Our project aims to increase the wax synthesis content in plants by increasing the light intensity. On the one hand, it provides a method reference for cultivating high stress resistant crop varieties, and on the other hand, it provides abundant high wax raw materials for industrial production. Therefore, we have designed a plant light controlled cultivation device, which can not only provide suitable cultivation conditions for our experimental verification stage, but also achieve large-scale wax production based on our device principle in the future. The design of the lighting device is based on our experimental results, which found that by increasing the light intensity, the wax content in the plant body can be increased. We use full spectrum LED lights as the core device and draw on the principles of existing plant incubators [1] to design an efficient and high-yield wax synthesis device. By accurately controlling the following key parameters, we can achieve year-round plant cultivation and research without being limited by external natural conditions.

Schematic diagram of plant light controlled incubator

The light controlled incubator is a box type equipment, mainly composed of an outer box, an inner cavity, a door, a control system, and a lighting system. The overall design can be seen as a vertical refrigerator or a square box. The outermost layer is the outer casing of the device, including the cavity and sealing door. Opening the sealing door reveals the most intuitive internal structure of the device, which consists of three layers from top to bottom. The first and second layers are both plant cultivation racks, and the third layer is the inner container. The control system mainly includes a control panel, an LED light control device for controlling the brightness, a circulating fan device for maintaining air circulation inside the box, a temperature and humidity regulator for controlling temperature and humidity, and a sensor alarm for real-time detection of environmental changes inside the box. After transplanting the tobacco and cultivating it for two weeks, we can transfer it to a light controlled incubator. We adjust the light control equipment to the maximum light intensity during the period when the plant generates the highest wax content, control the temperature and humidity to achieve the most suitable growth conditions for the plant, and maintain a constant temperature. After continuous cultivation for one month, we can cultivate the plant's own wax. If the main purpose is to improve the plant's stress resistance and collect its own products (such as seeds, leaves, etc.), we can bypass the wax extraction step and harvest directly.

After cultivating high wax plant materials, in order to achieve intuitive utilization of wax, we plan to create a simple wax extraction device to separate the wax from the plant body for our use. Plant epidermal wax is a hydrophobic lipid mixture that covers the surface of plants. Its main components are long-chain fatty acids, aldehydes, alcohols, alkanes, and esters, all of which are non-polar or weakly polar organic compounds. Therefore, it is necessary to use organic solvents (such as chloroform, n-hexane, benzene, ether, etc.) as extraction media, utilizing their polarity similar to wax to dissolve and remove wax [2].

Plant epidermal wax extraction device diagram

The entire device mainly adopts the washing/dripping method for extraction. From top to bottom, the device consists of a fixed sample rack, a solvent storage bottle (constant pressure dripping funnel), and a receiving dish located below the sample (such as a beaker or chicken heart bottle). Take out the high wax plants that have been treated with light, weigh and fix them on a bracket, and tilt the surface to be extracted (at an angle of about 45 degrees) so that the solvent can flow down smoothly and drip. Open the piston and slowly and evenly rinse or drip the pre cooled organic solvent onto the surface of the sample. It can be seen that the solvent forms a liquid film on the surface of the sample and carries away the wax. The solvent that dissolved the wax dripped from the bottom of the sample and was completely collected by the chicken heart bottle below. Wax may undergo morphological changes (such as melting) or chemical changes (such as oxidation) at higher temperatures. Therefore, the entire extraction process, especially the soaking stage, is usually carried out at room temperature or lower to maintain the original state of the wax. This method requires less solvent usage and minimal physical damage to the sample, but requires more precise operation to ensure that all surfaces are washed away.

The cavity shell is the main frame structure of the incubator, made of high-quality cold-rolled steel plate (SPCC) or stainless steel (such as SUS 304), and the surface is treated with powder coating or electrophoresis. The closed door is the key sealing component of the cavity, which adopts a double-layer hollow glass structure. The outer layer is tempered glass, and the inner layer is ordinary glass. Dry air or inert gas is injected between the two layers of glass, and magnetic or silicone sealing strips are embedded around the door frame. This structural design and material selection can not only provide the mechanical strength and stability of the entire device, protect the internal core components, but also shield the electromagnetic interference generated by the internal circuit to a certain extent, and protect the internal environment from external interference. In addition, the air layer in the middle of the double-layer glass is an excellent insulation layer, which can effectively prevent heat loss and condensation at the largest opening of the door.

Double layered glass enclosed door design

The tank shell is almost all made of stainless steel (SUS 304 or SUS 316), and the middle layer is filled with high density polyurethane (PU) foam or rock wool and other efficient thermal insulation materials. It can resist corrosion from high humidity environments, nutrient solutions, and disinfectants (such as alcohol and sodium hypochlorite), prevent rust, and is not easy to breed bacteria and mold. It is easy to thoroughly clean and disinfect, ensuring a sterile experimental environment. The middle layer can effectively isolate the heat exchange inside and outside the box, ensuring uniform and stable internal temperature, greatly reducing the energy consumption of the compressor (during cooling) and heating tube (during heating).

The full spectrum LED light enables us to design the core light source of the plant light controlled incubator, which includes multiple monochromatic chips of different wavelengths (such as deep blue 450nm, royal blue 465nm, red light 660nm, far red light 730nm) integrated in specific proportions on the same substrate. This is the most core advantage, not only can the light intensity be freely controlled, but also the required spectral ratio can be accurately configured according to different plants and growth stages (such as seedling cultivation, nutritional growth, flowering and fruiting). The energy is concentrated in the photosynthetically effective range, and the photoelectric conversion efficiency is extremely high, with energy consumption 50% -60% lower than traditional light sources.

Full spectrum LED light group

Circulating fans are mainly made of engineering plastic material for fan impellers and brushless DC motors (BLDC). Engineering plastic is currently the mainstream choice for fan blades, with lightweight (low inertia, fast start stop, low motor load), high strength and fatigue resistance (long-term rotation without deformation), self-lubricating (low noise), excellent corrosion resistance (resistance to high humidity environments and disinfectants), and low cost. DC brushless motors can achieve stepless speed regulation through a controller, accurately controlling the air volume as needed, while maintaining uniformity and avoiding strong winds from causing damage to seedlings. The circulating fan we designed can forcibly drive the air flow inside the box, creating a uniform and stable internal climate environment.

A temperature and humidity regulator is a system consisting of sensors, controllers, and actuators (cooling/ heating / humidification / dehumidification components). The refrigeration system mainly uses copper and aluminum, which are not only lightweight but also have excellent thermal conductivity. The main material of the heating system is nickel chromium alloy, which has the advantages of strong high-temperature oxidation resistance, stable electrical resistivity (power stability), long service life, and is not easily deformed or damaged under high and low temperature cycles. The humidification system is mainly made of ultrasonic atomization sheets, which have the advantages of low energy consumption, fast response speed, high humidification accuracy, and miniaturization. Platinum resistors are commonly used in sensing systems due to their high measurement accuracy, excellent long-term stability (not prone to drift), and good linearity, making them the gold standard in industrial and high-precision measurement fields.

Sample holder: used to fix the tested plant organs (such as leaves, fruits, stem segments) in an ideal position, ensuring that the solvent can evenly cover the target surface. It can be fixed with clips, flexible cords, or needles. Solvent storage bottles usually use constant pressure drop funnels because they can maintain the internal pressure of the system in equilibrium with atmospheric pressure through side branch pipes, ensuring that the solvent can drop very smoothly and uniformly, and the flow rate is not affected by changes in liquid level height. The receiving device uses a heart-shaped bottle (also known as a pear shaped bottle) or a round bottom flask, as they can be directly connected to a rotary evaporator for subsequent concentration steps, reducing losses and contamination during the transfer process.

We will further improve our equipment in the future based on the actual needs of the industry. The core of industrialization is that equipment needs to be able to operate continuously and stably 24/7, and be easy to produce, install, and maintain on a large scale.

Implementing spectral programmability not only adjusts the intensity of light, but also allows users to customize spectral formulas for different growth stages (seedling, growth, flowering) (red blue light ratio, increased UV, far red light, etc.). Integrated cameras can also be introduced to use computer vision AI technology to automatically monitor crop growth, identify pests and diseases, and adjust environmental parameters or issue warnings.

We have designed two devices in the hardware part, one is a plant light controlled incubator that can freely adjust the light intensity, and the other is a simplified plant wax extraction device, aiming to achieve artificial controllability of high-yield wax synthesis.

The preparation of plant light controlled incubators mainly draws on some plant climate incubators on the market today, and on this basis, the light controlled adjustment device is further refined to increase the light intensity, which is also a necessary condition for us to synthesize high-yield wax. The plant wax extraction device is mainly based on the characteristics of plant epidermal wax, a hydrophobic lipid mixture, mainly composed of non-polar or weakly polar organic compounds such as long-chain fatty acids, aldehydes, alcohols, alkanes, and esters, which can be extracted by organic solvents (such as chloroform, n-hexane, benzene, ethyl ether, etc.).

In the future, we will further improve our equipment according to the needs of the industry and the development of technology. We suggest using greener and more sustainable materials to reduce the harm to the ecological environment. We can also consider introducing computer AI technology to achieve full process monitoring of plant growth.

[1] Zhao, D., Reddy, K. R., Kakani, V. G., Mohammed, A. R., Read, J. J., & Gao, W. (2004). Leaf and canopy photosynthetic characteristics of cotton (Gossypium hirsutum) under elevated CO2 concentration and UV-B radiation. Journal of plant physiology, 161(5), 581–590.

[2] Zou, J., Zhao, M., Chan, S. A., Song, Y., Yan, S., & Song, W. (2024). Rapid and simultaneous determination of ultrashort-, short- and long- chain perfluoroalkyl substances by a novel liquid chromatography mass spectrometry method. Journal of chromatography. A, 1734, 465324.