Showing papers by "Chris D. W. Wilkinson published in 2002"
TL;DR: The response of cells to micron-sized features, the response of Cells to nano-metric features and the effects of soft materials are discussed.
297 citations
TL;DR: It is shown that the area of cells spreading on a structured nanotopography is reduced compared with that on a planar substrate, and cytoskeletal organization is disrupted as indicated by a marked decrease in number and size of focal contacts.
Abstract: Animal cells live in a complex and diverse environment where they encounter a vast amount of information, a considerable amount of which is in the nanometer range. The surface topography that a cell encounters has a role to play in influencing cell behavior. It has been demonstrated widely that surface shape can directly influence the behavior of cells. In this paper, we discuss the interactions of animal cells with engineered nanotopography, fabricated in quartz and reverse embossed into polycaprolactone, fibroblast cells show reduced adhesion to the ordered nano pits. We show that the area of cells spreading on a structured nanotopography is reduced compared with that on a planar substrate. Furthermore, cytoskeletal organization is disrupted as indicated by a marked decrease in number and size of focal contacts.
146 citations
TL;DR: A new type of extracellular micro-electrode array mounted on a flexible transparent polyimide substrate that can be rapidly moved from one part of a culture of vertebrate neurons to another, which permits co-culture of glia under the neurons and is easily and rapidly replaceable in the event of damage.
29 citations
TL;DR: In this article, the authors studied the switching characteristics of 10 nm thick permalloy elements with submicron widths and found that bending the end-shape of the elements led to a reduction in switching field compared with an equivalent element with square ends.
Abstract: The switching characteristics of 10 nm thick permalloy elements with submicron widths has been studied by Lorentz microscopy. Of particular interest were the changes that occurred when the end-shape of the elements was modified. Gentle curving of the ends led to a reduction in switching field compared with an equivalent element with square ends. The principal reason for this was the different magnetization configurations found close to the element ends. At a temperature of 150 °C switching fields fell markedly, though those for elements with gently curved ends remained consistently lower. While most of the elements under study supported only high moment remanent states, intermediate low moment remanent states could be induced in elements of a certain size. The conditions under which this occurred are discussed.
17 citations
30 Jun 2002
TL;DR: In this paper, an analytic model of channel channelling was developed and its accuracy was checked by measuring the penetration of ions produced by a very low energy implantation in high electron mobility transistors (HEMT's).
Abstract: Ion-induced damage is an important issue in III–V and Si–Ge devices. The principal cause of damage is the introduction of traps and point defects by ions penetrating into the semiconductor. At the low ion energies used in modern process technology (100 eV say) the bulk of the ions remain on or within a few nm of surfaces. However some channel along the direction and so penetrate into the semiconductor to a depth of 30 to 50 nm. In high electron mobility transistors (HEMT's) with fT greater than 100 GHz, the active current carrying layer is only 30 to 50 nm below the surface. In compound semiconductors it is usually impossible to anneal such damage away. An analytic model of this channelling has been developed and its accuracy checked by measuring the penetration of ions produced by a very low energy implantation. An important finding is while atomic ions (e.g. Cl+) can channel and so cause damage, molecular ions (e.g. Cl2+) do not. This can be used to predict processes that will be suitable for low damage.
12 citations
TL;DR: In this article, an analytic model of channel channelling was developed and its accuracy was checked by measuring the penetration of ions produced by a very low energy implantation in high electron mobility transistors (HEMT's).
Abstract: Ion-induced damage is an important issue in III–V and Si–Ge devices. The principal cause of damage is the introduction of traps and point defects by ions penetrating into the semiconductor. At the low ion energies used in modern process technology (100 eV say) the bulk of the ions remain on or within a few nm of surfaces. However some channel along the direction and so penetrate into the semiconductor to a depth of 30 to 50 nm. In high electron mobility transistors (HEMT's) with fT greater than 100 GHz, the active current carrying layer is only 30 to 50 nm below the surface. In compound semiconductors it is usually impossible to anneal such damage away. An analytic model of this channelling has been developed and its accuracy checked by measuring the penetration of ions produced by a very low energy implantation. An important finding is while atomic ions (e.g. Cl+) can channel and so cause damage, molecular ions (e.g. Cl2+) do not. This can be used to predict processes that will be suitable for low damage.
11 citations
07 Aug 2002
TL;DR: In this paper, the switching properties of 10nm thick Permalloy elements with widths of 500-700nm and lengths of 2000-3500nm were investigated and the switching fields at room temperature were typically a few 10's of Oe, and increased with decreasing element width and were relatively insensitive to element length.
Abstract: Summary form only given. In previous a work we have shown that acicular elements with pointed or highly-curved ends switch at considerably higher fields than similarly-sized elements with square ends (Kirk et al. (1997)). Here we report on switching properties of 10nm thick Permalloy elements with widths of 500-700nm and lengths of 2000-3500nm; elements with square or gently-rounded ends were both studied. Specimens were prepared by electron beam lithography and lift-off whilst all observations were made using transmission Lorentz microscopy in a modified Philips CM20 TEM. About 40 notionally identical and well-separated elements of each size and shape were examined. Switching fields at room temperature were typically a few 10's of Oe, and increased with decreasing element width and were relatively insensitive to element length. Standard deviations of the switching fields within each array were /spl sim/2-30e, attesting to the high quality with which the elements were defined. At elevated temperature (150-250/spl deg/C), switching fields fell markedly to only a few Oe.