Collapse-free thermal bonding technique for large area microchambers in plastic lab-on-a-chip applications

Bonding is an essential step to form microchannels or microchambers in lab-on-a-chip applications. In this paper, we present a novel plastic thermal bonding technique to seal and form large area microchambers (planar characteristic width and length on the order of 1 mm and characteristic thickness on the order of 10–100 μm) without collapse by introducing a holed pressure equalizing plate (HPEP) that includes holes of the same size and shape as the microchambers. To demonstrate the proposed technique, two types of large area microchambers [(1) 20 × 10 mm and 40 μm thick and (2) 12 × 2.5 mm and 120 μm thick] with microchannels were designed and replicated on plastic substrates by means of hot embossing and injection molding processes with prepared two nickel mold inserts. The replicated large area microchambers as well as the microchannels in the plastic lab-on-a-chip were successfully sealed (i.e., no leakage) and formed without any collapse by the proposed thermal bonding technique with the help of the HPEP.     

Ambient‐light sensor system with wide dynamic range enhanced by adaptive sensitivity control

Abstract— A new digital ambient‐light sensor system is presented which employs two linear light sensors with different sensitivities and automatically adjusts the sensitivity based on the illumination condition. The adaptation mechanism allows a very wide range of light intensity to be detected, and the input dynamic range of the system is substantially improved from 22.5 to 45.1 dB. The proposed method does not require any additional precision bits for output data. Due to the small number of the output bits and the simple conversion process, the system can be easily integrated on the display panel.     

Touch‐screen panel integrated into 12.1‐in. a‐Si:H TFT‐LCD

Abstract— A touch‐screen‐panel (TSP) embedded 12.1‐in. LCD employing a standard existing a‐Si:H TFT‐LCD process has been successfully developed. Compared with conventional external touch‐screen panels, which use additional components to detect touch events, the new internal TSP exhibits a clearer image and improved touch feeling, as well as increased sensing speed using discrete sensing lines to enable higher‐speed sensing functions including handwriting. The new internal digital switching TSP can be fabricated with low cost because it does not require any additional process steps compared to a standard a‐Si:H TFT‐LCD.     

12.1‐in. WXGA AMOLED display driven by InGaZnO thin‐film transistors

Abstract— A full‐color 12.1‐in.WXGA active‐matrix organic‐light‐emitting‐diode (AMOLED) display was, for the first time, demonstrated using indium‐gallium‐zinc oxide (IGZO) thin‐film transistors (TFTs) as an active‐matrix backplane. It was found that the fabricated AMOLED display did not suffer from the well‐known pixel non‐uniformity in luminance, even though the simple structure consisting of two transistors and one capacitor was adopted as the unit pixel circuit, which was attributed to the amorphous nature of IGZO semiconductors. The n‐channel a‐IGZO TFTs exhibited a field‐effect mobility of 17 cm²/V‐sec, threshold voltage of 1.1 V, on/off ratio >10⁹, and subthreshold gate swing of 0.28 V/dec. The AMOLED display with a‐IGZO TFT array is promising for large‐sized applications such as notebook PCs and HDTVs because the a‐IGZO semiconductor can be deposited on large glass substrates (larger than Gen 7) using the conventional sputtering system.     

DEVS-Based modeling of VoIP spam callers’ behavior for SPIT level calculation

At the present time the VoIP (Voice over Internet Protocol) service is generally accepted as an alternative for people seeking cheaper means to make a phone call. Users of VoIP service may fall anywhere along a spectrum between types at two extremes: one of which is an ordinary caller who doesn’t use the telephone for commercial purposes, while the other is a person who generates spam calls for commercial purposes. The focus of this paper concerns modeling of spam callers’ behavior to calculate the SPIT (Spam over Internet Telephony) level for management of the quality of service. From the perspective of a VoIP service provider’s view, spam callers are also a type of customer and sometimes they are valuable for increasing revenue. However, if a service provider does not manage spam calls, it can harm their business, because ordinary users might not receive phone calls using the phone numbers of the VoIP service. Thus, there is a trade-off between revenues and usability in managing spam calls in the VoIP service. This work presents a model of spam caller’s behavior using the DEVS (Discrete Event System Specification) formalism. The DEVS formalism is applicable as a model of behavior, by defining the state and state transition of the target of the model. In our model, we use six main parameters to define the states and state transitions. Each state is represented by a number which indicates the SPIT level of a caller. If the value is 1.0 then the caller is more similar to a spam caller. Based on the model definition, we constructed a SPIT level Calculation UI (User Interface) that is used to manage spam calls to improve VoIP service quality.     

Electron beam lithography-assisted fabrication of Au nano-dot array as a substrate of a correlated AFM and confocal Raman spectroscopy

This paper documents a study of an Au nano-dot array that was fabricated by electron beam lithography on a glass wafer. The patterns that had features of 100nm dots in diameter with a 2-mum pitch comprised a total area of 200x200mum(2). The dot-shaped Cr underlayer was open to the air after developing Poly(methyl methacrylate) (PMMA). When dipped into the Cr etchant, the exposed Cr layer was eliminated from the glass wafer in a short period of time. In order to ultimately fabricate the Ti/Au dot arrays, Ti and Au were deposited onto the arrays with a thickness of 2 and 40nm, respectively. The lift-off procedure was carried out in the Cr etchant using sonication in order to completely remove the residual Cr/PMMA layer. The fabricated Au nano-dot array was then immersed in an Ag enhancing solution and then into an ethanol solution containing (N-(6-(Biotinamido)hexyl)-3'-(2'-pyridyldithio)-propionamide (Biotin-HPDP). The substrate was analyzed using a correlated atomic force microscopy (AFM) and confocal Raman spectroscopy. Through this procedure, position-dependent surface-enhanced Raman spectroscopy (SERS) signals could be obtained.     

Design and characterization of coherent integrated fiber-optic imaging probes

An integrated fiber-optic probe comprising a short length of multimode fiber that is fusion spliced to a monomode optical fiber has been fabricated for imaging and nonimaging applications. The fiber probe, typically 250 μm in diameter, can deliver a focused Gaussian spot approximately 25 μm in diameter at a distance of approximately 500 μm from the tip. Two off-the-shelf graded-index multimode fibers have been used in the fabrication of imaging and nonimaging probes. These integrated probes have considerably improved the spatial resolution of backscatter lensless fiber probes being utilized in the dynamic light-scattering characterization of colloidal suspension.     

Preparation of PbTiO3 thin films using an alkoxide-alkanolamine sol-gel system

The stable range of PbTiO₃ sol and the processing conditions of uniform thin films were investigated using a solution of titanium isopropoxide, three kinds of alkanolamines (monoethanolamine, diethanolamine, triethanolamine), lead acetate trihydrate and isopropanol. Depending on the sol state with various alkanolamine/alkoxide molar ratios, diethanolamine (DEA) was very effective in preparing uniform and dense oxide films through room-temperature reaction, owing to its superior stability during the hydrolysis and condensation reaction. Perovskite PbTiO₃ thin films were obtained on oxidized silicon wafer above 550 °C and completely pure films were obtained at 650 °C using DEA as a complexing agent. The dielectric constant and loss tangent of these thin films fired at 650 °C for 30 min were found to be 240 and 0.01 at 1 kHz, respectively.     

Effect of matrix liquid phase on interphase formation in SiC fibre-reinforced Si2N2O-Al2O3-CaO composites

Matrix compositions based on Si₂N₂O, with Al₂O₃ and CaO additions, were used to hot press Nicalon SiC fibre-reinforced composites at 1600 °C. With both CaO and Al₂O₃ additions, eutectic melting formed an appreciable volume of liquid phase during hot pressing, which remained as a stable glassy phase in the cooled composites. This liquid phase fostered formation of 240 nm thick carbon-rich interphases between the fibres and the matrix. These interphases showed relatively low interfacial shear strength and resulted in composites which showed non-catastrophic, notch-independent fracture. Matrices using either Al₂O₃ or CaO did not form adequate liquid phase to form coarse interphases, and fracture was catastrophic in nature. Post-heat treatment of the composites at 1000 °C showed peripheral oxidation (removal of the carbon content of the interphase) indicating limited protection afforded when glassy phase was present in the matrix. Controlled cooling in the hot press did not cause the liquid regions to devitrify.     

3D Printable One-Part Carbon Nanotube-Elastomer Ink for Health Monitoring Applications

3D printing of conductive elastomers is a promising route to personalized health monitoring applications due to its flexibility and biocompatibility. Here, a one-part, highly conductive, flexible, stretchable, 3D printable carbon nanotube (CNT)-silicone composite is developed and thoroughly characterized. The one-part nature of the inks: i) enables printing without prior mixing and cures under ambient conditions; ii) allows direct dispensing at ≈100 µm resolution printability on nonpolar and polar substrates; iii) forms both self-supporting and high-aspect-ratio structures, key aspects in additive biomanufacturing that eliminate the need for sacrificial layers; and iv) lends efficient, reproducible, and highly sensitive responses to various tensile and compressive stimuli. The high electrical and thermal conductivity of the CNT-silicone composite is further extended to facilitate use as a flexible and stretchable heating element, with applications in body temperature regulation, water distillation, and dual temperature sensing and Joule heating. Overall, the facile fabrication of this composite points to excellent synergy with direct ink writing and can be used to prepare patient-specific wearable electronics for motion detection and cardiac and respiratory monitoring devices and toward advanced personal health tracking and bionic skin applications.