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Friday, March 15th, 2019

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    12:00a
    Quantum sensing method measures minuscule magnetic fields

    A new way of measuring atomic-scale magnetic fields with great precision, not only up and down but sideways as well, has been developed by researchers at MIT. The new tool could be useful in applications as diverse as mapping the electrical impulses inside a firing neuron, characterizing new magnetic materials, and probing exotic quantum physical phenomena.

    The new approach is described today in the journal Physical Review Letters in a paper by graduate student Yi-Xiang Liu, former graduate student Ashok Ajoy, and professor of nuclear science and engineering Paola Cappellaro.

    The technique builds on a platform already developed to probe magnetic fields with high precision, using tiny defects in diamond called nitrogen-vacancy (NV) centers. These defects consist of two adjacent places in the diamond’s orderly lattice of carbon atoms where carbon atoms are missing; one of them is replaced by a nitrogen atom, and the other is left empty. This leaves missing bonds in the structure, with electrons that are extremely sensitive to tiny variations in their environment, be they electrical, magnetic, or light-based.

    Previous uses of single NV centers to detect magnetic fields have been extremely precise but only capable of measuring those variations along a single dimension, aligned with the sensor axis. But for some applications, such as mapping out the connections between neurons by measuring the exact direction of each firing impulse, it would be useful to measure the sideways component of the magnetic field as well.

    Essentially, the new method solves that problem by using a secondary oscillator provided by the nitrogen atom’s nuclear spin. The sideways component of the field to be measured nudges the orientation of the secondary oscillator. By knocking it slightly off-axis, the sideways component induces a kind of wobble that appears as a periodic fluctuation of the field aligned with the sensor, thus turning that perpendicular component into a wave pattern superimposed on the primary, static magnetic field measurement. This can then be mathematically converted back to determine the magnitude of the sideways component.

    The method provides as much precision in this second dimension as in the first dimension, Liu explains, while still using a single sensor, thus retaining its nanoscale spatial resolution. In order to read out the results, the researchers use an optical confocal microscope that makes use of a special property of the NV centers: When exposed to green light, they emit a red glow, or fluorescence, whose intensity depends on their exact spin state. These NV centers can function as qubits, the quantum-computing equivalent of the bits used in ordinary computing.

    “We can tell the spin state from the fluorescence,” Liu explains. “If it’s dark,” producing less fluorescence, “that’s a ‘one’ state, and if it’s bright, that’s a ‘zero’ state,” she says. “If the fluorescence is some number in between then the spin state is somewhere in between ‘zero’ and ‘one.’”

    The needle of a simple magnetic compass tells the direction of a magnetic field, but not its strength. Some existing devices for measuring magnetic fields can do the opposite, measuring the field’s strength precisely along one direction, but they tell nothing about the overall orientation of that field. That directional information is what the new detector system can n provide.

    In this new kind of “compass,” Liu says, “we can tell where it’s pointing from the brightness of the fluorescence,” and the variations in that brightness. The primary field is indicated by the overall, steady brightness level, whereas the wobble introduced by knocking the magnetic field off-axis shows up as a regular, wave-like variation of that brightness, which can then be measured precisely.

    An interesting application for this technique would be to put the diamond NV centers in contact with a neuron, Liu says. When the cell fires its action potential to trigger another cell, the system should be able to detect not only the intensity of its signal, but also its direction, thus helping to map out the connections and see which cells are triggering which others. Similarly, in testing new magnetic materials that might be suitable for data storage or other applications, the new system should enable a detailed measurement of the magnitude and orientation of magnetic fields in the material.

    Unlike some other systems that require extremely low temperatures to operate, this new magnetic sensor system can work well at ordinary room temperature, Liu says, making it feasible to test biological samples without damaging them.

    The technology for this new approach is already available. “You can do it now, but you need to first take some time to calibrate the system,” Liu says.

    For now, the system only provides a measurement of the total perpendicular component of the magnetic field, not its exact orientation. “Now, we only extract the total transverse component; we can’t pinpoint the direction,” Liu says. But adding that third dimensional component could be done by introducing an added, static magnetic field as a reference point. “As long as we can calibrate that reference field,” she says, it would be possible to get the full three-dimensional information about the field’s orientation, and “there are many ways to do that.”

    Amit Finkler, a senior scientist in chemical physics at Israel’s Weizmann Institute, who was not involved in this work, says “This is high quality research. … They obtain a sensitivity to transverse magnetic fields on par with the DC sensitivity for parallel fields, which is impressive and encouraging for practical applications.”

    Finkler adds, “As the authors humbly write in the manuscript, this is indeed the first step toward vector nanoscale magnetometry. It remains to be seen whether their technique can indeed be applied to actual samples, such as molecules or condensed matter systems.” However, he says, “The bottom line is that as a potential user/implementer of this technique, I am highly impressed and moreover encouraged to adopt and apply this scheme in my experimental setups.”

    While this research was specifically aimed at measuring magnetic fields, the researchers say the same basic methodology could be used to measure other properties of molecules including rotation, pressure, electric fields, and other characteristics. The research was supported by the National Science Foundation and the U.S. Army Research Office.

    11:45a
    Robot hand is soft and strong

    Fifty years ago, the first industrial robot arm (called Unimate) assembled a simple breakfast of toast, coffee, and champagne. While it might have looked like a seamless feat, every movement and placement was coded with careful consideration.

    Even with today’s more intelligent and adaptive robots, this task remains difficult for machines with rigid hands. They tend to work only in structured environments with predefined shapes and locations, and typically can’t cope with uncertainties in placement or form.

    In recent years, though, roboticists have come to grips with this problem by making fingers out of soft, flexible materials like rubber. This pliability lets these soft robots pick up anything from grapes to boxes and empty water bottles, but they’re still unable to handle large or heavy items.

    To give these soft robots a bit of a hand, researchers from MIT and Harvard University have developed a new gripper that’s both soft and strong: a cone-shaped origami structure that collapses in on objects, much like a Venus' flytrap, to pick up items that are as much as 100 times its weight. This motion lets the gripper grasp a much wider range of objects — such as soup cans, hammers, wine glasses, drones, and even a single broccoli floret.

    “One of my moonshots is to create a robot that can automatically pack groceries for you,” says MIT Professor Daniela Rus, director of MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) and one of the senior authors of a new paper about the project.

    “Previous approaches to the packing problem could only handle very limited classes of objects — objects that are very light, or objects that conform to shapes such as boxes and cylinders — but with the Magic Ball gripper system we’ve shown that we can do pick-and-place tasks for a large variety of items ranging from wine bottles to broccoli, grapes and eggs,” says Rus. “In other words, objects that are heavy and objects that are light. Objects that are delicate, or sturdy, or that have regular or free-form shapes.”

    The project is one of several in recent years that has researchers thinking outside the box with robot design. Ball-shaped grippers, for example, can handle a wider range of objects than fingers, but still have the issue of limited angles. Softer robotic fingers typically use compressed air, but aren’t strong enough to pick up heavier objects.

    The structure of this new gripper, meanwhile, takes an entirely different form. Cone-shaped, hollow, and vacuum-powered, the device was inspired by the “origami magic ball” and can envelope an entire object and successfully pick it up.

    The gripper has three parts: the origami-based skeleton structure, the airtight skin to encase the structure, and the connector. The team created it using a mechanical rubber mold and a special heat-shrinking plastic that self-folds at high temperatures.

    The magic ball’s skeleton is covered by either a rubber balloon or a thin fabric sheet, not unlike the team’s previous research on fluid-driven origami-inspired artificial muscles, which consisted of an airtight skin surrounding a foldable skeleton and fluid.

    The team used the gripper with a standard robot to test its strength on different objects. The gripper could grasp and lift objects 70 percent of its diameter, which allowed it to pick up and hold a variety of soft foods without causing damage. It could also pick up bottles weighing over four pounds.

    “Companies like Amazon and JD want to be able to pick up a wider array of delicate or irregular-shaped objects, but can’t with finger-based and suction-cup grippers,” says Shuguang Li, a joint postdoc at CSAIL and Harvard’s John A. Paulson School of Engineering and Applied Sciences. “Suction cups can’t pick up anything with holes — and they’d need something much stronger than a soft-finger-based gripper.”

    The robot currently works best with cylindrical objects like bottles or cans, which could someday make it an asset for production lines in factories. Not surprisingly, the shape of the gripper makes it more difficult for it to grasp something flat, like a sandwich or a book.

    “One of the key features of this approach to manipulator construction is its simplicity,” says Robert Wood, co-author and professor at Harvard’s School of Engineering and Wyss Institute for Biologically Inspired Engineering. “The materials and fabrication strategies used allow us to rapidly prototype new grippers, customized to object or environment as needed.”  

    In the future, the team hopes to try to solve the problem of angle and orientation by adding computer vision that would let the gripper “see”, and make it possible to grasp specific parts of objects.

    “This is a very clever device that uses the power of 3-D printing, a vacuum, and soft robotics to approach the problem of grasping in a whole new way,” says Michael Wehner, an assistant professor of robotics at the University of California at Santa Cruz, who was not involved in the project. “In the coming years, I could imagine seeing soft robots gentle and dexterous enough to pick a rose, yet strong enough to safely lift a hospital patient.”

    Other co-authors of the paper include MIT undergraduates John Stampfli, Helen Xu, Elian Malkin, and Harvard Research Experiences for Undergraduates student Evelin Villegas Diaz from St. Mary's University. The team will present their paper at the International Conference on Robotics and Automation in Montreal, Canada, this May.

    This project was supported in part by the Defense Advanced Research Projects Agency, the National Science Foundation, and Harvard's Wyss Institute.

    3:28p
    MIT celebrates 50th anniversary of historic moon landing

    On Sept. 12, 1962, in a speech given in Houston to pump up support for NASA’s Apollo program, President John F. Kennedy shook a stadium crowd with the now-famous quote: “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard.”

    As he delivered these lines, engineers in MIT’s Instrumentation Laboratory were already taking up the president’s challenge. One year earlier, NASA had awarded MIT the first major contract of the Apollo program, charging the Instrumentation Lab with developing the spacecraft’s guidance, navigation, and control systems that would shepherd astronauts Michael Collins, Buzz Aldrin, and Neil Armstrong to the moon and back.

    On July 20, 1969, the hard work of thousands paid off, as Apollo 11 touched down on the lunar surface, safely delivering Armstrong and Aldrin ScD ’63 as the first people to land on the moon.

    On Wednesday, MIT’s Department of Aeronautics and Astronautics (AeroAstro) celebrated the 50th anniversary of this historic event with the daylong symposium “Apollo 50+50,” featuring former astronauts, engineers, and NASA adminstrators who examined the legacy of the Apollo program, and MIT faculty, students, industry leaders, and alumni who envisioned what human space exploration might look like in the next 50 years.

    In welcoming a large audience to Kresge Auditorium, some of whom sported NASA regalia for the occasion, Daniel Hastings, head of AeroAstro, said of today’s prospects for space exploration: “It’s the most exciting time since Armstrong and Aldrin landed on the moon.”

    The event kicked off three days of programming for MIT Space Week, which also included the Media Lab’s “Beyond the Cradle: Envisioning a New Space Age” on March 14, and the student-led “New Space Age Conference” on March 15.

    “We could press on”

    As a “baby boomer living through Apollo,” retired astronaut Charles Bolden, NASA’s 12th administrator, said the Apollo program illustrated “how masterful we were at overcoming adversity.” In a keynote address that opened the day’s events, Bolden reminded the audience that, at the time the ambitious program got underway in the 1960s, the country was in the violent thick of the civil rights movement.

    We were killing each other in the streets,” Bolden said. “And yet we had an agency like NASA, and a small group of people, who were able to bear through everything and land on the moon. … We could recognize there were greater things we could do as a people, and we could press on.”

    For MIT’s part, the push began with a telegram on Aug. 9, 1961, to Charles Stark Draper, director of the Instrumentation Laboratory, notifying him that NASA had selected the MIT lab “to develop the guidance navigation system of the Project Apollo spacecraft.” Draper, who was known widely as “Doc,” famously assured NASA of MIT’s work by volunteering himself as a crew member on the mission, writing to the agency that “if I am willing to hang my life on our equipment, the whole project will surely have the strongest possible motivation.”

    This of course proved unnecessary, and Draper went on to lead the development of the guidance system with “unbounded optimism,” as his former student and colleague Lawrence Young, the MIT Apollo Program Professor, recalled in his remarks.

    “We owe the lighting of our fuse to Doc Draper,” Young said.

    At the time that MIT took on the Apollo project, the Instrumentation Laboratory, later renamed Draper Laboratory, took up a significant footprint, with 2,000 people and 15 buildings on campus, dedicated largely to the lunar effort.

    “The Instrumentation Lab dwarfed the [AeroAstro] department,” said Hastings, joking, “it was more like the department was a small pimple on the Instrumentation Lab.”

    Apollo remembered

    In a highlight of the day’s events, NASA astronauts Walter Cunningham (Apollo 7) and Charles Duke SM ’64 (Apollo 16), and MIT Instrumentation Laboratory engineers Donald Eyles and William Widnall ’59, SM ’62 — all from the Apollo era — took the stage to reminisce about some of the technical challenges and emotional moments that defined the program.

    One of the recurring themes of their conversation was the observation that things simply got done faster back then. For instance, Duke remarked that it took just 8.5 years from when Kennedy first called for the mission, to when Armstrong’s boots hit the lunar surface.

    “I would argue the proposal for such a mission would take longer [today],” Duke said to an appreciative rumble from the audience.

    The Apollo Guidance Computer, developed at MIT, weighed 70 pounds, consumed 55 watts of power — half the wattage of a regular lightbulb — and took up less than 1 cubic foot inside the spacecraft. The system was one of the first digital flight computers, and one of the first computers to use integrated circuits.  

    Eyles and Widnall recalled in detail the technical efforts that went into developing the computer’s hardware and software. “If you’re picturing [the computer code] on a monitor, you’d be wrong,” Eyles told the audience. “We were writing the program on IBM punch cards. That clunking mechanical sound of the key-punch machine was the soundtrack to creating the software.”

    Written out, that code famously amounted to a stack of paper as tall as lead software engineer Margaret Hamilton — who was not able to participate in Wednesday’s panel but attended the symposium dinner that evening.

    In the end, the Apollo Guidance Computer succeeded in steering 15 space flights, including nine to the moon, and six lunar landings. That’s not to say that the system didn’t experience some drama along the way, and Duke, who was the capsule communicator, or CAPCOM, for Apollo 11, remembers having to radio up to the spacecraft during the now-famous rocky landing.

    “When I heard the first alarm go off during the braking phase, I thought we were dead in the water,” Duke said of the first in a series of alerts that the Apollo astronauts reported, indicating that the computer was overloaded, during the most computationally taxing phase of the mission. The spacecraft was several miles off course and needed to fly over a “boulder field,” to land within 60 seconds or risk running out of fuel.

    Flight controllers in Houston’s Mission Control Center determined that if nothing else went wrong, the astronats, despite the alarms, could proceed with landing.

    “Tension was high,” Duke said of the moment. “You didn’t want to touch down on a boulder and blow a nozzle, and spoil your whole day.”

    When the crew finally touched down on the Sea of Tranquility, with Armstrong’s cool report that “the Eagle has landed,” Duke, too wound-up to properly verbalize the callback “Tranquility,” recalls “I was so excited … it came out as ‘Twang,’ or something like that.’ The tension — it was like popping a balloon.”

    Since the Apollo era, NASA has launched astronauts on numerous missions, many of whom are MIT graduates. On Wednesday, 13 of those graduates came onstage to be recognized along with the Apollo crew.

    In introducing them to the audience, Jeffrey Hoffman, a former astronaut and now AeroAstro professor of the practice, noted MIT’s significant representation in the astronaut community. For instance, in the five missions to repair the Hubble Space Telescope, which comprised 24 spacewalks, 13 of those were performed by MIT graduates.

    “That’s pretty cool,” Hoffman said.

    On the horizon

    The Apollo moon rocks that were were brought back to Earth have “evolved our understanding of how the moon formed,” said Maria Zuber, MIT’s vice president for research and the E.A. Griswold Professor of Geophysics in the Department of Earth, Atmospheric and Planetary Sciences. These rocks “vanquished” the idea that the moon originally formed as a cold assemblage of rocks and “foo foo dust,” she said.

    Instead, after carefully analyzing samples from Apollo 11 and other missions, scientists at MIT and elsewhere have found that the moon was a dynamic body, with a surface that at one time was entirely molten, and a metallic core, or “dynamo,” powering an early, lunar magnetic field. Even more provocative was the finding that the moon was not in fact “bone-dry,” but actually harbored water — an idea that Zuber said was virtually unpublishable until an MIT graduate reported evidence of water in Apollo samples, after which the floodgates opened in support of the idea.

    To consider the next 50 years of space exploration, the MIT symposium featured a panel of faculty members — Paulo Lozano, Danielle Wood, Richard Binzel, and Sara Seager — who highlighted, respectively, the development of tiny thrusters to power miniature spacecraft; an effort to enable wider access to microgravity missions; an MIT student-designed mission (REXIS) that is currently analyzing the near-Earth asteroid Bennu; and TESS and ASTERIA, satellite missions that are currently in orbit, looking for planets and possibly, life, outside our solar system.

    Industry leaders also weighed in on the growing commercialization of space exploration, in a panel, moderated by Oliver de Weck, Professor of Aeronautics and Astronautics and Engineering Systems, featuring MIT alums who currently head major aerospace companies.

    Keoki Jackson, chief technology officer of Lockheed Martin, noted the pervasiveness of space-based technologies, such as GPS-dependent apps for everything from weather and news, to Uber.

    “[Commercial enterprises] have made space a taken-for-granted part of life,” said Jackson, noting later in the panel that in 2015, 1 billion GPS devices had been sold around the world. “This shows you what can happen exponentially when you come up with something truly enabling.”

    “The challenge we face is talent, and in particular, diversity,” said John Langford, CEO and founder of Aurora Flight Sciences, who noted the panel’s all-male participants as an example. “It’s an industry-wide challenge. We’re working to reform ourselves, as we move from the brigade-type technologies that we grew up with, to incorporating technologies such as computer technology and artificial intelligence.”

    Future missions

    In a glimpse of what the future of space exploration might hold, MIT students presented lightning talks on a range of projects, including a custom-designed drill to excavate ice on Mars, a system that makes oxygen on Mars to fuel return missions to Earth, and a plan to send CubeSats around the world to monitor water vapor as a measure of climate change.

    Audience members voted online for the best pitch, which ultimately went to Raichelle Aniceto and her presentation of a CubeSat-enabled laser communications system designed to transmit large amounts of data from the moon to Earth in just five minutes.

    In the last keynote address of the symposium, Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, told the audience that there is still a lot of research to be done on the moon, which he said is changing, as evidenced by new craters that have formed in the last 50 years.

    “The moon of the Apollo era is not the same moon of today,” said Zurbuchen, who noted that just this week, NASA announced it will open previously unlocked samples of soil collected by the Apollo missions.

    In closing the symposium, Dava Newman, the Apollo Program Professor of Astronautics and former NASA deputy administrator, envisioned a future dedicated to sending humans back to the moon, and ultimately to Mars.

    “I’m a rocket scientist. I got here because of Apollo, and Eleanor Roosevelt said it best: Believe in the beauty of your dreams,” Newman said. “The challenge is, within 50 years, to be boots on Mars. I think we have the brains and the doers and inspiration to really make that happen.”

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