Study on Nitridation of Silicon Added With Amorphous Silicon Nitride

The direct nitridation process of silicon added with amorphous silicon nitride powder at atmospheric pressure was investigated and the product was analyzed by XRD and SEM. Based on the relationship between the conversion ratio of silicon and the reaction time at different temperatures, a physical and mathematical model was derived to describe the nitridation process of silicon particles. The results showed that the conversion ratio of silicon increased rapidly at the early stage of reaction. And the reaction would be accelerated by reducing the size of silicon particle and increasing the pressure of N2. At the range of experimental temperature, the conversion ratio of silicon increases with improving temperature.

Pool Boiling Enhancement via Micro Ratchets

Preliminary experiments on nucleate pool boiling using asymmetric micro ratchets with de-ionized (DI) water as the working fluid were investigated. Two brass surfaces were tested for comparison; one surface was manually polished while the second was composed of asymmetric ratchets with 30μm height and 150 μm period. Small test aquariums (114.8 mm × 54 mm × 152.4 mm) were fabricated and tested on a hot plate. Results show that the ratchet surface made significant heat transfer improvements over the polished surface.

Intensity-Dependent Dispersion in Nonlinear Phononic Layered Systems

Phononic crystals are typically considered to operate in regimes where a linear constitutive relationship provides an adequate representation. For high intensity wave propagation, however, weak nonlinearities can affect performance. For example, a cubic nonlinearity gives rise to frequency shifting and thus a shift in band gap location. In the study of nonlinear optics, a cubic term has been treated using a quasi-linear constitutive relationship with intensity dependent properties. This technique is explored herein for generating nonlinear dispersion relationships for the elastic case. In addition, a perturbation method developed previously for discrete systems, used in conjunction with a finite element discretization, is proposed as an alternative dispersion analysis tool. Simulations of the fully nonlinear governing equations are provided as validation of the predicted dispersion curves.

Integrated Heterogeneous Micro-Nano Systems via Modular Designing and Flexible Assembly

One of the major challenges in commercializable micro-nano systems development is the high cost and turnaround that are incurred through multiple product-optimization iterations and expensive fabrication processes for specific systems. Development of complex and heterogeneous micro-nano systems, that are only possible through assembly and not by conventional surface machining approaches, are further impeded by lack of standard design rules and off-the-shelf robotic manipulation systems. Dedicated hardware and system specific component designs, although possible, are not commercially viable for addressing the wide range of opportunities that exists in the prevailing micro-nano domain. In this paper, we present an alternative and holistic top-down approach for micro-nano manufacturing using modular part designs and flexible assembly systems. We incorporate, seamlessly, multiple novel algorithms related to microrobotics and scaling of physics, obtained both analytically as well as experimentally; in order to predict, track and control the uncertainty propagation in a typical manufacturing process, in micro-nano scale, throughout production steps including design, machining, setup, assembly, testing etc. We demonstrate, through multiple examples, the implementation of the proposed framework in micro-nano scale manufacturing.

Flexible Graphene Sensors for Explosive Trace Detection

This paper presents an explosives sensor. The sensor consists of graphene spray coated onto a substrate with electrodes patterned on the surface. The substrates included glass and flexible polyethylene terephthalate (PET), and the leads were gold and silver respectively. Testing utilizing dinitrotoulene 2,4 (DNT) in a closed container showed the validity of using glass/gold based substrate with a graphene oxide coating as explosive sensors.

Device Packaging Techniques for Implementing a Novel Thermal Flux Method for Fluid Degassing and Charging of a Planar Microscale Loop Heat Pipe

A novel two-port thermal flux method is implemented for degassing a microscale loop heat pipe (mLHP) and charging it with a working fluid. The mLHP is fabricated on a silicon wafer using standard MEMS micro-fabrication techniques, and capped by a Pyrex wafer, using anodic bonding. For these devices, small volumes and large capillary forces render conventional vacuum pump-based methods quite impractical. Instead, we employ thermally generated pressure gradients to purge non-condensible gases from the device, by vapor convection. Three different, high-temperature-compatible, MEMS device packaging techniques have been studied and implemented, in order to evaluate their effectiveness and reliability. The first approach uses O-rings in a mechanically sealed plastic package. The second approach uses an aluminum double compression fitting assembly for alignment, and soldering for establishing the chip-to-tube interconnects. The third approach uses a high temperature epoxy to hermetically embed the device in a machined plastic base package. Using water as the working fluid, degassing and filling experiments are conducted to verify the effectiveness of the thermal flux method.

Clay Dispersion Effects on Excimer Laser Ablation of Polymer-Clay Nanocomposites

The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this paper. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration.

Reliable Design of TSV in Free-Standing Wafers and 3D Integrated Packages

Through-silicon via (TSV), being one of the key enabling technologies for three dimensional (3D) Integrated Circuit (IC) stacking, silicon interposer technology, and advanced wafer level packaging (WLP), has attracted tremendous interest throughout the semiconductor industry. However, limited work addresses TSV reliability issue, and most of the existing reliability studies focus on the thermo-mechanical performance of TSVs in a free-standing wafer, rather than in an integrated package. In this paper, three-dimensional thermomechanical Finite-Element (FE) models with TSVs in both free-standing wafers and 3D integrated packages have been built and analyzed. In addition, Design of Experiments (DOE) based approach has been used to understand the effect of various parameters. Results show that the selection of underfill materials between stacked dies is the most dominating design factor for TSV/microbump reliability.

Flexoelectric Materials and Structures for M/NEMS

Recent research progress on flexoelectricity suggests that dramatic enhancement of effective piezoelectric properties desirable for advanced M/NEMS, in principle, is attainable through flexoelectric (FE) effect and scale effect. In this paper, the transverse flexoelectric coefficient μ12 of barium strontium titanate (BST) microcantilevers with thicknesses ranging from 1.4 mm down to 30 μm was measured at room temperature. It was found that μ12 remains to be constant (8.5 μC/m) for all fabricated microcantilevers. Effective piezoelectric coefficients of these microcantilevers were also calculated, indicating that significantly increased effective piezoelectric coefficients can be obtained from microcantilevers with thickness of microns and nanometers, which is promising for micro/nano electromechanical systems (M/NEMS).

Low Cost, Open-Loop Temperature Controller for MEMS and Modular Microfluidics Applications

A commercially manufactured thermostat (Model C Thermostat, Portage Electronic Products Inc., North Canton, OH) was employed as a precision MEMS temperature controller for a simulated continuous flow thermal reactor, with three temperature zones to mimic a polymerase chain reaction (CFPCR) device but different temperature set points to allow use of off-the-shelf controllers and thermally-responsive fluids. The ability of the commercial thermostats to maintain the temperatures within given tolerance bands in the thermal reactor was investigated. The factory supplied and calibrated thermostats were actuated by trimetallic strips, and supplied in a normally-closed configuration. Each thermostat was arranged in series with a 28 VDC power supply, a Kapton heater, and an aluminum thermal block to establish a constant temperature boundary condition for each temperature zone. Calibration temperatures for each thermostat reflected the three temperature set points of the simulated PCR device in the testing apparatus. Temperatures were collected by fixing Type K thermocouples in the fluidic channels of the simulated PCR device, and recording the temperature over time. The commercial, off-the-shelf, open-loop controllers successfully maintained ±1°C tolerance bands within each thermal zone. The ±1°C variation in the channel temperature was caused by the chatter due to the switching of the thermostat.