Open Source Model
The proposed design was inspired by the Robohand Project, the brainchild of two amateur inventors who sought to build a low-cost prosthetic hand for individuals with amniotic band syndrome. The Robohand design combines 3D printing technology and readily available hardware to create a customizable, low-cost prosthetic hand. Furthermore, all of the designs and instructions are freely available online, creating an open-source community to facilitate production and further development of this invention. In designing the proposed transradial prosthetic arm, this open-source model was kept in mind. Rather than designing a purely commercial product, our vision is to join the Robohand movement and make it possible for anyone with basic mechanical and electrical knowledge and access to a 3D printer to assemble our product.
Design Specifications
1. Target Population: The device will be designed for individuals with a unilateral, 1/3 transradial limb difference, ages five and older.
2. Cost: The total parts cost should not exceed $150. This number includes the cost of manufacturing custom parts and the cost of all parts that would have to be purchased from a supplier. It does not include additional labor costs for assembling the device and fitting it to the user, the cost of tools, or the non-material costs of 3D printing.
a. Note: Tools for assembling the device were not included because most are basic tools commonly found around the home. The non-material costs of 3D printing were eliminated because the open-source, "Robohand model" of production, will be used. In this model owners of 3D printers can volunteer their printers in a database. Individuals in need of a prosthetic hand can then search the database for the 3D printers nearest to their location. This model eliminates the need to buy a 3D printer, order custom 3D-printed parts online, or rent 3D printer time, all three of which are costly.
3. Weight: The socket and terminal device should not weigh more than the missing limb.
4. Aesthetics: The terminal device should roughly resemble the form of the human hand.
5. Joints:
a. Each finger should have at least one joint.
b. The thumb should have two joints.
c. Each joint should have at least one degree of freedom.
6. Functionality:
a. Fingers and thumb should open and close at least at the mouth, waist, and in front of the user. "In front" is defined as within the region bounded by the user's arm length at a 60 degree angle above and below the horizontal plane and a 60 degree angle away from the median sagittal plane.
b. There should be independent thumb movement with key pinch grip (see Footnote[1]).
c. The terminal device should have the ability to lift and hold at least a 500 g object (see Footnote[2]).
7. Comfort: The device should not cause pain, skin abrasions, or infection.
8. Donning and Doffing: The user should be able to don and doff the device independently in fewer than 30 seconds.
9. Attachment: The device should not come off unless intentionally removed.
10. Manufacturing Skill:
a. Modification of any customizable parts should be able to be completed by anybody with basic skill in the use of computer-aided design.
b. Manufacturing of 3D components should be able to be completed by anybody with basic knowledge of a 3D printer.
[1] This grip is used when plugging an electrical plug into an outlet, using a zipper, inserting an ATM card into the machine, using a key, among others.
[2] The approximate mass of a 12-ounce cup of water is 500 g.
The proposed design was inspired by the Robohand Project, the brainchild of two amateur inventors who sought to build a low-cost prosthetic hand for individuals with amniotic band syndrome. The Robohand design combines 3D printing technology and readily available hardware to create a customizable, low-cost prosthetic hand. Furthermore, all of the designs and instructions are freely available online, creating an open-source community to facilitate production and further development of this invention. In designing the proposed transradial prosthetic arm, this open-source model was kept in mind. Rather than designing a purely commercial product, our vision is to join the Robohand movement and make it possible for anyone with basic mechanical and electrical knowledge and access to a 3D printer to assemble our product.
Design Specifications
1. Target Population: The device will be designed for individuals with a unilateral, 1/3 transradial limb difference, ages five and older.
2. Cost: The total parts cost should not exceed $150. This number includes the cost of manufacturing custom parts and the cost of all parts that would have to be purchased from a supplier. It does not include additional labor costs for assembling the device and fitting it to the user, the cost of tools, or the non-material costs of 3D printing.
a. Note: Tools for assembling the device were not included because most are basic tools commonly found around the home. The non-material costs of 3D printing were eliminated because the open-source, "Robohand model" of production, will be used. In this model owners of 3D printers can volunteer their printers in a database. Individuals in need of a prosthetic hand can then search the database for the 3D printers nearest to their location. This model eliminates the need to buy a 3D printer, order custom 3D-printed parts online, or rent 3D printer time, all three of which are costly.
3. Weight: The socket and terminal device should not weigh more than the missing limb.
4. Aesthetics: The terminal device should roughly resemble the form of the human hand.
5. Joints:
a. Each finger should have at least one joint.
b. The thumb should have two joints.
c. Each joint should have at least one degree of freedom.
6. Functionality:
a. Fingers and thumb should open and close at least at the mouth, waist, and in front of the user. "In front" is defined as within the region bounded by the user's arm length at a 60 degree angle above and below the horizontal plane and a 60 degree angle away from the median sagittal plane.
b. There should be independent thumb movement with key pinch grip (see Footnote[1]).
c. The terminal device should have the ability to lift and hold at least a 500 g object (see Footnote[2]).
7. Comfort: The device should not cause pain, skin abrasions, or infection.
8. Donning and Doffing: The user should be able to don and doff the device independently in fewer than 30 seconds.
9. Attachment: The device should not come off unless intentionally removed.
10. Manufacturing Skill:
a. Modification of any customizable parts should be able to be completed by anybody with basic skill in the use of computer-aided design.
b. Manufacturing of 3D components should be able to be completed by anybody with basic knowledge of a 3D printer.
[1] This grip is used when plugging an electrical plug into an outlet, using a zipper, inserting an ATM card into the machine, using a key, among others.
[2] The approximate mass of a 12-ounce cup of water is 500 g.