Creating the TERRA Adaptor
Check back soon for our design of the TERRA Adaptor!
Designing the XY-Plane
In order for TERRA to select for specific locations to dispense fluids, we needed a method of either moving the output tube or the vessel, such as a 96-well plate. We ultimately decided to move the vessel, as that would minimize the length of and amount of dead volume in the output tube. Our team designed an active XY-plane, which would allow us to move the platform in the X- and Y-direction to target a specific location. This XY-plane needed to have the following functions and features: the ability for translational motion; a homing system; a control system; a manufacturing method; material; and motors.
The following morphological chart illustrates our potential means of accomplishing each function or feature and the chosen options are written in green.
Translational Motion:
Homing: Our team chose to utilize contact switches in order to home our system as they were the easiest to integrate into the existing design of TERRA and were low-cost . We had briefly considered manual, user-controlled homing, but realized that it would result in a great amount of human error, as the user would need to approximate the distance from the nozzle to the well A1. Optical sensors and ultrasonic sensors would result in accurate locations, but would increase the cost of TERRA and are harder to integrate to our system.
Control: We decided to use the Arduino Mega to control our XY-plane and syringe pumps, as the addition of Arduino shields allowed for more motors, and therefore syringe pumps, to be connected per microprocessor. Our team also considered the use of a Raspberry Pi, but it would have been harder to integrate into TERRA and it contained more functions than needed for our project.
Manufacturing Method: TERRA is composed of 3D-printed supports, as 3D-printing is more accessible, lower-cost, and allows for quick prototyping. While traditional machining, such as milling and turning, would result in tighter tolerances and more accurate parts, we realized the cost of manufacturing parts in a machine shop were high. In fact, many of these parts only include clearance holes, which will serve its purpose as long as they meet a minimum dimension.
Material: Since our team chose to manufacture our system with 3D-printing, we chose to create our parts with ABS. The typical material for 3D-printing is resin, as it is inexpensive, but resin lacks the resolution needed to create the negative features on certain parts. ABS is stiffer and allows for more accurate parts and is more durable than resin.
Motors: We chose to incorporate stepper motors to the XY-plane as it allowed for a minimum step resolution of 1.8 degrees, which translates to 0.20 mm per step. Stepper motors also allow for microstepping, which allows us to further improve the resolution to 1/16 of a step, or 0.0125 mm.
Design 1
Design 2
Integrating the Syringe Pumps
Check back soon for our design of the syringe pumps!
