Sensor Review

Concepts and Issues in Piezo-on-3D Silicon Structures. : Table of Contents

Mr. John Henry Sweet, David Hutson, Dr. Sandy Cochran, Ms. Anne Lyse Bernassau — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - Exploration of concepts and manufacturing issues for the emerging piezo on silicon technology being used in Ultra-Sound devices.Development of 3D silicon-on-silicon structures is now under way. Additional functionality can be achieved using piezoelectric-on-silicon structures and work in this area has started (Trolier-McKinstry et al, 2009). A commercialisation road map is required, specifying development of the design and fabrication techniques from research to high volume and lower volume high-value manufacture of niche products.Design/methodology/approach - This conceptual paper outlines processes needed, along with their possible sources with illustrations of present capabilities. Included are surface finishing techniques such as grinding, bonding technology for dissimilar materials, and through-wafer-via fabrication. Control of acoustic propagation, thermal expansion and electric field fringing effects will be consideredFindings - Areas that require research and development are identified with possible starting points using techniques already used in other applications. Strong emphasis on empirical research highlights possible issues with examples including surface finishing and wafer dicing to show current methods.Research limitations/implications - Archetypal pixellated piezoelectric-on-silicon structures highlight critical points. In the authors’ work, such pixellated structures occur in 1-3 connectivity piezoelectric ceramic-polymer composites with unit cell length scales from several millimetres, manufactured with mechanical dicing, to less than 50 ?m, manufactured with micro-moulding. Practical implications - A forward looking approach of "thinking freely" is taken, this opens up potential manufacturing routes and ideas precluded from an iterative approach. .Originality/value - The conclusion suggests the criteria for a "design for" approach linked to either bottom up or top down assembly techniques for the integration of conventional and unusual piezoelectric materials with silicon in 3D structures

Progress Towards Wafer-scale Fabrication of Ultrasound Arrays for Real-time High-resolution Biomedical Imaging : Table of Contents

Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - High frequency transducer arrays that can operate at frequencies above 30 MHz are needed for high resolution medical ultrasound imaging. The fabrication of such devices is challenging not only because of the fine-scale piezocomposite fabrication typically required but also because of the small size of arrays and their interconnects. This paper presents an overview of research to develop solutions for several of the major problems in high frequency ultrasound array fabrication.Design/methodology/approach - Net-shape 1-3 piezocomposites operating above 40 MHz have been developed. High quality surface finishing has made photolithographic patterning of the array electrodes on these fine scale piezocomposites possible, thus establishing a fabrication methodology for high frequency kerfless ultrasound arrays. Findings - Structured processes have been developed and prototype components have been made with them, demonstrating the viability of the selected fabrication approach. A 20-element array operating at 30 MHz has been patterned and characterised. Furthermore, an electrode pattern suitable for a 20-element array operating at 100 MHz has been created to demonstrate the state of the art of photolithography processing directly on piezocomposite. Research limitations/implications - Practical implications - The work reported suggests that ultrasound arrays for real time biomedical imaging will be viable at higher frequencies than presently available commercially or previously reported in the research literature. Originality/value - The main elements of a novel, fully mask-based process for high frequency ultrasound transducer array fabrication are presented in outline in this paper.

Productionisation Issues for Commercialisation of Microfluidic Based Devices : Table of Contents

Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - Microfluidic or "lab-on-a-chip" technology is seen as a key enabler in the rapidly expanding market for medical point-of-care (POC) and other kinds of portable diagnostic device. In this paper we discuss two proposed packaging processes for large scale manufacture of microfluidic systems.Design/methodology/approach - In the first packaging process, polymer overmoulding of a microfluidic chip is used to form a fluidic manifold integrated with the device in a single step. The anticipated advantages of the proposed method of packaging are ease of assembly and low part count. The second process involves the use of low frequency induction heating (LFIH) for the sealing of polymer microfluidics. The method requires no chamber, and provides fast and selective heating to the interface to be joined.Findings - Initial work with glass microfluidics has demonstrated feasibility for overmoulding through two separate sealing principles. One is using the overmould as a physical support structure and providing sealing using a compliant ferrule. The other relies on adhesion between the material of the overmould and the microfluidic device to provide a seal. As regards LFIH work on selection and structuring of susceptor materials is reported, together with analysis of the dimensions of the heat affected zone. Acrylic plates have been joined using a thin (<10 ?m) nickel susceptor providing a fluid seal that withstood a pressure of 590kPa.Originality/value - Microfluidic chips have until now been produced in relatively small numbers. To scale-up from laboratory systems to the production volumes required for mass markets, packaging methods need to be adapted to mass manufacture.

SPECTROSCOPIC MEASUREMENTS ON 3D OBJECTS IN THERMAL PLASMAS : Table of Contents

Dr. Pierre Freton — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - The purpose of the paper consists to develop a mathematical tool and a experimental platform able to reconstruct thermal plasmas in three dimensions (3D) in order to characterize 3D plasma and to be able to validate models in 3D. Indeed a lack of experimental data allowing validating 3D models exists.Design/methodology/approach - The study is realized with a transferred argon arc configuration. The 3D character is due to the form of the cathode electrode. The reactor design is defined by a previous theoretical study. This previous study has shown that tomographic method through four views allows reconstructing 3D object. The light emitted by the plasma along four directions (four windows) is so spectrally resolved and treated by a MART algorithm. Following the emissivity profiles, two methods are used, the absolute line intensity method, and for an out off axis maximum of the emissivity the Folwer Milne method.Findings - After a validating approach of the optical measurements in symmetrical configuration using Abel inversion, the reconstructed method is used. The results show the possibility of the tomographic method spectrally and spatially resolved to be applied to thermal plasma in order to characterize the medium and to validate the 3D models. The plasma medium was well described with a spatial resolution equal to 0.2mm.Research limitations/implications - The method is applicable to thermal plasma presenting high emissivity. Even if the theoretical reconstruction method was apply to low temperatures or to theoretical plasma presenting out off axis of emissivity, future researches need to be performed to analyse the ability of the method to spatially resolve the areas presenting low emissivity.Originality/value - The paper originality can be demonstrated by the poor number of studies in thermal plasma reconstruction in 3D. Studies on plasma imaging can be found but not spectrally resolved. The special care on the spectral acquisition along the plasma radius combined with the tomographic reconstruction method lead to the originality of this paper.

FERRITE CORES AS BACK YOKE FOR ENHANCING HALL SENSOR SENSITIVITY IN CALIPER TOOL FOR PIPELINE INSPECTION : Table of Contents

Mr. Rajesh Keshwani, Mr. Shiben Bhattacharya — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - This paper aims for arriving at improved magnetic pick up sensor for detection of weak magnetic field. A magnetic marker detection system build using hall sensors, is improved by providing ferrite cores as back yoke to obtain benchmarked performance with reduced number of hall sensors in an equipment for pipeline inspection called caliper tool. Design/methodology/approach - The paper opted for an exploratory study by making various configurations of sensors possible under given constraints, analyzing results of each one of them and correcting the configuration. Findings - Instead of using highly sensitive hall sensors, one can increase the sensitivity of sensor by putting simple ferrite core as back yoke in order to detect weak magnetic field. Originality/value - This paper fulfills the need of detection of weak magnetic field by changing field direction and maximizing field component in direction of sensitive axis of magnetic sensor.

Fabrication of a MEMS Accelerometer to Detect Heart Bypass Surgery Complications : Table of Contents

Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - This paper reviews the design and fabrication of a micro-accelerometer to be used to measure the heart wall motion of patients who have just undergone coronary artery bypass graft (CABG) surgery. The sensor will provide a means of early warning for the medical staff of associated complications with this surgery occurring. Design/methodology/approach - A feasibility study was carried out with the use of commercially available MEMS three-axis accelerometers. The sensors were used in animal studies during which the sensor is stitched directly to the surface of the pig’s heart. A need for smaller sensors was required and these were designed in-house and fabricated using a MEMS process. The final dimensions of the sensors were 2.5x3.5x1.4 mm in width, length and height respectively.Findings - The results of the feasibility studies demonstrate the viability of this type of sensor for heart wall motion measurement. It was possible to detect abnormalities which can indicate complications associated with CABG. The sensors presented here were fabricated within the tight overall size specifications deemed necessary for this application.Research limitations/implications - This research demonstrates an application of MEMS for implantable medical sensors.Practical implications - In the UK, approximately 300,000 people have a heart attack each year. One of the most common surgeries that is used to treat this is CABG. This sensor is to be used by the medical staff in post-surgery to provide "real-time" monitoring of the heart and give early warning of regional cardiac ischemia which can save lives and reduce hospital waiting times and costs.Originality/value - This research demonstrates an original way of measuring heart wall motion. Results from the feasibility studies have proven that this can provide an invaluable way of providing early warning of complications after heart surgery.

Segmentation of Unevenly Illuminated Line Scanned Images : Table of Contents

Prof. Yih-Chih Chiou, Mr. Meng-Ru Tsai — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - Though many segmentation methods have been published, few of them are developed especially for line scanned images. An ill iluminated line scanned (IILS) image tends to have a uniform intensity distribution in column direction while non-uniform intensity distribution in the row direction. So, it is improper to segment IILS images using either a pixed threshold or threshold surface. In view of this, the objective of the paper is to develop a segmentation method that is suitable for segmented IILS images.Design/methodology/approach - To obtain satisfactory segmentation results, we took illumination variation across the column of a line scanned image into account and developed a column-based segmentation method. The method first calculates each column's standard deviaition. Then a threshold value is automatically assigned to each column based on the derived values. Finally by assembling each columns threshold value, a so-called threshold line is formed. We named the method TLSTD (threshold-line segmentation method based on standard deviation).Findings - The developed threshold-line-based segmentation method was compared with Otsu?s fixed threshold segmentation method and Niblack?s threshold-surface-based segmentation method. The results show that our threshold-line-based segmentation method is more suitable for segmenting IILS images Research limitations/implications - Despite TLSTD outperforms Otsu?s and Nilblack?s segmentation methods, there are some limitations to it. The most obvious one is that the predetermined allowable deviation has influences on the integrality of the extracted flaws. Besides, since the proposed method is designed specifically for segmenting images captured by line scan cameras with a slant line light source, it is suitable for segmenting the kind of images only. In other words, the method show no advantages in segment area-scanned images. Practical implications - Generally, the approach is useful in automated visual inspection where line-scan cameras are employed. Originality/value - The merit of the proposed method is that the slant of the line light source is now allowed. In other words, even if a grabbed line scanned image is unevenly illuminated, the proposed segmentation method is still able to successfully detect desired flaws.

US research group develops world's smallest radio receiver : Table of Contents

Mr. Robert Bogue — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - To describe the world’s smallest radio receiver, fabricated from a single carbon nanotube (CNT). Design/methodology/approach - This article describes the construction and mode of operation of the CNT radio and the experiments used to test its functionality. Findings - This shows that a single CNT can act as an antenna, adjustable tuner, amplifier and demodulator, resulting in a fully functional radio with the ability to receive and faithfully reproduce audio signals.Originality/value - This describes the world’s smallest radio receiver which has the potential to be used in a range of both conventional and novel applications.

Implantable Electronic Devices Technology Challenges for Long-Term Human Implantation : Table of Contents

Dr. Anne Vanhoestenberghe — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - To discuss the requirements for long-term implantation of electronic devices with a focus on packaging and encapsulation. Design/methodology/approach - Approach Due to their intended long-term use in the human body, implants for electrical stimulation present specific challenges to the engineers. The respective roles of packaging and encapsulation must be clearly understood to make the most of new materials and modern machining technologies. This paper offers an introduction to the current situation and highlights challenges for future developments. Findings - The innovative application of modern technologies may be useful to tackle key issues of encapsulation and sealing of small electrical devices for long term implantation. Originality/value - Two examples of innovative application of alternative package manufacture and sealing method are described.

MEMS ultra low leak detection methods: a review : Table of Contents

Ms. Suzanne Millar, Prof. Marc P.Y. Desmulliez — Sun Jun 21 14:15:05 BST 2009

Abstract:
Purpose - To review traditional hermeticity test methods when applied to typical MEMS cavity volumes and to propose potential solutions.Design/methodology/approach - Standards for traditional testing have been applied to typical MEMS cavity volumes and the resulting issues of range and sensitivity discussed. In-situ test structures have been designed and fabricated with access to the internal cavities to allow characterisation of the structures as a function of pressure.Findings - The ultra low leak rates necessary to guarantee hermeticity of MEMS cannot be measured using traditional methods. Optical test methods are possible although in-situ test structures currently provide the greatest sensitivity. A portfolio of test techniques is required to allow accurate hermeticity testing of MEMS.Research limitations/implications - This research provides a starting point for further investigation into several methods of MEMS hermeticity testing.Originality/value - This paper provides a review of the limitations of traditional testing and proposals for future testing as the trend towards smaller volume packaging continues.