Michela Meister's Summer Research Blog
I made more posts with settings #3 and #4 on cleaned and primed copper Radioscreen.
I cut and lined with copper tape some more sheets of cleaned and primed copper Radioscreen with which to make sensor posts.
I sandpapered and cleaned the sensor's circuit board.
I made a second set of molds with settings #3 and #4 on yellow SHIM stock. I also made a second batch of posts with these molds.
Cooked hamburgers and hot dogs for about 200 people at the MERL barbeque. I have never cooked such a large volume of food.
I tested the sensor with the #3 posts glued onto it. It was very sensitive and worked well. However, I had forgotten to sandpaper and clean the sensor's circuit board, so it was not very durable. This meant that it was also very easy to peel off the posts and the layer of RTV 162 in order to try again.
I removed the posts from their molds. The #3 posts worked well and were very uniform. I had no trouble with losing posts. The #4 posts did not work as well. They did not get pressed flat, so there was a slant to the mold.
I went on a very long CostCo run with Matt and Morgan to buy hamburgers, hot dogs, buns, and soda for about 200 people. It was my first time at CostCo, and it was overwhelming.
I sprayed thinned RTV 162 (4g RTV 162 : 12g Hexanes) onto the sensor's circuit board and glued on the #3 posts.
I removed the posts from their molds. The #3 posts did not work well, but the #4 posts did. John advised me to try spreading some Dragon Skin on the molds and then degassing them before pressing. So I molded some more #3 and #4 posts onto cleaned and primed copper Radioscreen using this method. I also cleaned and primed more sheets of copper Radioscreen for making more posts. I lined some with conducting tape.
I compared the bonding of standard and thickened Dragon Skin. There did not seem to be much of a difference in bonding strength. However, all the samples I tested had medium bonding strength. I think this was because I put too little primer on them.
I tested the adhesion of the posts glued to the PCB. They looked good but needed another day to cure.
I removed the sampler posts from their molds and examined them under a microscope. Settings #3 and #4 worked best with the Dragon Skin. The thickened Dragon Skin did not mold well.
Because the standard Dragon Skin molded well, I decided to see whether it bonds as well as the thickened Dragon Skin. So I spread standard and thickened Dragon Skin on cleaned and primed copper Radioscreen to test their bonding strengths.
I made larger molds using settings #3 and #4 on the laser cutter. I molded standard Dragon Skin to copper Radioscreen using these. I placed them in the press, because the molds were slightly warped.
I sprayed a PCB heavily with thinned RTV 162 (4g RTV 162: 12g Hexanes). I emptied nearly all 16g on the circuit board. Then I glued on of the sampler Dragon Skin post sets I made yesterday onto the curcuit board to test how well the posts adhere.
I cleaned and primed more Radioscreen sheets on which I will hopefully make the sensor's posts tomorrow.
I cut more sampler molds with many different sizes of holes on them. I molded standard and thickened Dragon Skin into these.
I organized a bunch of molds and post samples that I had from before so that I can reuse them easily now.
My plan for the sensor: I will mold standard Dragon Skin posts onto copper Radioscreen primed with PR-1200. Then I will glue the ends of the posts to the circuit board by spraying on thinned RTV 162.
I cleaned and primed strips on which to test how standard Dragon Skin bonds.
I did tensile testing on the standard Dragon Skin bone molds.
I created a plan and began working on making a sensor. I laser cut another mold with many different sizes of holes on it.
I did some tensile tests with the Tap Blue bones I made on 07/20/11.
I molded some standard (unthickened) Dragon Skin bones for comparison with the thickened ones.
I analyzed and organized data from my bonding and tensile tests in Excel.
I removed the second batch of (labeled) Dragon Skin bones. We were right about the FX-Pro. It is the stretchiest.
I molded Tap Blue bones (one thickened, one standard) to see how the thickener affects its stretching.
I analyzed my data from the RTV 162 "glue-on" tests.
I did more tensile testing with the new (labeled) Dragon Skin bone molds.
I continued testing whether Tap Blue and Dragon skin can be glued onto PCBs with RTV 162. I had not sanded the PCBs I used yesterday, which was a problem. John explained to me that the rough surface created by sandpapering helps with adhesion. With that knowledge I sandpapered and then cleaned more PCBs with Acetone & Methanol. I also laid down strips of Dragon Skin to cure so that I could glue them on, too. After the Dragon Skin was ready, I thinned some RTV 162 (1g RTV 162 : 3g Hexanes) and sprayed it onto some PCBs. I also painted RTV 162 onto some PCBs. I laid down cured Tap Blue and Dragon Skin nearly immediately after. I let all of the PCBs cure in the hood.
I removed the bone molds of Dragon Skin but lost my labels for them in the process. I poured another set of Dragon Skin molds into bones (Fast, Slow, FX-Pro) and made sure to label them securely.
John showed me how to do tensile tests and calculations with the unlabeled Dragon Skin molds. The fact that they were unlabeled actually was not much of a problem. The FX-Pro Dragon Skin has different properties from the Fast and Slow molds, which seem to only differ in cure time. The FX-Pro Dragon Skin stretched a lot more than the Fast or Slow Dragon Skin.
A note: I have been thickening all of my Dragon Skin. The thickener is .5% of the total mass.
I tested the strength of the Dragon Skin's bonds to copper and nickel Radioscreen. Dragon Skin Fast had the strongest bonding of the three types.
I poured the three types of Dragon Skin into bone molds. The cured pieces will be used for tensile testing.
Whatever silicone we end up using will need to be able to adhere to a printed circuit board. I poured strips of Tap Blue, and, when they cured, I glued them to PCBs with painted RTV 162 and thinned RTV 162 (1g RTV 162 : 3g Hexanes). The thinned RTV 162 was wiped on.
John and I tried gluing Dragon Skin to a PCB with RTV 162. I also got to try out John's pressure sensor.
I spread three types of Dragon Skin, Fast, Slow, and FX-Pro, on both copper and nickel Radioscreen for bonding tests.
I examined the second half of the strips from the adhesion tests. (The RTV had 2 days to cure on these before the Tap Blue was poured on.) After testing the bonds on each sample, I concluded that a thicker coat of RTV 162 is better for adhesion. For both the nickel and the copper Radioscreen the 4.7g RTV 162 : 12.5g Hexanes spray and painted RTV 162 worked best. Also, RTV 162 should be given two full days to cure well.
I spread Tap Blue on the strips from the second half of the RTV-162 adhesion tests.
John and I sprayed his pressure sensor with Tap Blue thinned with Hexanes. The ratio was 1g Tap Blue : 4g Hexanes. I did some test runs on brass to find the right speed and distance to spray with. I put down a very thin coat that I could not even see. Then we molded another set of posts onto a Radioscreen strip so that we have posts to repeat the spray with if the first one does not work.
I got to ride John's motorized skateboard!
I tested the bonding of the Tap Blue on the first half of the RTV 162 and RTV 108 strips. For both the copper and the nickel Radioscreen it is clear that a heavier coat of RTV 162 is better. The samples that were most successful were either painted with RTV 162 or sprayed with a mixture of 4.7g RTV 162 : 12.5g Hexanes. Some samples had not completely cured, and it was clear that both RTV 162 and RTV 108 need more time to cure.
I spread Tap Blue on half of the samples from the spray gun tests with RTV 162 and RTV 108. The RTV 162 is supposed to take two days to cure. I wanted to see how important the cure time was, so I decided to coat half with Tap Blue after one day and the other half after two.
I cleaned and primed copper and nickel Radioscreen for the Dragon Skin tests. I primed by them by spraying PR-1200 on them.
I completed the Solidworks candlestick tutorial, which uses revolves and sweeps.
I talked to John about adhering one of his pressure sensors to a sheet of Radioscreen with posts molded onto it. We decided to spray thinned Tap Blue onto the sensor but could not do it because of a class.
Following up on my work from yesterday, I began the spray gun tests with thinned RTV 162. I cut and cleaned many more strips of copper and nickel Radio Screen, which were then sprayed with one of the three mixtures below, painted with a coat of RTV 162 or RTV 108, or left bare for a control. There were either two or four samples each of copper and nickel Radio Screen for each combination.
4.7g 162 RTV/12.5g Hexanes mixture
2g RTV 162/12g Hexanes mixture
1g 162/10g Hexanes mixture
painted RTV 162
painted RTV 108
John gave me some Dragon Skin samples to test tomorrow. Dragon Skin is another brand of silicone and has some exciting applications. It is used on movie sets as make up for scars or masks.
I began another adhesion test. RTV 162 is a silicone adhesive paste that John has used to attach the silicone posts to the Radio Screen (copper or nickel mesh). However, he has only applied it by painting it on, which works but is not uniform. Spraying RTV 162 thinned with Hexanes through the spray gun might be more uniform, so I began testing RTV 162's adhesion when thinned. I cut and cleaned many strips of copper and nickel Radio Screen. Then I created mixtures by weight of RTV 162 and Hexanes. I painted these on the strips and then let the strips sit. Afterward I realized that it would be better to just test the ratios through the spray gun instead of finding the best ratio through painting and then testing that one with the spray gun.
I wrote the updates below from the past two weeks.
Update: Weeks 06/27/11-07/01/11 and 07/05/11-07/08/11
In the past two weeks I have focused on making molds on the laser cutter and doing silicone bonding tests. I spent nearly all the time I had between testing molds and bonding on SolidWorks tutorials. With SolidWorks I edited a leg piece and created another leg piece for Alexis's and Morgan's planes.
I tested the cured silicone on the copper mesh strips. I wrote up a report of both bonding tests which I will post here soon. SoldiWorks: Finished the hammer tutorial. The loft and flex features are super cool!
I tested the cured silicone on the mesh, brass, and fiberglass bonding tests. I also spread the standard silicone mixture on the primed copper mesh strips for the second round of bonding tests. Read "Coding and use of tactile signals from the fingertips in object manipulation tasks" (Johansson and Flanagan). Solidworks: Worked on the over rack, hinge, and hammer tutorials.
I tested the cured posts by trying to rip the silicone off the mesh, brass, or fiberglass it was attached to. This test was much more successful. The SHIM Stock materials worked best; some samples had hardly any posts missing. Sample #8 (pressed) also worked well. I also began a bonding test. I spread the standard silicone mixture across pieces of brass, fiberglass, and mesh, and let them cure overnight. The materials had been primed and washed differently (on 07/01), so I conducted the bonding test to find out which combination worked best. I also cleaned and primed strips of copper mesh for a second bonding test.
I molded the posts onto the primed materials using the standard silicone mixture (no thickener or thinner). I put the molds that had some warping in the press. I read the paper "Attenuation of Self-Generated Tactile Sensations is Predictive, Not Postdictive" (Bays, Flanagan, Wolpert). SolidWorks.
I tested the silicone posts. The silicone did not stick to the molds. I had not used a primer for this test and it showed. I cut 8 more molds on the laser cutter with which to repeat the process. John showed me how to use the spray gun. We primed many pieces of brass, fiberglass, and mesh to test. We used primers PR-1200 and 607. We let them sit over the long weekend.
I made posts from the most promising laser cut molds. For half of the post samples I used a thinned silicone, and in the other half I used a thickened silicone. I let them sit overnight.
I cut 14 different sample plastics on the laser cutter. I tried out different settings in order to find a combination that created circular holes that punched through the material. With some of the thicker plastics I tried calibrating the power in order to create holes that did not punch all the way through but instead have different depths. The SHIM Stock plastics worked best.