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The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The primary parameter was the surface temperature, which ranged from 24°C to above the Leidenfrost temperature of the liquid. Experiments were also performed on a droplet impacting a surface on which there existed a liquid film created by deposition of a prior droplet. The evolution of wetted area and spreading rate, both of a droplet on a stainless steel surface and of a droplet spreading over a thin liquid film, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects, and in consequence the measurements made during the early period of the impact process were in good agreement with previously published analyses which neglected these effects. A single bubble was observed to form within the droplet during impact at low temperatures. As surface temperature was increased the population of bubbles within the droplet also increased because of progressive activation of nucleation sites on the stainless steel surface. At surface temperatures near to the boiling point of heptane, a spoke-like cellular structure in the liquid was created during the spreading process by coalescence of a ring of bubbles that had formed within the droplet. At higher temperatures, but below the Leidenfrost point, numerous bubbles appeared within the droplet, yet the overall droplet shape, particularly in the early stages of impact (< 0.8 ms), was unaffected by the presence of these bubbles. The maximum value of the diameter of liquid which spreads on the surface is shown to agree with predictions from a simplified model.

This work provides a critical compilation of the homogeneous nucleation limits of liquids. Data for 90 pure substances and 28 mixtures have been compiled over a range of pressures, nucleation rates, and compositions. Detailed descriptions of the experimental methods used to obtain the included data are given to assess the accuracy of measured values. Criteria used to select the measurements included in the final listing are discussed.

BackgroundNanocarrier-based antibody targeting is a promising modality in therapeutic and diagnostic oncology. Single-walled carbon nanotubes (SWNTs) exhibit two unique optical properties that can be exploited for these applications, strong Raman signal for cancer cell detection and near-infrared (NIR) absorbance for selective photothermal ablation of tumors. In the present study, we constructed a HER2 IgY-SWNT complex and demonstrated its dual functionality for both detection and selective destruction of cancer cells in an in vitro model consisting of HER2-expressing SK-BR-3 cells and HER2-negative MCF-7 cells.MethodsThe complex was constructed by covalently conjugating carboxylated SWNTs with anti-HER2 chicken IgY antibody, which is more specific and sensitive than mammalian IgGs. Raman signals were recorded on Raman spectrometers with a laser excitation at 785 nm. NIR irradiation was performed using a diode laser system, and cells with or without nanotube treatment were irradiated by 808 nm laser at 5 W/cm2 for 2 min. Cell viability was examined by the calcein AM/ethidium homodimer-1 (EthD-1) staining.ResultsUsing a Raman optical microscope, we found the Raman signal collected at single-cell level from the complex-treated SK-BR-3 cells was significantly greater than that from various control cells. NIR irradiation selectively destroyed the complex-targeted breast cancer cells without harming receptor-free cells. The cell death was effectuated without the need of internalization of SWNTs by the cancer cells, a finding that has not been reported previously.ConclusionWe have demonstrated that the HER2 IgY-SWNT complex specifically targeted HER2-expressing SK-BR-3 cells but not receptor-negative MCF-7 cells. The complex can be potentially used for both detection and selective photothermal ablation of receptor-positive breast cancer cells without the need of internalization by the cells. Thus, the unique intrinsic properties of SWNTs combined with high specificity and sensitivity of IgY antibodies can lead to new strategies for cancer detection and therapy.

We describe a method for measuring the average surface temperature of a small square thin metallic film deposited on a silicon substrate and immersed in subcooled water during a voltage pulse of short duration. The thin film studied is a material used in the current generation of commercial 'desk-jet' printers and comprises a mixture of tantalum and aluminium 65 µm wide and 0.2 µm thick. The experiment uses a bridge circuit with a dynamic amplifier design to measure the evolution of electrical resistance, coupled with a separate calibration of the thin film resistor element with temperature to determine average surface temperature. Voltage pulses of 5 µs typical duration are applied to the thin films. An 'inflection' point in the resulting evolution of heater surface temperature identifies bubble nucleation.The calibration of the heater resistance with temperature showed a hysteresis effect that required a burn-in process to stabilize the electrical resistance. With the calibration curve obtained, resistance was converted to temperature and the results analysed. For low power input the average surface temperature exhibited an oscillatory behaviour which indicated a cyclic growth/collapse process often found in nucleate boiling. At higher powers, the oscillatory behaviour disappeared and gave way to an exponential variation of temperature with time similar to a lumped capacitance behaviour of a thermal system. An inflection point in the evolution of surface temperature was found that signified bubble nucleation. The largest heating rate and highest nucleation temperature measured were 0.25 × 10 9 • C s −1 and 556 K, respectively. This temperature is in good agreement with homogeneous nucleation theory as applied to a surface. The contact angles needed for measured nucleation temperatures to agree with predictions are within the range that is typical for water on metallic surfaces.