Background
The 2022 Hopkins iGEM team wants to make it easier for teams to perform experiments with applications in space and microgravity. In order to effectively simulate microgravity on earth, a clinostat, or random positioning machine, is essential. Team Concordia-Montreal developed an excellent 3D clinostat in 2021, which rotates in 2 axes to average the gravity vector in X, Y, and Z.
Some experiments that are constrained to a flat surface like an agar plate may not require the additional electrical and mechanical complexity of a 3D clinostat. To this end, we created an open-source design for a 2D clinostat to achieve random positioning of agar plates, and is usable for microgravity experiments including plants.
Our design was highly inspired by the device described in Wang et al.’s 2016 publication “2-D Clinostat for Simulated Microgravity Experiments with Arabidopsis Seedlings.” Our design has nearly identical functionality, but most parts are 3D-printable, the stepper motor is more inexpensive, and design files are accessible on GitLab.
The Clinostat-coil assembly
The clinostat-coil assembly mainly consists of the clinostat, the sample chamber, and the magnetic coils. The assembly is mostly 3D-printable, excluding the bearing, the acrylic sample chamber cover, sealing silicone, and injection port fittings, the stepper motor with integrated encoder, and fasteners and heat set inserts. The non-3D-printable parts are all low-cost and widely available.
(Fig. 1): Render of the clinostat-coil assembly.
The clinostat:
The clinostat provides the constant-rate rotation needed to average the effects of gravity. It consists of the bearing mount, the stepper motor with integrated encoder, the drive shaft, and the two support arms for the bearing mount and the stepper.
The bearing mount attaches directly to the left support arm with M3 screws, while the stepper attaches to the right support arm with M3 screws
The drive shaft is 3D-printable but can also be repurposed from other sources. It connects the stepper to the sample chamber and the sample chamber to the bearing through M3 set screws..
The coils:
The coil holders attach to the clinostat frame with M5 screws. The coils provide the magnetic field gradient needed to direct root growth. Since the gradient is directional, the left and right coil holders are asymmetrical at the mounting points to prevent incorrect assembly. The mounting points are cantilevered to provide better access for maintenance and more room for the sample chamber.
The sample chamber:
The sample chamber is designed to hold two standard agar plates. The sample chamber cover is laser-cut acrylic and mates to the sample chamber through M3 screws and silicone, creating a watertight seal. There are two ports for M5 pneumatic fittings in the sample chamber cover to provide vent and injection ports for rapid fixation of the samples at the end of experiments.
Figures
The clinostat-coil assembly’s geometry was optimized through design iterations guided by finite element analysis and manufacturing outcome:
