Investigation of transition from thermal- to solutal-Marangoni flow in dilute alcohol/water mixtures using nano-plasmonic heaters.

We experimentally investigated Marangoni flows around a microbubble in diluted 1-butanol/water, 2-propanol/water, and ethanol/water mixtures using the thermoplasmonic effect of gold nanoisland film. A laser spot on the gold nanoisland film acted as a highly localized heat source that was utilized to generate stable air microbubbles with diameters of 32-48 µm in the fluid and to induce a steep temperature gradient on the bubble surface. The locally heated bubble has a flow along the bubble surface, with the flow direction showing a clear transition depending on the alcohol concentrations. The fluid is driven from the hot to cold regions when the alcohol concentration is lower than the transition concentration, whereas it is driven from the cold to hot regions when the concentration is higher than the transition concentration. In addition, the transition concentration increases as the carbon number of the alcohol decreases. The observed flow direction transition is explained by the balance of the thermal- and solutal-Marangoni forces that are cancelled out for the transition concentration. The selective evaporation of the alcohol at the locally heated surface allows us to generate stable and rapid thermoplasmonic solutal-Marangoni flows in the alcohol/water mixtures.

Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

Physically unclonable functions taggant for universal steganographic prints.

Counterfeiting of financial cards and marketable securities is a major social problem globally. Electronic identification and image recognition are common anti-counterfeiting techniques, yet they can be overcome by understanding the corresponding algorithms and analysis methods. The present work describes a physically unclonable functions taggant, in an aqueous-soluble ink, based on surface-enhanced Raman scattering of discrete self-assemblies of Au nanoparticles. Using this stealth nanobeacon, we detected a fingerprint-type Raman spectroscopy signal that we clearly identified even on a business card with a pigment mask such as copper-phthalocyanine printed on it. Accordingly, we have overcome the reverse engineering problem that is otherwise inherent to analogous anti-counterfeiting techniques. One can readily tailor the ink to various information needs and application requirements. Our stealth nanobeacon printing will be particularly useful for steganography and provide a sensitive fingerprint for anti-counterfeiting.

Heat-generating property of a local plasmon resonator under illumination.

We have investigated the heat generation from gold nanoparticles resulting from their local plasma resonance. We have demonstrated the self-assembly of Au nanoparticle arrays/dielectric layer/Ag mirror sandwiches, i.e., a local plasmon resonator, using a dynamic oblique deposition technique. The thicknesses of the Au and dielectric layers were changed combinatorially on a single substrate. As a result, local plasmon resonator chips were successfully fabricated. Because of strong interference, their optical absorption can be controlled between 0.0% and 97% in the near-IR region, depending on the thickness of the dielectric layer. We evaluated the heat generation from Au nanoparticles by measuring the temperature of water with which a cell prepared on a chip is filled under laser illumination. The change in the water temperature is proportional to the optical absorption of the local plasmon resonator chips. This suggests that the photothermal conversion efficiency can be controlled by interference. These features make the application of the local plasmon resonator to nanoheaters, which can spatiotemporally control heat generation, suitable.

Water droplet bouncing on a non-superhydrophobic Si nanospring array.

Self-cleaning surfaces often make use of superhydrophobic coatings that repel water. Here, we report a hydrophobic Si nanospring surface that effectively suppresses wetting by repelling water droplets. The dynamic response of Si nanospring arrays fabricated by glancing-angle deposition is investigated. These hydrophobic arrays of vertically standing nanosprings (about 250 nm high and 60 nm apart) allow the droplets to rebound within a few milliseconds after contact. Amazingly, the morphology of the nanostructures influences the impact dynamics. The rebound time and coefficient of restitution are higher for Si nanosprings than for vertical Si columns. By considering the droplet/nanospring surface as a coupled-spring system, we argue that the restoring force of the nanosprings may be responsible for the water-droplet rebound. The bouncing phenomena studied here are essential in the design of self-cleaning surfaces and are also of fundamental importance for the study of wetting behavior on nanostructures.

Plasmonic Nanoslit Arrays Fabricated by Serial Bideposition: Optical and Surface-Enhanced Raman Scattering Study.

Recently, studies have been carried out to combine surface-enhanced Raman spectroscopy substrates that are based on either localized surface plasmon or surface plasmon polariton structures. By combining these two systems, the individual drawbacks of each can be overcome. However, the manufacturing methods involved so far are sophisticated, labor-intensive, expensive, and technically demanding. We propose a facile method for the fabrication of a flexible plasmonic nanoslit surface-enhanced Raman scattering (SERS) sensor. We utilized the pattern on periodic optical disks as an inexpensive substitute for printing the periodic pattern on polydimethylsiloxane with soft imprint lithography. The Ag nanoslits were fabricated by serial bideposition using the dynamic oblique angle deposition technique. The nanoslit structures were physically and optically characterized, and the experimental results were compared to the results of the numerical simulation: Monte Carlo and finite-difference time-domain simulation. The AgNS samples showed excellent SERS performance with an enhancement factor of ∼105 and a limit of detection of 5 × 10-7 g/mL for a Rhodamine 6G solution. Their biosensing capability was demonstrated by the sensing of bilirubin.

Direction control of quasi-stokeslet induced by thermoplasmonic heating of a water vapor microbubble.

We investigate the control of flow direction around a water vapor bubble using the thermoplasmonic effect of a gold nanoisland film (GNF) under laser irradiation with multiple spots. By focusing a laser spot on the GNF immersed in degassed water, a water vapor bubble with a diameter of ~10 µm is generated. Simultaneously, a sub laser spot was focused next to the bubble to yield a temperature gradient in the direction parallel to the GNF surface. Consequently, rapid flow was generated around the bubble, whose flow direction was dependent on the power of the sub laser spot. The observed flow was well-described using a stokeslet; the latter contained components normal and parallel to the GNF surface and was set to 10 µm above the GNF. This technique allows us to apply a significant force on the microfluid at the vicinity of the wall in the direction parallel to the wall surface, where the flow speed is generally suppressed by viscosity. It is expected to be useful for microfluidic pumping and microfluidic thermal management.

Demonstration of temperature-plateau superheated liquid by photothermal conversion of plasmonic titanium nitride nanostructures.

A liquid can be heated up above its boiling point, known as superheating. In this metastable state, the liquid temperature keeps increasing as the liquid is being heated. In contrast, we experimentally demonstrate that the temperature of superheated water can be kept constant even at elevated heating power. Water heating is done by the photothermal conversion of plasmonic titanium nitride nanostructures on a sapphire substrate under the illumination of continuous wave laser irradiation. The temperature-constant superheating is also observed for ethylene glycol and 2-acetoxy-1-methoxypropane, and is attributed to the high thermal conductivity of the substrate. This unique superheating yet achieved by a simple method can be useful in optical trapping and various optical heating applications.

Quasi-stokeslet induced by thermoplasmonic Marangoni effect around a water vapor microbubble.

Rapid Marangoni flows around a water vapor microbubble (WVMB) is investigated using the thermoplasmonic effect of a gold nanoisland film (GNF). By focusing a laser onto the GNF, a stable WVMB with a diameter of ~10 µm is generated in degassed water, while an air bubble generated in non-degassed water is larger than 40 µm. Under continuous heating, the WVMB involves significantly rapid Marangoni flow. This flow is well-described by a stokeslet sat ~10 µm above the surface of GNF, from which the maximum flow speed around the WVMB is estimated to exceed 1 m/s. This rapid flow generation is attributed to the small bubble size, over which the temperature is graded, and the superheat at the bubble surface in contact with the GNF. It is expected to be useful not only for microfluidic mixing but also for fundamental research on viscous flow induced by a single stokeslet.

Plasmacytoma of the urinary bladder in a renal transplant recipient.

A 28-year-old woman underwent renal transplantation in 1993. Eight years later, she experienced macroscopic hematuria, and Epstein-Barr virus-negative solitary extramedullary plasmacytoma (EMP) of the urinary bladder was diagnosed. After the reduction of immunosuppressive therapy, she received combined chemotherapy, resulting in complete tumor disappearance. However, 10 months later, she relapsed with aggressive multiple EMP and died of disease progression in 2003. This report is the first of a case of solitary EMP of the urinary bladder appearing as posttransplantation plasma cell dyscrasias after renal transplantation.

Unique three-way translocation, t(3;14;18)(q27;q32;q21), in follicular lymphoma.

A 43-year-old woman was diagnosed as having stage IV follicular lymphoma. Phenotypically, the lymphoma cells were CD5(-), CD10(+), CD19(+), CD20(+), CD23(-), HLA-DR(+), and IgM-lambda(+). Conventional chromosomal analysis showed a three-way t(3;14;18)(q27;q32;q21) in the lymphoma cells, which was confirmed by spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). Immunohistochemistry revealed that both BCL2 and BCL6 proteins were expressed in the lymphoma cells, whereas only the BCL6 gene, and not the BCL2 gene, was rearranged by Southern blotting. The patient received combination chemotherapy and has been well for 3 years. This is the first reported case showing a three-way translocation involving 2 major lymphoma-specific abnormalities, 3q27 and t(14;18)(q32;q21).

Dispersion relations for coupled surface plasmon-polariton modes excited in multilayer structures.

The coupled surface plasmon-polariton (SPP) modes excited in an Al/SiO2/Al multilayer structure were analyzed using angle-resolved electron energy-loss spectroscopy (AREELS) with a relativistic electron probe. The dispersion relations for the coupled SPP modes were then directly observed and compared with predicted relations obtained via calculations. Good agreement was noted between the experimental and calculated results. In the multilayer structures, the dispersion relation for the coupled SPP modes was found to be sensitive to the thickness of each film, which could be interpreted qualitatively by the electron energy-loss probability calculated for thin aluminum (Al) films and narrow Al gaps using Kröger's formula. It was demonstrated that significant differences in the excitation probability for SPPs could be observed depending on the coupling modes.

Nanostructured copper/porous silicon hybrid systems as efficient sound-emitting devices.

In the present work, the photo-acoustic emission from nanostructured copper/porous silicon hybrid systems was studied. Copper nanoparticles were grown by photo-assisted electroless deposition on crystalline silicon and nanostructured porous silicon (nanoPS). Both the optical and photo-acoustic responses from these systems were determined. The experimental results show a remarkable increase in the photo-acoustic intensity when copper nanoparticles are incorporated to the porous structure. The results thus suggest that the Cu/nanoPS hybrid systems are suitable candidates for several applications in the field of thermoplasmonics, including the development of sound-emitting devices of great efficiency.

Cytotoxic T-cell non-Hodgkin's lymphoma of the thyroid gland.

An 86-year-old female was diagnosed with peripheral T-cell lymphoma, unspecified, which affected only her thyroid gland. Lymphoma cells were TIA-1(+), suggesting cytotoxic T-cell origin. She had not suffered from autoimmune thyroiditis and showed normal thyroid function. Without any specific therapies, the lymphomatous lesion showed the partial spontaneous regression before diagnostic hemithyroidectomy, and she had been well for 2 years without relapse. This is the first case of primary thyroid lymphoma of cytotoxic T-cell origin that showed spontaneous regression.

CD5-negative chronic lymphocytic leukemia with indolent clinical course and autoimmune thrombocytopenia, successfully treated with rituximab.

A 59-year-old male with lymphocytosis and thrombocytopenia was asymptomatic without lymphadenopathy or hepatosplenomegaly over 10 years. He was admitted to our hospital because his thrombocytopenia had worsened. The clonal lymphocytes appeared as regular small mature lymphocytes on blood films, and bone marrow biopsy showed diffuse infiltration of mature lymphocytes. However, megakaryocytes also presented. The immunophenotypic analysis by flow cytometry revealed that the lymphocytes were positive for CD19, CD20, CD22, and surface membrane immunoglobulin (SmIg) M and D-lambda and were negative for CD5, CD10, CD11c, CD23, and other lineage markers. Expression levels of CD20 and SmIg were strong. The markers were consistent with CD5- CLL with autoimmune thrombocytopenia. He received rituximab, and a rapid decrease of lymphocytes with concomitant increase of platelets was observed. A few cases of CD5- CLL with a stable clinical course have been reported, thought to be B lymphocytosis of undetermined significance (MLUS). This is the first report of CD5- CLL with indolent clinical course associated with autoimmune thrombocytopenia, successfully treated with rituximab.