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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1846-1851 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The widespread acceptance of thermomigration technology to produce through-chip interconnects has been impaired by (i) a random walk of the Si-Al liquid eutectic inclusion as it traverses the wafer, and (ii) a "surface barrier'' which allows thermomigration of only relatively large inclusions. In this paper it is shown that these problems can be mitigated by thermomigrating at high wafer temperatures and with large temperature gradients through the wafer. It has been possible to achieve these high wafer temperatures and large gradients using a bank of infrared lamps and a bilaminar structure of silicon carbide powder compressed onto the top of a silicon wafer. This increases the delivery of energy to the wafer and reduces the random walk of the liquid inclusion. Further, the high wafer temperatures and enhanced temperature gradients created with this bilaminar silicon carbide structure allow relatively small, square aluminum pads (35 μm on a side) to thermomigrate through a 16-mil-thick silicon wafer.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 20 (1992), S. 439-449 
    ISSN: 1573-9686
    Keywords: Phosphene simulation ; Visual prosthesis ; Visual acuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A visual prosthesis for the blind using electrical stimulation of the visual cortex will require the development of an array of electrodes. Passage of current through these electrodes is expected to create a visual image made up of a matrix of discrete phosphenes. The quality of the visual sense thus provided will be a function of many parameters, particularly the number of electrodes and their spacing. We are conducting a series of psychophysical experiments with a portable “phosphene” simulator to obtain estimates of suitable values for electrode number and spacing. The simulator consists of a small video camera and monitor worn by a normally sighted human subject. To simulate a discrete phosphene field, the monitor is masked by an opaque perforated film. The visual angle subtended by images from the masked monitor is 1.7° or less, depending on the mask, and falls within the fovea of the subject. In the study presented here, we measured visual acuity as a function of the number of pixels and their spacing in the mask. Visual acuity was inversely proportional to pixel density, and trained subjects could achieve about 20/26 visual acuity with a 1024 pixel image. We conclude that 625 electrodes implanted in a 1 cm by 1 cm area near the foveal representation of the visual cortex should produce a phosphene image with a visual acuity of approximately 20/30. Such an acuity could provide useful restoration of functional vision for the profoundly blind.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 20 (1992), S. 423-437 
    ISSN: 1573-9686
    Keywords: Micromachining ; Electrode array ; Neural interface ; Intracortical electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A new manufacturing technique has been developed for creating silicon-based, penetrating electrode arrays intended for implantation into cerebral cortex. The arrays consist of a 4.2 mm×4.2 mm glass/silicon composite base, from which project 100 silicon needle-type electrodes in a 10×10 array. Each needle is approximately 1,500 μm long, 80μm in diameter at the base, and tapers to a sharp point at the metalized tip. The technique used to manufacture these arrays differs from our previous method in that a glass dielectric, rather than ap-n-p junction, provides electrical isolation between the individual electrodes in the array. The new electrode arrays exhibit superior electrical properties to those described previously. We have measured interelectrode impedances of at least 1013 Ω, and interelectrode capacitances of approximately 50 fF for the new arrays. In this paper, we describe the manufacturing techniques used to create the arrays, focusing on the dielectric isolation technique, and discuss the electrical and mechanical characteristics of these arrays.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 20 (1992), S. 413-422 
    ISSN: 1573-9686
    Keywords: Penetrating electrode array ; Impact insertion ; Cortical neurophysiology ; Neuroprosthetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The goal of this research was to find a practical means by which an array of 100 needle-shaped electrodes could be implanted into the cerebral cortex with minimal brain tissue trauma. It was found that insertion of these structures into cortical tissues could only be performed using high insertion speeds. A pneumatically actuated impact insertion system has been developed that is capable of inserting an electrode array into feline brain tissue at speeds from about 1 to 11 m/s. We found that a minimum array insertion speed of 8.3 m/s was necessary for a complete, safe insertion of all 100 electrodes in the array to a depth of 1.5 mm into feline cortex. The performance of the impact insertion system is discussed in terms of a simplified representation of cortical tissue.
    Type of Medium: Electronic Resource
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