Why design?

When we came up with the idea of having two different types of bacteria work together to break down dihydrotestosterone (DHT), we were faced with a serious challenge. We suspected that consumers would be discouraged by a product requiring the application of two different types of bacteria and,in addition, we were hesitant about the safety repercussions. While our project involved using genetically engineered bacteria for two purposes, and therefore two types of bacteria, we wanted to find a way to prevent the Escherichia coli from reaching the consumer's scalp, in order to increase the chances of the Bacillus subtilis's survival, and to minimize side effects that may occur with the use of such a product.

The solution was found through consulting with multiple academics and an industrial engineer. After the final prototype was printed, we conducted a focus group survey about the comfort and efficiency of using the comb.

The Brainstorming Process

Once we set out to search for a solution for combining the components of our project, we quickly came to consider the idea of a comb. After much consultation with academics, an industrial engineer, and friends, we designed a comb composed of a comb body with inside tubes/liquid pathways, a handle, and a syringe.

The Comb Prototypes

The comb was designed in "solidwork" and was print in a 3D printer.

As explained in the slideshow above, prototype #3 took into consideration the flow geometry required for uniform distribution of liquids exiting the comb. To obtain even flow for each tube and each comb tooth, we used a specially designed tube geometry. From the syringe entry at the top of the comb, each tube splits into two tubes, periodically, resulting 16 parallel, even-flow tubes at the comb fluid exit to the scalp. We used fluid mechanics equations with different tube sizes (different widths, lengths, and shapes) until we converged to our current ideal dimensions. The equations we used are presented in Figure 1 below.

The mini-tubes within each comb tooth enable uniform distribution of the treatment formula to the scalp while massaging it, removing excessive fat and other substances that may block the hair follicle from the treatment, preventing its efficiency.

The Syringe

The comb, on its own, is not customized enough to fit our purposes. Therefore, we needed to consider how exactly our formula would be incorporated into the comb. At first we considered using two small containers which would be opened by the consumer and placed in the comb. However, after putting some thought into it, we realized that this strategy could be messy and inconvenient. It also left us with a product requiring two different types of genetically modified bacteria being placed on the head. Therefore, we developed the idea of using a syringe.

The syringe above is a model of our syringe design.

• The E. coli overproducing NADPH is represented by the red section. It will be present in the syringe at the time the consumer purchases it.
• The blue section represents the B. subtilis secreting the 3α-HSD. The B. subtilis will be sucked into the syringe from a container also purchased by the consumer.
• In between the sections is a filter membrane- small enough to allow the NADPH to pass through, while preventing the E. coli from passing through and reaching the user's scalp. As the piston is pressed during use, the NADPH will pass through the membrane and into the B. subtilis containing solution. In other words, while pushing down the piston, the NADPH mixes with the enzyme, making the process more efficient.

This mixture will reach the scalp of the user, creating an environment which contains enough NADPH for the 3α-HSD enzyme to work efficiently to break down the DHT in the hair follicles.

The movie below simulates the structure of the comb.

Checking real-life conditions

Our final dimensions suit the viscosity we chose to work with. For testing out the come, we created a solution with the proper viscosity, composing of 80% glycerol and 20% LB. In order to check if this solution would allow our bacteria to live, we did a “shelf-life” experiment. In that experiment, we also checked the conditions in which our bacteria could exist inside the syringe and containers, respectively. We found out that the most suitable temperature is at -20^oC (same temperature in home freezer). Check out our protocols to see how we did the experiment. Click here to see the full results.

Focus Group Survey

Consumer feedback and comfort of use was one of our main concerns when developing the comb and syringe. Once the final prototype of the comb was printed, we developed a focus group survey. The 15 respondents including balding and bald men. Their responses to our questions are featured below.

Conclusion

After much though and effort, the final comb apparatus presented for the competition was the result.

The comb provides clear and defined benefits compared to a topical mixture applied with the hands or gloves:

1. Cleanliness- The comb and syringe combination allows the consumer to apply the product, whilst never having to touch the bacteria.
2. Reusable-The reusable comb can be sterilized with ethanol between uses, while the syringe can be sterilized with ethanol as well and then discarded. The result is a relatively environmentally friendly product.
3. Uniform application-The comb apparaturs, along with the syringe, offers an integrative solution to combining the components of our formula, while allowing for comfortable and uniform application on the scalp of the consumer. This helps ensure that each hair follicle is reached, making our product as effective as possible.
4. Efficient-The scalp is covered by a thin, oily layer of fatty deposits, as well as dead skin cells, which must be penetrated in order to reach the hair follicle. Our comb offers a gentle way to overcome this layer, hopefully leading to better penetration of the 3α-HSD protein into the hair follicle. Additionally, stimulation of the scalp has been found to increase blood flow to the area, helping encourage hair growth and hair follicle restoration. The comb teeth can provide this stimulation.