The promising automation of flexible surgical instruments and robots is impeded by the lack of sensory means, which allow for sensing of an instrument's position to the surrounding tissue. This work presents a novel sensory method utilizing capacitive proximity sensing to derive a relative localization of a flexible instrument inside a hollow organ. The method is evaluated by exemplary integration of a sensor in a commercial gastroendoscope and accuracy analysis using a high precision robot. The results show an accuracy of distance sensing from a medical phantom's center of 2%. The method is also evaluated for the irregularly shaped surrounding of ex-vivo tissue in a dynamic scenario. This promising approach holds potential for transfer to clinical scenarios and for further development towards pose estimation of flexible surgical robots and shape sensing of a minimally invasive environment.

Magnetic resonance tomography typically applies the Fourier transform to k-space signals repeatedly acquired from a frequency encoded spatial region of interest, therefore requiring a stationary object during scanning. Any movement of the object results in phase errors in the recorded signal, leading to deformed images, phantoms, and artifacts, since the encoded information does not originate from the intended region of the object. However, if the type and magnitude of movement is known instantaneously, the scanner or the reconstruction algorithm could be adjusted to compensate for the movement, directly allowing high quality imaging with non-stationary objects. This would be an enormous boon to studies that tie cell metabolomics to spontaneous organism behaviour, eliminating the stress otherwise necessitated by restraining measures such as anesthesia or clamping. In the present theoretical study, we use a phantom of the animal model C. elegans to examine the feasibility to automatically predict its movement and position, and to evaluate the impact of movement prediction, within a sufficiently long time horizon, on image reconstruction. For this purpose, we use automated image processing to annotate body parts in freely moving C. elegans, and predict their path of movement. We further introduce an MRI simulation platform based on bright field videos of the moving worm, combined with a stack of high resolution transmission electron microscope (TEM) slice images as virtual high resolution phantoms. A phantom provides an indication of the spatial distribution of signal-generating nuclei on a particular imaging slice. We show that adjustment of the scanning to the predicted movements strongly reduces distortions in the resulting image, opening the door for implementation in a high-resolution NMR scanner.

Inkjet printing has been used to produce resonant radio frequency coils that are comparable to those produced by conventional printed circuit board (PCB) methods. The coils, which consist of a conductive loop and in-series capacitors, form part of a receiver circuit that is used for magnetic resonance imaging (MRI). The resonant circuit is selective at the predetermined frequency of 400 MHz. The required electrical components (resistor, capacitor, and inductor) were produced by inkjet printing, with scaling experiments for resistor and capacitor performed before the complete loops with integrated capacitors were printed. Numerical simulation was used to determine the required values for the components. The inkjet printed circuit was combined with a small tuning and matching board before being connected to a network analyzer and the MRI hardware. With a matching of - 38 dB at 400 MHz the achieved results were comparable to those from standard PCB techniques. The performance of the inkjet printed component as a receiver device for nuclear magnetic resonance and MRI was verified by imaging reference phantoms and a whole kiwifruit; it compares favorably to standard MRI devices. Inkjet printing can, therefore, be considered a feasible technique for producing MRI receiver circuits on flexible substrates.

Electrowetting is an elegant method to realize the motion, dispensing, splitting, and mixing of single droplets in a microfluidic system without the need for any mechanical—and fault-prone—components. By only applying an electric voltage, the interfacial energy of the fluid–solid interface is altered and the contact line of the droplet is changed. However, since the droplet shape is usually heavily distorted, it is difficult to estimate the droplet shape during the process. Further, it is often necessary to know if a process, e.g., droplet splitting on a given geometry, is possible at all, and what can be done to increase the system's reliability. It is thus important to use computer simulations to gain an understanding about the behavior of a droplet for a given electrode geometry and voltage curve. Special care must be exercised when considering surface-tension effects. We present computer simulations done with the Surface Evolver program and a template library combined with a graphical user interface (GUI) that facilitates standard tasks in the simulation of electrowetting arrays.

Compact thermal models are often used during joint electrothermal simulation of microelectromechanical systems (MEMS) and circuits. Formal model reduction allows generation of compact thermal models automatically from high-dimensional finite-element models. Unfortunately, it requires fixing a film coefficient employed to describe the convection boundary conditions. As a result, compact models produced by model reduction do not comply with the requirements of being boundary condition independent. In the present paper, the authors suggest an approach of successive series expansion with respect to the film coefficient as well as to the frequency during model reduction that allows to overcome the problem and keep the film coefficient as a symbolic parameter in the reduced model. The approach is justified with a numerical example of electrothermal simulation of a microthruster unit.

Abstract This paper describes a tool that serves as an automatic mesh adaptivity driver program for general purpose finite element (FE) software packages. Many commercially available FE programs lack a feature to control the numerical solution's accuracy properly. Our tool implements a mesh adaptive method that, in conjunction with separate finite element software, allows one to fully automatically improve the quality of the numerical solution up to a user specified accuracy. We demonstrate the use of the package with selected computational examples performed with a commercial FE package, ANSYS, and with our FE program FEMEngine. Copyright © 2003 John Wiley & Sons, Ltd.

Micromachined picoliter vials in silicon dioxide with a typical depth of 6.0 /spl mu/m are filled with a liquid sample. Epi-illuminated microscopic imaging during evaporation of the liquid shows dynamic fringe patterns. These fringe patterns are caused by interference between the direct part and the reflected part of an incident plane wave (reflected from the bottom of the vial). The optical path difference (OPD) between the direct and the reflected wave is proportional to the distance to the reflecting bottom of the vial. Evaporation decreases the OPD at the meniscus level and causes alternating constructive and destructive interference of the incident light resulting in an interferogram. Imaging of the space-varying OPD yields a fringe pattern in which the isophotes correspond to isoheight curves of the meniscus. When the bottom is flat, the interference pattern allows monitoring of the liquid meniscus as a function of time during evaporation. On the other hand, when there are objects on the bottom of the vial, the height of these objects are observed as phase jumps in the fringes proportional to their height. First, this paper presents the underlying optical model. Secondly, an image processing method is described to retrieve the meniscus profile from the interference pattern. This algorithm is based on estimating the wrapped (relative) phase of the fringe pattern in the recorded images. Finally, this algorithm is applied to measure height differences on the bottom in other micromachined vials with a precision of about five nanometer.

This paper describes a C++ idiom for replacing types. This idiom allows effective and elegant implementations of patterns such as virtual object construction, message dispatching and tables. It also improves compile-time checks and simultaneously allows rows to be added dynamically to tables.SmartEnums have been developed within a project of numerical software for microsystem simulation. Copyright © 1999 John Wiley & Sons, Ltd.

We present an automatic method to produce compact equivalent circuit models of spatially inhomogeneous resistors. Local variations in space of the resistivity due to physical interactions such as magnetic fields or mechanical stress are automatically included. The equivalent circuit model is computed using symbolic algebra, such that the functional relation between the resistivity and the fields interacting with it is included in the circuit design model. Modeling is based on the discretization of the sensor geometry with a mesh of elements and vertex nodes together with the current continuity equation using the box integration method. The resistivity is described by the tensor field of electrical conductivity and depends on the physical interactions to be modeled. The element internode conductivity is mapped to a set of lumped conductances and transconductances (voltage controlled current sources) between the nodes of the discretization mesh. These conductances and transconductances are translated into an equivalent circuit net list. Optionally, the electrical network representing the sensor is simplified before translation by symbolic linear algebra. Thus, equivalent circuit models consisting of many simple elements can be generated as well as models with only a few, algebraically complicated elements. The method is demonstrated using the public domain circuit simulator SPICE3 for the example of a magnetic Hall sensor, with and without the piezoresistive effect.

Accurate electrostatic simulations are required for the analysis of micro electromechanical systems (MEMS) and interconnects in very large scale integration (VLSI) design. Typical simulations involve complex three-dimensional (3-D) geometries together with various dielectric materials, conductors, and boundary conditions. The boundary element method is well suited for such computations. For highly accurate solutions, the meshing of the geometry becomes increasingly important. A scheme is presented which allows generating an optimal mesh automatically based on a coarse initial discretization, e.g., a CAD model. An error indicator derived from boundary integral equations monitors the solution accuracy in each boundary element. H-type or p-type mesh refinement is applied to areas which contribute strongly to the overall error. The method applies to both two-dimensional (2-D) and 3-D simulations containing elements of various orders and shapes. The generated refined meshes result in significantly higher solution accuracy for a given simulation size.

The solution of Poisson's simulations in large, geometrically complex domains with various boundary conditions are of interest in many physical computations. In this paper, we focus on electrostatic analysis. This is important for microactuator (MEMS) and interconnect modeling and also in the simulation of the electrostatic properties in VLSI chips, such as CCD sensors and DRAM cells. The computation of the static electric potential and field distribution involves the solution of the Poisson's equation, or in case of charge free space, Laplace's equation. The boundary element method has proven to be well suited for the solution of these partial differential equations in both 2- and 3-D. The required computational resources can be significantly reduced with the use of multipole acceleration techniques. An enhanced multipole (MP) acceleration technique is presented, allowing for reduced computational time and memory requirements in all stages of the computational process: the assembly of the global system of equations, the solution of the system and the evaluation of the potential and flux at specified internal positions. Contrary to previous applications of MP acceleration to Poisson's equation, the method allows the treatment of a wider class of boundary conditions, including Neumann and floating. The method is applicable both in two and three dimensions using a constant or high order boundary elements.