In this project, my team and I made replicates of the LUCIA cyst models using 3D printing and molding and casting techniques. LUCIA stands for Low-Cost Universal Cervical Cancer Instructional Apparatus, and this device is intended to be a training tool for various cervical health procedures.

First, we downloaded the SLDPRT files for each cyst model and the chamfered box that would be used to create the negative mold. Using Fusion360, each cervix was mated to a quadrant of the box to create the positive for molding (Figure 1). Each cervix model and the assembled box were downloaded as STL files for 3D printing.

Next, we 3D printed the 4 cervix models and the positive using the Bambu printers. In our first iteration, we set the layer height to 0.1 mm, but this led to visible layer lines near the rounded top of the cervix (Figure 2). For our next iteration, we used a layer height of 0.08 mm, the extra-fine setting, and this noticeably improved smoothness (Figure 3). We printed the 3D printed set and the positive separately, and they took 1 hour and 50 minutes and 4 hours and 9 minutes to print, respectively.

To create the silicone mold, we first had to calculate the volume of the assembled box to determine how much silicone we needed. To accomplish this, we poured water into the box and measured the amount of water needed to fill the mold nearly completely. Through this method, we determined the volume to be 248 mL.

Since the Parts A and B of the BJB Platinum Based Silicone had to be assembled in a 1:1 ratio by weight, we first measured the weight of 124 mL of Part A and then added that same weight of Part B into the same cup (Figure 4). While this did not yield exactly 248 mL, Part A and B’s densities were close enough to each other that we poured nearly 248 mL.

We sprayed a mold release all over the inside of the box to ensure easy removal of the mold after curing. After thoroughly mixing Parts A and B, we poured the silicone mixture into the positive. To minimize the formation of air bubbles, we slowly poured the silicone into a corner of the box (Figure 5). To remove any air bubbles that did form, we tapped the box on the table to bring the air bubbled to the surface. After 48 hours, we demolded using a screwdriver as a lever (Figure 6).

To create the polyurethane casts, we used Smooth-Cast 300. Since we estimated the volume of our cervix negatives to be about 60 mL, we created 80 mL of polyurethane, just in case. Because Parts A and B of the Smooth-Cast 300 need to be added in a 1:1 ratio by volume, we simply poured 40 mL of Part A into 1 cup and 40 mL of Part B into another and combined (Figure 7).

Since the polyurethane mix only had a pot life of 3 minutes, we had to move quickly to combine and pour. We stirred the mixture for roughly 1 minute and 20 seconds and then used the remainder of time to pour it into the mold. After 15 minutes, we were able to remove the casts from the mold (Figure 8).

We decided to redo models 1C and 1D due to imperfections in the lettering, but this yielded similar results. We deduced that the imperfection stemmed from small bubbles that formed in the mold, not from pouring the polyurethane cast.

Lastly, we post-processed our replicas. First, we leveled the bottoms of the polyurethane casts using a lower-grit sandpaper and smoothed out the tops and sides of the 3D printed and polyurethane models using a higher-grit sandpaper (Figure 9).

We first spray painted our models using a combination of pink and red spray paint sprayed into a cup and applied with a brush. However, white spots appeared while drying, so we decided to paint over the spray paint with acrylic paint instead. The models were painted using pink, red, and white acrylic paint to match the reference provided in the project description (Figure 10). After the acrylic paint dried, we spray painted it with a clear gloss to protect the models and improve the finish (Figure 11).

Midterm BIOE 555 Cost Analysis