So the short course is over, my mind is melted and I probably know more about tissue engineering/regenerative medicine than I ever should (it's not a bad thing!). I've been back in the lab and back at getting the DLP fully constructed (still not 100%, I'm on the Z axis stuff though...last pieces). On top of building things, I started to put together all the other components of my project, like more testing and test models.
Testing, I've been getting trained on a photo rheometer. What's this thing? It's a device that can help determine the polymerization rate of the hydrogel or resin. How does it do this? A small sample of your hydrogel/resin is compressed and spun, while its spinning, a UV light source is introduced to cure your material. Essentially as it cures from the exposure, the friction that is generated between the rotating surface is captured. From there one could extrapolate the time it takes for a liquid to go gel (solid). That's putting it REALLY, REALLY simple. I think I'd just butcher things if I tried to explain it in depth, I've only spent four hours with the machine after all.
The photo rheometer had some issues with the data captured so I wasn't able to get all the data I wanted. It was still a great learning experience to play with such a tool. After all the hydrogels are done, I plan on sampling all the different resins we can get on the market at the moment. From there, the hope is to dial in the light source and get some really precise cure times. On the photo rheometer, I can control the power output of the UV light. From there I can determine specific layer heights by controlling the gap when the liquid is compressed/squished. Put all that together with the right testing method and we should have really awesome cure times with some nice charts and data.
So I have also been curing gels outside of the photo rheometer, but sadly still stuck in 2D land until I get the Z axis going. But it's still exciting! I started out with basic texts just to get a feel for what kind of form I'd be getting, the plan was to then move onto other forms to test other attributes, like fine details and dense areas. First thing I polymerized was the "AMRI" text...and it looked bad ass!
The one thing to take away from this test is how it did on sharp corners. There is some very clear definition achieved. Texts polymerized nice and crisp, and thats with a really thick layer height of about 1mm. The layer heights we'll be working with with be sub-100 microns. So to get such a level of definition with a larger layer height is very promising for when we go smaller layers.
The "AMRI" text was a good test, but it's a very simple geometry. We need something more complicated, something similar to what the end purpose is like. Luckily we had a image of some art work for Jordan's lab (the lab I'm working out of), and on that there is an image of a tree with really dense packing of branches and voids (kind of like vasculature!). One thing you can also notice is the grey scale on the tree. That'll be an interesting thing to look at to see if that has any effect. Which leads me to something I forgot to mention. The hydrogel we are using has a photo initiator that reacts with white light (514 nm) and not the normal UV light (325 nm to 420 nm) we use with the typical resins.
So how did it work out. It worked out absolutely amazing! The dense branches had very clear gaps and spacing. We were able to get really small feature sizes in close proximities. It's really exciting!
I plan on getting the Z axis up today, and have some interesting structure to try out. I think I'm going to try the vasculature torture test Jordan had created for last years World MakerFaire at some point to, since that's a geometry we'd be interested in creating in the end.
