Meta-Skin-Based Ultrasonic Instrument Enabling Highly Selective Ultrasound Stimulation and Treatment
Zong-Lin Li, Ping Chen, Kun Chen, Hu Cai, Wang Yun, Lai-Xin Huang, Guang Yang, Jinjing Zhang, Yu-Gui Peng, Xue-Feng Zhu
Advanced Devices & Instrumentation 2025 · 10.34133/adi.0099
Abstract
The rapid development of metasurface has produced new possibilities for manipulating the sound waves with unprecedented precision and versatility. Leveraging advanced processing techniques such as 3-dimensional (3D) printing and nano-/micro-etching, various metasurface devices were implemented with remarkable capabilities in achieving the exceptional sound reflection and transmission. In biomedical engineering, successful applications of acoustic metasurface devices remain elusive due to many challenges such as impedance mismatching between instruments and issues, and the requirement of 2D fingerprint for integration and biocompatibility. Here, we propose a prototype of meta-skin-based ultrasonic instrument for applications of highly selective ultrasound neurostimulation and treatment. The meta-skin is flexible and biocompatible, with a thickness of only 20 μm (~ 1 / 15 of ultrasound wavelength at 5 MHz). The meta-skin can be further patterned into a meta-lens, which is sealed in hydrogel with a transducer. The meta-skin-based device can be seamlessly attached to tissues or skulls of animals with acoustic transparency and subwavelength-scale focusing (focal spot size ~220 μm). As an example, we utilized the meta-skin-based instrument to selectively stimulate sciatic nerves in rats. Moreover, the proposed device can make the focused ultrasound beam penetrate the skull and accurately stimulate small nucleus in target regions of the brain, which provides a potential therapeutic treatment for Parkinson’s disease.
Abstract via crossref.
Exposures
Exposure 1: Meta-skin lens, peroneal and tibial nerve bundles
Target: sciatic nerve, peroneal nerve, tibial nerve — “sciatic nerves (peroneal and tibial nerve bundles)”
Device: custom-built · meta-skin acoustic meta-lens sealed in hydrogel with a piezo-transducer
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | not reported | ⚑ |
| Pulse duration (ms) | not reported | |
| Pulse repetition frequency (Hz) | 1,000 | ✓✓✓⚑ |
| Duty cycle (%) | not reported | |
| Sonication duration (s) | 2 | ✓✓✓⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Periodic electric pulses with a repetition period of 1 ms, each pulse containing 100 to 550 cycles (increased from 100 to 550 in steps of 50; 300 cycles for the lens comparison); ultrasound output paused for 4 s after every 2 s of stimulation. Frequency varied to shift focal depth.
Exposure 2: Meta-skin lens through skull, subthalamic nucleus (PD rats)
Target: subthalamic nucleus — “STN”
Device: custom-built · meta-skin acoustic meta-lens sealed in hydrogel with a piezo-transducer
| Waveform | not reported | |
|---|---|---|
| Fundamental frequency (kHz) | 5,000 | ✓✓✓⚑ |
| Pulse duration (ms) | not reported | |
| Pulse repetition frequency (Hz) | not reported | |
| Duty cycle (%) | not reported | |
| Sonication duration (s) | 1,800 | ✓✓✓⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | measurementsingle value | |
| In-situ pressure (kPa) | 540 | ✓✓✓⚑ |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
30 min of daily ultrasound stimulation followed by an L-DOPA injection, for 14 days; pulse timing for the STN experiment is not stated.
Flags from extraction
exposures[1].in_situ.pressure_kpa— 0.54 MPa was measured through a skull model immersed in water (Fig. 1D), not in the animals; recorded as in_situ measurement, peak or peak-to-peak not stated.exposures[1].fundamental_frequency_khz— 5 MHz is the frequency at which the focal spot was described; the STN stimulation frequency is not restated and the paper says focal depth is tuned by frequency.exposures[0].fundamental_frequency_khz— Frequency for the sciatic experiments not stated (varied to adjust focal depth).exposures[0].timing.pulse_repetition_frequency_hz— Text says 'the pulse repetition frequency is 1 ms'; read as a 1 ms period, converted to 1000 Hz.exposures[0].timing.sonication_duration_s— 2 s of stimulation then 4 s pause.n_subjects— Only the STN experiment states group size (10 PD rats with ultrasound); sciatic nerve rat number not stated.anaesthesia— Sciatic experiments under pentobarbital; anaesthesia during daily STN stimulation not stated.exposures[1].timing.sonication_duration_s— 30 min daily stimulation session; duty of pulses not given.n_sessions_per_subject— 14 days of daily stimulation described, but the count of sessions per rat is not stated as a number in the stimulation sentence; left not_reported.conditions— Sciatic nerve rats are normal rats; 'healthy' inferred from absence of a disease model.