BME100 s2017:Group1 W1030AM L2

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Sole Searchers

Amber Nicole Mani
Amber Nicole Mani
Symone Griffith
Symone Griffith
Haylee Holland
Haylee Holland
Jazmine John
Jazmine John
Tarun Suresh
William Sweeten
William Sweeten


Device Image and Description

File:BME 100 first prot all pic.docx

Click the link and click to open and view the large document with detailed pictures

Our prototype is a wedge with a rounded back with springs which fit inside. This simple design can be 3d printed to fit the vast majority of shoe sizes so Americans suffering from chronic knee pain can reduce stress from the impact pressure of routine walking and running. The wedge will attach underneath a person's shoe which will be able to absorb some of the impact while walking.

Technical and Clinical Feasibility

Technical Feasibility
Technologies Needed: The technologies needed for our design would involves 3D printing as well as spot welding. The heel of our device would be 3D printed plastic and the springs implemented would be spot welted. In order to keep the device together, we are going to utilize LocTite glue as it is the world’s #1 brand in engineering adhesives and sealants. The other items would be purchased rather than manufactured, such as the rubber gripping soles used to attach the device to the shoe, the elastic attaching straps, and something similar to a work boot sole for the bottom of the device.

Challenges and What Could Go Wrong: One major challenge that we are facing with the device is making sure that all the parts move in a fluid manner. There are a lot of pieces incorporated into our device and an important goal for our team is to make them move in a way that does not reveal these pieces. We want to make the device aesthetically appealing as well, so we are struggling with how to make it not only function properly, but be versatile enough in appearance to go with multiple shoe types and styles. Another challenge is finding a durable and reliable material to attach the device to the shoe without damaging it. As of now we are considering a rubber material, rather than something that pierces the shoe. A major thing that could go wrong would be the shoes durability during extreme weather conditions. In potentially using the gripping soles to attach the device to the shoe, weather, specifically rain, could cause the shoes to fall apart as the liquid would weaken the gripping of the soles to the shoe. This problem could be potentially dangerous and a major setback in our design as it would keep the people using our device from going out during a storm or even walking somewhere with a wet surface.

Clinical Feasibility
Will it Work in Clinic? Under the Z-Coil study, the researchers at Sandia National Laboratories studied the gait of 6 subjects. Most participants for the Z-Coil study have shown to have a significant decrease in acceleration over the trial (5 out 6) compared a competitor. There is a bright outlook. Springs lower the impact and force on the floor (absorbs shock), and over time, the acceleration decreases. This is because the weight of the person is no longer a major factor in impact. Accelerations decreased on average by 13% while walking, and 17% while running. In 2008, another study was done with New Mexico Highlands University. They used 19 participants. The results were that “ the whole foot averaged a 13% reduction, with a 16% reduction at the heel, 14% at the midfoot, and 0.05% in the forefoot.”

What are the Clinical Risks? Heavy weights and uneven distribution to the springs can cause more stress to a person’s joints, and misalign their backs even more. These risks are limited, however, for the most part, they are functional and beneficial.

Have Similar Products been Made? Z-Coil has done a study in July 2005 spanning one month. The results were promising. Longer trials, such as several months to a year could also be duable to receive long-term effects.

Technical and Clinical Feasibility Scores: We believe based on the fundability worksheet that the technical feasibility deserves a score of a 3 as the materials are known and easily accessible. The methods to make our device are also established and can be done by one of our team members. We also gave the clinical feasibility the score of a 3 because the previous trials were successful for similar designs. The trials produce no large range of risk and are easily testable. A period of one month was large enough for the competitors, but an even larger time period will be prefered. Testing the acceleration of gait is easily recorded and measured with the right technology.

Market Analysis

Value Creation
The value creation of our product is to improve the lifestyle of those who have knee or joint problems in their legs and to reduce impact absorbed by the joints, while still remaining appealing to the eye and versatile for most shoes. There are some shoes out on the market at the moment that also claim to alleviate or reduce joint pain. However, many of them are either too expensive, lack aesthetic appeal, or both. With our product both of these issues will be resolved and will make joint friendly footwear more versatile. The value is created through the miniscule cost of manufacturing the product that will make it more attainable for everyone. In addition to the reduction in price there will also be value created through the fact that they will be able to be worn on a multitude of different shoes so the customer doesn’t have to sacrifice style for comfort or vice versa.

Manufacturing Cost

The cost to manufacture is dependent 5 main categories. The cost of the individual springs plus, the cost of 3D printing of the wedge device, the total cost of the additional pieces for the elastic attaching straps, the price of gripping soles for holding the wedge to the bottom of the existing shoes and the final cost of labor and assembly.

The cost of all parts, including assembly and labor, total approximately $31 per pair of wedges. (All expenses are broken down below).

The initial cost of the springs starts with the larger, weight supporting spring sold by McMaster: part number 9657K252. This compression spring is sold in a pack of six for a total cost of $13.35 making each individual spring $2.23. Each pair of wedges will contain 2 total larger springs for a total cost of $4.46. The smaller springs (4 contained inside each wedge) are also available by McMaster, part number 9657K101. These springs come sold in packs of six for a total cost of $7.18. This means each spring has a cost of $1.20 for a total cost per pair of wedges of $9.57. So far the combined cost of the springs for each pair of wedges is $14.03.

The next cost determinant is the cost to 3D print the wedge design from SolidWorks. This is exact price is yet to be determined however, research leads us to believe that the total cost of 3D printing the wedge should not exceed $5-7 per pair of wedges because of the simple design..

The next expense in manufacturing was determining the cost of all the additional accessories involved with attaching the wedge to existing shoes. Starting with the round elastic straps that attach to the back plate of the wedge. These are available from for a cost of $13.44 per 10 meters of elastic (approximately 32 feet of elastic). Each wedge should need no more than 1 foot of elastic for a total of 2 feet per wedge. Dividing out 32 feet by $13.44 gives us a cost of $0.42 cents per foot. 2 feet of cord total per pair of wedges gives us a total elastic cost of $0.82 per pair of wedges.

The second expense with attaching the wedges to the shoe is the laces that go over the top of each shoe and the small fabric loops that the laces attach to the wedge through. Each pair of wedges will require one pair of shoelaces and pair of fabric loops that attach to the wedge itself along the sides. On the laces are available (including shipping) for $1.04 per pair and can be purchased in 13 different colors to match the person's existing shoes and blend in. The small fabric loops that will attach the laces to the wedges are almost negligible in cost as they can be made with simple hand sewing and adhesive to the outside of the wedges. Not including labor we can assume this portion will not exceed a cost of $2.00 per pair of wedges.

The next cost to consider is the cost of the “gripping rubber” pieces that will be used on the top of the wedge to help grip the sole of the shoe better and the “new sole” that will be used on the bottom of the wedge to give traction to the bottom of the device. Both rubber pieces are very inexpensive and can be purchased for a combined total cost of $4.00 per pair of wedges when purchased from

Our final cost considerations are the time and labor involved with the manufacturing process. Since most of the manufacturing can be done by spot welding and quick adhesive assembly, the total time for assembly, per pair of wedges, is estimated to be about 5-10 minutes. With such a simple and quick assembly, the total cost of labor is estimated to not exceed $2-4 per pair of wedges.

Market Size
As 2013, the U.S. Census Bureau estimates that there are 242,470,820 adults living in the United States. 47% of adults are said to suffer from chronic knee pain. 47% of the 242.4 million adults living in the united states is 113,961,285. Using the 5% figure for revenue prediction, 5% of the 113.9 million is 5,698,064. With an average cost per device at $45, $45 multiplied by 5.7 million is $256,412,892 for our market size/ per year. This is a huge market cap, leading to a score of 3 for the category of Market Size regarding overall prototype fundability.

Fundability Discussion

Customer Validation -3

Market Size -3

Competition -2

IP Position -2

Technical Feasibility -3

Clinical Feasibility -3

Total - 324 (out of a possible 729)

Given the completed categories - prototype funding is worth pursuing.

Focusing on the strengths of the prototype:

The simplicity of design and huge potential market give it a high likelihood of seeing strong returns if it catches on as a market trend and manages to secure a strong patent of the design. These two "ifs" are issues of competition and IP position that are reasons for caution, but easily overcome.

Addressing Potential Weaknesses:

Leading competition in the category of knee pain reduction is highly priced with brand-leaders like Z-coil charging 150-250$ per pair of shoes. Our design is adaptable to many shoe styles while competitors are forced to invest in many different fashion options. Ortho Feet's transferable insoles pose the highest threat in the market as they are in a competitive price range, starting at only 25$ to improve cushioning. They also have the advantage of lower visibility and possible impact on style.
Plenty of patents exist in the field, however given the differences between them tend to be design minutia. This is a double-edged sword as it either means that patents are well enforced but prosecuting over such patents may prove difficult, weakening the patent.