Objective: Build a tool to enable closer investigation of the process of freezing a cryogel sample
Outcome: A working programmable cryogenic recirculating bath for testing and data collection
Skills: Hardware design, Python, Raspberry Pi, heat transfer
While working at the Hixon Lab, some of my colleagues and I were baffled and frustrated by the seemingly random nature of supercooling. I designed and built a programmable recirculating bath, known affectionately as the ReFreezer, to monitor the formation of ice in a cryogel and investigate this phenomenon.
This machine uses a peristaltic pump, running in a PID loop according to temperature feedback from a probe in the insulated benchtop vessel, to circulate chilled propylene glycol through a copper loop in the benchtop vessel. The end result is liquid bath that can be cooled to any temperature down to -17C, and several more temperature probes for monitoring samples.
The whole machine was programmed in Python and runs on a Raspberry Pi, allowing for very convenient data collection and real-time visualization. It was instrumental to shedding light on the phenomenon of supercooling within a cryogel and how that affects ice crystal, and thus pore, structure.
Under construction
Initial testing
Draining the old refrigerant (it initially used ethanol)