By levitating nanoparticles with laser beams, scientists have built an antenna 10,000 times smaller than typical low-frequency receivers.

This innovation sidesteps the usual size limitations, enabling strong signal reception despite its microscopic dimensions. With high tunability and real-world transmission tests proving its viability, the nano-antenna could transform communications in extreme environments.

A Tiny Antenna with Big Potential

A research team led by Professor Huizhu Hu from Zhejiang University and Zhejiang Lab has developed an innovative low-frequency receiving antenna using optically levitated nanoparticles. This breakthrough has resulted in an antenna that is nearly 10,000 times smaller than traditional designs. Their findings, published in PhotoniX on January 29, 2025, address major challenges in miniaturizing antennas for critical low-frequency (LF) applications, including underwater communication, underground sensing, and ionospheric waveguides.

Why It Matters

Low-frequency wireless signals (30–300 kHz) are essential for long-range transmission, penetrating obstacles, and resisting interference. However, making antennas smaller has always come at the cost of reduced sensitivity. Conventional solutions, such as magnetoelectric coupling antennas, remain relatively large — limited to centimeter-scale sizes because their resonant frequency is tied to their physical dimensions.

How It Works

The team’s nano-antenna leverages laser-trapped silica nanoparticles (143 nm diameter) levitated in a high vacuum. Key advancements include:

1. Charge Enhancement: Using focused electron beams, nanoparticles stably carry over 200 net charges—boosting electric field sensitivity.
2. Size-Frequency Decoupling: The nanoparticles’ resonant frequency depends on laser trapping parameters (e.g., optical power) rather than physical dimensions, enabling 100 nm size antennas to operate across 30 kHz–180 kHz.
3. High-Fidelity Signal Demodulation: With binary frequency-shift keying (2FSK) modulation, the system achieved a at 0.5 kbit/s under weak fields (0.1 V/m), validated in a vacuum of 2×10⁻⁷ mbar.

Technical Highlights

• Tunability: Optical trap power adjustment allows continuous frequency tuning, achieving sensitivity better than 10 μV/cm/√Hz.
• Vector Detection: 3D motion tracking enables omnidirectional signal reception, outperforming scalar-based traditional antennas.
• Real-World Validation: Successful image transmission with controlled error rates demonstrated practical viability.

Current Limitations & Future Prospects

While the nano-antenna’s sensitivity remains 3–4 orders lower than conventional designs, its nanoscale size and tunability offer unique advantages in extreme environments (e.g., deep-sea or confined spaces). Future work will focus on:

• Array Integration: Expanding bandwidth via multi-particle coordination.
• Frequency Extension: Adapting the platform to even lower frequencies using magnetic levitation or optimized materials.
• Chip-Scale Deployment: Merging vacuum trapping systems with semiconductor fabrication for portable devices.

Expert Perspective

“This fascinating paper considers the use of a levitated nanoparticle as a compact antenna for signals communicated as an electric field,” commented a PhotoniX reviewer.

Reference: “Optically levitated nanoparticles as receiving antennas for low frequency wireless communication” by Zhenhai Fu, Jinsheng Xu, Shaochong Zhu, Chaoxiong He, Xunming Zhu, Xiaowen Gao, Han Cai, Peitong He, Zhiming Chen, Yizhou Zhang, Nan Li, Xingfan Chen, Ying Dong, Shiyao Zhu, Cheng Liu and Huizhu Hu, 29 January 2025, PhotoniX.
DOI: 10.1186/s43074-025-00159-6