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US-12624805-B2 - LED bulbs incorporating negative Poisson's ratio structures

US12624805B2US 12624805 B2US12624805 B2US 12624805B2US-12624805-B2

Abstract

An LED bulb includes a bulb body, with a first set of components composed of an NPR material, and a second set of components composed of a PPR material. The first set of components include thermal encapsulants, thermal pottants, a heat sink, thermal interface materials, and LED chip encapsulants. The second set of components include a socket, a base, an LED driver, conformal coating, adhesives, reflector materials, an LED module, LEDs, primary optics, and secondary optics. The incorporation of NPR materials into LED bulb components can provide various advantages over LED bulbs that include only positive Poisson's ratio (PPR) materials. For example, NPR materials can facilitate improved heat dissipation from, and/or cooling of, integrated components of LED bulbs, among other benefits.

Inventors

  • Joon Bu Park

Assignees

  • Joon Bu Park

Dates

Publication Date
20260512
Application Date
20241025

Claims (6)

  1. 1 . A light emitting diode (LED) bulb, comprising: a bulb body, one or more LEDs housed within the bulb body, one or more LED chip encapsulants encapsulating the one or more LEDs, wherein the one or more LED chip encapsulants include a material having a negative Poisson's ratio (NPR material), and the NPR material comprises a re-entrant structure.
  2. 2 . The LED bulb of claim 1 , in which the one or more LED chip encapsulants are formed of epoxy resin, polyurethane, acrylic, or silicone.
  3. 3 . The LED bulb of claim 1 , in which the one or more LED chip encapsulants are formed of a transparent polymer foam NPR material.
  4. 4 . The LED bulb of claim 3 , in which the transparent polymer foam NPR material is composed of a cellular structure having a characteristic dimension of between 0.1 μm and 3 mm.
  5. 5 . The LED bulb of claim 1 , in which the one or more LED chip encapsulants form a substantially circular and convex shape, configured to cover the one or more LEDs.
  6. 6 . The LED bulb of claim 1 , in which the one or more LED chip encapsulants comprise an index of refraction between 1 and 2.5.

Description

BACKGROUND The present disclosure relates generally to LED bulbs that incorporate structures having negative Poisson's ratios. LED bulbs are often used as a light source over existing alternatives, such as fluorescent and incandescent bulbs. While LED bulbs are more efficient in light production than other bulb types, they still suffer from energy losses. LED bulbs have various components that perform heat management functions. For example, LED bulbs can include heat sinks, thermal transfer pads, or various encapsulants to effectively transfer heat or protect circuit elements. As LED color can affect heat emission and the number of color options in LED bulbs has increased, heat dissipation has emerged as a notable aspect of LED bulb design. SUMMARY We describe here LED bulbs that feature negative Poisson's ratio (“NPR”) materials. An NPR material is a material that has a Poisson's ratio that is less than zero, such that when the material experiences a positive strain along one axis (e.g., when the material is stretched), the strain in the material along the two perpendicular axes is also positive (e.g., the material expands in cross-section). Conversely, when the material experiences a negative strain along one axis (e.g., when the material is compressed), the strain in the material along a perpendicular axis is also negative (e.g., the material compresses along the perpendicular axis). By contrast, a material with a positive Poisson's ratio (“PPR”) has a Poisson's ratio that is greater than zero. When a PPR material experiences a positive strain along one axis (e.g., when the material is stretched), the strain in the material along the two perpendicular axes is negative (e.g., the material compresses in cross-section), and vice versa. The incorporation of NPR materials into LED bulb components can provide various advantages over LED bulbs that include only positive Poisson's ratio (PPR) materials. For example, NPR materials can facilitate improved heat dissipation from, and/or cooling of, integrated components of LED bulbs. In some implementations, the NPR materials can allow the LED bulb components to be lighter than PPR-only LED bulbs. In some implementations, the NPR materials can provide improved mechanical and/or thermal stability based on comparative mechanical and/or thermal responses of the NPR materials and PPR portions of the LED bulbs. Some aspects of this disclosure describe a light emitting diode (LED) bulb, comprising a bulb body, with one or more LEDs housed within the bulb body. One or more LED chip encapsulants encapsulate the one or more LEDs, wherein the one or more LED chip encapsulants are composed of a material having a negative Poisson's ratio. This and other light emitting diodes (LEDs) described herein can have one or more of at least the following characteristics. In some implementations, the LED chip encapsulants are formed of epoxy resin, polyurethane, acrylic, or silicone. In some implementations, the LED chip encapsulants are formed of a transparent polymer foam NPR material. In some implementations, this transparent polymer foam NPR material is composed of a cellular structure having a characteristic dimension of between 0.1 μm and 3 μm. In some implementations, the LED chip encapsulants form a substantially circular and convex shape, configured to cover the one or more LEDs. In some implementations, the LED chip encapsulants comprise an index of refraction between 1 and 2.5. In another aspect, the light emitting diode (LED) bulb, comprises an LED driver circuit and a base electrically connected to the driver circuit. A heatsink is coupled to the base, wherein the heatsink is composed of a material having a negative Poisson's ratio. In some implementations, this LED bulb comprises a thermal transfer pad thermally coupled to the base and heatsink. In some implementations, the thermal transfer pad is composed of a material having a negative Poisson's ratio. In some implementations, the heatsink is formed of a porous material. In some implementations, the heatsink has one or more fans to dissipate heat. In some implementations, the heatsink is formed of silicone, graphite, aluminum, or copper. In some implementations, the heatsink and thermal transfer pad are formed of a common material. In another aspect, the light emitting diode (LED) bulb, comprises a bulb body and an LED driver circuit. Thermal pottants encapsulate the LED driver circuit, wherein the thermal pottants are composed of a material having a negative Poisson's ratio. In some implementations, the thermal pottants are formed of epoxy resin, polyurethane, acrylic, ceramic, glass-ceramic or silicone. In some implementations, the LED driver circuit is composed of materials having a positive or negative Poisson's ratio. In some implementations, some or all parts of the LED driver circuit are coated with the thermal pottants through an AM process. In some implementations, the LED driver circuit is formed separately from