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1 0 A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 0 OLED ULTRASOUNDS Researchers from North Carolina State University, Raleigh, developed a simpler and more cost effective approach for creating ultrasound images that eliminates the electrical signal processing step. To do this, they created a receiver that incorporates a piezoelectric crystal and an organic light-emitting diode (OLED). When an ultrasonic wave hits the crystal, it produces voltage, which causes the OLED to light up. Essentially, the image appears on the OLED screen, which is built into the receiver itself. The proof-of-concept prototype is designed with a 10 x 10 pixel OLED array, but researchers say they can easily increase the pixels for better resolution. “Conventional ultrasound imaging probes can cost upward of $100,000 because they contain thou- sands of transducer array elements, which drives up manufacturing costs,” they say. “We can make ultrasound receiver-display units for $100 or so.” Potential near-term applications could TESTING | CHARACTERIZATION RECONFIGURABLE METALENSES Over the past decade, research- ers at Harvard University, Cambridge, Mass., have begun to transform the field of optics by engineering flat optics metasurfaces, employing an array of millions of tiny, microscopically thin and transparent quartz pillars to dif- fract and mold the flow of light similar to glass lenses, but without the aber- rations that naturally limit the glass. Now, the researchers and their collabo- rators have taken a step toward making these metalenses even more useful—by making them reconfigurable. Harness- ing nanoscale forces to infiltrate liquid crystals between microscopic pillars A simplified illustration of the newly developed ultrasound imaging device. Courtesy of North Carolina State University. allows the scientists to shape and diffract the light in com- pletely new ways and essen- tially fine-tune the focusing power. Liquid crystals are espe- cially useful because they can be manipulated thermally, electrically, magnetically, or optically, which creates the potential for the flexible, or reconfigurable, lenses. Until recently, researchers say, once a glass lens was shaped into a rigid curve, it could only bend the light in one direction, unless combined with other lenses or physically moved. Metalenses changed that, since they allow engi- neering of the wavefront by controlling phase, amplitude, and polarization of the light. Now, by controlling the liq- uid crystal, the researchers have been able move this new class of metalenses toward new scientific and technological endeavors to generate reconfigurable structured light. The technology was selected as among the “Top 10 Emerging Technol- ogies” by the World Economic Forum in 2019, which remarked that these increasingly smaller, clearer lenses would soon begin to be seen in camera phones, sensors, optical fiber lines, and medical imaging devices such as endo- scopes. “These tiny, thin, flat lenses could replace existing bulky glass lenses and allow further miniaturization in sensors and medical imaging devices.” harvard.edu . An illustration depicting how a metalens refracts light. Courtesy of Giuseppe Strangi & Federico Capasso. Case Western Reserve University researchers, Cleveland, are collabo- rating with the U.S. Army and three industry partners to advance man- ufacturing approaches for lightweight and high-performance polymeric materials. The Army’s new five-year agreement awards $5.4 million to a team led by Case, with part of the funding to be used for lab equipment, including an electron microscope. cwru.edu . The National Science Founda- tion awarded a $1 million grant to a team from the University of California, San Diego, University of Minnesota, Carnegie Mellon University, and Cornell University to create the X-ray Imaging of Mi- crostructures Gateway (XIMG), de- signed to help researchers study the behavior of new and existing materials using x-ray diffraction. ucsd.edu . BRIEFS