Senior Capstone PRoject

HIV Implant Manufacturing

Prof. Ping Guo, Northwestern University

Read the full design report here.
View our final presentation.

Problem and Mission statment

HIV (Human Immunodeficiency Virus) is a virus that attacks the body’s immune system, making a person more susceptible to other diseases and infections. HIV can be transmitted through contact with certain bodily fluids of an infected person. There is currently no effective cure for HIV. If left untreated, HIV can eventually lead to AIDS (Acquired Immunodeficiency Syndrome). A person who has contracted AIDS usually survives for only about three years. However, a strict adherence to an HIV treatment regimen ― a combination of HIV medicines that aims to slow the progression of the virus ― can give people with HIV the opportunity to live longer and healthier lives. 

Our clients, Professor Ping Guo and Professor Kornel Ehmann, have been working with a drug company to create a methodology of manufacturing drug implants that have the potential to treat HIV. We have been asked to design and create an automated process for the assembly of the implants, as shown in Figure 1. 

Figure 1: Cab Gen 2 HIV Implant

These implants are designed to be inserted into a patient’s arm. The drug pellets inside the implant will then dispense medication through the tubing and into the user over time. 

The implant consists of four drug pellets inserted into a proprietary plastic tube, sealed with two TPU plugs placed on both ends of the tube. Following insertion, the TPU plugs are then melted with the plastic tubing into sealed, hemispherical ends. Currently, these implants are being hand-assembled. The client would like to produce one fully assembled implant in under five seconds. However, such a rate is not possible with hand assembly methods. The current process of how the implants are assembled is illustrated below in Figure 2, with the steps listed out under the figure.

Figure 2: Current Assembly Process

Assembly Steps:

1. A mandrel and then a TPU plug is inserted into one end of the tube

2. The end with the TPU tube is placed into a sealer that uses thermal heat to melt the TPU and tubing together into a spherical end, and then cool the formed end back to room temperature

3. The mandrel is removed and four drug pellets are inserted

4. A second TPU plug is inserted into the open end of the tube

5. Step 2 is repeated to seal the second end of the implant

6. Steps 1 through 5 are repeated for each unit produced

Our project is to automate the assembly of an HIV drug implant so that the process efficiently and reliably encloses four drug pellets and two TPU sealing plugs inside plastic tubing and seals the implants with smooth edges.

Work and Outcome

Throughout the course of two quarters, the team successfully built an automated system that filled 5 tubes with 4 medicated pellets and two TPU plugs. We determined that sealing the ends of the implants was beyond the scope of the project, since there was an already existing solution for this phase of the project.

Our solution incorporated 3 stations. The first station deposited tubes into our carriage mechanism to be driven through the rest of the process. 5 tubes are deposited as the carriage moves under the hopper. From there, the tubes pass into the filling station, where a lid is clamped over the tubes and pellets are pushed in from either side. Once filling has been completed, tubes are moved under the “tube scooper” for removal from the carriage and deposited into a container below.

This project took many, many rounds of design, prototyping and iteration to arrive at this final stage. I could (and have) write 100 pages on how we arrived at the solution, which you can read.

In our team, I was responsible for the design and implementation of the insertion mechanism for the drug pellets and TPU. Utilizing CAD and prototyping, I developed the 5 piston system that actuated linearly along the 80-20 track. This mechanism allowed for gentle insertion to not damage the pellets, but was repeatable and reliable for inserting pellets. Pellets would drop from the container into a channel, and then stepper motors actuate the piston to push the items into the tubes.

While this system worked, it could use improvement by making it more rigid. Occasionally the pistons would jam, resulting in incomplete insertion or broken pellets. This could be solved with further development, but was unfortunately not something we had time for.

I was also responsible for most manufacturing on the project, including most aluminum machining and 3D printing. CAD work was shared, as was technical report writing, which I also contributed to.

TEam Feedback

Feedback from my team:

“Sofia you did such an amazing job this quarter driving the project and making everything happen. You are super on top of everything and I really enjoyed being on your team. Sofia you are so amazing both as a person and as a team member. You took on so much responsibility throughout this project and it’s so great being able to work with you and learn from you! It was great seeing you so excited for the final prototype.

Sofia has been such a great team member. She is honest, very hard working and optimistic. Talking to her and seeking feedback for work done on the project is very easy. She also does a very good job at keeping the team focused and on track.

Sofia, I truly think you were the glue that held this team together. More than anyone else on our team, you were an active participant in all the prototyping and document deliverables. You also always made sure you got everything done ahead of time.

Sofia is a manufacturing goddess and design hero, all while somehow being just an all around lovely person to work with. She kept us on track and focused, was always the last one to leave the meetings, and was willing to help any member either with their project directly or learn new skills. We would not have been the same team without her.

I wish that every team had a Sofia on it. The world would be a better place for that. “