The system, described March 15 in the journal PLOS ONE, could help make sophisticated robots more useful to people who do not have experience operating complex robotic systems. Study participants interacted with the robot interface using standard assistive computer access technologies — such as eye trackers and head trackers — that they were already using to control their personal computers.

The paper reported on two studies showing how such “robotic body surrogates” — which can perform tasks similar to those of humans — could improve the quality of life for users. The work could provide a foundation for developing faster and more capable assistive robots.

“Our results suggest that people with profound motor deficits can improve their quality of life using robotic body surrogates,” said Phillip Grice, a recent Georgia Institute of Technology Ph.D. graduate who is first author of the paper. “We have taken the first step toward making it possible for someone to purchase an appropriate type of robot, have it in their home and derive real benefit from it.”

Grice and Professor Charlie Kemp from the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University used a PR2 mobile manipulator manufactured by Willow Garage for the two studies. The wheeled robot has 20 degrees of freedom, with two arms and a “head,” giving it the ability to manipulate objects such as water bottles, washcloths, hairbrushes and even an electric shaver.

“Our goal is to give people with limited use of their own bodies access to robotic bodies so they can interact with the world in new ways,” said Kemp.

In their first study, Grice and Kemp made the PR2 available across the internet to a group of 15 participants with severe motor impairments. The participants learned to control the robot remotely, using their own assistive equipment to operate a mouse cursor to perform a personal care task. Eighty percent of the participants were able to manipulate the robot to pick up a water bottle and bring it to the mouth of a mannequin.

“Compared to able-bodied persons, the capabilities of the robot are limited,” Grice said. “But the participants were able to perform tasks effectively and showed improvement on a clinical evaluation that measured their ability to manipulate objects compared to what they would have been able to do without the robot.”

In the second study, the researchers provided the PR2 and interface system to Henry Evans, a California man who has been helping Georgia Tech researchers study and improve assistive robotic systems since 2011. Evans, who has very limited control of his body, tested the robot in his home for seven days and not only completed tasks, but also devised novel uses combining the operation of both robot arms at the same time — using one arm to control a washcloth and the other to use a brush.

“The system was very liberating to me, in that it enabled me to independently manipulate my environment for the first time since my stroke,” said Evans. “With respect to other people, I was thrilled to see Phil get overwhelmingly positive results when he objectively tested the system with 15 other people.”

The researchers were pleased that Evans developed new uses for the robot, combining motion of the two arms in ways they had not expected.

“When we gave Henry free access to the robot for a week, he found new opportunities for using it that we had not anticipated,” said Grice. “This is important because a lot of the assistive technology available today is designed for very specific purposes. What Henry has shown is that this system is powerful in providing assistance and empowering users. The opportunities for this are potentially very broad.”

The interface allowed Evans to care for himself in bed over an extended period of time. “The most helpful aspect of the interface system was that I could operate the robot completely independently, with only small head movements using an extremely intuitive graphical user interface,” Evans said.

The web-based interface shows users what the world looks like from cameras located in the robot’s head. Clickable controls overlaid on the view allow the users to move the robot around in a home or other environment and control the robot’s hands and arms. When users move the robot’s head, for instance, the screen displays the mouse cursor as a pair of eyeballs to show where the robot will look when the user clicks. Clicking on a disc surrounding the robotic hands allows users to select a motion. While driving the robot around a room, lines following the cursor on the interface indicate the direction it will travel.

Building the interface around the actions of a simple single-button mouse allows people with a range of disabilities to use the interface without lengthy training sessions.

“Having an interface that individuals with a wide range of physical impairments can operate means we can provide access to a broad range of people, a form of universal design,” Grice noted. “Because of its capability, this is a very complex system, so the challenge we had to overcome was to make it accessible to individuals who have very limited control of their own bodies.”

While the results of the study demonstrated what the researchers had set out to do, Kemp agrees that improvements can be made. The existing system is slow, and mistakes made by users can create significant setbacks. Still, he said, “People could use this technology today and really benefit from it.”

The cost and size of the PR2 would need to be significantly reduced for the system to be commercially viable, Evans suggested. Kemp says these studies point the way to a new type of assistive technology.

“It seems plausible to me based on this study that robotic body surrogates could provide significant benefits to users,” Kemp added.

“At the same time, however, there needs to be a mechanism in the body that prevents an uncontrolled differentiation of stem cells — because otherwise the supply of these cells in the muscles would be quickly depleted,” says Professor Carmen Birchmeier, head of the research group on Developmental Biology / Signal Transduction at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC).

Oscillation was previously only known to occur in brain stem cells

Birchmeier teamed up with colleagues from Berlin, Cologne, London, Paris, and Kyoto on mouse experiments that examined how this mechanism works. The group of researchers has now reported in the journal Genes & Development that the MyoD and Hes1 proteins regulate the differentiation of muscle cells. They are produced in the stem cells in an oscillatory manner — i.e., there are periodic fluctuations in the number of cells produced.

“This observation, first of all, was astonishing in itself,” says Birchmeier, “because no one before us had detected the oscillation of proteins in muscle.” Such a phenomenon was previously only observed in stem cells of the brain. The MDC researcher hopes her studies will one day lead to better treatments of muscular dystrophies and of sarcopenia, a syndrome characterized by the progressive loss of muscle mass with advancing age.

Production runs at full tilt every two to three hours

“In our experiments, we started off by connecting the Hes1 and MyoD to proteins to luminescent — i.e., light-emitting — proteins so that we could better track their development,” explains Dr. Ines Lahmann, the study’s lead author and a member of Birchmeier’s research group. The team was then able to observe — in isolated cells, in muscle tissue, and in living animals — that the Hes1 protein, which is part of the Notch signaling pathway, is produced in an oscillatory manner.

“Production reaches its peak every two to three hours and then declines again,” reports Lahmann, adding that they encountered the same phenomenon in the MyoD protein. “As long as the quantity of MyoD in the stem cells fluctuates periodically, the cells grow and divide, thus renewing themselves,” says Lahmann. This, according to her, ensures there is always a sufficient supply of stem cells in the muscle.

Stable protein production is crucial for differentiation

When a muscle stem cell starts to differentiate and develop into a muscle cell, one result is the formation of long muscle fibers. This occurs, for example, when a muscle grows in a young organism or when it tries to repair itself after an injury. “Every time we observed this conversion of cells under the microscope, we had previously noticed that the oscillation had stopped and MyoD was expressed stably — regardless of whether we were looking at newborn or adult animals,” reports Birchmeier.

Her team then proceeded to turn the gene for Hes1 completely off, so that the protein is no longer produced in the stem cells. The researchers also conducted this experiment on both cells and living animals. “The lack of Hes1 led to MyoD no longer being produced in an oscillatory manner, but rather in a stable pattern. All stem cells began to differentiate as a result,” says Birchmeier.

The goal is new therapies for muscular disorder patients

“Our experiments show that when it comes to stem cell differentiation and probably many other cellular processes, genes are not simply turned on or off — and that we are still a long way from understanding all the developments that occur when we use genetic tricks to do exactly that,” Birchmeier stressed.

She and her team next want to study why the oscillation of MyoD leads to stem cell differentiation not taking place in the muscles, and why a stable production of the protein is needed to trigger this process. “Once we gain a better understanding of the whole process,” says the researcher, “we will be able to better help people with muscular disorders whose natural capacity for muscle regeneration has been impaired.”

Over the last two decades, colloidal semiconductor nanocrystals, known as quantum dots (QDs), have emerged as novel materials for applications ranging from biological sensing and imaging to LED displays and solar energy harvesting. The new system can be used to continuously manufacture high-quality QDs for use in these applications.

“We call this system the Nanocrystal (NC) Factory, and it builds on the NanoRobo microfluidic platform that we unveiled in 2017,” says Milad Abolhasani, an assistant professor of chemical and biomolecular engineering at NC State and corresponding author of a paper on the work.

“Not only can we create the QDs in any color using a continuous manufacturing approach, but the NC Factory system is highly modular,” Abolhasani says. “This means that, coupled with continuous process monitoring, the system allows modifications to be made as needed to eliminate the batch-to-batch variation that can be a significant problem for conventional QD manufacturing techniques. Additionally, the chemistry we have developed in this work allows the perovskite QD processing to take place at room temperature.”

The fluorescence color of QDs is a result of the chemical composition, the size, and the way the nanocrystals are processed. The original QD synthesis strategy utilized in the NanoRobo system allowed for the room temperature synthesis of green-emitting perovskite QDs, which are made using cesium lead bromide. NC Factory starts with cesium lead bromide perovskite quantum dots, but then introduces various halide salts to precisely tune their fluorescence color across the entire spectrum of visible light. Anions in these salts replace the bromine atoms in the green-emitting dots with either iodine atoms (to move toward the red end of the spectrum) or chlorine atoms (to move toward blue).

“Because the NC Factory can precisely control both chemical composition and processing parameters, it can be used to continuously manufacture perovskite quantum dots in any color with the highest quality,” Abolhasani says.

The NC Factory system consists of three “plug and play” modules. The researchers developed a pre-mixing module to expedite the mixing of halide salts and quantum dots, in order to improve product quality. The system also incorporates a velocity sensor that allows users to monitor reaction times accurately. The synthesized QDs are then monitored in situ using the NanoRobo process-monitoring module.

“From a scientific standpoint, the NC Factory system allowed us to discover that this halide exchange process takes place in three stages,” Abolhasani says. “That’s very important for better understanding the reaction mechanism. But the system can also impact practical issues related to quantum dot applications and manufacturing.”

For example, perovskite quantum dots are attractive to the solar power industry for their efficiency, but they are still too expensive to be adopted on a large scale. And more than 60 percent of that cost is attributed to manufacturing labor.

“The NC Factory system would require far less labor to operate continuously,” Abolhasani says. “We estimate that the system could cut overall manufacturing costs by at least 50 percent. It should reduce manufacturing costs of QDs for any application and should at least preserve — if not improve — the quality of the quantum dots.

“We’ve submitted a patent for the system, and are working with industry collaborators to commercialize the technology,” Abolhasani says.

The paper, “Facile Room Temperature Anion Exchange Reactions of Inorganic Perovskite Quantum Dots Enabled by a Modular Microfluidic Platform,” is published in the journal Advanced Functional Materials. Co-first authors are Kameel Abdel-Latif and Robert Epps, who are Ph.D. students in chemical and biomolecular engineering at NC State. The paper was co-authored by Corwin Kerr, an undergraduate student at NC State; Christopher Papa, a Ph.D. student in chemistry at NC State; and Felix Castellano, the Goodnight Innovation Distinguished Chair of Chemistry at NC State.

The research was done with support from a UNC General Assembly Research Opportunities Initiative grant and the Air Force Office of Scientific Research, under grant number FA9550-18-1-0331. The work was also done with assistance from NC State’s Analytical Instrumentation Facility, which is supported by the National Science Foundation under grant ECCS-1542015.

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.”

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.

“In this study, we aimed to investigate how odor mixtures of opposite valence, that is, a mix of odors that are attractive and repellent, are processed and perceived,” explains Ahmed Mohamed, lead author of the study, adding: “By taking advantage of the sophisticated genetics available in Drosophila, we elucidated the neural mechanism that enables the animal to evaluate such conflicting situations in order to take the appropriate decision.”

The scientists exposed the vinegar fly Drosophila melanogaster to artificial odor mixtures, each containing an attractive and repellent odor, in defined ratios. By analyzing the brain activity of these opposing odor mixtures using functional imaging techniques, they were able to show that a repellent component in an odor mixture specifically inhibits the odor channels for attractants. “This inhibition correlates with a reduced attraction to the odor source” explains Silke Sachse. The underlying neuronal mechanism and the specific neurons involved could also be identified.

“Our data demonstrate a specific, inhibitory cross-talk in the olfactory center of the fly’s brain. Using further genetic tools we were able to show that glomeruli, spherical functional units in the olfactory center, that respond to attractive odors, are linked via specific inhibitory neurons to the repellent-specific glomeruli,” Ahmed Mohamed describes from the results.

However, not all odor mixtures show the same inhibitory effect. An exception is geosmin, the typical smell of toxic bacteria or mold. Geosmin is recognized in the fly brain by only one receptor type, and thus only a highly specific glomerulus is activated. “It is conceivable that this geosmin glomerulus has no strong interactions with other glomeruli and cannot influence them accordingly,” speculates Markus Knaden, another author of the study. Similar specialized pathways have been described only for the detection of sex pheromones, carbon dioxide and iridomyrmecin, the latter of which is the smell specific to a parasitic wasp that infests vinegar flies.

The scientists assume that this neuronal mechanisms of the fly brain might also occur in other olfactory systems, such as the olfactory bulb of mammals, and therefore also potentially in humans. Such a mechanism could help protect not only flies, but also we as humans to recognize and avoid, for example, contaminated food that emits pleasant as well as bad odors. In the future, the researchers want to investigate whether this neuronal mechanism is modified by other factors, such as physiological state, e.g. hunger [KG/AO].

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