Search

Since LEDs (light emitting diodes) have many advantages as a light source in vehicle headlamp, such as good reliability, energy and space saving, and flexible headlamp design. On the other hand, the dependence of its performance and life on temperature have great influence on its practical use. In this study, design and fabrication of heat sink for vehicle LED headlamp were performed using thermally-conductive plastics. This study focused on the effective heat sink structure with limited space in the vehicle LED headlamp. We designed two different prototype of heat sink by thermal simulation using SolidWorks program, which had excellent temperature characteristics. The two different prototype of heat sink were fabricated by injection molding with thermally-conductive plastics. The results showed that LED (junction temperature) of sample B (model 1) and sample C (model 1, 2) was below then when applying the thermally-conductive plastics in heat sink of vehicle LED headlamp.

We report novel transport properties of the individual single‐walled carbon nanotube (SWNT) field effect transistors (FETs) decorated with the protein (streptavidin)‐coated nanoparticles. Upon adsorption of the protein‐coated nanoparticles at the metal‐nanotube contact, the metallic SWNT devices abruptly exhibit a p‐type semiconducting behavior. In the case of semiconducting SWNT devices, the adsorptions of protein‐coated nanoparticles make the gating more effective, resulting in a far suppressed off‐state leakage current as well as an enhanced on‐state p‐channel current. Through the ab initio electronic structure calculations, it is suggested that such an apparent metal‐semiconductor transition may be due to the intervening charged species in the contact area, originated from the surface of the proteins. Noting the separation of the semiconducting nanotubes from metallic ones would be a formidable task; we suggest that the device concept here could be another breakthrough for the nanotube‐based ...

The electrical transport and chemical sensing properties of single-walled carbon nanotube field effect transistors (SWNT-FETs) coated with metal clusters have been investigated. The source–drain current passing through an SWNT-FET coated with Pd nanoparticles showed no change over a range of gate voltages. Nevertheless, the magnitude of the current was still sensitive towards NO2, NH3 and H2 exposure. The Pd nanoparticles coating on the nanotube generated hole carriers, which either became diluted upon NH3 or H2 adsorption, or enhanced upon NO2 adsorption. Unlike the ohmic behaviour demonstrated by SWNT-FETs coated with Pd nanoparticles, the transfer characteristics of SWNT-FETs coated with Al nanoparticles revealed Schottky barrier formations at the metal–nanotube contacts. Here, the conductance through the nanotube decreased, while the device sensitivity towards NO2 and NH3 gases improved greatly. We suggest that coating SWNT-FETs with metal nanoparticles could be exploited for the development of highly sensitive nanotube-based molecular sensors.

The influence of water molecule on the electrical properties of single-walled carbon nanotube field effect transistors (SWNT-FETs) was reported. Conductance suppression was observed with the increase of the humidity. This can be explained by doping of the SWNT-FETs, which has p-type semiconductor characteristic, with the water molecules acting as an electron donor. However, after 65 % of humidity, conductance of the SWNT-FETs started to increase again, due to the opening of electron channels. Upon annealing at in Ar atmosphere, conductance increases more than 500 %, and the threshold voltage shifts toward further positive gate voltages. The results of this experiment support possible application of single-walled carbon nanotubes for humidity sensing material.

A thermoelectric flow sensor for small quantity of gas flow rate was fabricated using silicon wafer semiconductor process and bulk micromachining technology. Evanohm R alloy heater and chromel-constantan thermocouples were used as a generation heat unit and sensing parts, respectively. The heater and thermocouples are thermally isolated on the laminated membrane. The characteristics of this sensor were observed in the flow rate range from 0.2 slm to 1.0 slm and the heater power from 0.72 mW to 5.63 mW. The results showed that the sensitivities : voltage difference, : flow rate) were increased in accordance with heater power rise and decreasing of flow rate.

Electrical transport properties of individual double‐wall carbon nanotube (DWNT) are studied. Negative differential conductance (NDC) was observed for the DWNT with a defected outer shell. Such NDC was explained in terms of the resonant tunneling through multiple quantum dots. Also observed is the Fano resonance for the low‐resistance samples. The Fano resonance was manifested by asymmetric peaks in the gate modulation and also by the zero‐bias peak in the differential conductance curve. Both NDC and Fano resonance in DWNT demonstrates the interplay of inner and outer shells via the inter‐shell hopping of electrons.

We report the real-time detection of protein using SWNT-FET-based biosensors comprising DNA aptamers as molecular recognition elements. Anti-thrombin aptamers that are highly specific to serine protein thrombin were immobilized on the sidewall of a SWNT-FET using CDI-Tween linking molecules. The binding of thrombin aptamers to SWNT-FETs causes a rightward shift of the threshold gate voltages, presumably due to the negatively charged backbone of the DNA aptamers. While the addition of thrombin solution causes an abrupt decrease in the conductance of the thrombin aptamer immobilized SWNT-FET, no noticeable change was observed with elastase.

We have studied electrical transport characteristics of individual double-wall carbon nanotubes (DWNT) under high bias voltages. As the bias voltage applied to the carbon nanotubes increases, the outermost shell of the DWNTs broke down sequentially, which enabled us to determine the current-carrying capacity of each shell. The maximum current-carrying capacity per shell was about 150??A, which is well above that of any other previous reports.

We investigated the effect of humidity on the electrical transport properties of single-walled carbon nanotube field effect transistors (SWNT-FETs). Water molecules are found to behave as electron donors to the nanotube: Current through the p-type carbon nanotube device is found to decrease under a modest humidity, and starts to increase as the humidity increases over 65%, which is believed to be due to the opening of electron channels. Through first principles calculations based on the density functional theory, we found that water molecules can donate electrons to the carbon nanotube. Moreover, a hydrogen-bonded water monolayer will be formed around the nanotube at fully covered conditions. We suggest that this result could provide a systematic understanding of the humidity effect on SWNT-FETs, which has been believed to be essential in the development of nanotube-based sensors.