Micro Cantilever Movement Detection with an Amorphous Silicon Array of Position Sensitive Detectors

The movement of a micro cantilever was detected via a self constructed portable data acquisition prototype system which integrates a linear array of 32 1D amorphous silicon position sensitive detectors (PSD). The system was mounted on a microscope using a metal structure platform and the movement of the 30 μm wide by 400 μm long cantilever was tracked by analyzing the signals acquired by the 32 sensor array electronic readout system and the relevant data algorithm. The obtained results show a linear behavior of the photocurrent relating X and Y movement, with a non-linearity of about 3%, a spatial resolution of less than 2 μm along the lateral dimension of the sensor as well as of less than 3 μm along the perpendicular dimension of the sensor, when detecting just the micro-cantilever, and a spatial resolution of less than 1 μm when detecting the holding structure

Amorphous silicon e 3D sensors applied to object detection

Nowadays, existing 3D scanning cameras and microscopes in the market use digital or discrete sensors, such as CCDs or CMOS for object detection applications. However, these combined systems are not fast enough for some application scenarios since they require large data processing resources and can be cumbersome. Thereby, there is a clear interest in exploring the possibilities and performances of analogue sensors such as arrays of position sensitive detectors with the final goal of integrating them in 3D scanning cameras or microscopes for object detection purposes. The work performed in this thesis deals with the implementation of prototype systems in order to explore the application of object detection using amorphous silicon position sensors of 32 and 128 lines which were produced in the clean room at CENIMAT-CEMOP. During the first phase of this work, the fabrication and the study of the static and dynamic specifications of the sensors as well as their conditioning in relation to the existing scientific and technological knowledge became a starting point. Subsequently, relevant data acquisition and suitable signal processing electronics were assembled. Various prototypes were developed for the 32 and 128 array PSD sensors. Appropriate optical solutions were integrated to work together with the constructed prototypes, allowing the required experiments to be carried out and allowing the achievement of the results presented in this thesis. All control, data acquisition and 3D rendering platform software was implemented for the existing systems. All these components were combined together to form several integrated systems for the 32 and 128 line PSD 3D sensors. The performance of the 32 PSD array sensor and system was evaluated for machine vision applications such as for example 3D object rendering as well as for microscopy applications such as for example micro object movement detection. Trials were also performed involving the 128 array PSD sensor systems. Sensor channel non-linearities of approximately 4 to 7% were obtained. Overall results obtained show the possibility of using a linear array of 32/128 1D line sensors based on the amorphous silicon technology to render 3D profiles of objects. The system and setup presented allows 3D rendering at high speeds and at high frame rates. The minimum detail or gap that can be detected by the sensor system is approximately 350 μm when using this current setup. It is also possible to render an object in 3D within a scanning angle range of 15º to 85º and identify its real height as a function of the scanning angle and the image displacement distance on the sensor. Simple and not so simple objects, such as a rubber and a plastic fork, can be rendered in 3D properly and accurately also at high resolution, using this sensor and system platform. The nip structure sensor system can detect primary and even derived colors of objects by a proper adjustment of the integration time of the system and by combining white, red, green and blue (RGB) light sources. A mean colorimetric error of 25.7 was obtained. It is also possible to detect the movement of micrometer objects using the 32 PSD sensor system. This kind of setup offers the possibility to detect if a micro object is moving, what are its dimensions and what is its position in two dimensions, even at high speeds. Results show a non-linearity of about 3% and a spatial resolution of < 2µm

Imaging by Detection of Infrared Photons Using Arrays of Uncooled Micromechanical Detectors

The objective of this dissertation was to investigate the possibility of uncooled infrared imaging using arrays of optically-probed micromechanical detectors. This approach offered simplified design, improved reliability and lower cost, while attaining the performance approaching that contemporary uncooled imagers. Micromechanical infrared detectors undergo deformation due to the bimetallic effect when they absorb infrared photons. The performance improvements were sought through changes in structural design such as modification and simplification of detector geometry as well as changes in the choice of materials. Detector arrays were designed, fabricated and subsequently integrated into the imaging system and relevant parameters, describing the sensitivity and signal-to-noise ratio, were characterized. The values of these parameters were compared to values published for other uncooled micromechanical detectors and commercial uncooled detectors. Several designs have been investigated. The first design was made of standard materials for this type of detectors - silicon nitride and gold. The design utilized changes in detector geometry such as reduction in size and featured an optical resonant cavity between the detector and the substrate on which arrays were built. This design provided decrease in levels of noise equivalent temperature difference (NETD) to as low as 500 mK. The NETD parameter limits the lowest temperature gradient on the imaged object that can be resolved by the imaging device. The second design used silicon dioxide and aluminum, materials not yet fully investigated. It featured a removed substrate beneath each detector in the array, to allow unobstructed transmission of incoming IR radiation and improve the thermal isolation of the detector. Second design also featured an amorphous silicon layer between silicon dioxide and aluminum layers, to serve as an optical resonant cavity. The NETD levels as low as 120 mK have been achieved. The only difference between the third and the second design was the modification of the geometry to minimize the noise. Successfully obtained thermal images and improved NETD values, approaching those of modern uncooled imagers (20 mK for commercial bolometer-based detectors), confirm the viability of this approach. With further improvements, this approach has a potential of becoming a lowcost alternative for uncooled infrared imaging

Mechanical resonating devices and their applications in biomolecular studies

To introduce the reader in the subjects of the thesis, Chapter 1 provides an overview on the different aspects of the mechanical sensors. After a brief introduction to NEMS/MEMS, the different approaches of mechanical sensing are provided and the main actuation and detection schemes are described. The chapter ends with an introduction to microfabrication. Chapter 2 deals with experimental details. In first paragraph the advantages of using a pillar instead of common horizontal cantilever are illustrated. Then, the fabrication procedures and the experimental setup for resonance frequencies measurement are described. The concluding paragraph illustrates the technique, known as dip and dry, I used for coupling mechanical detection with biological problems. In Chapter 3, DNA kinetics of adsorption and hybridization efficiency, measured by means of pillar approach, are reported. Chapter 4 gives an overview of the preliminary results of two novel applications of pillar approach. They are the development of a protein chip technology based on pillars and the second is the combination of pillars and nanografting, an AFM based nanolithography. Chapter 5 starts with an introduction about the twin cantilever approach and of the mechanically induced functionalization. Fabrication procedure is described in the second paragraph. Then the chemical functionalizations are described and proved. Cleaved surface analyses and the spectroscopic studies of the mechanically induced functionalization are reported. In Appendix A there is an overview of the physical models that are used in this thesis

Cantilever systems for the next generation of biomechanical sensors

Ieder interactief systeem gebruikt apparaten om informatie over de omgeving te verkrijgen. Ook de mens gebruikt apparaten om zijn omgeving te onderzoeken; tast- en gehoor-apparatuur voor mechanische impulsen, zicht- voor elektromagnetische en smaak- en reuk- voor chemische eigenschappen. Het gaat om thermometers, microfoons, ccd camera’s, enzovoort: allemaal sensoren die onze waarnemingsmogelijkheden vergroten, prestaties verbeteren en soms zelfs de mens vervangen in autonome systemen. In de laatste decennia is door de opkomst van nano- en biotechnologie de ontwikkeling van chemische sensoren, in het bijzonder biosensoren, in een stroomversnelling geraakt. Biosensoren worden gekenmerkt door de aanwezigheid van een biologische component (bv. een antilichaam, enzym of DNA molecuul) die een interactie aangaat met het te detecteren chemische element. Deze interactie wordt omgezet in een macroscopisch signaal welke vervolgens kan worden uitgelezen door een mens of machine. In ons dagelijks leven zijn biosensoren al terug te vinden in de vorm van zwangerschapstesten en glucosemeters, maar ook in minder opvallende toepassingen zoals voedsel- en waterveiligheid. Er zijn echter nog vele gebieden, in het bijzonder in de geneeskunde, waarin biosensoren een belangrijke rol kunnen spelen. In geval van ziekte (eenvoudige griep of allergie tot levensbedreigende kanker) produceert ons lichaam biologische markers, eiwitten, die inzicht kunnen geven in wat er zich in ons lichaam afspeelt. Daardoor kan er een betere inschatting worden gemaakt van de prognose en kan de therapie mogelijk specifiek op de patiënt worden afgestemd. Helaas is vaak niet bekend welke markers een rol spelen, en als dit wel bekend is, is de detectie veelal zeer kostbaar of zelfs niet mogelijk. In my thesis work I investigated alternative geometries of nanomechanical oscillators to be employed as biomolecular sensors. Simple mechanical oscillators, such as cantilevers and double clamped beams have been deeply investigated in the last decade and single molecule sensitivity was demonstrated. However, beside few marginal exceptions, the proof of principle demonstrations did not yet evolve into commercial devices. Alternative geometries can, in principle, improve the simple micromechanical systems studied so far, with more complex transfer functions suitable to operate also in demanding environments. The thesis work was divided in two major sections. In the first section twin cantilevers are discussed. Couples of cantilevers facing each other and separated by a nanometer gap may change their resonance response when one or more molecules are absorbed in the gap. Two different geometries have been fabricated and tested. One, with identical cantilevers, takes advantage of the shift in resonance frequency occurring upon molecular detection; the second with asymmetrical cantilevers, uses the shortest one to actuate the motion of the longer one through a molecular link. In the second part the structure of the twin cantilevers is the starting point for creating a spatially confined chemical reaction in the gap between two cantilevers facing each other. This original process is extremely precise and represents an important milestone towards the future realization of complex micro- and nanomechanical systems for biomolecular detection.

Protein Impregnated Polymer (PIP) Film Infrared Sensor Using Suspended Microelectromechanical Systems (MEMS) Pixels

The Air Force Research Laboratory Materials and Manufacturing Directorate have developed a novel protein impregnated polymer (PIP) suspension that changes resistivity as a function of absorbed infrared radiation. Due to this property, the PIP is a potential material for use as an uncooled bolometer, or thermal sensor. In this research, a thermally-isolated pixel design, sensor characterization methods, and sensor fabrication and processing steps were developed. To create a microbolometer, the PIP was applied to two prototype micro-electro-mechanical systems (MEMS) surface micro-machined structures. The first is a raised cantilever pixel array that uses residual stress polysilicon and metal film arms to bend the pixels away from their substrate. The second is a suspended membrane pixel array in which the backside silicon wafer substrate is removed. The thermal sensor\u27s figures of merit responsivity, detectivity, noise equivalent power, noise equivalent temperature difference, and thermal time constant, were modeled. An attempt was made to evaluate the performance of the fabricated microbolometer pixels by comparing measured data to model predictions. This research shows the PIP material can be used to make a practical thermal sensor

Approaches to Generating Selectivity in Microcantilever Sensors

Microcantilever (MC) sensors have emerged as sensing transducers that offer greater sensitivity than comparable sensors due in large part to their very small dimensions. MCs have been utilized in many chemical sensing applications. Not only do MCs demonstrate greater sensitivity, but they also are relatively low in cost, they can be used in an array format, and they can be integrated into on-chip electronic circuitry. While MC sensors demonstrate great sensitivity, an area of weakness that MC sensors must overcome is that of selectivity. The response of a MC sensor to analyte is mechanical; these mechanical responses lack the information rich spectral features like those found in vibrational spectroscopic techniques. Thus the underlying goal of this research is to develop approaches to enhancing selectivity in MC sensors. The initial research focused simply on demonstrating that MC sensors could be functionalized with thiolated self-assembled monolayers (SAMs) and then used to detect metal ions in the liquid phase. The initial research not only demonstrated the moderate selectivity of SAMs to metal ions, but also the good sensitivity at which these metal ions could be detected. The second phase of the research represented the first time that microcantilever array sensors (MCAs) were functionalized with SAMs having different ligand functionalities on one sensor chip. The MCA was exposed to different metal ions and the response signatures used in conjunction with pattern recognition algorithms to identify and quantitate the metal ion injected. In an extension of the metal ion array research, the SAM MCA was coupled to an ion-exchange chromatography (IEC) column for the separation and detection of metal ions. The second major division of research presented in this work involves improving the selectivity of detection of analytes in the gas phase. MCAs differentially coated with polymeric RPs by way of PVD were made. Experimental parameters were adjusted to determine if the parameters would impact the selectivity of the MCA. The final project involved taking the former gas phase project a step further by invoking the use of gas chromatography (GC) to impart selectivity to the system

Characterisation of ion-beam deposited thin-film coating materials for use in future gravitational wave observatories

No abstract availableNo abstract availabl