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Pressure–volume–temperature measurements in phenylphthalein-dimethylether (PDE) are reported, in combination with recently published dynamic light scattering data obtained under high pressure. We discuss the role that volume and thermal effects play in controlling the dynamics in the vicinity of the glass transition. Although volume is not the unique thermodynamical parameter characterizing the relaxation dynamics in PDE, its contribution to the super-Arrhenius behavior of the relaxation times in the vicinity of the glass transition is remarkable. The contribution of volume to the temperature dependence of the relaxation times has been characterized by means of the ratio of the activation energy at constant volume to the enthalpy of activation at constant pressure, EV/HP. We point out that this quantity is correlated with the temperature behavior of the nonexponentiallity parameter, βKWW. Moreover, the τ(T,P) values were analyzed in terms of an extension of the Adam–Gibbs model. It was shown that this model gives a satisfactory interpretation of the pressure sensitivity of the dynamics (d log10(τ)/dP)|T in terms of thermodynamic properties of the material.

From pressure–volume–temperature measurements, in combination with published dielectric spectroscopy results, we assess the volume dependence of structural relaxation in cresolphthalein–dimethylether (KDE). Structural relaxation in KDE cannot be described as either a volume activated or thermally activated process, and unlike results for some other molecular glass formers, temperature is not the dominant control variable. The inflection point of the PVT data yields a glass temperature, Tg, that corresponds to a dielectric relaxation time equal to 10 s. There is a marked variation with pressure, dTg/dP=307 K/GPa at low pressure. We also carried out dynamic mechanical measurements on KDE near Tg. The shape of the mechanical and dielectric relaxation functions, as well as both the magnitude and temperature dependence of the respective relaxation times, are the same. Such equivalence is not generally expected, and arises herein due to the rigid structure of the KDE molecule.

We use a multiwell micromechanical cantilever sensor (MCS) device to measure surface stress changes induced by specific adsorption of molecules. A multiplexed assay format facilitates the monitoring of the bending of 16 MCSs in parallel. The 16 MCSs are grouped within four separate wells. Each well can be addressed independently by different analyte liquids. This enables functionalization of MCS separately by flowing different solutions through each well. In addition, each well contains a fixed reference mirror which allows measuring the absolute bending of MCS. In addition, the mirror can be used to follow refractive index changes upon mixing of different solutions. The effect of the flow rate on the MCS bending change was found to be dependent on the absolute bending value of MCS. Experiments and finite element simulations of solution exchange in wells were performed. Both revealed that one solution can be exchanged by another one after 200 microl volume has flown through. Using this device, the adsorption of thiolated DNA molecules and 6-mercapto-1-hexanol on gold surfaces was performed to test the nanomechanical response of MCS.

In order to study the failure mechanism of micron sized particles, ruby (α‐Al2O3:Cr3+) spheres of R=75μm radius were compressed between two sapphire (α‐Al2O3) plates. A confocal microscope was used to measure the local spectral shifts of the luminescence lines in the ruby sphere while slowly increasing the load up to failure at 6–7N. From the spectral shifts the local stress was calculated. The results show a steplike decrease of stress starting at a load of 4.3–4.7N. We interpret this as the formation of microcracks, which lead to a relaxation of stress. In the vicinity of the contact area luminescence spectra with multiple distinct peaks were observed. This indicates the presence of regions of homogeneous stress, which are mechanically decoupled and which are even smaller than the observation volume of ≈(2μm)3.

We verify an important prediction of Hertz theory [J. Reine Angew. Math. 92, 156 (1882)] for hard microcontacts, namely, the hemispherical pressure distribution in the contact area. Therefore, a confocal microscope was used to measure the local spectral shifts of the fluorescence lines in a ruby (Al2O3:Cr3+) sphere of R=78μm radius compressed between two sapphire (Al2O3) plates. From the spectral shifts the local stress was calculated. At a load of 4.3N the radius of the circular contact area was measured to be a=(11.2±1.0)μm. A hemispherical pressure distribution was observed with a maximal normal pressure of P0=(12.7±2.2)GPa.