|LED diagram on a black background / Photo by Martin Konopka via 123RF|
Light received during manufacture influences the properties of both electronics and plants. New studies have shown that a component of electronics called semiconductor materials -- usually inflexible -- can be made more flexible by keeping them in total darkness. Semiconductors also form the basis of Light Emitting Diodes or LEDs which can be used in food production. By fine tuning the color and intensity of the light emitted by the LEDs, plants with different growths and nutritional properties can be produced.
Semiconductors in electronics
A semiconductor is a material that conducts electricity less than that of a strong conductor such as copper but more than an insulator such as glass. Unlike metals, semiconductor resistance decreases as the temperature rises. The most common semiconductors used in electronics are silicon, germanium, and compounds of gallium. Semiconductor materials are useful due to the ability to tune conductance/ resistance. They are used commonly in electronics such as smart phones and computers.
Although inorganic semiconductors which include silicon are commonly used in electronics, they are normally brittle. There is an ongoing search for semiconductor materials that will allow the manufacture of smart devices that have increased flexibility which would make them more resistant to damage and would also allow a broader range of applications. Few had considered that light exposure might influence the flexibility of semiconductors.
Semiconductor flexibility increases under total darkness
Katsuyuki Matsunaga of Nagoya University, Japan and colleagues investigated the properties of the semiconductor zinc sulfide under different light conditions. They published their results in the journal Science. They attempted deformation tests of zinc sulfide crystals, that is, they twisted the crystal gradually until it shattered.
In the case of room temperature and in full light, the crystal immediately fractured. In contrast, they found that in complete darkness, the crystals could be put under significant torsional strain before they fractured. This result shows that inorganic semiconductors have flexibility in total darkness.
This has implications for manufacturing which could potentially make use of this property to engineer unique processes that may allow the design of more flexible smartphones, for example.
The properties of light not only influence the electronics industry -- these also need to be considered in the food production industry. Although more awareness exists regarding the importance of light conditions for plant growth, few studies have quantified the effect, which is important information to have when calibrating the cost-benefit of different light intensities when growing at scale.
LEDs in food factories
LEDs are a semiconductor-based light source. Their principal advantages include very low energy consumption, long life, resistance to breakage, small size, and ability to turn on and off rapidly without degradation. These properties are extremely attractive to multiple industries that want to reduce their lighting costs, including the food industry looking to provide year-round plant production.
|Various GU10 LED bulbs on photovoltaics in the grass / Photo by ludinko via Shutterstock|
Plant factories aim to provide a year-round supply of high quality crops. LEDs are the most commonly used light sources in these establishments. Examples of crops that are grown under these conditions include radish, buckwheat, strawberries, grapes, spinach, and lettuce.
An advantage of closed type plant factories is the exclusion of pests, meaning that pesticides and washing of the produce are not required. This has benefits both in costs but also food quality. Plants are highly sensitive to the type and intensity of light received during the initial growth stages.
LED type influences food characteristics
A study recently published in Scientific Reports, led by Miyako Kusano of the RIKEN Center for Sustainable Resource Science in Japan, investigated the effect of different LED colors and light intensities on lettuce leaf properties. They adopted a systems biology approach analyzing gene expression and metabolomics.
They were able to discern that a blue color LED and a specific light intensity regime was optimal for antioxidant production. They found that supplementing the blue light with green light promoted the growth of the lettuce.
The study demonstrates that the properties of commercially produced crop products can be influenced by the light color and intensity that they receive. The effect of LED light sources has also been investigated in the production of other crops such as broccoli.
It may be possible to design LEDs that specifically fulfill the optimal requirements of specific plants. Lettuce and strawberries, for example, are likely to require LEDs of different colors and intensities.
Creating nutrition switches with LEDs
A variety of rice has been created called golden rice, which incorporates the beta-carotene gene derived from carrots that gives the rice a golden color. The purpose of this rice innovation is to prevent blindness associated with beta-carotene deficiency in areas of the world in which rice consumption is high but few other food sources are available.
It could be possible to put the beta-carotene gene under the control of an LED light-controlled promoter, making this an optional variant, that would give food producers flexibility to manage their crops.