A laser-microfabricated electrohydrodynamic thruster forcentimeter-scale aerial robots
Hari Prasad, Hari Krishna et al. (2020), A laser-microfabricated electrohydrodynamic thruster forcentimeter-scale aerial robots, Dryad, Dataset, https://doi.org/10.5061/dryad.x95x69pdn
To date, insect scale robots capable of controlled flight have used flapping wings for generating lift, but this requires a complex and failure-prone mechanism. A simpler alternative is electrohydrodynamic (EHD) thrust, which requires no moving mechanical parts. In EHD, corona discharge generates a flow of ions in an electric field between two electrodes; the high-velocity ions transfer their kinetic energy to neutral air molecules through collisions, accelerating the gas and creating thrust. We introduce a fabrication process for EHD thruster based on 355 nm laser micromachining and our approach allows for greater flexibility in materials selection. Our four-thruster device measures 1.8 * 2.5 cm and is composed of steel emitters and a lightweight carbon fiber mesh. The current and thrust characteristics of each individual thruster of the quad thruster is determined and agrees with Townsend relation. The mass of the quad thruster is 37 mg and the measured thrust is greater than its weight (362.6 µN). The robot is able to lift off at a voltage of 4.6 kV with a thrust to weight ratio of 1.38.
Electrical characterization of the individual thruster in the quad thruster was performed first. A high voltage positive DC power supply (Bertan 205B-20R) was used to create the potential difference between the emitter and collector. The current associated with the discharge was determined from the power supply's built-in ammeter. The thruster was held directly above the balance with 0.1 mg resolution (Mettler Toledo) such that the collector grid was aligned parallel to the scale surface using a ceramic tweezer. This arrangement, with the thruster fixed, reduces the confounding effect of electrostatic forces acting on the aircraft through the tether wire. The distance between the collector grid and the weight scale is 21 mm. The scale reading was set to zero and each individual thruster was energized to measure the thrust. A piece of Teflon was placed between the balance plateau and the collector to electrically isolate the balance and to avoid any leakage current. The measured thrust is the force exerted by the accelerated ionic wind on the precision scale. Each measurement is repeated four times at a given actuation voltage to obtain independent statistical samples.
Air Force Office of Scientific Research, Award: FA9550-14-1-0398