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ABSTRACT Self-organization is ubiquitous in biology, with viruses providing an excellent illustration of bioassemblies being much more than the sum of their parts. Following nature's lead, molecular self-assembly has emerged as a new synthetic strategy in the past 3 decades or so. Self-assembly approaches promise to generate complex supramolecular architectures having molecular weights of 0.5 to 100 MDa and collective properties determined by the interplay between structural organization and composition. However, biophysical methods specific to mesoscopic self-assembly, and presentations of the challenges they aim to overcome, remain underrepresented in the educational laboratory curriculum. We present here a simple but effective model for laboratory instruction that introduces students to the world of intermolecular forces and virus assembly, and to a cutting-edge technology, atomic force microscopy nanoindentation, which is able to measure the mechanical properties of single virus shells in vitro. In addition, the model illustrates the important idea that, at nanoscale, phenomena often have an inherent interdisciplinary character. 

In nanoparticle-assisted photothermal microscopy, absorption of radiation by a nanoparticle is followed by non-radiative relaxation which leads to changes in the surrounding medium temperature, pressure, and density. Under harmonically modulated irradiation, the finite heat diffusion rate causes a phase delay between the thermal oscillation at a location in the medium relative to that at the nanoparticle surface. The phase delay averaged over the probe laser volume can be measured concomitantly with the amplitude of detected probe power modulation. In this study we show that, in conjunction with the more widespread measurement of the modulation amplitude, the photothermal phase can provide a complementary, sensitive probe of thermally-induced changes in the local medium properties. As proof of principle, we study a widely used, technologically important polymer resist -- polydimethylsiloxane (PDMS). In addition we show how, with the help of simulations, it is possible to extract from phase/amplitude data the temperature-dependent properties of the photoannealed medium.