{"id":13216,"date":"2021-04-09T21:45:02","date_gmt":"2021-04-10T01:45:02","guid":{"rendered":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/?p=13216"},"modified":"2021-04-09T21:45:02","modified_gmt":"2021-04-10T01:45:02","slug":"thumb-prosthetic","status":"publish","type":"post","link":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/thumb-prosthetic\/","title":{"rendered":"Thumb Prosthetic"},"content":{"rendered":"<div class=\"wrapper\">\n<article class=\"post\">\n<div class=\"post-content\">\n<h2>Thumb prosthetic<\/h2>\n<h2 id=\"process-images-and-review\">Overview<\/h2>\n<div id=\"attachment_13229\" style=\"width: 650px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13229\" loading=\"lazy\" class=\"size-full wp-image-13229\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2670-1.jpg\" alt=\"\" width=\"640\" height=\"854\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2670-1.jpg 640w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2670-1-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2670-1-508x678.jpg 508w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><p id=\"caption-attachment-13229\" class=\"wp-caption-text\">Final prosthetic<\/p><\/div>\n<p>A prosthetic device for congenital trigger thumb that mechanically remaps the fused thumb joint further up the digit, using a flex sensor to sense compression and a servo to modulate the upper thumb.<\/p>\n<div style=\"width: 620px;\" class=\"wp-video\"><!--[if lt IE 9]><script>document.createElement('video');<\/script><![endif]-->\n<video class=\"wp-video-shortcode\" id=\"video-13216-1\" width=\"620\" height=\"1102\" preload=\"metadata\" controls=\"controls\"><source type=\"video\/mp4\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2306-1.mp4?_=1\" \/><a href=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2306-1.mp4\">https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2306-1.mp4<\/a><\/video><\/div>\n<div id=\"attachment_13218\" style=\"width: 1281px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13218\" loading=\"lazy\" class=\"size-full wp-image-13218\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14.jpg\" alt=\"\" width=\"1271\" height=\"874\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14.jpg 1271w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14-300x206.jpg 300w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14-1024x704.jpg 1024w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14-768x528.jpg 768w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14-973x669.jpg 973w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/prostheticframe.14-508x349.jpg 508w\" sizes=\"(max-width: 1271px) 100vw, 1271px\" \/><p id=\"caption-attachment-13218\" class=\"wp-caption-text\">Rendering of printed components on hand model<\/p><\/div>\n<div id=\"attachment_13224\" style=\"width: 500px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13224\" loading=\"lazy\" class=\"size-full wp-image-13224\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb.jpg\" alt=\"\" width=\"490\" height=\"534\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb.jpg 490w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb-275x300.jpg 275w\" sizes=\"(max-width: 490px) 100vw, 490px\" \/><p id=\"caption-attachment-13224\" class=\"wp-caption-text\">thumb in use grasping object<\/p><\/div>\n<div id=\"attachment_13225\" style=\"width: 491px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13225\" loading=\"lazy\" class=\"size-full wp-image-13225\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb2.jpg\" alt=\"\" width=\"481\" height=\"472\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb2.jpg 481w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/usethumb2-300x294.jpg 300w\" sizes=\"(max-width: 481px) 100vw, 481px\" \/><p id=\"caption-attachment-13225\" class=\"wp-caption-text\">thumb in use demonstrating ease of pinch grip<\/p><\/div>\n<div id=\"attachment_13228\" style=\"width: 650px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13228\" loading=\"lazy\" class=\"size-full wp-image-13228\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2671.jpg\" alt=\"\" width=\"640\" height=\"854\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2671.jpg 640w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2671-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2671-508x678.jpg 508w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><p id=\"caption-attachment-13228\" class=\"wp-caption-text\">controller box<\/p><\/div>\n<ul>\n<li style=\"list-style-type: none\"><\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h2 id=\"process-images-and-review\">Process images and review<\/h2>\n<p>I began by determining the electronic hardware that I needed to use to make this work, and after doing some basic research into hand mechanics decided that a flex sensor would work well to detect joint tension and compression. I decided on the electronics early in the process and spent much of the time working mechanically to achieve an ergonomic and functional device.<\/p>\n<p>To understand the necessary structures I worked initially in wood, springs, and rubber bands to create a rough works-like prototype.<\/p>\n<div id=\"attachment_13221\" style=\"width: 663px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13221\" loading=\"lazy\" class=\"size-full wp-image-13221\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_1961-1.jpg\" alt=\"\" width=\"653\" height=\"871\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_1961-1.jpg 653w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_1961-1-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_1961-1-508x678.jpg 508w\" sizes=\"(max-width: 653px) 100vw, 653px\" \/><p id=\"caption-attachment-13221\" class=\"wp-caption-text\">wood mechanical prototyping<\/p><\/div>\n<p>After I had joined those pieces and made a non-electronic, physically manipulated prototype model, I decided to move to a purely electronic prototype to resolve the sensing and actuation.<\/p>\n<div id=\"attachment_13219\" style=\"width: 663px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13219\" loading=\"lazy\" class=\"size-full wp-image-13219\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2281.jpg\" alt=\"\" width=\"653\" height=\"871\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2281.jpg 653w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2281-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2281-508x678.jpg 508w\" sizes=\"(max-width: 653px) 100vw, 653px\" \/><p id=\"caption-attachment-13219\" class=\"wp-caption-text\">breadboard prototyping<\/p><\/div>\n<p>I used a breadboard and the sensors to visualize and debug the electronics. Once I had them working, I moved to a soldered protoboard that I would use on the final device. I had no issues with the electronics and found that the direct mapping of the values was a very straightforward process. The adjustment came once the device was finally assembled and I had to modify the value ranges to reflect the physical constraints provided by the spatial range of motion.<\/p>\n<div id=\"attachment_13222\" style=\"width: 716px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13222\" loading=\"lazy\" class=\"size-full wp-image-13222\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2184.jpg\" alt=\"\" width=\"706\" height=\"942\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2184.jpg 706w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2184-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2184-508x678.jpg 508w\" sizes=\"(max-width: 706px) 100vw, 706px\" \/><p id=\"caption-attachment-13222\" class=\"wp-caption-text\">printed components<\/p><\/div>\n<p>I printed a clamshell main structure and a separate digit. The main structure has mechanical interfacing for the servo motor to rest on the back. These parts were very successful and I was able to construct complex geometry in Solidworks that conformed well to my thumb contours.<\/p>\n<div id=\"attachment_13226\" style=\"width: 663px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13226\" loading=\"lazy\" class=\"size-full wp-image-13226\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2186.jpg\" alt=\"\" width=\"653\" height=\"871\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2186.jpg 653w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2186-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2186-508x678.jpg 508w\" sizes=\"(max-width: 653px) 100vw, 653px\" \/><p id=\"caption-attachment-13226\" class=\"wp-caption-text\">elastic prototyping for restorative force<\/p><\/div>\n<p>After some of the parts were assembled and the prints had been processed, I did test fitting and began seeing what level of restorative force I needed from elastic. I ended up not needing the rubber band and used an elastic internal hinge.<\/p>\n<div id=\"attachment_13220\" style=\"width: 663px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13220\" loading=\"lazy\" class=\"size-full wp-image-13220\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2283.jpg\" alt=\"\" width=\"653\" height=\"871\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2283.jpg 653w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2283-225x300.jpg 225w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/IMG_2283-508x678.jpg 508w\" sizes=\"(max-width: 653px) 100vw, 653px\" \/><p id=\"caption-attachment-13220\" class=\"wp-caption-text\">test fitting and finalizing measurements<\/p><\/div>\n<p>To finish I soldered the final electronics and then attached the structures to an elastic band to hold it on my hand.<\/p>\n<h2 id=\"discussion\">Discussion<\/h2>\n<p>I received a lot of positive feedback during the critique that supported my decisions and device. I think given the time frame and project constraints my device was very effective, although the brittleness of the flex sensor leads led to performance issues after user testing.\u00a0 I received feedback that &#8220;<span style=\"font-weight: 400\">The attachment of an extra digit to the thumb would change the whole way a person uses their hand. A next step if the project continued might be researching ways to make that more intuitive whether it be by having a shorter extension or something else.&#8221; I totally agree with this feedback and I was sad that I couldn&#8217;t explore this more in this project. I tried to focus on the electromechanical and ergonomic aspects of the device but given more time and resources I would&#8217;ve absolutely considered physical behavior changes and the enhancement possibilities that this device affords. &#8220;Would a spring make the thumb stronger?&#8221;- Yes, but the force curve of springs leads to a lot more strain on the servo I was using so I couldn&#8217;t achieve the modulation fidelity that I desired. I had prototyped with springs and different types of rubber bands and found my restorative solution to be effective.\u00a0 &#8220;How would this react when actually grabbing something? Is the grip strong enough?&#8221;-I actually tried picking up some objects and had difficulty, I think it has to do with the nerve pressure that is lost and the &#8216;settling&#8217; effect of flesh when grabbing something. I also think this device requires a long break-in period to get a strong mind-body connection that would allow it to be used effortlessly. I&#8217;m very happy with how the project came out. I obviously wish that things could&#8217;ve been made more miniature, but this project was not focused on those constraints. I was really surprised with how fluid of motion that I was able to achieve and how natural the movement seemed. I learned a lot about human movement and designing for human contact. I think that directly translating the compression of the human form to the movement of a motor allowed for movement curves to be accurate to human movements, so this sort of natural actuation is really important instead of more artificial methods. I think moving forward I would change the form to be a little more simpler in terms of geometry and hopefully have smaller, more reliable, and stronger electronic components but those are all in an ideal world. I don&#8217;t think I would significantly change my design process or my method because I found it to be successful. I may build another version of this in the future, but after significant time to reflect and maybe have different insights into actuation and electronic integration.<\/span><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2 id=\"technical-information\">Technical information<\/h2>\n<p>&nbsp;<\/p>\n<div id=\"attachment_13227\" style=\"width: 821px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-13227\" loading=\"lazy\" class=\"size-full wp-image-13227\" src=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1.jpg\" alt=\"\" width=\"811\" height=\"821\" srcset=\"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1.jpg 811w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1-296x300.jpg 296w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1-768x777.jpg 768w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1-88x88.jpg 88w, https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-content\/uploads\/2021\/04\/Untitled-Diagram-1-508x514.jpg 508w\" sizes=\"(max-width: 811px) 100vw, 811px\" \/><p id=\"caption-attachment-13227\" class=\"wp-caption-text\">functional block diagram and schematic drawing<\/p><\/div>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"c\">\/*Project 2: An assistive device for someone you know very well\r\n * Prosthetic Trigger finger thumb\r\n * \r\n * This code uses a flex sensor mounted to a users inner hand to modulate a servo to bend a prosthetic thumb.\r\n * The more the flex sensor is deformed, the further the servo (and thumb) travel. \r\n * \r\n * Thank you to Last Minute Engineers for their guide on using flex sensors, which was referenced for this project.\r\n * https:\/\/lastminuteengineers.com\/flex-sensor-arduino-tutorial\/\r\n * \r\n *\/\r\n\r\nconst int flexPin = A4; \/\/read flex sensor analog input\r\n#include &lt;Servo.h&gt;\r\n\r\nServo thumbMotor; \/\/ servo actuator\r\nconst int servoPin = 4; \/\/ pin the servo is connected to \r\nint value; \/\/analog value \r\n\r\n\r\nvoid setup(){\r\n\r\n  thumbMotor.attach(servoPin); \/\/ set up the servo on that data pin\r\n}\r\n\r\nvoid loop(){\r\n  \r\n  value = analogRead(flexPin);\/\/read and store flex value\r\n  value = map(value, 800, 900, 0, 180); \/\/map flex value to servo modulation\r\n  thumbMotor.write(value); \/\/activate servo\r\n}<\/pre>\n<\/div>\n<\/article>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Thumb prosthetic Overview A prosthetic device for congenital trigger thumb that mechanically remaps the fused thumb joint further up the digit, using a flex sensor to sense compression&#8230;<\/p>\n","protected":false},"author":174,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[89],"tags":[],"_links":{"self":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/13216"}],"collection":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/users\/174"}],"replies":[{"embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/comments?post=13216"}],"version-history":[{"count":1,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/13216\/revisions"}],"predecessor-version":[{"id":13230,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/13216\/revisions\/13230"}],"wp:attachment":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/media?parent=13216"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/categories?post=13216"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/tags?post=13216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}