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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 | F E B R U A R Y / M A R C H 2 0 1 8 has a focus spot less than 10 nm in diameter and an efficiency of more than 80%, the team turned to multi- layer Laue lenses (MLLs). Unlike con- ventional optics, which refract light, MLLs have a layered structure that acts like a crystal to diffract incident x-rays, concentrating them on a focus point. The structure consists of alternating layers of two different materials, the thickness and orientation of which vary to achieve the desired diffraction, with the smallest layer thickness in the structure proportional to the size of the focus spot. To produce such a tiny spot, the DESY lens employs more than 10,000 alternating layers of a new material combination—tungsten carbide and sil- icon carbide—and focuses an x-ray beam in vertical and horizontal direc- tions by passing it through two per- pendicularly oriented lenses. With this setup, a spot size of 8.4 × 6.8 nm was measured at Brookhaven National Laboratory, and in further tests at DESY, the lens produced high-resolu- tion holograms of a single-celled mar- ine plankton. The new lens can be used in applications such as nanoresolu- tion imaging and spectroscopy, and TESTING | CHARACTERIZATION SURFACE CHARACTERIZATION TECHNIQUE IS ALL WET Researchers at Aalto University, Finland, developed a new measure- ment technique to characterize the wetting properties of superhydropho- bic materials that is 1000 times more precise than current methods. While existing instruments for measuring droplet adhesion can detect forces at the micronewton level, scanning drop- let adhesionmicroscopy (SDAM) records the nanonewton forces that occur when a water droplet touches and separates from a surface. By taking multiple mea- surements at micrometer-length inter- vals, the instrument constructs a 2D image of surface repellency. Until now, contact angle measure- ment has been the go-to method for wetting property characterization, but that approach is prone to inaccuracies for highly hydrophobic surfaces and it requires direct line of sight, which eliminates measurement of uneven sur- faces such as fabrics or biological sur- faces—a task SDAM can tackle. SDAM also detects the previously hard-to- measure wetting properties of micro- scopic functional features important in many biochips, chemical sensors, and microelectromechanical components. In addition to characterizing wetting properties, SDAM can also measure minuscule surface features and incon- sistencies, which could contribute to improved quality control in anti-icing, anti-corrosion, and anti-biofouling pro- ducts. www.aalto.fi/en. LAYERED X-RAY LENS NARROWS THINGS DOWN Scientists at DESY, Germany, de- veloped a new x-ray microscopy lens that can produce resolutions five times sharper than current state-of-the-art lenses. To develop the new lens, which BRIEF For the first time, a team of scientists headed by researchers at the Universi- ty of California, San Diego observed nanoscale changes deep inside hybrid perovskite crystals, a promising class of solar cell materials. Using x-ray beams and lasers, researchers study how the material behaves at the nanoscale, pro- viding insights that could lead to low cost, high efficiency cells. ucsd.edu . Illustration shows how ionmigration in a hybrid perovskite crystal affects solar cell performance in different areas of the crystal. Courtesy of AMOLF. Droplet probe of a microscope on a superhydrophobic golden birdwing (Troides aeacus) butterfly wing. Courtesy of Matti Hokkanen/Aalto University.