Random and ordered macropore formation in p-type silicon have been studied experimentally. We found that the density of macropores in a random macropore nucleation regime is linearly depending on the samples doping concentration. Macropore etching rate depends linearly on the current density up to the critical current density value; a saturation in the etching rate takes place when this value is exceeded. The so-called proximity effect was discovered for the ordered macropore formation regime. This phenomenon, and large pore diameters and pore wall thickness, and their variations have been observed in the experiments which can be accounted for in the frame of a simple model of the current localization at the pore bottom. An analysis of the experimental data based on the at present time existing theoretical models has been done. This analysis leads to the conclusion that none of these models can describe the existing experimental data including data of this work. It is clear that new experimental data are needed to come to a universal model of the electrochemical macropore formation. © 2001 The Electrochemical Society. All rights reserved.

Numerous chemomechanical processes of cells, such as pseudopod formation during cell locomotion [1] and the capping process preceding the engulfment of pathogens by macrophages during immunological responses, [2,3] are mediated by the actin-based cytoskeleton. In quiescent cells, the cytoskeleton consists of a partially crosslinked network of actin filaments forming a shell, several hundreds of nanometers thick, called the actin cortex. On the other hand, the activation of cells (for example, the endothelial cells lining the inner walls of blood vessels, by inflammation-mimicking agents such as thrombin) often leads to the formation of actin bundles coexisting within the random actin network. [2, 4] Several families of actin-manipulating proteins control the structure and viscoelastic properties of the actin cytoskeleton. These proteins include: 1) sequestering molecules which control the fraction of polymerized actin; 2) severing proteins which control the filament length; and 3) linker proteins mediating crosslinking between actin filaments and their coupling to membranes.Several studies of the structural reorganization of the actinbased cytoskeleton during pseudopod formation, [5] the centripetal contraction of endothelial cells by inflammation signalers, such as thrombin, [6] and the formation of focal contacts to stabilize cell adhesion [7, 8] have yielded some insight into the regulation of the actin cytoskeleton by biochemical signaling. Micromechanical studies of cell membranes have provided some information on the correlation between the viscoelastic behavior of cells and the structure of the actin cortex, [9] and on its role for the generation of forces. [10] of 700 mV in 0.2 M LiClO 4 0.1 M monomer (pyrrole or 1-methylpyrrole) acetonitrile solution.2) By consecutive square waves of potential (3 seconds at À 300 mV followed by 8 seconds at 700 mV and back to À 300 mV until established polymerization charge (oxidation minus reduction charge) was completed. Polythiophene and poly(3-methylthiophene) were generated in 0.2 M LiClO 4 0.1 M monomer (thiophene or 3-methylthiophene) acetonitrile solution by those consecutive potential steps.3) By potential cycling (polyaniline and poly(methylaniline) films were grown by potential cycling at 50 mVs À1 between À 100 and 900 mV in 0.2 M aniline 0.1 M H 2 SO 4 aqueous solutions, until the overall polymerization charge was completed.The thickness of the obtained films was around 0.22 mm, according to SEM observations of the dry films. After electrogeneration each polymer-coated electrode was rinsed with acetonitrile and transferred into the solution in which both electrochemical and electrochromic control would take place: 0.2 M lithium perchlorate acetonitrile solutions. There the electrodes were reduced at the compaction potential (E c ) for 1 min. Each of the studied polymers has a different value for its closing potential [22] (E s ) and the selected compaction potentials, À 600 mV for polythiophene, À 900 mV for poly(3-methylthiophene), À 1800 mV for p...

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