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Liquid Magnetic Bubble Display

IP.com Disclosure Number: IPCOM000082398D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Thompson, DA: AUTHOR

Abstract

Magnetized fluid located between two surfaces may be used for noncontact testing and high-contrast display. The magnetized fluid is comprised of droplets of magnetic liquid in an immiscible nonmagnetic host fluid.

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Liquid Magnetic Bubble Display

Magnetized fluid located between two surfaces may be used for noncontact testing and high-contrast display. The magnetized fluid is comprised of droplets of magnetic liquid in an immiscible nonmagnetic host fluid.

In the case where the magnetic droplets are confined between two approximately parallel surfaces, a constant-magnetic field is applied perpendicular to these surfaces (plates). This magnetic field induces a magnetization in the magnetic fluid. Droplets, large compared to the spacing between the plates, will spontaneously break up into labyrinth patterns when the field exceeds a threshold value. These patterns are similar to magnetic domains in crystalline materials and droplets comparable in size to the plate spacing form cylindrical bubbles, which are identical in appearance to magnetic bubble domains.

Fluid magnetic bubbles have many of the properties of magnetic bubble domains. Their shape is determined by an interplay of forces, in which surface tension plays the role of domain wall energy for the magnetic bubble domain situation. Since the amount of liquid bubble material is fixed whereas magnetic bubble domains are not bounded in size, a liquid bubble generator or annihilator must generally have a fluid reservoir. In other respects, the liquid bubbles can be moved around in the same manner as magnetic bubble domains are moved around; that is, by current loops, permalloy overlays, etc. High-Contrast Display.

Liquid bubble domains for displays have several advantages, among which is the larger size range that is available. The liquid bubbles can be produced from a few mils in diameter to a quarter inch or more. Surface tension, saturation moment, and plate spacing can be varied to obtain the desired bubble size. The plates can be ordinary window glass so that magnetic liquid displays are potentially low cost. No expensive single crystals or vacuum seals are required to limit the size which is practical.

Another advantage to liquid bubble displays is that of optical efficiency, which is nearly 100%. As an example, a water-base ferrofluid in a host liquid of kerosene and freon offers a very large optical contrast. The ferrofluid is opaque for the tiniest spacings and the host fluid is optically transparent.

Another advantage of liquid bubble displays, is that it is possible to detect the presence of a liquid bubble by all of the magnetic means used for detection of magnetic bubble domains. However, complicated and insensitive equipment is not required, since the liquid bubbles can be detected directly...