Presented in this paper is a study of the biocompatibility of an atomic layer-deposited (ALD) alumina (Al 2 O 3 ) thin film and an ALD hydrophobic coating on standard glass cover slips. The pure ALD alumina coating exhibited a water contact angle of 558 6 58 attributed, in part, to a high concentration of À ÀOH groups on the surface. In contrast, the hydrophobic coating (tridecafluoro-1,1,2,2-tetrahydro-octyl-methyl-bis(dimethylamino)silane) had a water contact angle of 1088 6 28. Observations using differential interference contrast microscopy on human coronary artery smooth muscle cells showed normal cell proliferation on both the ALD alumina and hydrophobic coatings when compared to cells grown on control substrates. These observations suggested good biocompatibility over a period of 7 days in vitro. Using a colorimetric assay technique to assess cell viability, the cellular response between the three substrates can be differentiated to show that the ALD alumina coating is more biocompatible and that the hydrophobic coating is less biocompatible when compared to the control. These results suggest that patterning a substrate with hydrophilic and hydrophobic groups can control cell growth. This patterning can further enhance the known advantages of ALD alumina, such as conformality and excellent dielectric properties for biomicro electro mechanical systems (Bio-MEMS) in sensors, actuators, and microfluidics devices.

Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of common manufacturing processes, such as welding, cutting, ablation, or vaporization. To address this growing need for radiometry at extremely high power densities, we demonstrate multiwalled carbon nanotube (MWCNT) coatings with damage thresholds exceeding 15 000 W/cm2 and absorption efficiencies over 90% at 1.06 μm. This result demonstrates specific design advantages not possible with other contemporary high-power laser coatings. Furthermore, the results demonstrate a performance difference between MWCNTs and single-walled carbon nanotube coatings, which is attributed to the lower net thermal resistance of the MWCNT coatings. We explore the behavior of carbon nanotubes at two laser wavelengths (1.06 and 10.6 μm) and also evaluate the optical-absorption efficiency and bulk properties of the coatings.

High power laser radiometry requires efficient and damage-resistant detectors. The current study explores the evolving nature of carbon nanotube coatings for such detectors upon their exposure to incrementally increasing laser power levels. Electron microscopy images along with the D-band to G-band intensity ratios from the Raman spectra from eight irradiance levels are used to evaluate changes before and after the exposure. Electron microscopy images of the exposed multiwalled carbon nanotubes revealed the formation of intermittent pockets of moundlike structures at high power densities exceeding 11 kW/cm2. Raman spectroscopy measurements also demonstrated higher values for the ratio of the D-band intensity to that of the G-band, suggesting the possible transformation of nanotubes into structurally different forms of carbon. Exposure to a sample of single-walled nanotubes did not demonstrate the evolution of structural changes, which could be due in part to the higher irradiance levels relative to the damage threshold, employed in the experiment.

The injection-locking of laser diodes with adjustable frequency difference of the order of 1 GHz with respect to the frequency of a master lber is demonstrated. Each slave laser frequency can be individually switched between up to five discrete values simply by changing its operation current. The presented scheme does not need any RF sew0 loop or optical filters in the locking path of the slave diodes.

We report damage threshold measurements of novel absorbers comprised of either liquid-cooled silicon carbide or vitreous carbon foams. The measurements demonstrate damage thresholds up to 1.6 ϫ 10 4 W͞cm 2 at an incident circular spot size of 2 mm with an absorbance of 96% at 1.064 m. We present a summary of the damage threshold as a function of the water flow velocity and the absorbance measurements. We also present a qualitative description of a damage mechanism based on a two-phase heat transfer between the foam and the flowing water.