FLUIDS/INTERFACES AND MORE Manuel G Velarde, IP-UCM (http://www.ucm.es/info/fluidos)

CONVECTIVE PATTERNS AND DEFECTS Bubbles & Drops 2015, Golm

CONVECTIVE PATTERNS AND DEFECTS (AFRICA)

CONVECTIVE PATTERNS AND DEFECTS (AMERICA)

BENARD CONVECTIVE PATTERNS AND DEFECTS

WAVES AND SOLITONS LAB EXPERIMENTS WITH FLUIDS AND SURFING Bubbles & Drops 2015, Golm

FROM SURFING TO ELECTRON SURFING (MECHANICAL CONTROL OF ELECTRONS) FROM MACROHYDRODYNAMICS TO NANOELECTRONICS.

LINEAR VS NONLINEAR WAVES/SOLITONS

Normal vs free ride near shore

Normal vs free ride near shore

Surfing off-shore (could it be on a periodic wave 1m high and over 100 km length at “high speeds”?; think about tsunami and cavitation)

SURFACE ACOUSTIC WAVE (SAW)

HOPPING ELECTRONS ALONG THE CRYSTAL

PHOTOEXCITATION LEADING TO SOLITONA AND ELECTRON AND THEN TRANSFER FROM DONOR TO ACCEPTOR

Wave (lattice soliton-red) and wave (Schrödinger probability density electron-green)

Time evolution of electron and soliton created at same lattice site coupled together (tight binding approx) and creation of solectron

Time evolution of electron and soliton created at separate sites (200-300) coupled together (tight binding approx) and creation of solectron

Extraction of an electron from a potential well (a donor /E/= 10) and ballistic transport to an acceptor observed using the electron probability density /Cn/2.

Perfect crystals of polymer PDA

Electron microscopy-PDA

DROPS/BUBBLES/INTERFACES UNDER SURFACE TENSION GRADIENTS FORCES

WETTING-SPREADING

Partial wetting case. The adsorbed layer due to ambient air/atmosphere/vapor (Kelvin) (…”precursor” film)

Complete wetting case. Left part: as the drop spreads out completely the dynamic (i.e. time-dependent) contact angle q(t) tends to zero i.e. to a vanishing static, equilibrium contact angle. Otherwise said, no liquid drop (with finite radius) can be at thermodynamic equilibrium with the solid substrate. Example: a “pure” oil drop on a glass surface. Right part: the final structure of a wetted solid surface at equilibrium with its own vapor.

NANOLEVEL-SURFACE FORCES-DLVO THEORY Bubbles & Drops 2015, Golm

Porous substrate/solid support. Complete or partial wetting Porous substrate/solid support. Complete or partial wetting. Cross-section of an axi-symmetric spreading drop over an initially dry thin porous substrate (thickness, ). 1. Liquid drop. 2. Wetted region inside the porous substrate. 3. Dry region inside solid support. r, z define the co-ordinate system.

Overall drop profile (exaggerated)

Derjaguin pressure (isotherm) showing the Born repulsion combined with the attraction, vs liquid thickness or plate/surface separation. If the surfaces (including air-solid) attract each other any liquid in between tends to be expelled, hence non-wetting case. If Pe is given (negative) it cuts the isotherm P on two points (thicknesses) each one defining an equilibrium value but only the one with negative slope is stable. In practical terms if we are not able to shift to the right the repulsive part this means no liquid film survives.

DERJAGUIN pressure/ isotherms (hundred nm down): (1) EDL repulsion forces dominate (complete wetting ); (2) combination of L-VdW attraction and EDL repulsion (partial wetting); and (3) L-VdW attraction dominates (non-wetting).

Contact angle: S-— S+ (different isotherms: wetting transitions).