems is intimately connected to the creation of simple models that capture the essential features of the phenomena involved. Experience shows that, although such efforts might not pay off immediately, they come to be useful many years later when new problems are confronted. The merit of applying old lessons to new problems is described herein by using examples from the author's career in characterizing and understanding the mechanical properties of materials. It is hoped that these lessons are sufficiently general to be applied to other areas of materials research. Problems ranging from the high-temperature creep resistance of titanium aluminides, to the residual stresses in deposited thin films, to diffusive relaxation processes in thin films, to the size dependence of the strength of crystalline materials at the nanometer scale, all provide examples of how applying lessons of the past can help to understand new problems. An effort is also made to identify new, emerging problems in materials research where the application of the lessons of the past, together with new capabilities of the future, can come together to produce a fresh understanding of material behavior.

A mnemonic scheme is presented to help recall the equations in classical thermodynamics that connect the four state variables (temperature, pressure, volume, and entropy) to the four thermodynamic potentials (internal energy, Helmholtz free energy, enthalpy, and Gibbs free energy). Max Born created a square to help recall the thermodynamic equations. The new scheme here separates the Max Born square into two squares, resulting in easier recalling of several sets of equations, including the Maxwell equations, without complicated rules to remember the positive or negative signs.

When light is absorbed in organic semiconductors, bound electron–hole pairs known as excitons are generated. The electrons and holes separate from each other at an interface between two semiconductors by electron transfer. It is advantageous to form well-ordered nanostructures so that all of the excitons can reach the interface between the two semiconductors and all of the charge carriers have a pathway to the appropriate electrode. This article discusses charge and exciton transport in organic semiconductors, as well as the opportunities for making highly efficient solar cells and for using carbon nanotubes to replace metal oxide electrodes.

The continuous improvement in luminous efficacy of “white” light-emitting-diode (LED) sources offers the potential of considerable energy savings in general lighting applications. Recent experiments at UCSB have demonstrated 117 lumens per watt (lm/W) in white LEDs, with further improvements expected in the near future. Considerable progress has also been achieved using nonpolar GaN, such as a-plane {1120} and m-plane {1100} GaN, or semipolar GaN substrates. Such devices avoid the deleterious effects of charge separation due to spontaneous and piezoelectric polarization inherent in most c-axis-oriented devices.

Carbon dioxide (CO2) is arguably the most high-profile molecule of recent times. Although much of its bad press comes from environmental concerns associated with greenhouse gas emissions, there exists the possibility to harness this abundant resource for application to the synthesis and processing of useful materials. This article describes a selection of recent successes in using supercritical carbon dioxide (scCO2) as a solvent for polymerizations. Further, the uses of compressed CO2 as a processing tool in the fabrication of materials for applications such as coatings and biomaterials are discussed. Finally, the application of scCO2 to photolithography is demonstrated, with particular focus on CO2 as a processing solvent for the patterning of organic electronic devices.