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Microdroplet deposition is a technology that spans applications from tissue engineering to microelectronics. Our new high-speed imaging measurements reveal how sequential linear deposition of overlapping droplets on flat uniform substrates leads to striking non-uniform morphologies for moderate contact angles. We develop a simple physical model, which for the first time captures the post-impact dynamics drop-by-drop: surface-tension drives liquid redistribution, contact-angle hysteresis underlies initial non-uniformity, while viscous effects cause subsequent periodic variations.

We consider nonlinear elastic deformations of a magneto-elastic beam, using a combined experimental and theoretical approach. In the experiments, a beam had one end clamped with a magnet attached at its free end. When it was placed in an external magnetic field, it was susceptible to Euler beam buckling. However, the classic supercritical bifurcation associated with this buckling became subcritical when an attracting magnet was introduced in close proximity to the beam. To understand these experiments, we develop a model that couples the Euler elastica and dipole magnetic interactions with a uniform external field. The numerical model captures the observed behaviour well and shows that the supercritical magnetic field strength depends almost exclusively on elastic properties of the beam and strength of the permanent magnet, whereas the subcritical behaviour also depends on the separation distance between the attracting pair of magnets. We examine the bifurcation behaviour of the nonlinear system and show that for sufficiently small intermagnet separation distances, other buckled states coexist with the fundamental mode.

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We report results of an experimental study of Faraday waves that were formed on the interface between two immiscible liquids in a cylindrical cell when it was oscillated vertically. The effects of the volume filling ratio on the bifurcation set associated with the onset of the fundamental axisymmetric mode was investigated systematically. In particular, results are presented for the subharmonic regime of the control parameter space where the response was greatest. Both superand subcritical bifurcations are uncovered, with hysteresis in the latter case. The extent of the hysteresis is observed to strongly depend on , suggesting that nonlinear damping effects are influenced by this parameter. At large drive amplitudes, a precessional periodic motion was found to develop via a Hopf bifurcation. This mode was observed to disappear catastrophically at an excitation frequency equal to 1.853Ϯ0.006 times the natural frequency of the resonant mode.