ملخص البحث :

Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repetition rate allowed wire arrays across an area of 4 mm x 0.18 mm to be patterned in 85 s.

ملخص البحث :

A 2-D permalloy (Ni81Fe19) microstructures have been patterned using laser direct writing (LDW). The magnetic structures were designed and fabricated in a single-step process using scanning stage system based on A3200 software from a thin film. This process was implemented under atmospheric conditions and room temperature by removing unwanted areas of thin film by laser. The 2-D magnetic structures included: nanowire array. These elements exhibited shape-sensitive magnetic behavior with the increase in shape aspect ratio. The average fabrication time per element was 15–120 min at the scan speed was varied between 5–20 μm/s, and a laser repetition rate of 6 kHz. This demonstration of flexibility and speed of laser direct write processing being applied to magnetic microstructures may assist in prototyping and rapid manufacture of devices such as sensors and magnetic wires for interactions with biological cells.

ملخص البحث :

The abilities of laser direct writing have been explored on thin films of permalloy (Ni81Fe19) for range of film thicknesses with two types of substrates for creating micro-scale magnetic structures. The thin films of Permalloy were deposited on both silicon and glass substrates using thermal evaporator with ranging from 5 to 100 nm. The permalloy films were successively patterned using a laser system containing of a pico-second pulsed laser with an 800 ps pulse width and wavelength of 532 nm. A series of magnetic wires were patterned then characterised by Magneto-Optic Kerr Effect system and Scanning Electron Microscopy. The patterned magnetic wires showed good responses to an applied magnetic field. The corresponding coercivities of the patterned magnetic wires were affected by their observed quality. These results can improve the understanding of laser direct writing technique to fabricate the micromagnetic structures for future application as easy, low cost and high throughput technique.1

ملخص البحث :

This work focuses on the fabrication of excellent magnetic structures for trapping breast cancer cells. Micro- magnetic structures were patterned for trapping cancer cells by depositing 30 nm of permalloy on a silicon substrate. These structures were designed and fabricated using two fabrication techniques: electron beam lithography and laser direct writing. Two types of magnetic structures, rectangular wire and zig-zagged wire, were created on a silicon substrate. The length of each rectangular wire and each straight line of zig-zagged wire was 150 μm with a range of widths from 1 to 15 μm for rectangular and 1, 5, 10 and 15 μm for zigzag, respectively. The magnetic structures showed good responses to the applied magnetic field despite adding layers of silicon nitride and polyethylene glycol. The results showed that Si + Si3N4 + PEG exhibited the best adhesion of cells to the surface, followed by Si + Py + Si3N4 + PEG. concentration of 5-6 with permalloy indicates that this layer affected silicon nitride in the presence of Polyethylene glycolPEG.

ملخص البحث :

The separation and overlap between the laser pulses were controlled through sample's scan speed and pulse repetition frequency using a laser system of 0.8 nanosecond pulse width with a repetition frequency of 50 kHz. The laser beam has been focused on the sample surface using an objective lens with 0.6 numerical aperture to a spot with a diameter of 2.83 μm. The laser diode driver has been used for controlling the pulse repetition frequency through controlling the supplied electrical current, whereas the speed of the scanning stage has been used to control the pulses train under computer control. The pulses were successfully controlled from sorting with distance (single pulse per point), contiguous pulses to the overlapping of up to 90%. This control of overlapping between pulses offers an enhanced definition of wires width compared to our previous attempts [1]. This improvement is a further endorsement to Laser direct writing (LDW) as a simple rapid technique that can be used to produce micro/nano scale structures.

ملخص البحث :

An overlap and separation between the laser pulses was sufficiently controlled. The 800- picosecond pulse width laser system that have a repetition rate of 40 KHz have been engaged to implement this path. The system with 532 nm wavelength was focused with a 0.75 NA lens to a 1.83μm diameter spot. Two parameters were used to separate/overlap on sample using the pulses from laser system: the pulse repetition rate and the sample scanning speed. An electric current was supplied to the laser diode driver (LDD) to control the repetition rate of pulsed laser. The second parameter was implemented to control the train of pulses and the speed of scanning stage under computer-control. The distance or overlap between the pulses have been successfully controlled for an arrange from separate the pulses with distance) all to get 90% overlap between pulses. The aim of this method was to get a single pulse from high repetition rate pulsed laser and to scale down the damage of material that result from applied multi pulses. This method was studied and implemented to make the price more reasonable and simpler to use comparing it with using the complex and expensive optics equipment.

ملخص البحث :

In this work a laser scanning setup was designed and constructed by using Laser speckle technique, in which a linear relationship between Laser speckle Contrast and surface roughness . During the work standard stainless steel rough Surface was been used. From the results it is found that incident angle HAS a great influence on the measurements and this due to the saturation phenomena. For Incident angle (15°) saturation takes place with(R=0.12 μm) AND for more roughness the contrast decreased .When the incident angel become (30°) the contrast saturated at ( R= 0.12 μm) and stay constant for more roughness . At angle (75°) saturation in CONTRAST TAKES place at(R=0.4μm) and the value of contrast less than that of 15° and 30° angles.