{"id":10315,"date":"2016-10-24T09:37:25","date_gmt":"2016-10-24T09:37:25","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=10315"},"modified":"2016-10-24T09:37:25","modified_gmt":"2016-10-24T09:37:25","slug":"stretchy-optical-fibers-for-implanting-in-the-body-2","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/stretchy-optical-fibers-for-implanting-in-the-body-2\/","title":{"rendered":"Stretchy Optical Fibers for implanting in the body"},"content":{"rendered":"
\"MIT<\/a>
MIT researchers have developed a stretchy optical fiber in which they have injected multiple organic dyes (yellow, blue, and green regions). In addition to lighting up, the dyes act as a strain sensor, enabling researchers to quantify where and by how much a fiber has been stretched. (Image: Courtesy of the researchers)<\/figcaption><\/figure>\n

Researchers from MIT and Harvard Medical School have developed a biocompatible and highly stretchable optical fiber made from hydrogel \u2014 an elastic, rubbery material composed mostly of water. The fiber, which is as bendable as a rope of licorice, may one day be implanted in the body to deliver therapeutic pulses of light or light up at the first sign of disease.<\/span><\/p>\n

The researchers say the fiber may serve as a long-lasting implant that would bend and twist with the body without breaking down. The team has published its results online in the journal\u00a0Advanced Materials.<\/em><\/span><\/p>\n

Using light to activate cells, and particularly neurons in the brain, is a highly active field known as optogenetics, in which researchers deliver short pulses of light to targeted tissues using needle-like fibers, through which they shine light from an LED source.<\/span><\/p>\n

\u201cBut the brain is like a bowl of Jell-O, whereas these fibers are like glass \u2014 very rigid, which can possibly damage brain tissues,\u201d says Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT\u2019s Department of Mechanical Engineering. \u201cIf these fibers could match the flexibility and softness of the brain, they could provide long-term more effective stimulation and therapy.\u201d<\/span><\/p>\n

Getting to the core of it<\/strong><\/span><\/p>\n

Zhao\u2019s group at MIT, including graduate students Xinyue Liu and Hyunwoo Yuk, specializes in tuning the mechanical properties of hydrogels. The researchers have devised multiple recipes for making tough yet pliable hydrogels out of various biopolymers. The team has also come up with ways to bond hydrogels with various surfaces such as metallic sensors and LEDs, to create stretchable electronics.<\/span><\/p>\n

\u00a0[pullquote]\u201cThese efforts in optimizing and managing the physical and mechanical properties of fibers are necessary and important next steps that will enable practical applications of medical relevance.\u201d[\/pullquote]<\/span><\/p>\n

The researchers only thought to explore hydrogel\u2019s use in optical fibers after conversations with the bio-optics group at Harvard Medical School, led by Associate Professor Seok-Hyun (Andy) Yun. Yun\u2019s group had previously fabricated an optical fiber from hydrogel material that successfully transmitted light through the fiber. However, the material broke apart when bent or slightly stretched. Zhao\u2019s hydrogels, in contrast, could stretch and bend like taffy. The two groups joined efforts and looked for ways to incorporate Zhao\u2019s hydrogel into Yun\u2019s optical fiber design.<\/span><\/p>\n

Yun\u2019s design consists of a core material encased in an outer cladding. To transmit the maximum amount of light through the core of the fiber, the core and the cladding should be made of materials with very different refractive indices, or degrees to which they can bend light.<\/span><\/p>\n

\u201cIf these two things are too similar, whatever light source flows through the fiber will just fade away,\u201d Yuk explained. \u201cIn optical fibers, people want to have a much higher refractive index in the core, versus cladding, so that when light goes through the core, it bounces off the interface of the cladding and stays within the core.\u201d<\/span><\/p>\n

Happily, they found that Zhao\u2019s hydrogel material was highly transparent and possessed a refractive index that was ideal as a core material. But when they tried to coat the hydrogel with a cladding polymer solution, the two materials tended to peel apart when the fiber was stretched or bent.<\/span><\/p>\n

To bond the two materials together, the researchers added conjugation chemicals to the cladding solution, which, when coated over the hydrogel core, generated chemical links between the outer surfaces of both materials.<\/span><\/p>\n

\u201cIt clicks together the carboxyl groups in the cladding, and the amine groups in the core material, like molecular-level glue,\u201d Yuk said.<\/span><\/p>\n

Sensing strain<\/strong><\/span><\/p>\n

The researchers tested the optical fibers\u2019 ability to propagate light by shining a laser through fibers of various lengths. Each fiber transmitted light without significant \u00a0attenuation, or fading. They also found that fibers could be stretched over seven times their original length without breaking.<\/span><\/p>\n

Now that they had developed a highly flexible and robust optical fiber, made from a hydrogel material that was also biocompatible, the researchers began to play with the fiber\u2019s optical properties, to see if they could design a fiber that could sense when and where it was being stretched.<\/span><\/p>\n

They first loaded a fiber with red, green, and blue organic dyes, placed at specific spots along the fiber\u2019s length. Next, they shone a laser through the fiber and stretched, for instance, the red region. They measured the spectrum of light that made it all the way through the fiber, and noted the intensity of the red light. They reasoned that this intensity relates directly to the amount of light absorbed by the red dye, as a result of that region being stretched.<\/span><\/p>\n

In other words, by measuring the amount of light at the far end of the fiber, the researchers can quantitatively determine where and by how much a fiber was stretched.\u00a0\u00a0<\/span><\/p>\n

\u201cWhen you stretch a certain portion of the fiber, the dimensions of that part of the fiber changes, along with the amount of light that region absorbs and scatters, so in this way, the fiber can serve as a sensor of strain,\u201d Liu explained.<\/span><\/p>\n

\u201cThis is like a multistrain sensor through a single fiber,\u201d Yuk added. \u201cSo it can be an implantable or wearable strain gauge.\u201d<\/span><\/p>\n

The researchers imagine that such stretchable, strain-sensing optical fibers could be implanted or fitted along the length of a patient\u2019s arm or leg, to monitor for signs of improving mobility.<\/span><\/p>\n

Zhao envisions the fibers may also serve as sensors, lighting up in response to signs of disease.<\/span><\/p>\n

\u201cWe may be able to use optical fibers for long-term diagnostics, to optically monitor tumors or inflammation,\u201d he said. \u201cThe applications can be impactful.\u201d<\/span><\/p>\n

\u201cHydrogel fibers are very interesting and provide a compelling direction for embedding light within the human body,\u201d said Fiorenzo Omenetto, a professor of biological engineering at Tufts University, who was not involved in the work. \u00a0\u201cThese efforts in optimizing and managing the physical and mechanical properties of fibers are necessary and important next steps that will enable practical applications of medical relevance.\u201d<\/span><\/p>\n

This research was supported, in part, by the National Institutes of Health, and the Department of Defense.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

The researchers say the fiber may serve as a long-lasting implant that would bend and twist with the body without breaking down. The team has published its results online in the journal Advanced Materials.<\/p>\n

Using light to activate cells, and particularly neurons in the brain, is a highly active field known as optogenetics, in which researchers deliver short pulses of light to targeted tissues using needle-like fibers, through which they shine light from an LED source.<\/p>\n","protected":false},"author":6,"featured_media":10316,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26,22,17],"tags":[],"class_list":["post-10315","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicine","category-other","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/10\/bt1610_mit-stretchy-optics.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Medicine<\/a> Other<\/a> Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10315","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=10315"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10315\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/10316"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=10315"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=10315"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=10315"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}