What’s an LED – The Missing Link Between Diodes and Biology

Today I’m going to discuss LEDs.  These tiny “light-emitting diodes” entered my consciousness in the 80’s when we bought our first wireless remote TV.  Later in the 2000’s, it seemed everyone was carrying around a small keychain LED pendant.  I knew the technology was improving with new availabilities but never took the time to understand how it all worked.  For years I took LEDs for granted until I realized LEDs weren’t just for electronic devices, I could use this technology to understand and control another type of complex machine – a living organism.

The living organisms I studied for my PhD were tiny microscopic cyanobacteria that make unique carotenoids (anti-oxidative compounds that have many uses).  No one had investigated the effects of different environmental stimuli on these bacteria.  By using LEDs, I could separate the quality of light they were exposed to and understand how light wavelength effects growth and carotenoid metabolism.

Below is a link to the photobioreactor I built, featured in a New York Times article, showing three separate tubes of different cyanobacteria growth media treatments. In this reactor I used three types of LEDs and controlled their intensities separately.

http://www.nytimes.com/2011/10/02/us/ut-making-a-big-bet-on-the-future-of-algae.html?_r=0

This is when I really began to appreciate LEDs.  Since then I have used LEDs to provide light and test many different photosynthetic microorganisms including cyanobacteria, microalgae, and land plants.  Earlier this year I had the opportunity to talk about LEDs at the 2016 Greenhouse Crop Production & Engineering Design Short Course at the University of Arizona Controlled Environment Agriculture Center (CEAC).

The title of the talk was “LED Lighting for Controlled Environment Agriculture.”  In this first section, “What is an LED?” I go into the basics of LEDs where I cover the following:

(I) Basics of the diode structure (n-side/p-side/boundary layer/size)

  • What happens when current is applied
  • Energy transfer and conversion

(II) Types of LED Components

  • Surface patterns and treatments
  • Photon extraction with optics
  • Binning of chips
  • Chip bonding
  • Lens considerations

(III) Standardization Terms & Testing Methods

  • L70
  • LM-79
  • LM-80

As always, I hope you find this presentation informative.  Please leave us your comments and feel free to contact us (illumitex.com/contact) with questions about your application of LEDs in controlled environment agriculture.  Stay tuned for more educational videos from myself and other experts here at illumitex.