​Fighter plane windshields already benefit from ultrasonic-wave cleaning systems. The systems are effective, but not very discreet: The piezoelectric transducers are contained in bulky ceramic housings. "We want to come up with a system that is invisible to the naked eye," said CEA-Leti Program Director Jean-Philippe Polizzi. "Windshields, PV solar panels, and automotive camera lenses are just a few of the many transparent surfaces that must be perfectly clean at all times."

Electrodes as thin as a human hair

• Silicon Valley startup Innovasonic, which has been working with Leti since mid-2019, patented the concept. The conventional ceramic assembly will be replaced by an array of transducers no thicker than a human hair (100 µm, possibly less) made up of a stack of two electrodes and a piezoelectric material. An electrical current causes the devices to vibrate, emitting ultrasonic waves. Grime is dislodged and water droplets are vaporized instantly.
  

• CEA-Leti is ideally positioned to produce the transducers. The institute has the capacity to fabricate high-quality, high-coefficient piezoelectric materials like PZT (lead zirconate titanate) and aluminum nitride and integrate electrodes around these materials.
  

• The project will also address the system as a whole. CEA-Leti researchers will determine what type of wave is most efficient and at what frequency and amplitude. They will also optimize the spacing of the electrodes. "We plan to use simulations to resolve these issues before we build the first demonstrator system," said Polizzi. The objective is to have a proof-of-concept prototype by mid-2020.