BME100 f2017:Group4 W1030 L2

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Lab Write-Up 1 | Lab Write-Up 2 | Lab Write-Up 3
Lab Write-Up 4 | Lab Write-Up 5 | Lab Write-Up 6
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Name: Quentin Ellis
Name: Nazima Ansari
Name: Jacob Schuler
Name: Alexis Chavez
Name: Ryan Dougherty


Device Image and Description

Assembly hand.JPG Finger proximal thingiverse 2.JPG Fingertip thingiverse1.JPG Finger joint thingiverse.JPG View2 assembly.JPG

Image 1 is the top left. Image 2 is the top right. Image 3 is center left. Image 4 is center right. Image 5 is bottom left.


In image 2, 3, and 4, 3 parts are seen that form an entire finger. These are to be assembled for a total of 5 fingers.

In image one and five the two large cylinders seen are the outside components of the arm. As the arm is compressed the cylinder with the piston is pushed around the larger cylinder, and the piston deeper into it. The two sets of teeth seen in image one are placed inside the larger cylinder. The 2 very small pieces that look like a cylinder attached to a triangle (one is larger than the other) fit together with a spring in between and are assembled in a hole 3 inches above the base of the piston. The block with 5 holes cut is attached to the top of the smaller cylinder (functions as the palm). A finger is placed in each hole and the remaining two small cylinders (pins) are slid through a circular openings in the side to keep that fingers in place. This entire assembly amounts to a forearm with function fingers for grasping objects. This address the health issue because of the limited technology necessary and basic parts it ensures costs will be cheaper than other arms on the market. Because of the mechanism, it gives more functionality than other arms on the market.

Technical and Clinical Feasibility

Technical Feasibility-3
The design is completely feasible, even for freshman students with no experience. This device is currently being 3D printed and assembled. This prosthetic arm operates off of applying force to any given object. As the force is applied, the forearm compresses pushing a piston against a spring. 9 teeth line either side of the large cylinder for 3 inches (total compression length) and two separate teeth, in opposite orientation, are connected by a spring through the center of the piston 3 inches from the base of it. As the piston is pushed through, these teeth on the piston will be pushed against a slope that is the inverse to its own. This compresses the spring in the piston and pushes the teeth in the piston together. After traveling a length of .33 inches, these inner teeth will extend back out once more to be firmly lodged against the underside of the previous tooth. This process can occur for a total 2.97 inches (9 connected outer teeth). In order for he forearm to expand, the forearm is turned 90 degrees counter-clockwise. The spring at the bottom of the large cylinder and piston will then provide upward force and thrust the upper portion back to its original position. There is a string connected to the end of the piston that runs up through the forearm and into the center of the palm. From the center of the palm, the string separates into 5 separate strings that attach to each portion of the finger. Elastic bands on the back side of the fingers insure that the fingers always stay in an extend position when to in use. As the piston is pushed the the string is subsequently pulled, which in turn slowly closes the fingers in a grabbing like motion. To let go off an object the forearm is rotated 90 degrees, which allows the forearm to re-expand, the tension on the string to be alleviated, and the elastic bands to pull back the fingers to their initial position. The forearm can then be turned 90 degrees clockwise to reset the mechanism. It relies on 2 springs of different spring forces, and string and elastic tension. These are basic physics concepts and do not present a challenge. Errors that can occur with the device are simply pieces breaking or becoming worn out. The elastic can lose its elasticity and the spring can slowly lose its ability to compress.

Clinical Feasibility-3
Because of the basic concepts used within the design, we expect it to succeed in clinical trials. Because this device doesn't enter the body and attaches to a sleeve molded to the patient's amputation the only risk is the chance of infection at the amputation site. This is a common risk associated with all prosthetics. Lower arm non-invasive prosthetics have been brought to market before and are considered class 1 devices. This means that they do no have to be submitted to the FDA and require no clinical trials (Center for Devices and Radiological Health).

Sources: Center for Devices and Radiological Health. (n.d.). Implants and Prosthetics - Regulatory History. Retrieved September 20, 2017, from

Market Analysis

Value Creation
Our product seeks to provide not only a cheaper alternative to most prosthesis, but an alternative that is both durable and multi-functional. The hand is made of a sturdy machined metal (TBD), and the system of its hand movements is purely mechanical. The system in itself is composed of a ratchet system, with tensions springs as a way of maintaining grip on an object that has been pressed into the palm of the device. In terms of price, the device would cost a total of $5000 dollars to the consumer, far cheaper then the average $10,000 dollars needed for a hook based prosthesis. (How Much Does a Prosthetic Arm Cost)

Manufacturing Cost
The cost of materials for the device is relatively low, but machining, manufacturing, and delivery to a foreign country drive that price up to $1000 dollars. 1. $150 for Parts 2. $300 for labor 3. $500 for Shipping 4. $50 for tariff/taxes Whether machining is done in house or at a manufacturing plant is still up for debate, but the price still stays the same.

Sales Price
The actual sales price of the item will be 5000, according to the idea that that would actually make us profit and allow for growth into different sectors. We were also told to do this a general guideline by the professors of BME 100 lab.

Market Size
We calculated the market size by taking the percentage of China that makes up the world population, or 18.3%, and multiplying that by the estimated number of arm amputees in the world, 3,000,000. This roughly equally 555,685. Now, assuming 5% market penetration with $5000 dollars per unit sold, to an approximate population of 555,685 we approach the number of $138,921,250 total market. This would provide us the score of a 1 on market value.

Sources: How Much Does a Prosthetic Arm Cost? - (n.d.). Retrieved September 20, 2017, from

Fundability Discussion

Scores: Customer validation: 1

Market size: 1

Competition: 2

IP postion: 2

Technical Feasibility: 3

Clinical Feasibility: 3

Regulatory Pathway: 3

Our total score is 108. The Reimbursement category has not yet been filled out. As of currently our device will not be funded through the criteria provided by the investor. If market size were larger and this product were given the expected score of 2, that would increase the over all score to 432, which is easily fundable. However, we believe this device to be unique and solve the issues of durability and cost on the prosthetic market, and thus make it fundable.