# A laser-microfabricated electrohydrodynamic thruster for centimeter-scale aerial robots

## TL;DR

This paper presents a laser-microfabricated electrohydrodynamic thruster for small aerial robots, offering a simpler, reliable alternative to flapping wings by generating lift through ion flow without moving parts.

## Contribution

It introduces a novel fabrication process for EHD thrusters using laser micromachining, enabling lightweight, flexible, and effective thrusters for centimeter-scale robots.

## Key findings

- Thrust exceeds the robot’s weight at 362.6 microNewtons.
- The thruster lifts off at 4.6 kV with a thrust-to-weight ratio of 1.38.
- Measured thruster characteristics align with Townsend relation.

## Abstract

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 x 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 uN). The robot is able to lift off at a voltage of 4.6 kV with a thrust to weight ratio of 1.38.