William J. Arora

Membrane folding to achieve three-dimensional nanostructures : Nanopatterned silicon nitride folded with stressed chromium hinges

Silicon nitride membranes were nanopatterned and then folded into three-dimensional (3D) configurations. The out-of-plane folding was achieved using stressed metal hinges. The concept of folding nanopatterned membranes into 3D shapes is referred to as nanostructured origami because of the similarity to the Japanese paper-art of origami, in which two-dimensional surfaces are folded into volumetric shapes. The stressed metal hinges were modeled analytically and compared to experiment. Experimental results demonstrated controllable folding of nanopatterned silicon nitride membranes.

Thin membrane self-alignment using nanomagnets for three-dimensional nanomanufacturing

In this article the authors present the use of nanomagnets as fine alignment features for structures assembled by folding nanopatterned membranes. The membranes are patterned with arrays of nanomagnets that passively align to other arrays. They analyze the scaling of the force between magnets and calculate the required structural compliance for the magnetic forces to actuate the membranes. A model of the alignment system that captures the magnetic forces and the membrane dynamics has been developed. They show that an external magnetic field provides magnetic saturation of the nanomagnets and aligns the membranes rotationally. The magnetic dipole approximation used in the model was confirmed experimentally by patterning cobalt and iron nanomagnets on silicon nitride cantilevers and actuating in an external magnetic field. Self-alignment between the two arrays of cobalt nanomagnets was achieved confirming the magnetic alignment principle.

Membrane folding by helium ion implantation for three-dimensional device fabrication

The authors demonstrate that silicon nitride membranes can be folded out of plane into three-dimensional structures by helium ion implantation. The folds have a radius of 1μm and can be directed both up or down by varying implant energy.

Integration of Reactive Polymeric Nanofilms Into a Low-Power Electromechanical Switch for Selective Chemical Sensing

This paper presents the fabrication and demonstration of an ultrathin microelectromechanical chemical sensing device. Microcantilevers are etched from 100-nm-thick silicon nitride, and a 75-nm-thick reactive copolymer film for sensing is deposited by initiated chemical vapor deposition. Cross-linking densities of the polymer films are controlled during the deposition process; it is shown that greater cross-linking densities yield greater cantilever deflections upon the polymers reaction with the analyte. Considering that chemical reactions are necessary for stress formation, the sensing is selective. Cantilever deflections of greater than 3 ¿m are easily attained, which allow a simple switch to be designed with resistance-based outputs. When exposed to a hexylamine vapor-phase concentration of 0.87 mol%, the resistance of the switch drops by over six orders of magnitude with a response time of less than 90 s.

Dynamics of Nanostructured Origami

The nanostructured origami approach to 3-D nano manufacturing is a novel way to gain functionality from the third dimension in nanotechnology applications. After first patterning devices onto a structural membrane using traditional 2-D tools, the segments can be folded along predefined creases in order to realize a final shape in 3-D. In order to manufacture increasingly complex devices, knowledge of the origamis dynamics is imperative. This paper describes a method to model the dynamics of two types of origamis using methods that were originally developed for use in robotic manipulation tasks. The stability of the devices in the folded state is also discussed.

The nanostructured Origami/sup TM/ 3D fabrication and assembly process for nanomanufacturing

Nanostructured Origami/sup TM/ 3D fabrication and assembly process is a method of manufacturing 3D nanosystems using exclusively 2D litho tools. The 3D structure is obtained by folding a nanopatterned 2D substrate. We report on the materials, actuation, and modeling aspects of the manufacturing process, and present experimental results from fabricated structures.

The nanostructured Origami 3D fabrication and assembly process for nanopatterned 3D structures

Nanostructured Origami 3D Fabrication and Assembly Process is a method of manufacturing 3D nanostructured devices using exclusively 2D micro- and nanofabrication techniques. The origami approach consists of first patterning a large 2D membrane and then folding the membrane along predefined regions to obtain the final 3D configuration. We report on the materials, actuation, and modeling aspects of building an origami structure. Experimental results from fabricated devices as well as future applications of the technique are also presented.

Kinematics and Dynamics of Nanostructured Origami

Two-dimensional (2D) nanofabrication processes such as lithography are the primary tools for building functional nanostructures. The third spatial dimension enables completely new devices to be realized, such as photonic crystals with arbitrary defect structures and materials with negative index of refraction [1]. Presently, available methods for three-dimensional (3D) nanopatterning tend to be either cost inefficient or limited to periodic structures. The Nanostructured Origami method fabricates 3D devices by first patterning nanostructures (electronic, optical, mechanical, etc) onto a 2D substrate and subsequently folding segments along predefined creases until the final design is obtained [2]. This approach allows almost arbitrary 3D nanostructured systems to be fabricated using exclusively 2D nanopatterning tools. In this paper, we present two approaches to the kinematic and dynamic modeling of folding origami structures. The first approach deals with the kinematics of unfolding single-vertex origami. This work is based on research conducted in the origami mathematics community, which is making rapid progress in understanding the geometry of origami and folding in general [3]. First, a unit positive “charge” is assigned to the creases of the structure in its folded state. Thus, each configuration of the structure as it unfolds can be assigned a value of electrostatic (Coulomb) energy. Because of repulsion between the positive charges, the structure will unfold if allowed to decrease its energy. If the energy minimization can be carried out all the way to the completely unfolded state, we are simultaneously guaranteed of the absence of collisions for the determined path. The second method deals with dynamic modeling of folding multi-segment (accordion style) origamis. The actuation method for folding the segments uses a thin, stressed metal layer that is deposited as a hinge on a relatively stress free structural layer. Through the use of robotics routines, the hinges are modeled as revolute joints, and the system dynamics are calculated.Copyright

Three dimensional optics for three dimensional imaging: physics, fabrication, and computation

In three-dimensional (3D) optical elements, light interacts with the element throughout its entire volume (as opposed to a discrete set of surfaces, which is done in traditional optics.) This allows for more degrees of freedom in shaping the optical response, in particular creating shift-variant responses. We have used this property in a number of ways to acquire 3D object information from both reflective and fluorescent objects under a variety of illumination conditions, including laser-line-scan, rainbow and uniform white light. The key benefits of using 3D optics are summarized as excellent resolution over long working distances, reduced or completely eliminated scanning, and simultaneous spectral imaging. Our research addresses the physics of 3D optical elements, their fabrication, and computational methods for maximal information extraction. In this paper, we first overview the properties of 3D optical elements and then we describe a fabrication and assembly method. Our approach, termed Nanostructured Origami, is appropriate for manufacturing micro-scale optical components which also include sub-wavelength optical elements and non-optical components, e.g. energy storage.

Adiabatic focusing of light in subwavelength high-index contrast dielectrics

Nano-photonic structures with slowly varying periodicity offer rich possibilities for simultaneous space-variant wavefront and dispersion control. Here, we investigate the use of Hamiltonian optics as a tool to design and analyse such structures in the capacity of well corrected imaging lenses. Hamiltonian optics uses the dispersion relation as conservable to solve a set of dynamic equations for ray trajectories. It is computationally efficient and thus appropriate for optimisation, and provides good agreement compared with the more rigorous finite difference in time domain (FDTD) method.