We used nanomaterials to demonstrate light-powered levitation of microflyers. For the first time, we devised macroscopic objects that can fly without any moving parts using photophoresis, or light-induced airflow. This new flight mechanism will enable 1) sunlight-powered meter-scale vehicles in the upper atmosphere collecting information about our changing climate and 2) millimeter-scale photophoretic microflyers that will surround us on Earth’s surface, providing ubiquitous sensor data.

Historically, flight has been achieved using balloons, propellers or flapping wings, or rockets but all these technologies “hit a wall” at some point. For example, rockets can fly no more than about 10 minutes per stage, while balloons and airplanes cannot rise about the stratosphere, with altitude records maxing out at ~50 km. In addition, balloons, propellers, or flapping-wing flyers must be a few centimeters or larger to work. Despite the commonly used name “microflyers”, no man-made structures of less than 1 cm can fly sustainably due to the increased effects of viscosity at small sizes.

Using photophoresis as a completely new physical mechanism to fly, we can break through these walls. Large photophoretic aircraft can fly at altitudes of 50 to 100 km using only sunlight, finally enabling long-term studies of the mesosphere. Different physics also means that photophoretic microflyers work better as their size decreases, finally allowing the creation of true microflyers (< 1 mm). Tags: Levitation, Microflyers, Mesosphere, Photophoresis

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