Running an acrylic to full conversion using photocuring is going to be rough. You'll be stuck with 1% residual most of the time.
Another option would be to make the dlp 3d print, extract and then e-beam, or gamma to push the cure further. This would just make the scaffold as all living things would be killed by the ebeam or gamma (it would sterilize it too). Gamma or Ebeam will also crosslink most acrylic polymers to form tighter networks. You could potentially leave your network under cured (lower exposure and lower di-functional content) and flexible so the extraction of the monomers is easy.
What materials are you going to try? PEG acrylates and Diacrylates, Hydroxyethylmethacrylate, glycerol methacrylate, N,N-dimethylacrylamide, Silicone modified glycerol methacrylates would be interesting to investigate.
Statistics: Posted by Pie — Fri Aug 22, 2014 10:29 pm
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In terms of phototoxicity, I've seen data suggesting that the initiators that rely on 365-405 photoinitiation are often less cytotoxic than those in the visible spectrum, although the excitation wavelength itself isn't so friendly. It seems like UV photoinitiators are good for cases where you are patterning something without cells in it, and where you can subsequently elute out any unreacted PI. Has that been your experience?
Bone scaffolds are pretty cool! Are you planning on working with them? Once upon a time, I did UV laser machining of titanium for bone. Now that was a 3D fab system--blast metal with a high energy UV laser
.Statistics: Posted by raptordan — Fri Aug 22, 2014 4:17 pm
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I printed for a postgrad student at a medical university but I don't think he has published his research yet. If you're interested, I can ask him if he can email you about his research. This is something I'm also very interested in and hope to be able to spend more time playing with in the future. I'm especially interested in printing bone implants with trabecular structures as this technology seems perfect for printing the complex structures that can enable osseointegration.
Raptordon,
I can't view your image. I'm not sure if that's a problem with my browser or the upload.
100 x 100 microns isn't too hard with this technology so give it a try. Even just a simple lens mod and/or close up filter will get you below 25 microns on the xy and the PEG-based acrylics are nice to work with. Good cytocompatibility and they crosslink quickly. I haven't tried it yet but research suggests riboflavin is the way to go for eliminating the toxicity of the PI.
Keep us updated on your progress, I love this stuff
Statistics: Posted by Liquid Garden — Fri Aug 22, 2014 5:45 am
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Brief background--I'm at Stanford/Berkeley as a post-doc. I've done a lot of different kinds of biofab and tissue engineering in the past, and now I'm getting excited about the high throughput that DLP methods seem to offer. I'd use 2 photon if I had cheap access to a 2P system, but I don't. It's also pretty slow, and at >$50/hr, not so good for prototyping. Congrats on the new job, Anderson! I enjoyed your AMRI blogging.
I was a bit over eager with the resolution specs--I'd be fine starting out with the ability to make 100 um x 100 um x 15-50 um thick blocks, as shown in the attached picture. I made those using traditional photolithography with a physical photomask. It's nice when it works, but it's expensive, tedious, and limited for some of the work I eventually want to do. In the short-term, 2.5 D patterning is actually fine--I just need extruded structures rather than true 3D printing. I'm planning on using very tightly controlled thickness resin layers of about 15 um thick, and then I just need to start by making some blocks. Do you guys think that it makes more sense to use a pico for this sort of application than a big gun projector? PacManFan, I'm glad to hear that your pico system is working! Dangre, thanks for the link. It's nice that people share their lamp characterizations!
I'm still exploring different material options, some of which come directly from traditional photolithography, like SU-8 (365 nm cure), and others being things like PEG-based hydrogels with various 'enone photoinitiators. I guess it helps to have easy access to academic chemical suppliers
. Liquid-Garden--riboflavin is a neat idea, but I haven't looked into it yet. Maybe I should...In terms of the resolution, I was excited by several papers I've come across where quite high resolutions are obtained using basic DLP set-ups. See and from Tingrui Pan's group at UC Davis. I particularly like the photoresist film they use. It's a great way to get controllable and repeatable layer thickness for thin builds. It's hard to get a hold of some, but I'm working on that. A more friendly (no pay-wall) source is this video from a great paper from Sunghoon Kwon's lab in Korea: . Hydrogel patterning is accomplished using a custom-designed DLP system based on the TI Dev Kit and some optics. I'm an academic, so I take access to these papers for granted, but let me know if anyone is curious and I can provide a lot more information. For my part, I've got some some very nice XY/Z CNC stages (~1 um precision) scavenged from an old sequencing machine via ebay (~$1.5k), so I'm not too bothered by the small build footprint since I can use the stages to take XY steps around to make arrays.
Edit: Changed figure to JPG
Statistics: Posted by raptordan — Fri Aug 22, 2014 3:38 am
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Statistics: Posted by dangre — Thu Aug 21, 2014 6:01 pm
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I've poked around on the forum for a while, but I haven't seen too much geared towards what I'm trying to do, so I thought I'd ask here.
I'm a bioengineer looking into using DLP for both 2.5D and 3D patterning of biopolymers at resolutions down to about 5-10 um. I'm basically building toys for cells and scaffolds to shape tissue growth. I'm looking to start with off the shelf projectors, and eventually move to the TI DLP dev. kit if I need more control. The work is definitely doable with DLP, and there are a number of nice papers where simple DLP set-ups can hit this resolution target. There are even cases where fancier DLP systems (but still no lasers) have hit 0.6 um resolutions! While these papers are nice, they aren't so great at conveying the practical ins-and-outs of their methods, and this community seems like a much better, more collaborative environment for getting advice! Many of these papers are at least a few years old now as well, so I thought I'd get some advice from people on the front lines.
Here are some questions:
1. I can blend most of the polymers I want to use with 365 nm photoinitiators, so the 365-400 nm UV band is important for me and I'm having a hard time finding reliable spectra for commercial DLP projectors. I've seen really good things about the Acer H6510BD that make me assume it already has reasonable, native UV transmission. Does anyone here have more specific data on the emission spectra of the UHP lamps used in many DLPs? I'm also considering LED sources, but they tend to be much lower power and I'm not sure how well those will jive with my photoinitiators. Thoughts?
2. My understanding is that the resolution I want requires that I reduce the build-footprint to accommodate it. I need to 'demagnify' the image output from the projector, I think. I'm looking into different methods of doing this, including placing an f/1.8 50 mm lens in front of the projector lens (decent demag) and removing the projector optics altogether and replacing them with a tube lens and 5X microscope objective. The latter arrangement should hit a theoretical resolution limit of < 2.5 um. Does anyone have advice on good methods of demagnifying, or alternative approaches?
I'll stop here for now, and thanks very much for your time and help!
Toodles,
D
Statistics: Posted by raptordan — Thu Aug 21, 2014 5:23 pm
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