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.

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.

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.

Parametric Study of Nanostructure Variations on the Macroscopic Thermal and Electrical Behavior of Neat CNT Thin Film Networks

Carbon nanotube thin films are considered by many researchers as a material for the future in many electrical and thermal applications, but a lack of systematic physics-based modeling approaches to quantify the bulk thermal and electrical response due to nanostructure variations makes employing these thin films difficult for commercial applications. In this work we employ the previously presented 3D physics-based computational model for characterizing the bulk thermal and electrical response of a neat carbon nanotube thin film network involving stochastic distributions of length, diameter, chirality, orientation and values of intercontact resistivity obtained from the literature. The model is employed to test the sensitivity of bulk thermal and electrical conductivity on stochastic variations in the nanostructure parameters. We examine the sensitivity of the thin film networks to the experimentally obtained Weibull probability distribution for length and diameter. Additionally, we present a study to quantify the macroscopic conductivity dependence on the nanotube chirality ratio. Through these studies we present an approach that is very generic and can be used for the sensitivity analysis due to variations within the nanostructure.

Passive Multi-Scale Alignment

Methods are presented for self-alignment and assembly of objects with micron and nanometer-level features. The approach is a combination of kinematic coupling and elastic averaging in which mating alignment features spanning multiple length scales are successively brought into contact. When the objects are pressed together, the larger alignment features cause necessary deformation to ensure adequate alignment at the smaller length scales. Analytical and numerical modeling indicate that the largest alignment features can be designed to generally resolve global systematic errors while the smaller alignment features can correct local errors to achieve sub-micron alignment. Physical realization with ion beam etching, deposition, and thermal imprint lithography are also discussed.

Influence of Nanochannel Inlet Structure Upon DNA Capture Ratio

DNA molecule will be stretched to its near full contour length inside a nanochannel when the channel diameter is less than the DNA persistence length.1–3 It provides the possibility of real time lab-free-analysis of analysis, such as screening of sequence variations of DNA molecules.3 The key process for this nanochannel-based analysis is to drive DNA molecule electrophoretically through the nanochannel and read out the information of the DNA chain while it is passing the channel.2, 3

A Silicon Thermomechanical In-Plane Microactuation System for Large Displacements in Aqueous Environments

This paper presents an underwater, silicon, thermal microactuation system capable of moving a 200 μN load to a displacement of 110 μm. Its function relies on a thermal actuator capable of 9 μm of displacement in an aqueous environment. This actuator is combined with a ratcheting device to achieve the 110 μm of displacement. The system is a microelectromechanical system (MEMS) fabricated with a two layer surface-micromachining process, PolyMUMPS. The actuation system is designed to provide motion to biological microelectromechanical systems (BioMEMS) in aqueous environments. This paper presents the design and experimental demonstration of the actuation system. The in-depth analysis of the thermal, mechanical, and fabrication aspects of the actuation system are outlined, and the experimental procedure and test parameters are discussed.

Computational Analysis of Strain Effects on Electrical Transport Properties of Crystalline Nanocomposite Thin Films

In this work, we model the strain effects on the electrical transport properties of Si/Ge nanocomposite thin films. We utilize a two-band k·p theory to calculate the variation of the electronic band structure as a function of externally applied strains. By using the modified electronic band structure, electrical conductivity of the Si/Ge nanocomposites is calculated through a self-consistent electron transport analysis, where a nonequilibrium Green’s function (NEGF) is coupled with the Poisson equation. The results show that both the tensile uniaxial and biaxial strains increase the electrical conductivity of Si/Ge nanocomposite. The effects are more evident in the biaxial strain cases.