Nobuyuki Takama

High-Spatial-Resolution Surface-Temperature Mapping Using Fluorescent Thermometry**

The characterization of temperature and thermal properties is of particular importance in micro- and nanotechnology. Considering the highly increased density of structures and the increased power dissipation per unit area associated with miniaturization, good thermal design is of great importance for device reliability and performance. Locating hot spots, for example, on a microelectronic circuit, can be of great value in evaluating a design, optimizing the performance, and performing failure analysis. [1,2] Apart from the industrial applications of micro- and nanoscale thermometry, fundamental questions of the thermal behavior, for example, thermal transfer at a scale comparable to the phonon wavelength, [3] could be more effectively addressed with improved characterization tools. The common approach for mapping temperature on the microscale is based on infrared microscopy, which relies on the analysis of the thermal radiation that is emitted from any material. IR microscopy is a well-established technique and can be used with relative ease for temperature mapping on large scales. However, the technique suffers from a diffractionlimited resolution, giving it an optimal spatial resolution of around 5 mm. [2,4,5] Nanoscale scientists typically use scanning thermal microscopy (SThM) for high-resolution measurements. Since the invention of the scanning probe microscope at the beginning of the 1980s, [6] several scanning probes for thermal characterization have been developed. The thermal probes used are generally based on either thermocouple or thermistor elements. [7–11] Other approaches have proposed bimaterial cantilevers or fluorescent particles as temperaturesensing probes. [12–14] The highest spatial resolution obtained

Optical-softlithographic technology for patterning on curved surfaces

We have established a novel concept of hybrid lithographic technology for non-planar surface patterning. Softlithography and photolithography are properly combined to transfer micro-patterns onto a curved area in an easy, low-cost way. As a first step, a film type of a photomask with micro-metal features is fabricated by the direct pattern transfer technique that has been presented in our preliminary work. Then, a flexible polymer photomask is wrapped on a curved surface to make conformal contact, and a variety of micro-features are formed on the surface via the photolithographic process. We have confirmed the validity of the technique for application in the industrial process by comparing the results transferred via the conventional photolithography with a rigid flat photomask. Subsequently, 3D polymer structures with a high aspect ratio (A/R) are fabricated on curved surfaces using this technique, followed by a discussion on several drawbacks due to the shape of the substrate. Overall, this paper has demonstrated a new method of micro-patterning, which would promise an emerging field of micro-fabrication on non-planar substrates.

CMOS-compatible fabrication of top-gated field-effect transistor silicon nanowire-based biosensors

Field-effect transistor (FET) nanowire-based biosensors are very promising tools for medical diagnosis. In this paper, we introduce a simple method to fabricate FET silicon nanowires using only standard microelectromechanical system (MEMS) processes. The key steps of our fabrication process were a local oxidation of silicon (LOCOS) and anisotropic KOH etchings that enabled us to reduce the width of the initial silicon structures from 10 ?m to 170 nm. To turn the nanowires into a FET, a top-gate electrode was patterned in gold next to them in order to apply the gate voltage directly through the investigated liquid environment. An electrical characterization demonstrated the p-type behaviour of the nanowires. Preliminary chemical sensing tested the sensitivity to pH of our device. The effect of the binding of streptavidin on biotinylated nanowires was monitored in order to evaluate their biosensing ability. In this way, streptavidin was detected down to a 100 ng mL?1 concentration in phosphate buffered saline by applying a gate voltage less than 1.2 V. The use of a top-gate electrode enabled the detection of biological species with only very low voltages that were compatible with future handheld-requiring applications. We thus demonstrated the potential of our devices and their fabrication as a solution for the mass production of efficient and reliable FET nanowire-based biological sensors.

Simple fabrication of Si nanowire and its biological application

A novel, relatively simple and cost effective method is reported to fabricate suspended silicon nanowires. This method allows for the production of suspended silicon nanowires using anisotropic wet etching and thermal oxidation of single crystalline silicon. The dimensions of the silicon nanowires fabricated with the proposed method are evaluated. The vibration properties of the nanowires obtained by heterodyne laser doppler interferometer show the potential of being nanomechanical sensors.

MEMS-based biochip for the characterization of single red blood cell

We introduce a novel biosensor device for various biocell measurements by singular cell level with parallel analysis and high throughput. This paper deals with the details of its fabrication, including device packaging, and the practical measurement of red blood cells using a twin microcantilever type sensor array. Based on a simple measurement of the electrical impedance of a living single red blood cell and its suspension, an important set of data, which can be used to describe living matter, could be obtained.

Using Dried Rhodamine B Fluorescence for Temperature Characterization of Sub-Micron Scale Devices

We present here preliminary investigations on the use of dried Rhodamine B as a probe for micrometer scale and submicrometer scale temperature measurements. It is shown that even in dry conditions, Rhodamine B maintains a temperature dependent fluorescent intensity. Investigations on its photostability as well as its thermal stability in dry conditions are presented. It is concluded that Rhodamine B holds good promise for temperature mapping with submicrometer spatial resolution when confined to the vicinity of a sample surface.

Surface-Temperature Control of Silicon Nanowires in Dry and Liquid Conditions

In this paper we present the results of surface temperature control of silicon nanowires by using fluorescent thermometry at the nanometer scale. Rhodamine B is one of the stable fluorescent molecules, which rely on the characteristic of temperature-dependent change in fluorescent intensity, and it was used for nano-scale surface temperature sensing interface. The resistive heating on Si nanowires was carried out with applying voltage potential of 6 ~ 12 V. Surface-temperature measurement was performed by converting the changes in fluorescent intensity with calibration curve of Rhodamine B. The temperature at the central line along nanowires increasing from 30 degrees to 35~70 degrees was observed.

A Silicon-Based Single-Cell Electroporation Microchip for Gene Transfer

In our contribution, we present the fabrication of electroporation microchip in detail. The practical experiments of single-cell electroporation with our fabricated microchip will be carried out. Electroporation test efficiency and cell viability tests will be provided. This device enables to reduce the size of samples and thus the use of small amount of reagents. It may also permit to avoid cell separation (transfected cells versus non transfected cells) encountered when traditional bulk electroporation is held

Surface Phonon Polariton Mediated Thermal Conduction of a Micrometric Glass Waveguide

Calculations of the dispersion relation and of the propagation length of surface phonon-polariton modes in a micrometric glass waveguide have been performed. The dispersion relation was solved in two ranges of frequency where SPP appear in glass. We succeeded in showing a maximal propagation length of 35 μm in a 10 μm radius waveguide with a 1 μm thick wall.

Visual Observation of PDMS Tip in Liquid Microcontact Printing

Microcontact printing has been shown to be a viable lithographic technique for the fabrication of microstructures, through the deposition of molecules by conformal contact between a surface and an elastomeric stamp. However, the diffusion of the molecules on the substrate and the deformation of the stamp during the contact are severe drawbacks when considering the resolution of the technique. In this paper, we show the effect of the diffusion of the molecules on the size of gold patterns on silicon and we observe in-situ the deformation of the PDMS stamp in liquid and air environment using an interferential microscopy technique.