Monday, June 1st, 2020

Time	Event
9:00a	Giving soft robots feeling One of the hottest topics in robotics is the field of soft robots, which utilizes squishy and flexible materials rather than traditional rigid materials. But soft robots have been limited due to their lack of good sensing. A good robotic gripper needs to feel what it is touching (tactile sensing), and it needs to sense the positions of its fingers (proprioception). Such sensing has been missing from most soft robots. In a new pair of papers, researchers from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) came up with new tools to let robots better perceive what they’re interacting with: the ability to see and classify items, and a softer, delicate touch.  “We wish to enable seeing the world by feeling the world. Soft robot hands have sensorized skins that allow them to pick up a range of objects, from delicate, such as potato chips, to heavy, such as milk bottles,” says CSAIL Director Daniela Rus, the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science and the deputy dean of research for the MIT Stephen A. Schwarzman College of Computing.  One paper builds off last year’s research from MIT and Harvard University, where a team developed a soft and strong robotic gripper in the form of a cone-shaped origami structure. It collapses in on objects much like a Venus' flytrap, to pick up items that are as much as 100 times its weight.  To get that newfound versatility and adaptability even closer to that of a human hand, a new team came up with a sensible addition: tactile sensors, made from latex “bladders” (balloons) connected to pressure transducers. The new sensors let the gripper not only pick up objects as delicate as potato chips, but it also classifies them — letting the robot better understand what it’s picking up, while also exhibiting that light touch.  When classifying objects, the sensors correctly identified 10 objects with over 90 percent accuracy, even when an object slipped out of grip. “Unlike many other soft tactile sensors, ours can be rapidly fabricated, retrofitted into grippers, and show sensitivity and reliability,” says MIT postdoc Josie Hughes, the lead author on a new paper about the sensors. “We hope they provide a new method of soft sensing that can be applied to a wide range of different applications in manufacturing settings, like packing and lifting.”  In a second paper, a group of researchers created a soft robotic finger called “GelFlex” that uses embedded cameras and deep learning to enable high-resolution tactile sensing and “proprioception” (awareness of positions and movements of the body).  The gripper, which looks much like a two-finger cup gripper you might see at a soda station, uses a tendon-driven mechanism to actuate the fingers. When tested on metal objects of various shapes, the system had over 96 percent recognition accuracy.  “Our soft finger can provide high accuracy on proprioception and accurately predict grasped objects, and also withstand considerable impact without harming the interacted environment and itself,” says Yu She, lead author on a new paper on GelFlex. “By constraining soft fingers with a flexible exoskeleton, and performing high-resolution sensing with embedded cameras, we open up a large range of capabilities for soft manipulators.”  Magic ball senses  The magic ball gripper is made from a soft origami structure, encased by a soft balloon. When a vacuum is applied to the balloon, the origami structure closes around the object, and the gripper deforms to its structure.  While this motion lets the gripper grasp a much wider range of objects than ever before, such as soup cans, hammers, wine glasses, drones, and even a single broccoli floret, the greater intricacies of delicacy and understanding were still out of reach — until they added the sensors.   When the sensors experience force or strain, the internal pressure changes, and the team can measure this change in pressure to identify when it will feel that again.  In addition to the latex sensor, the team also developed an algorithm which uses feedback to let the gripper possess a human-like duality of being both strong and precise — and 80 percent of the tested objects were successfully grasped without damage.  The team tested the gripper-sensors on a variety of household items, ranging from heavy bottles to small, delicate objects, including cans, apples, a toothbrush, a water bottle, and a bag of cookies.  Going forward, the team hopes to make the methodology scalable, using computational design and reconstruction methods to improve the resolution and coverage using this new sensor technology. Eventually, they imagine using the new sensors to create a fluidic sensing skin that shows scalability and sensitivity.  Hughes co-wrote the new paper with Rus, which they will present virtually at the 2020 International Conference on Robotics and Automation.  GelFlex In the second paper, a CSAIL team looked at giving a soft robotic gripper more nuanced, human-like senses. Soft fingers allow a wide range of deformations, but to be used in a controlled way there must be rich tactile and proprioceptive sensing. The team used embedded cameras with wide-angle “fisheye” lenses that capture the finger’s deformations in great detail. To create GelFlex, the team used silicone material to fabricate the soft and transparent finger, and put one camera near the fingertip and the other in the middle of the finger. Then, they painted reflective ink on the front and side surface of the finger, and added LED lights on the back. This allows the internal fish-eye camera to observe the status of the front and side surface of the finger.  The team trained neural networks to extract key information from the internal cameras for feedback. One neural net was trained to predict the bending angle of GelFlex, and the other was trained to estimate the shape and size of the objects being grabbed. The gripper could then pick up a variety of items such as a Rubik’s cube, a DVD case, or a block of aluminum.  During testing, the average positional error while gripping was less than 0.77 millimeter, which is better than that of a human finger. In a second set of tests, the gripper was challenged with grasping and recognizing cylinders and boxes of various sizes. Out of 80 trials, only three were classified incorrectly.  In the future, the team hopes to improve the proprioception and tactile sensing algorithms, and utilize vision-based sensors to estimate more complex finger configurations, such as twisting or lateral bending, which are challenging for common sensors, but should be attainable with embedded cameras. Yu She co-wrote the GelFlex paper with MIT graduate student Sandra Q. Liu, Peiyu Yu of Tsinghua University, and MIT Professor Edward Adelson. They will present the paper virtually at the 2020 International Conference on Robotics and Automation. (Comment on this)
10:59a	Carbon nanotube transistors make the leap from lab to factory floor Carbon nanotube transistors are a step closer to commercial reality, now that MIT researchers have demonstrated that the devices can be made swiftly in commercial facilities, with the same equipment used to manufacture the silicon-based transistors that are the backbone of today’s computing industry. Carbon nanotube field-effect transistors or CNFETs are more energy-efficient than silicon field-effect transistors and could be used to build new types of three-dimensional microprocessors. But until now, they’ve existed mostly in an “artisanal” space, crafted in small quantities in academic laboratories. In a study published June 1 in Nature Electronics, however, scientists show how CNFETs can be fabricated in large quantities on 200-millimeter wafers that are the industry standard in computer chip design. The CNFETs were created in a commercial silicon manufacturing facility and a semiconductor foundry in the United States. After analyzing the deposition technique used to make the CNFETs, Max Shulaker, an MIT assistant professor of electrical engineering and computer science, and his colleagues made some changes to speed up the fabrication process by more than 1,100 times compared to the conventional method, while also reducing the cost of production. The technique deposited carbon nanotubes edge to edge on the wafers, with 14,400 by 14,400 arrays CFNETs distributed across multiple wafers. Shulaker, who has been designing CNFETs since his PhD days, says the new study represents “a giant step forward, to make that leap into production-level facilities.” Bridging the gap between lab and industry is something that researchers “don’t often get a chance to do,” he adds. “But it’s an important litmus test for emerging technologies.” Other MIT researchers on the study include lead author Mindy D. Bishop, a PhD student in the Harvard-MIT Health Sciences and Technology program, along with Gage Hills, Tathagata Srimani, and Christian Lau. Solving the spaghetti problem For decades, improvements in silicon-based transistor manufacturing have brought down prices and increased energy efficiency in computing. That trend may be nearing its end, however, as increasing numbers of transistors packed into integrated circuits do not appear to be increasing energy efficiency at historic rates. CNFETs are an attractive alternative technology because they are “around an order of magnitude more energy efficient” than silicon-based transistors, says Shulaker. Unlike silicon-based transistors, which are made at temperatures around 450 to 500 degrees Celsius, CNFETs also can be manufactured at near-room temperatures. “This means that you can actually build layers of circuits right on top of previously fabricated layers of circuits, to create a three-dimensional chip,” Shulaker explains. “You can’t do this with silicon-based technology, because you would melt the layers underneath.” A 3D computer chip, which might combine logic and memory functions, is projected to “beat the performance of a state-of-the-art 2D chip made from silicon by orders of magnitude,” he says. One of the most effective ways to build CFNETs in the lab is a method for depositing nanotubes called incubation, where a wafer is submerged in a bath of nanotubes until the nanotubes stick to the wafer’s surface. The performance of the CNFET is dictated in large part by the deposition process, says Bishop, which affects both the number of carbon nanotubes on the surface of the wafer and their orientation. They’re “either stuck onto the wafer in random orientations like cooked spaghetti or all aligned in the same direction like uncooked spaghetti still in the package,” she says. Aligning the nanotubes perfectly in a CNFET leads to ideal performance, but alignment is difficult to obtain. “It’s really hard to lay down billions of tiny 1-nanometer diameter nanotubes in a perfect orientation across a large 200-millimeter wafer,” Bishop explains. “To put these length scales into context, it’s like trying to cover the entire state of New Hampshire in perfectly oriented dry spaghetti.” The incubation method, while practical for industry, doesn’t align the nanotubes at all. They end up on the wafer more like cooked spaghetti, which the researchers initially didn’t think would deliver sufficiently high CNFET performance, Bishop says. After their experiments, however, she and her colleagues concluded that the simple incubation process would work to produce a CNFET that could outperform a silicon-based transistor. CNFETs beyond the beaker Careful observations of the incubation process showed the researchers how to alter the process to make it more viable for industrial production. For instance, they found that dry cycling, a method of intermittently drying out the submerged wafer, could dramatically reduce the incubation time — from 48 hours to 150 seconds. Another new method called ACE (artificial concentration through evaporation) deposited small amounts of nanotube solution on a wafer instead of submerging the wafer in a tank. The slow evaporation of the solution increased the concentration of carbon nanotubes and the overall density of nanotubes deposited on the wafer. These changes were necessary before the process could be tried on an industrial scale, Bishop says: “In our lab, we’re fine to let a wafer sit for a week in a beaker, but for a company, they don’t have that luxury.” The “elegantly simple tests” that helped them understand and improve on the incubation method, she says, “proved really important for addressing concerns that maybe academics don’t have, but certainly industry has, when they look at setting up a new process.” The researchers worked with Analog Devices, a commercial silicon manufacturing facility, and SkyWater Technology, a semiconductor foundry, to fabricate CNFETs using the improved method. They were able to use the same equipment that the two facilities use to make silicon-based wafers, while also ensuring that the nanotube solutions met the strict chemical and contaminant requirements of the facilities. “We were extremely lucky to work closely with our industry collaborators and learn about their requirements and iterate our development with their input,” says Bishop, who noted that the partnership helped them develop an automated, high-volume and low-cost process. The two facilities showed a “serious commitment to research and development and exploring the edge” of emerging technologies, Shulaker adds. The next steps, already underway, will be to build different types of integrated circuits out of CNFETs in an industrial setting and explore some of the new functions that a 3D chip could offer, he says. “The next goal is for this to transition from being academically interesting to something that will be used by folks, and I think this is a very important step in this direction.” (Comment on this)
11:00a	Coatings for shoe bottoms could improve traction on slick surfaces Inspired by the Japanese art of paper cutting, MIT engineers have designed a friction-boosting material that could be used to coat the bottom of your shoes, giving them a stronger grip on ice and other slippery surfaces. The researchers drew on kirigami, a variation of origami that involves cutting paper as well as folding it, to create the new coating. Laboratory tests showed that when people wearing kirigami-coated shoes walked on an icy surface, they generated more friction than the uncoated shoes. Incorporating this coating into shoes could help prevent dangerous falls on ice and other hazardous surfaces, especially among the elderly, the researchers say. “Through this work we set out to address the challenge of preventing falls, particularly on icy, slippery surfaces, and developed a kirigami-based system that facilitates an increase of friction with a surface,” says Giovanni Traverso, an MIT assistant professor of mechanical engineering, a gastroenterologist at Brigham and Women’s Hospital, and an assistant professor at Harvard Medical School. Traverso and Katia Bertoldi, a professor of applied mechanics at Harvard University, are the senior authors of the study, which appears today in Nature Biomedical Engineering. MIT Research Scientist Sahab Babaee is the lead author of the paper, along with Simo Pajovic, an MIT graduate student, and Ahmad Rafsanjani, a former postdoc at Harvard University. Inspired by art Kirigami is an art form that involves cutting intricate patterns into sheets of paper and then folding them to create three-dimensional structures. Recently, some scientists have used this technique to develop new materials such as bandages that stick more securely to knees and other joints, and sensors that can be used to coat the skin of soft robots and help them orient themselves in space. In this case, the team applied this approach to create intricate patterns of spikes in a sheet of plastic or metal. These sheets, applied to the sole of a shoe, remain flat while the wearer is standing, but the spikes pop out during the natural movement of walking. “The novelty of this type of surface is that we have a shape transition from a 2D flat surface to a 3D geometry with needles that come out,” Babaee says. “You can use those elements to control friction, because the sharp needles can pop in and out based on the stretch that you apply.” The researchers created and tested several different designs, including repeating patterns of spikes shaped like squares, triangles, or curves. For each shape, they also tested different sizes and arrangements, and they cut the patterns into both plastic sheets and stainless steel. For each of the designs, they measured the stiffness and the angle at which the spikes pop out when the material is stretched. They also measured the friction generated by each design on a variety of surfaces, including ice, wood, vinyl flooring, and artificial turf. They found that all of the designs boosted friction, with the best results produced by a pattern of concave curves. The researchers then used the concave curve coatings for tests with human volunteers. They attached the coatings to a variety of types of shoes, including sneakers and winter boots, and measured the friction produced when subjects walked across a force plate — an instrument that measures the forces exerted on the ground — covered with a 1-inch-thick layer of ice. They found that with the kirigami coatings attached, the amount of friction generated was 20 to 35 percent higher than the friction generated by the shoes alone.  Preventing falls The researchers are now working on determining the best way to attach and incorporate the kirigami surfaces. They are considering embedding them into the soles or designing them as a separate element that could be attached when needed. They are also exploring the possibility of using different materials, such as a rubber-like polymer with a reinforced steel tip. While the researchers’ original motivation was preventing slips on icy surfaces, they expect that this kind of shoe grip could also be useful in other settings, such as wet or oily working environments. “We’re looking at potential routes to commercialize the system, as well as further development of the system through different use cases,” Traverso says. The research was funded by the MIT Department of Mechanical Engineering, the U.S. National Science Foundation, and the Swiss National Science Foundation. (Comment on this)
2:59p	A boost for cancer immunotherapy One promising strategy to treat cancer is stimulating the body’s own immune system to attack tumors. However, tumors are very good at suppressing the immune system, so these types of treatments don’t work for all patients. MIT engineers have now come up with a way to boost the effectiveness of one type of cancer immunotherapy. They showed that if they treated mice with existing drugs called checkpoint inhibitors, along with new nanoparticles that further stimulate the immune system, the therapy became more powerful than checkpoint inhibitors given alone. This approach could allow cancer immunotherapy to benefit a greater percentage of patients, the researchers say. “These therapies work really well in a small portion of patients, and in other patients they don’t work at all. It’s not entirely understood at this point why that discrepancy exists,” says Colin Buss PhD ’20, the lead author of the new study. The MIT team devised a way to package and deliver small pieces of DNA that crank up the immune response to tumors, creating a synergistic effect that makes the checkpoint inhibitors more effective. In studies in mice, they showed that the dual treatment halted tumor growth, and in some cases, also stopped the growth of tumors elsewhere in the body. Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science, and a member of MIT’s Koch Institute for Integrative Cancer Research and the Institute for Medical Engineering and Science, is the senior author of the paper, which appears this week in the Proceedings of the National Academy of Sciences. Removing the brakes The human immune system is tuned to recognize and destroy abnormal cells such as cancer cells. However, many tumors secrete molecules that suppress the immune system in the environment surrounding the tumor, rendering the T cell attack useless. The idea behind checkpoint inhibitors is that they can remove this “brake” on the immune system and restore T cells’ ability to attack tumors. Several of these inhibitors, which target checkpoint proteins such as CTLA-4, PD-1, and PD-L1, have been approved to treat a variety of cancers. These drugs work by turning off checkpoint proteins that prevent T cells from being activated. “They work incredibly well in some patients, and they’ve given what some would call cures, for about 15 to 20 percent of patients with particular cancers,” Bhatia says. “However, there’s still a lot more to do to open up the possibility of using this approach for more patients.” Some studies have found that combining checkpoint inhibitors with radiation therapy can make them more effective. Another approach that researchers have tried is combining them with immunostimulatory drugs. One such class of drugs is oligonucleotides — specific sequences of DNA or RNA that the immune system recognizes as foreign. However, clinical trials of these immunostimulatory drugs have not been successful, and one possible reason is that the drugs are not reaching their intended targets. The MIT team set out to find a way to achieve more targeted delivery of these immunostimulatory drugs, allowing them to accumulate at tumor sites. To do that, they packaged oligonucleotides into tumor-penetrating peptides that they had previously developed for delivering RNA to silence cancerous genes. These peptides can interact with proteins found on the surfaces of cancer cells, helping them to specifically target tumors. The peptides also include positively charged segments that help them penetrate cell membranes once they reach the tumor. The oligonucleotides that Bhatia and Buss decided to use for this study contain a specific DNA sequence that often occurs in bacteria but not in human cells, so that the human immune system can recognize it and respond. These oligonucleotides specifically activate immune cell receptors called toll-like receptors, which detect microbial invaders. “These receptors evolved to allow cells to recognize the presence of pathogens like bacteria,” Buss says. “That tells the immune system that there’s something dangerous here: Turn on and kill it.” A synergistic effect After creating their nanoparticles, the researchers tested them in several different mouse models of cancer. They tested the oligonucleotide nanoparticles on their own, the checkpoint inhibitors on their own, and the two treatments together. The two treatments together produced the best results, by far. “When we combined the particles with the checkpoint inhibitor antibody, we saw a vastly improved response relative to either the particles alone or the checkpoint inhibitor alone,” Buss says. “When we treat these mice with particles and the checkpoint inhibitor, we can stop their cancer from progressing.” The researchers also wondered whether they could stimulate the immune system to target tumors that had already spread through the body. To explore that possibility, they implanted mice with two tumors, one on each side of the body. They gave the mice the checkpoint inhibitor treatment throughout the entire body but injected the nanoparticles into only one tumor. They found that once T cells had been activated by the treatment combination, they could also attack the second tumor. “We saw some signs that you could stimulate in one location and then get a systemic response, which was encouraging,” Bhatia says. The researchers now plan to perform safety testing of the particles, in hopes of further developing them to treat patients whose tumors don’t respond to checkpoint inhibitor drugs on their own. To that end, they are working with Errki Ruoslahti of the Sanford Burnham Prebys Medical Discovery Institute, who originally discovered the tumor-penetrating peptides. A company that Ruoslahti founded has already taken other versions of the tumor-penetrating peptides into human clinical trials to treat pancreatic cancer. “That makes us optimistic about the potential to scale up, manufacture them, and advance them to help patients,” Bhatia says. The research was funded by the Koch Institute Support (core) Grant from the National Cancer Institute, a Core Center Grant from the National Institute of Environmental Health Sciences, and the Koch Institute’s Marble Center for Cancer Nanomedicine. Bhatia also has affiliations with the Ludwig Institute for Cancer Research, the Broad Institute of MIT and Harvard, the Wyss Institute for Biologically Inspired Engineering, the Howard Hughes Medical Institute, and Brigham and Women’s Hospital. (Comment on this)

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