{"id":11804,"date":"2017-03-24T06:53:39","date_gmt":"2017-03-24T06:53:39","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=11804"},"modified":"2017-03-26T06:03:11","modified_gmt":"2017-03-26T06:03:11","slug":"toward-printable-sensor-laden-skin-robots","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/toward-printable-sensor-laden-skin-robots\/","title":{"rendered":"Toward printable, sensor-laden \u201cskin\u201d for robots"},"content":{"rendered":"

New 3-D-printed device mimics the goldbug beetle, which changes color when prodded.<\/strong><\/em><\/span><\/p>\n

\"\"
A rendering of the 3-D printed device.
Image: Subramanian Sundaram<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0In this age of smartphones and tablet computers, touch-sensitive surfaces are everywhere. They\u2019re also brittle, as people with cracked phone screens everywhere can attest.<\/span><\/p>\n

Covering a robot \u2014 or an airplane or a bridge \u2014 with sensors will require a technology that is both flexible and cost-effective to manufacture in bulk. A team of researchers at MIT\u2019s Computer Science and Artificial Intelligence Laboratory thinks that 3-D printing could be the answer.<\/span><\/p>\n

In an attempt to demonstrate the feasibility of flexible, printable electronics that combine sensors and processing circuitry and can act on their environments, the researchers have designed and built a device that responds to mechanical stresses by changing the color of a spot on its surface.<\/span><\/p>\n

The device was inspired by the golden tortoise beetle, or \u201cgoldbug,\u201d an insect whose exterior usually appears golden but turns reddish orange if the insect is poked or prodded \u2014 that is, mechanically stressed.<\/span><\/p>\n

\u201cIn nature, networks of sensors and interconnects are called sensorimotor pathways,\u201d says Subramanian Sundaram, an MIT graduate student in electrical engineering and computer science (EECS), who led the project. \u201cWe were trying to see whether we could replicate sensorimotor pathways inside a 3-D-printed object. So we considered the simplest organism we could find.\u201d<\/span><\/p>\n

The researchers present their new design in the latest issue of the journal<\/span> Advanced Materials Technologies<\/a><\/em>. Sundaram is the first author on the paper, and the senior authors are Sundaram\u2019s advisor, Wojciech Matusik, an associate professor of EECS; and Marc Baldo, a professor of EECS and director of the Research Laboratory of Electronics. Joining them on the paper are Pitchaya Sitthi-Amorn, a former postdoc in Matusik\u2019s lab; Ziwen Jiang, an undergraduate EECS student; and David Kim, a technical assistant in Matusik\u2019s Computational Fabrication Group.<\/span><\/p>\n

Bottom up<\/strong><\/span><\/p>\n

Printable electronics, in which flexible circuitry is deposited on some type of plastic substrate, has been a major area of research for decades. But Sundaram says that the ability to print the substrate itself greatly increases the range of devices the technique can yield.<\/span><\/p>\n

For one thing, the choice of substrate limits the types of materials that can be deposited on top of it. Because a printed substrate could consist of many materials, interlocked in intricate but regular patterns, it broadens the range of functional materials that printable electronics can use.<\/span><\/p>\n

Printed substrates also open the possibility of devices that, although printed as flat sheets, can fold themselves up into more complex, three-dimensional shapes. Printable robots that spontaneously self-assemble when heated, for instance, are a\u00a0 topic of<\/span> ongoing research<\/a> at the CSAIL Distributed Robotics Laboratory, led by Daniela Rus, the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science at MIT.<\/span><\/p>\n

\u201cWe believe that only if you\u2019re able to print the underlying substrate can you begin to think about printing a more complex shape,\u201d Sundaram says.<\/span><\/p>\n

Selective signaling<\/strong><\/span><\/p>\n

The MIT researchers\u2019 new device is approximately T-shaped, but with a wide, squat base and an elongated crossbar. The crossbar is made from an elastic plastic, with a strip of silver running its length; in the researchers\u2019 experiments, electrodes were connected to the crossbar\u2019s ends. The base of the T is made from a more rigid plastic. It includes two printed transistors and what the researchers call a \u201cpixel,\u201d a circle of semiconducting polymer whose color changes when the crossbars stretch, modifying the electrical resistance of the silver strip.<\/span><\/p>\n

In fact, the transistors and the pixel are made from the same material; the transistors also change color slightly when the crossbars stretch. The effect is more dramatic in the pixel, however, because the transistors amplify the electrical signal from the crossbar. Demonstrating working transistors was essential, Sundaram says, because large, dense sensor arrays require some capacity for onboard signal processing.<\/span><\/p>\n

\u201cYou wouldn\u2019t want to connect all the sensors to your main computer, because then you would have tons of data coming in,\u201d he says. \u201cYou want to be able to make clever connections and to select just the relevant signals.\u201d<\/span><\/p>\n

To build the device, the researchers used the<\/span> MultiFab<\/a>, a custom 3-D printer developed by Matusik\u2019s group. The MultiFab already included two different \u201cprint heads,\u201d one for emitting hot materials and one for cool, and an array of ultraviolet light-emitting diodes. Using ultraviolet radiation to \u201ccure\u201d fluids deposited by the print heads produces the device\u2019s substrate.<\/span><\/p>\n

Sundaram added a copper-and-ceramic heater, which was necessary to deposit the semiconducting plastic: The plastic is suspended in a fluid that\u2019s sprayed onto the device surface, and the heater evaporates the fluid, leaving behind a layer of plastic only 200 nanometers thick.<\/span><\/p>\n

Fluid boundaries<\/strong><\/span><\/p>\n

A transistor consists of semiconductor channel on top of which sits a \u201cgate,\u201d a metal wire that, when charged, generates an electric field that switches the semiconductor between its electrically conductive and nonconductive states. In a standard transistor, there\u2019s an insulator between the gate and the semiconductor, to prevent the gate current from leaking into the semiconductor channel.<\/span><\/p>\n

The transistors in the MIT researchers\u2019 device instead separate the gate and the semiconductor with a layer of water containing a potassium salt. Charging the gate drives potassium ions into the semiconductor, changing its conductivity.<\/span><\/p>\n

The layer of saltwater lowers the device\u2019s operational voltage, so that it can be powered with an ordinary 1.5-volt battery. But it does render the device less durable. \u201cI think we can probably get it to work stably for two months, maybe,\u201d Sundaram says. \u201cOne option is to replace that liquid with something between a solid and a liquid, like a<\/span> hydrogel<\/a>, perhaps. But that\u2019s something we would work on later. This is an initial demonstration.\u201d<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

New 3-D-printed device mimics the goldbug beetle, which changes color when prodded. CAMBRIDGE, Mass. —\u00a0In this age of smartphones and tablet computers, touch-sensitive surfaces are everywhere. They\u2019re also brittle, as people with cracked phone screens everywhere can attest. Covering a robot \u2014 or an airplane or a bridge \u2014 with sensors will require a technology […]<\/p>\n","protected":false},"author":6,"featured_media":11805,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22,28],"tags":[],"class_list":["post-11804","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-other","category-techbiz"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",600,399,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",600,399,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",541,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",640,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/03\/MIT-Printable-Gold-Bug_0-1.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Other<\/a> Tech<\/a>","tag_info":"Tech","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/11804","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=11804"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/11804\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/11805"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=11804"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=11804"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=11804"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}