A reconfigurable tactile display based on polymer MEMS technology

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.Ph.D.Committee Chair: Allen,Mark; Committee Member: Bucknall,David; Committee Member: Book,Wayne; Committee Member: Griffin,Anselm; Committee Member: Yao,Donggan

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

Verbesserung der Anwendbarkeit von organischen Leuchtdioden durch integrierte Nanostrukturen

The organic light-emitting diode (OLED) is a promising technology for a variety of applications, such as displays, large-area lighting, integrated sensing, smart packaging, and signage. OLEDs are thin-film devices comprising organic semiconductors, which allow for cost-efficient high-volume manufacturing using solution-based fabrications methods and therefore hold great potential towards disposable and recyclable electronic products. In this thesis, three different approaches to improve the applicability of OLEDs through integrated nanostructures are explored. Nanostructuring the carrier substrate's outside surface provides a way to enhance light extraction as well as customize tactile and visual device perception. Here, a polymer coating containing tetrapodal zinc oxide nanoparticles and color pigments is investigated with respect to surface roughness characteristics and optical properties. Electrical device properties can be altered by integrating nanostructures directly into the OLED semiconductor stack. In this work, periodic nanopatterning of a metal electrode is shown to improve charge injection into the organic semiconductor layer of a single-carrier device through local electric field enhancements. A current increase of up to 300 % is observed, exceeding the planar current injection limit and indicating a local transition to space charge limited operation. Integration of a photonic crystal slab into the waveguide formed by the OLED can also lead to resonant light outcoupling. Here, a fabrication method is presented to create two-dimensional nanogratings with variable grating designs in the commonly used electrode material indium tin oxide. Furthermore, a novel device structure is investigated in which a fluorescent nanopatterned waveguide is placed outside the OLED for directional light emission leading to sharp angle-dependent outcoupling peaks in the emission spectra

Laser ultrasonic evaluation of human dental enamel during remineralization treatment

In this work a non-destructive laser ultrasonic technique is used to quantitatively evaluate the progressive change in the elastic response of human dental enamel during a remineralization treatment. The condition of the enamel was measured during two weeks treatment using laser generated and detected surface acoustic waves in sound and demineralized enamel. Analysis of the acoustic velocity dispersion confirms the efficacy, as well as illuminating the progress, of the treatment

The NASA SBIR product catalog

The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

Surface Functionalization of Fabrics and Threads for Smart Textiles

The future of electronics is moving toward wearable devices and therefore requires a shift away from hard, inflexible materials towards fibers, threads, and fabrics that conform to the shape of the body. Therefore new methods for incorporating textiles as electronic components are needed to replace conventional processing techniques used with smooth, flat substrates like glass, silicon, and many polymers. Toward this end, this work investigates different methods that can be used to tune textile surfaces for electronic functionality, including weaving, solution grafting, and initiated chemical vapor deposition (iCVD). While all of these methods were used to make triboelectrically-active textiles, iCVD combined with simple solution chemistry was also used to synthesize ionically conductive thin films on textiles for solid-state electrolytes. In general these methods elucidate facile pathways towards smart clothing fabrication

Active Inter-cellular Forces in Collective Cell Motility

The collective behaviour of confluent cell sheets is strongly influenced both by polar forces, arising through cytoskeletal propulsion and by active inter-cellular forces, which are mediated by interactions across cell-cell junctions. We use a phase-field model to explore the interplay between these two contributions and compare the dynamics of a cell sheet when the polarity of the cells aligns to (i) their main axis of elongation, (ii) their velocity, and (iii) when the polarity direction executes a persistent random walk.In all three cases, we observe a sharp transition from a jammed state (where cell rearrangements are strongly suppressed) to a liquid state (where the cells can move freely relative to each other) when either the polar or the inter-cellular forces are increased. In addition, for case (ii) only, we observe an additional dynamical state, flocking (solid or liquid), where the majority of the cells move in the same direction. The flocking state is seen for strong polar forces, but is destroyed as the strength of the inter-cellular activity is increased.Comment: 15 pages,22 figure

A Review of Wearable Computing Applications employing Acoustic Wave Propagation in Human Tissue

This paper presents a review of acoustic waves applied to wearable device applications.The Wearable Devices Market is described to provide insight into the future relevance of wearable devices. Recently published proposals for gesture recognition, Haptics and Intra-body Communications based on the use of acoustic waves are discussed to highlight the potentials and research opportunities that offer the acoustic waves intowearable devices

Review of Polyimides Used in the Manufacturing of Micro Systems

Since their invention, polyimides have found numerous uses in MicroElectroMechanical Systems (MEMS) technology. Polyimides can act as photoresist, sacrificial layers, structural layers, and even as a replacement for silicon as the substrate during MEMS fabrication. They enable fabrication of both low and high aspect ratio devices. Polyimides have been used to fabricate expendable molds and reusable flexible molds. Development of a variety of devices that employ polyimides for sensor applications has occurred. Micro-robotic actuator applications include hinges, thermal actuators and residual stress actuators. Currently, polyimides are being used to create new sensors and devices for aerospace applications. This paper presents a review of some of the many uses of polyimides in the development of MEMS devices, including a new polyimide based MEMS fabrication process

Marking and making : a characterisation of sketching for typographic design

This research rests on the premise that sketching in paper and pencil is crucial for typographic designers when designing documents. The aim has been to derive a characterisation of the salient aspects of sketching, through an ethnographically-oriented study of designers' use of paper and pencil. The people studied were professional typographic designers, but both the motivations for the research and the characterisation deriving from it relate to other design disciplines, notably industrial and engineering design and architecture. The goal was to identify the underlying functionality supported by sketching, in order to inform the design of future tools for document creation. The characterisation is presented as a framework, with seven main categories: visual characteristics of marks; basic semantic units of design; visual features of sketches; visual and tactile features of sheets of sketches; affordances of sketching; functionality required to support sketching; capacities of the traditional medium. The first four categories deal with the visual qualities of sketches, such as image quality within the line and recurring features in sketches such as different scale, closure, and degree of detail. The functions supported by sketching are suggested to be: interpretability, focus, comparison, simulation of experience, ideas capture and record making. The functionality identified as necessary to support sketching includes the appropriate speed of image generation, image emergence, image manipulation, and image capture and record making. Also necessary are high speed and ease of switching between all the strands mentioned above, and singularity of focus. The supportive capacities of the traditional medium include a rich vocabulary of marks, high image definition, and the continuum-of-activity through the continuity-at-medium, i.e. the natural progression from sketching on paper to making simulations out of paper. In recognition of the respective strengths of the traditional and electronic media, integration between the two is recommended for the design of optimal document creation systems