Efficient LED Lightbulbs Inspired by Fireflies

Innovation: Academia

Penn State

2019

Image: toan phan / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Transform Radiant Energy (Light)

The sun is the ultimate source of energy for many living systems. The sun emits radiant energy, which is carried by light and other electromagnetic radiation as streams of photons. When radiant energy reaches a living system, two events can happen. The radiant energy can convert to heat, or living systems can convert it to chemical energy. The latter conversion is not simple, but is a multi-step process starting when living systems such as algae, some bacteria, and plants capture photons. For example, a potato plant captures photons then converts the light energy into chemical energy through photosynthesis, storing the chemical energy underground as carbohydrates. The carbohydrates in turn feed other living systems.

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Send Light Signals in the Visible Spectrum

The visible spectrum is the portion of the electromagnetic spectrum that the human eye can detect. Visible light can be thought of in two ways–light as illumination (such as that used by fireflies) and colors that result from light being absorbed or reflected. Living systems use light for a variety of purposes. Sometimes, they use it to make themselves highly visible (like a peacock showing off his brilliant feathers to a potential mate). Other times, they use it to become virtually invisible (like an owl hiding in plain sight when it rests during the day). When a living system sends a light signal, it must create that light or color in an energy- and material-efficient way. Living systems create and enhance color using such strategies as non-toxic pigments, structures that bend and absorb different wavelengths, and chemical processes that create bioluminescence.

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Patents

Lightbulbs from Penn State have microstructures on the diode surfaces which increases light extraction efficiency.

Benefits

Efficient
Reduced energy usage
Environmentally friendly

Applications

Electronic displays
Consumer products
Electronics

UN Sustainable Development Goals Addressed

Goal 7: Affordable & Clean Energy
Goal 9: Industry Innovation & Infrastructure

The Challenge

Due to their low energy consumption and longer life span, light-emitting diode (LED) light bulbs have emerged as a low-cost and environmentally friendly alternative to incandescent lightbulbs. As interest in energy efficiency grows, there has been an effort to replace traditional lighting with LED light sources. However, light extraction efficiency measured in LED bulbs is less than 50%, as some photons are absorbed through the bottom side of the LED structure.

Innovation Details

Ultrahigh light extraction efficiency LED lightbulbs contain light-emitting diodes with unique asymmetric, obtuse-angle microstructured surfaces. These surfaces increase the interaction of light and promote greater randomization of reflections, increasing the light extraction efficiency to approximately 90%.

Biomimicry Story

Male fireflies attract mates by emanating bioluminescent light from a lantern in their abdomens. The surface of these lanterns has microstructures arranged in an asymmetrical pattern, which increases light extraction and enhances the glow that the lantern emits.

See Related Strategy

Biological Strategy

Nanostructures Help Transmit Light

Firefly

Nanostructures on the cuticle of the firefly's abdomen help transmit bioluminescent light efficiently because they perfectly match the wavelength of light being emitted.

References

Journal article

Ultrahigh light extraction efficiency light emitting diodes by harnessing asymmetric obtuse angle microstructured surfaces

ScienceDirect

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