Sand, at a glance…

Two weeks ago, we tuned into our bacteria cultures to observe what was happening. Upon looking at the few we had begun using, s. Pasturii was the bacteria strain that was yielding the most promising calcification. Looking in on the s. Pasturii samples a week later, in both the Jove and Malta media, we can see that the bacteria seem to be splitting even after being incased in calcium – which creates the barbell shapes present.

The s. Pasturii in the Jove media seems to be thriving the most post precipitate and yielding an average size of precipitate ranging from 10 micrometers to 33 micrometers.

Looking at the sand, we are looking not only at particle size but also the size of gapping between sand when lightly packed. the four sands that we tested were pool filter sand, play sand, coarse sand, and black sand from a sand blaster.

Pool Filter Sand

Play Sand

Coarse Sand

Black Sand 

After lightly packing the sand under a slide cover we attempted to observe the gap sizes, so that once we introduce the bacteria to the sand, we know that the gap sizes are roughly as big as the gaps in sand particles.

Pool Filter Sand (approx. 42um – 300um)

Play Sand (approx. 80um – 250um) 

Coarse Sand (approx. 4um – 350um)

*grain sizes are much larger and inconsistent compared to the play sand

Black Sand – Photo not possible 

Looking at the different sands in comparison, the pool filter sand seems to have particles that are much more rounded with smooth surfaces, the play and coarse sand are similar but the coarse sand might be a bit too inconsistent on its own without being sifted, were the play sand is on the smaller side of inconsistency and it seems like the really really small particles present may aid us in getting a solid calcified chunk of material.

The next week…

We decided to look a little closer at two other precipitations, one done without heat or stirring*, and then a sample from using Whiffin media – in effort to find samples closer to our sand gap size.

Slow Precipitate

*this info may have to be adjusted after double checking the label in the lab

Whiffin Media

 – The first sample in this section yielded results similar to the other examples of precipitate, but the Whiffin sample (while still having a fairly small grain size) presents a better ability to clump after precipitation giving us larger grains closer to the sizes of our sand gaps.

DLP Tests: smallest positive features

BUGSS Lab Notes – 8/1/16

Analysis of Prints from the Previous Lab Session:

150µm post with 100µm layer height 10 sec/layer

Our tests on 7/20/16 showed that increasing print time enabled us to print smaller posts. Increasing print time to 10 sec/layer  allowed us to print posts down to 150µm x 150µm in the x&y.  Looking at these prints under the microscope to determine the accuracy of the print dimension revealed that this feature size is effected considerably by the scalloping effect common to photopolymer based printing.   A 150µm wide feature printed with a 100µm layer height created a print with a 26% variation in width within a single layer. We determined that the simplest way to address this would be to half our layer height to 50µm.

New Test Prints:

2016-08-02_SC_postsWithLablesWe also expanded our test stamp to include 18 posts, ranging from 60µm to 400µm. Printing the posts at 6 sec/layer yielded a 160µm post as the smallest feature. However, the 180µm post did not print, suggesting that the light is may still not be perfectly even. This theory seemed to be confirmed by rotating the print 180 degrees and reprinting and by printing a field of 180µm posts.

These tests need to be repeated and tried with lateral shifts to the print (in software) to confirm that the issue is not due to where the features fall in relation to the pixels. Also several posts in the top row seemed to print fine but were pushed over at some point.

We will examine these prints under the microscope in hopes of determining:

  1. Did the change of layer height decrease the impact of scalloping?
  2. How does increased exposure time effect the accuracy of the size in x&y?
  3. Are the post from the single-size test all the same size?

Next Steps:

The results of this examination will guide the next test prints. Modifications to the digital mask used to even out inconsistencies in the projector may need to be adjusted. After any such errors are corrected, we plan to run a series of tests at different exposure times. This will help us to more fully determine the range of printable sizes, and optimum exposure times for each size feature. The goal is to be able to plot this data on a curve and then add a new capability to the DLP tools in Xylinus – detecting small features and adjusting the exposure time of those particular areas.






















BUGSS first post

We are excited to begin sharing our work. We will use posts as open lab notes. As such, the information found in our posts will typically be contingent and incomplete. This is a trade-off for getting the latest information that is relatively real-time and unfiltered.