Nanoindentation technology has proven to be an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to validate Hertz contact model, some studies assume that cells have infinite thickness which does not necessarily represent the real situation. In th...

Spheres at medium interfaces are encountered in many applications, including atomic force microscopy or indentation tests. Although the Hertz theory describes contact mechanics between an elastic sphere and half-space for static loading small deformations very well, there is a need to consider density of medium, mass radiation damping dynamic obtain reliable results. In this study, analytical m...

We address three problems that limit the use of the atomic force microscope when measuring elastic moduli of soft materials at microscopic scales. The first concerns the use of sharp cantilever tips, which typically induce local strains that far exceed the linear material regime. We show that this problem can be alleviated by using microspheres as probes, and we establish the criteria for their...

Laboratory exercises that illustrate quantum phenomena provide students with motivation for the study of quantum mechanics. That microscopic matter exists in quantized states can be demonstrated with modem versions of historic experiments: atomic line spectra (I), resonance potentials, and blackbody radiation. The resonance potentials of mercury were discovered by Franck and Hertz in 1914 (2). ...

– We investigated impacts of nearly elastic spherical gels (very soft balls) onto a solid substrate. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, a gel ball deformed into flattened forms like a pancake. We measured the size of gel balls at the maximal deformation and a contact time as a function of...