TITLE: Illuminated Orbital Shaker for Microalgae Culture
AUTHORS: Jakub Nedbal

[DESCRIPTION]
<div class = "text-blocks"><div class = "text-block"><span>Microalgae are grown for the research on photosynthesis, biotechnology, and water-environment ecology. Specialized laboratories typically use calibrated commercial equipment, which agitates the microalgae culture by shaking or bubbling, controls the irradiance, temperature, and CO</span><span style = "vertical-align:sub;">2</span><span> content. Such commercial incubators may be out of reach for some laboratories, like those not specializing in microalgae research, teaching laboratories, or laboratories in low resource settings. Our research uses microalgae cultures during the development and validation of advanced microscopy techniques. We lacked access to and the budget for a commercial incubator. We solved the problem by building a stand-alone orbital shaking incubator with an in-built variable light source and a 24-hour timer. The shaker features a homogeneously illuminated growth area of 20 cm × 15 cm, which is suitable for three T75 tissue culture flasks or four 100 ml Erlenmeyer flasks. The overall material cost was around £300 and assembly time of about two days. We tested the shaker with fresh-water microalgae </span><span style = "font-style:italic;">Desmodesmus quadricauda</span><span> and </span><span style = "font-style:italic;">Chlorella vulgaris</span><span>. Both microalgae cultures have been grown continuously for seven months in the incubator. We studied their growth under different light conditions to validate the function of the shaker. The protocol outlines the step-by-step process to the building of this microalgae shaker.</span></div><div class = "text-block">Here, we describe an illuminated orbital shaker designed for culture of microalgae suspensions. It was optimized for production cost, simplicity, low power consumption, design flexibility, and consistent and controllable growth light intensity. The instrument agitates and illuminates microalgae suspensions grown inside flasks. The agitation speed is variable while the light intensity is both variable and programmable (24-hour light/dark diurnal cycle).</div><div class = "text-block"><span>The instrument offers a vastly cheaper alternative to commercial instruments for many laboratory applications, making it especially well suited for teaching and poorly-resourced research laboratories. It improves on home-built microalgae growth systems by offering consistent and well characterized illumination light intensity, low power consumption and heat dissipation. The illuminated growth area is 20 cm × 15 cm, which is suitable for three T75 tissue culture flasks or six 100 ml Erlenmeyer flasks. The photosynthetic photon flux density, measured inside an Erlenmeyer flask, is variable in eight steps (26−800 μmol·m</span><span style = "vertical-align:super;">−2</span><span>·s</span><span style = "vertical-align:super;">−1</span><span>). The overall material cost is around £300 (including an entry-level orbital shaker). The build takes about two days, requiring electronics assembly and machine workshop skills. The instrument build is documented in a set of protocols, design files, and source code. Its design can be readily modified, scaled, and adapted for other orbital shakers and specific experimental requirements.</span></div><div class = "text-block">The illuminated orbital shaker is ideal for growing small volumes of microalgae for research and teaching. It can readily replace commercial systems in many common microalgae culture application for a fraction of their cost. It outperforms typical home-made systems by offering consistent and predictable illumination light intensity and low power consumption.</div></div>

[STEPS]
?. The components for the algal shaker can be sourced from four types of suppliers.Laboratory equipment supplierElectronics parts distributorPrinted circuit board manufacturer3D printing service (or in-house 3D printer)The orbital shaker can be sourced from laboratory equipment suppliers. The orbital shaker described in this protocol was bought on ebay.All electronics components and mechanical fixings can be bought from electronics parts distributors. In the described case, it was Farnell. The clear acrylic sheet can be bought from specialist local supplier of sheet plastic or can be ordered laser cut to size and shape local laser-cut service providers.The custom-made printed circuit board (PCB) simplifies and speeds up the assembly and results in a smaller, more robust circuit. Here, Seeed Technology was used for their low-cost, high-quality PCBs production service.The electronics is housed in a custom case. It can be produced on a fused-deposition modelling 3D printer - in-house or outsourced to third-party manufacturers. An in-house Stratasys Uprint SE Plus was used here.Go to: Procuring Parts for Algal Shaker
?. The LED controller electronics regulates the LED current, adjusting the irradiance of the sample according the experimental needs. It also powers the fans cooling down the LEDs. The electronic circuit assembly requires surface-mount component soldering equipment and skills. The smallest parts used are in 0603 package. This size allows soldering with a decent soldering station, flux, watch-makers tweezers, an a bit of experience. The soldering should take no more than 1-2 hours. It is followed by testing the circuit and finally cleaning any excess flux.Consider the safety of the soldering process and observe local regulations. Soldering creates risks of fire, exposure to hazardous fumes, and skin exposure to the soldering flux. Take all necessary precautions. Keep the work area tidy, especially devoid of any combustible materials. Never leave the soldering iron unattended while hot. Use fume extractor during soldering and laboratory gloves when handling the flux-stained PCB.Go to: Assembling LED Controller Electronics
?. The electronics circuit is housed inside a case, which protects the circuit from damage and the users from exposure to live voltage. The case for the LED controller can be 3D printed in-house or outsourced to a specialist supplier. I used Stratasys Uprint SE Plus, a fused-deposition modeling printer. The finishing is rough, but serves the purpose. A laser-sintering printer would produce a more detailed and premium finish.Go to: 3D Printing Case for LED Controller
?. The LED illuminator is built from LED strips mounted on top of a heatsink. The heat sink is passively cooled when the LEDs are operated at low current. It is actively cooled by small fans at higher current to avoid overheating the algal cultures. The assembly of the cooled LED illuminator consists of glueing the LED strips to the underside of the heat sink and soldering them in a daisy-chain fashion for connection to the LED controller. The fans are also glued to the heatsink and connected to  the LED controller.Go to: Assembling Cooled LED Illuminator
?. A clear acrylic sheet is mounted over the LEDs and serves as the platform on which the algal cultures are placed for shaking. The acrylic can be cut out and drilled using a hack saw and a drill in a workshop. Alternatively, it can be cut using a laser cutter in-house or externally.Go to: Cutting and Drilling Clear Acrylic Sheet
?. Assembling the Algal Orbital Shaker is the last an most rewarding step. The acrylic sheet is mounted on top of the orbital shaker on metal stand-offs. The cooled LED illuminator is laid underneath the acrylic. The antislip silicon mat supplied with the orbital shaker is placed on top of the acrylic. The LED controller is connected to a socket through a 24-hour timer with the day/night cycle programmed. Once powered, the algal shaker should be working.Go to: Assembling Algal Shaker