Tuesday, August 20, 2013

Gettin' It Done!

Those of you that follow me on the many social media outlets we have these days will find this post a bit bland, having seen all the photos and videos already :). For the rest of you that know better than to follow my random rants on the internets, this is the post for you!

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.

Saturday, August 17, 2013

Short Pause for the Short Course

So experimentation and overall work has been on hold since the last post (though I was able to cure some hydrogel! Pics at the end). In addition to having lab access and crazy tools, the fellows of AMRI also get the opportunity to participate in a short course on the Advances of Tissue Engineering. This is a chance to see all the cutting edge research and development going on in the ever changing field of tissue engineering/regenerative medicine in the bioengineering field. It's really something to see the many names you see listed on the papers you have read in person. 

For me this has been a great opportunity to immerse myself in all things related to tissue engineering/regenerative medicine. It's been about 7 years since I last took a biology class or a chemistry class. All I can say is thank god for wikipedia, I'd be absolutely lost without doing a bazillion searches through all the presentations. While most topics were over my head, getting an in depth overview helps to really contextualize things. 

Polymerizing hydrogels is not a new concept at all, it's been done by many researchers. What I think Open3DLP can offer is a much more affordable/adaptable platform for more research to happen. Looking over the basic schematics on different labs setup is really an eye opener. The costs of some of the setups are outrageous, makes me realize why its so inaccessible for most people. 

It cured! Cross-linking success!
Ultimately, how I'm bridging the vast abyss of my knowledge of polymerizing plastic to polymerizing hydrogels is to frame it as just another kind of resin. It is just that, hydrogel is just another kind of resin that can be applied to a DLP 3D printer. Just a different end product reacting with another kind of photo photoinitiator. Simple!

Having a little fun with the new label maker.

Short course ends today and I should get back to the usual grind.

Monday, August 12, 2013

First experiment

Experiments, experiments, experiments. It's part of the reason for participating in AMRI. So what I've decided to capture data on first is power output of the DLP projector I'm using. In this particular case, I'm using the same projectors as the B9, a Vivitek D535.

For capturing the power output, I have access to a power meter and sensor by Coherent. A FieldMaxII meter and a PM150-50C sensor. Couple of points of interest in experimentation is overall power output of the projector, the drop off in power due to to distance from light source and power density per cm^2. 


The first point of interest will be useful when I start testing other projector setups, it'll help form the baseline marker for the various other projectors folks would like to use in a DLP 3D printer. The values gathered will also be good to gauge what power levels are adequate for overall reasonable layer/print times. At the moment, in talking with others working on DLP's in the community, the most important aspect folks look for is lumens (followed by native resolution), most are recommending builders work with at least 2,500 lumens. It'll be nice to see the effect of lumens on power output.

Tested Red projection
Tested Black projection
Tested White projection
One of the question I see being asked a lot is how scalable a DLP 3D printer can be. One would think that pulling back the projector and enlarging to projection area would be all that's needed. Sadly, that's not the case at all, and the reason it'll be interesting to see the power output over various throw distances and size prints. There are a lot of hypothesis and ideas, but it'd be nice to get quantitative values to back things up.

Lastly, power density is interesting to me because it'll allow for us to fine tune our exposure times. The thought is that if we can find the power output over an area, we can use that data to help extrapolate cure times for a specific layer height. On the point of cure times, polymerization rate will also be a future experiment.

Experiments like this is what AMRI is all about, applying the scientific method to create quantitative data for the betterment of research and development. The hope is that having empirical data to back up a lot of things that are taken at just face value will help people make advancements and not stumble over the same problems as others have before them. It's all about anchoring a foundation for which contributors can build upon prior research quickly and adapt results for new ideas.

Friday, August 9, 2013

AMRI and then some...

So I've been pretty busy to say the least, and I apologize for not updating with more content.

I was invited to join the MAKE mag team for this years 3DP Shootout special (should be on news stands in November) and it was a great experience. Lots of great printers and lots of great "printerers" :). That's all I'll say on it as well! Just really glad I got to be involved and a thanks goes out to all that made it possible.

The 3DP Shootout Crew
Spent a couple of days out in San Francisco, CA area and now I'm currently melting in hot and humid Houston. So Houston, I'm currently one of 3 fellows at Rice University for the Advanced Manufacturing Research Institute (AMRI). Linked is Jordan Miller's, he's the awesome mind behind it all, post on the RepRap blog. Check it out and get involved!

I'm here to not only continue development on the DLP 3D printer this blog is built upon, but to also research and develop the same technology for other purposes (related to Jordan's work and tissue engineering) and gather data from various experiments. So other purposes? I did not bring the same DLP as I was building at work with me, so I've got to build a new one while I'm here. Everything is on order and enroute, that's just phase one. After building it out and getting back to where I am back home in the lab, it'll be time to apply some science! I can't do Jordan's work any good by trying to explain it myself, I'll let him post more about that on the AMRI site, but I can elaborate on the experiments and data I hope to collect.

The Gameplan

DLP printers are not something entirely brand new, folks have been working on this for years now. In my recent time with working on DLP printers, there's a lot of questions I've come across and thanks to AMRI, I'll have a chance to maybe answer some of them. Let's start with the peel/tilt/slide mechanism. Curious to find out how much force is needed to separate the recent print from the vat surface? I plan on measuring just that! What about the effects of dyes/pigments on cure times? How about I measure the rate of polymerization between uncolored and colored resin? Done and done! That's just a few things I'm hoping to look into. It'll all depend on time. My main interests lies within various surface coatings.

Aluminum plates for small actuators

Aluminum plates for large actuators 
Sylgard 184 (not all for me thankfully!)

Optically clear FEP tape
Any other thoughts on what I should look into? Now's your chance to ask...so ask! I'm here until at least the 26th of August. Machine should be built out again sometime next week.

Until next time, remember to keep your goggles on!