Patent Application
20090162666
New ultra-stretchable polymer tapes have recently become available. These tapes have many uses, including artificial muscles. One such example is VHB™ from 3M™. This tape is generally thin and pliant, but strong. Other such tapes have also recently become available due to advances in polymer science.
These tapes have a wide range of applications, including window glazing and other construction applications, as well as in electronics. Generally, these tapes are applied to structures but do not have a very robust mechanical structure themselves.
In the embodiment of
The elastomeric layers 12 and 14 enclose at least partially structural elements such as 18. The structural elements may be made from acrylic, such as polymethyl methacrylate (PMMA), other plastics, metals such as stainless steel, glass, ceramic, silicon, gallium arsenide, sapphire or plexiglass or other rigid or semi-rigid materials. The materials may have special properties such as high hardness, heat reflecting properties, strong heat absorbing properties or light reflecting or absorbing properties. The structural elements may be cut into various shapes by laser cutting, etching, dicing, stamping or they may be molded or otherwise grown such as via electroplating. Alternatively, the structures may be electrochemically grown by electroplating, and then remove the ‘free’ areas using photoresist to protect them.
An array of squares such as 18 separated by the area 20 may form the material, but the structural element 18 may be many other shapes, such as round, hexagonal, rectangular, etc. Spherical or elliptical structures also may be possible and they may be made by methods such as emulsion aggregation, jet-printing or grinding. This is shown by the element 19 to the far right of
For example, the shapes as seen from the top view of the structural elements include squares, rectangles, triangles, circular or hexagonal shapes. This is shown by
The side-walls of the structural elements may be perpendicular to the top surface or they may be sloped so that a structural element has a trapezoidal shape when viewed from the side. The walls could slope inward as shown at 11, making the structural elements narrower at the top than at the bottom. Similarly, the structural elements could have walls sloping outwards, making the structural elements narrower at the bottom than the top. Further, the walls could be rounded, such as that shown by 15. These shapes may allow enhanced bending of the material in one bending direction. The structural elements in this embodiment may bond to the elastomeric layers using an adhesive, such as a pressure-sensitive adhesive tape, hot lamination, heat-sensitive adhesives, epoxies, etc. The structural layer may also bond to the elastomeric layer through the intrinsic bonding forces of the elastomer layer.
The structural elements such as 18 may also have bonded or otherwise attached to them functional elements such as 16. The functional elements may be patterned onto the structural elements before or after the structural elements are divided into individual elements. The functional elements could take many forms, including sensors, microelectromechanical systems (MEMS) elements, bolometers for infrared sensing, photovoltaic (solar) cells, light emitting devices such as light emitting diodes or other visual display elements, electronic circuits, structures with optical functionality, etc. The functional elements could be electrically or optically active elements or they could be simple passive structures. Passive functional elements would include optical corner cube reflectors, passive antenna structures to absorb or reflect electromagnetic radiation, passive magnetic elements such as permanent magnets, etc.
Arranged in between the structural elements are pockets or other regions of a curable polymer, liquid or other easily deformable material. The curable material may be heat-curable, radiation-curable, including light or UV-light curable, or curable by exposure to oxygen or moisture, among other types of curing. Upon curing, the material transforms from a liquid, viscous, visco-elastic or elastomeric form into a significantly more rigid or hardened form. The thickness or width of the regions of curable material between the structural elements may be varied to achieve the desired pliability and the desired rigidity when cured.
Similarly, the size of the structural elements, the thickness of the elastomeric layers, as well as the spacing between the structural elements may also be varied. The manufacturer of the material will have several variables to allow control of the initial and final properties of the material.
Further, the structure of the material may take the form of a highly elastic elastomeric layer 12 with pockets or other self-contained regions of curable substance 20 such as those shown in
In one example, the pockets 20 in
As another alternative, the shape of the structural elements may be varied to increase the stretchability of the material in the uncured state. In the embodiment shown in
The manufacture of the material may be accomplished in several ways. One embodiment of a method of manufacturing the flexible material is shown in
In the embodiment using the two elastomeric layers, such as one similar to the one in
At 38, the intermediate substrate can be turned over and then removed from the surface of the structural elements. A second layer may be adhered to the surface of the structural elements that was previously attached to the intermediate substrate at 40. Once the second elastomeric layer is attached, the curable material is applied at 42. The curable material may be introduced by capillary filling, or it may be introduced before application of the second elastomeric layer.
In an alternative embodiment, such as the one shown in
Once formed, the material or structure can be molded, shaped, bent, or otherwise formed into whatever shape desired. The material is then cured, such as by applying UV light. The curable material hardens and retains the desired shape.
One possible implementation of a spherical surface is a wide-field-of-view image sensor or a spherical display.
Similarly, the flexure beams may support not only the connection between the structural components mechanically, but also allow formation of electrical connections by supporting connection lines on the flexure beams. This is shown in
Up to this point in the discussion, the embodiments have assumed that the elastomeric layers allow the curing force, such as heat or light, to penetrate to the curable material. In some instances, the elastomeric layer may block the light or heat or the curable material may be in an inaccessible location or it may be surrounded by material that blocks radiation, heat or light. In such cases, the material 10 from
The material 10 has first and second elastomeric layers 12 and 14, structural components such as 18, and the curable material 20 in between the structural components. In addition, an internal curing structure 70 cures the curable material upon application of some sort of energy. For example, for UV-curable material, the internal curing structure may be an optical fiber or another kind of light guide. Externally, a light source such as a laser, an LED, a mercury or halogen lamp or other light source is then attached to send light through the light guide in order to cure the material. The light guide may have to have surface features that allow the light to couple out of the light guide. This may be in form of a roughened surface or in form of an adjusted refractive index of the surrounding material. Light may couple out of the light guide only in certain regions that require stiffening, which is achieved e.g. by texturing the light guide only in these certain regions to allow light to couple out. For heat-curable materials, the internal curing structure may be a heating element or wire which heats up when an electrical current is passed through. The electrical resistance of the heating elements may be adjusted to allow preferential or faster curing in certain regions and slower curing in others.
The internal curing structure may be applied to any of the architectures of the material discussed here. After deforming the material, it may be internally hardened or cured to retain the desired shape. An example of this is shown in
In yet another variation, the formation of the bend may be performed by an actuator of some sort, such as a shape-memory polymer.
All of the variations discussed above can be used in various combinations of structures and material. The resulting material is an initially flexible material that can be formed into various shapes and then cured to become rigid in that shape. This material has many applications including engineering, construction and even sculpting.
It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
