Plasmonic directional antenna · serves as: Actuator, Locomotion Drive, Research and Education.
Which group Plasmonic nanoantenna belongs to and how it is built
This subcategory covers nanoscale actuators driven by a light beam, where force arises from photon momentum transfer (photon recoil) or from directional scattering of light on metallic structures. Unlike classical electromechanical actuators, they have no moving parts and no electrical power supply — energy and control are delivered remotely by an external laser beam. The direction of motion can be steered by the polarization of the light. Such elements typically operate in aqueous environments and are being developed for nanorobots that manipulate biological objects.
A plasmonic directional antenna is a type of optical nanoactuator built from metallic nanorods (usually gold) in which surface plasmons are excited. The antenna scatters incident light asymmetrically (directionally), and each deflected photon generates a recoil force that propels the structure. Suitable nanorod geometry makes the same structure provide both propulsion and orientation control: the direction of motion is locked to the linear polarization axis of the light, and circularly polarized light pulses select the sense of rotation through spin and momentum transfer. It requires no electrical power and no tight beam focusing.
A design class describing the construction of a directional plasmonic antenna from monocrystalline gold nanorods. The nanorods are fabricated by helium focused-ion-beam milling from thin (about 50 nm) monocrystalline gold platelets and then embedded in a rigid, transparent silica body (HSQ). The choice of nanorod lengths and mutual arrangement determines the directionality of scattering and the coupling of motion to the light polarization.
Basic physical properties of Plasmonic nanoantenna — dimensions, weight and materials
A plasmonic nanoantenna is an optical propulsion element developed by the Nano-Optics and Biophotonics Group (Experimentelle Physik 5) at Julius-Maximilians-Universität Würzburg (JMU), led by Prof. Bert Hecht. It is built from monocrystalline gold nanorods embedded in a transparent silica body and acts as the motor of a light-driven, sub-micrometer nanorobot.
Propulsion arises from photon recoil: the antenna scatters incident near-infrared laser light (980 nm) directionally, and each deflected photon produces a reaction force. The same structure provides both propulsion and orientation control — the direction of motion is locked perpendicular to the linear polarization axis, and short circularly polarized light pulses execute turns through spin and momentum transfer.
The nanorobots reach speeds of up to 50 µm/s and operate directly in aqueous solution. In a paper published in Nature Communications (2026, "A nanoscale robotic cleaner") they were demonstrated capturing, transporting, reversibly assembling and releasing bacteria using opto-thermophoretic forces — acting as a nanoscale robotic cleaner.
