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UW-Madison BME 300 - Product Design Specification - Prosthetic Finger Device

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Product Design Specification for BME 200/300 group 28E: Prosthetic Finger Device (October 15, 2007) Group members: Dustin Gardner, Karen Chen, Richard Bamberg, Allison McArton, & Alex Kracht Function The focus of this project is to design a substructure and connecting mechanism for an implant-retained finger prosthetic. Currently, the only method used in the United States is a slip-cover which holds the prosthetic onto the remaining portion of an amputated finger. New approaches have been used in other countries which involve implanting an object through the distal end of a partial digit bone. The object is such that a prosthetic finger with a solid substructure can be attached in order to achieve increased motility and use of the prosthetic finger without having any parts fall off. Our team is to design a prosthetic finger substructure and connection apparatus which will successfully match these characteristics. Client Requirements • Either new or improved attachment system from current system • Either new or improved prosthetic substructure from current system • Computer simulation of final design • Interested in experimental work with hand surgeon • Budget of $500 Design Requirements According to the client, the implant-retained finger prosthesis must hold firmly to the terminal amputated portion of the finger. This could be done either through a sleeve concept or through osseo-integration. The prosthesis should also be easy enough to remove such that maintenance and hygiene may continue, unimpeded and unobstructed. However, the implant must not detach too easily when certain external forces and shear forces are applied to the finger prosthesis. As such, the finger prosthesis must also maintain an element of support functionality and fulfill the aesthetic requirement of resembling a real finger in appearance, function and attachment. Our client wants the group to devise a new attachment system or build upon the existing system, in conjunction with a simulator model. The simulator model is necessary to obtain a clearer interpretation of what reactions occur when the prosthesis undergoes kinetic motion, and thus correct errors prior to implementation. The finger prosthesis may be constructed out of solid silicone polyurethane or a combination of silicone polyurethane with a dental acrylic sub-structure to strengthen the prosthesis for better durability. Medical improvements on this design have also requested by the client such that better flexibility around joint portions of the prosthesis could be present to improve durability, responsiveness and support of the implant-retained finger prosthesis. 1. Physical and Operational Characteristicsa. Performance requirements The device is meant to effectively connect the prosthetic finger to the hand, providing durability for usage while still allowing the patient to easily remove the finger. b. Safety This device must be able to easily be removed so that the patient can easily clean the prosthetic finger. In addition, the material used for the device must not create any physical reactions. c. Accuracy and Reliability The device will be used daily by patients so normal wear and tear will occur on the actual prosthetic. The device used to connect the prosthetic to the hand must be able to keep the prosthetic in the correct position when in use. Also, the device should be easily removable for cleaning and comfort purposes. d. Life in Service The connecting mechanism must be able to withstand normal finger usage over the course of a day. The life-limiting factor of this device would be the degradation on the actual prosthetic. e. Shelf Life The shelf life of this product is rather long. Metal for finger implant is usually Titanium (Ti), and the half-life of Ti is 63 years. The silicone rubber (polysiloxane) has relatively long lasting characteristics. This product will be able to remain new and unused for a minimum of 63 years. Establish environmental conditions while in storage, shelf-life of components such as batteries, etc. f. Operating Environment: Silicone rubber will be exposed in the air, since it is the material that covers the amputation. Ti will be implanted inside the finger, thus it will not be exposed to the air most of the time. Silicone rubber is able to operate at a large temperature range, from -40C to 200C. Ti has a high melting point of 1668 C. Thus, these materials will not self-deform under room temperature, at human body temperature, or during the summer time. Silicone rubber is highly inert, thus it does not react with most chemical and humidity. Ti also has a great resistance to corrosion; therefore it will be able to withstand the acidity and water of the human body. The shear modulus of Ti is 44GPa, thus it has a high shock loading. Also, the tensile strength of silicone rubber is 11N/mm. Silicone rubber will endure 490% of elongation before breaking. (I can’t find the atm pressure that both materials can withstand) Establish the conditions that the device could be exposed to during operation (or at any other time, such as storage or idle time), including temperature range, pressure range,humidity, shock loading, dirt or dust, corrosion from fluids, noise levels, insects, vibration, persons who will use or handle, any unforeseen hazards, etc. g. Ergonomics: This product should not generate a torque that is greater than the torque of regular finger muscles. For the best use of this product, the patient should not be using this prosthesis to pick up loadings heavier than 1 kg. Establish restrictions on the interaction of the product with man (animal), including heights, reach, forces, acceptable operation torques, etc… h. Size: The size of this product is roughly the size of a human finger length. This product will not excess 3 inches in length, and 1 inch in cross section diameter. It should be highly portable when attached to the human amputation. Establish restrictions on the size of the product, including maximum size, portability, space available, access for maintenance, etc. i. Weight: The weight of this product should not exceed 50 grams in order to remain its high flexibility and light loading. Establish restrictions on maximum, minimum, and/or optimum weight; weight is important when it comes to handling the product by the user, by the distributor, handling on the shop floor, during


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UW-Madison BME 300 - Product Design Specification - Prosthetic Finger Device

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