Presentation description

Discovered in the 1990s, carbon nanotubes (CNTs) are carbon tubes with diameters in the range of nanometers. CNTs have various unique mechanical, thermal and electrical properties owing to the one-dimensional conduction that occurs within the tubes. These properties mean they have applications in composite materials, microelectronics, and solar cells, among many others. However, of particular note for research in photonics is the response of CNTs to the polarization of light. Experimentation has shown that the optical absorption and transmission of films made of aligned carbon nanotubes varies strongly when light is polarized parallel or perpendicular to the alignment direction of the tubes.
Investigation of these properties requires reliable assembly of aligned CNT films on the scale of cm^2, but many proposed methods to prepare such films are either impractical to implement or cannot achieve sufficient CNT alignment or film area. One proven method that may circumvent these issues is to filter a carbon nanotube aqueous suspension through a membrane using a vacuum pump, allowing for large-area CNT films with high alignment. However, implementing this type of system without automation requires the time and attention of a human operator, and is difficult to scale.
The goal of this project is to fully automate the filtration process from the moment the CNT solution is placed into the filter by making use of a Raspberry Pi with a camera. An edge detection and measurement program was written in Python to detect the height of the liquid in the filtration beaker. Using serial communication protocols, the Raspberry Pi communicates with an analog-to-digital converter and a digital-to-analog converter to monitor the pressure in the system via a sensor and adjust it with a proportional valve. The pressure is held at a low vacuum until the liquid reaches a certain height, at which point a higher vacuum is pulled to drain the remaining liquid, leaving an aligned CNT film on the membrane.