Hardwares

Implementation Challenges

Combining the doctor suggestions and manufacturing experts advice, we are facing the following development challenge to address.

1) Control the sampling quantity of the menstrual blood when the flow quantity changes over time

2) Understand the influence of color and viscosity of artificial menstrual blood through layers of sanitary pad materials

Our proposal to solve the problems converges on the development of a small hardware including three major parts.

  1. Silicone Panel: This panel has a whole with certain depth to collect blood sample on one end, and a channel from the whole to guide menstrual fluid efficiently onto the test strip and to serve as a holder for the test strip, keeping it in place.
  2. Test Strip: The test strip works similar to COVID-19 antigen tests; it uses the lateral flow immunoassay mechanism where a line with specific scFv antibodies will be lined up and if the biomarker is detected in high abundance, the test strip would reflect this visually providing the user with a straightforward and immediate result.
  3. PVP Membrane: We designed a bottom for the whole with PVP film membrane, a water-soluble membrane that would dissolve after a few minutes exposure to liquid, such as water or blood. When dissolved, blood is no longer collected and thus ensure the test trip is not flooded with blood that would affect the reading of the result.

Silicone Panel for Blood Sample Collection

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The illustration explains the basic ideas behind the overall product design. The sample collection and read-out hardware will be installed under the blood absorption layer in the sanitary pads, to exclude the debris of dead cells and other organisms.

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We can adjust the depth and the area of the whole, and also the thickness of the PVP membrane, so that we can control the amount of blood to collect before the membrane is totally dissolved. Before it dissolves, we need to make sure the blood reach the upper level so that the blood sample will be drawn onto the test strip. After that, no blood will be drawn to the test strip.

We plan to create a 3D-printed mold, followed by injecting liquid silicone into the mold. After curing, the process will form the upper component with precise dimensions while ensuring the product remains soft and elastic, without affecting its usability.

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The figures illustrated the original solid works 3D model design (you can download the original files on our Hardware page), and as-printed model (middle figure), and the silicone panel model.

Fabricating PVP Film for Blood Sample Control

We fabricated a simple PVP membrane film.

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Depending on the thickness we prepare the film in the petri dish, and also the concentration of the PVP solution (10% and 15%), we can vary the time before the film dissolves around 2-3 minutes. See the following video.

https://video.igem.org/w/sPUbAEKKieAaPGiBN5jnSv

Making the Simulated Menstrual Blood from Literature

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We fabricated artificial menstrual blood based on the reference protocol. We tested an assortment of sanitary pad products. The effects and colors of the artificial blood and based on team member’s experience, the color and viscosity closely resemble the real-life materials.

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We sandwiched a sample test strip in the pad and soaked the pad with a typical amount of fluid. The results showed that the test strip can successfully draw the fluid, and also, very importantly, the color of the blood do not interfere with the color of reading the test lines.

User Assessments: Need for a thinner installation

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In previous test, we used a simpler option 2 design for installation. However, in the test we found the fluid has a chance of leakage through the bottom of the whole for sample collection. We changed our installation design to option 1.

We asked a few members to assess whether the silicone panel design is too thick. According to safety considerations, we did not ask any people to test the product in daily use, but we simply asked them to feel the thickness of the product with their hands and make suggestions based on experience. According to the feedback, we made a thinner version of the silicon panel.

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This figure shows the thinner silicone 3D mold, and the silicon panel. The middle figures show the interior of how the panel and the test paper is sandwiched between sanitary layers. The rightmost figures shows the overall thickness is a bit over 2 mm, which should not lead to any discernible discomfort according to hand-feeling tests.