Minimally invasive tissue penetration techniques are increasingly demanded in biomedical applications such as neural probe implantation, ophthalmic surgery, and single-cell puncture. These procedures require highly precise penetration of biological membranes with minimal tissue damage, often relying on real-time force feedback to control insertion forces. Traditional methods typically use sharp micro-tools or robotic systems, which can lead to rapid insertion speeds, increasing tissue damage and inflammation risks. Additionally, the heterogeneous nature of biological tissues complicates the ability to adjust to varying mechanical properties. "Most existing systems lack integrated force sensing, limiting their ability to adapt in real time." said the author Bingze He, a researcher at Shanghai Jiao Tong University, "In this article, we present an integrated piezoelectric module combining vibration-assisted penetration and real-time force sensing to reduce insertion forces and provide accurate force feedback, addressing the lack of adaptability and precision in current systems."
The integrated piezoelectric module (IPEM) presented in the paper combines vibration-assisted penetration with real-time force sensing, featuring a compact design that integrates both driving and sensing functions in a single component. The module uses two piezoelectric ceramic discs (PZT), one acting as the actuator and the other as the sensor. The driving PZT generates axial micro-vibrations through the application of voltage, which assists in membrane rupture and reduces insertion resistance. The sensor PZT, on the other hand, employs the piezoelectric effect to monitor force changes during tissue interaction, providing force measurement signals in real-time. In terms of its working principle, the driving PZT generates axial micro-vibrations via the inverse piezoelectric effect (mechanical displacement induced by an applied electric field), while the sensor PZT detects small forces generated during penetration through the direct piezoelectric effect (electric charge generated by mechanical deformation). This integrated design enables the module to perform efficient tissue penetration and real-time force feedback simultaneously, without the need for external sensors or additional hardware.
The authors provide a detailed characterization and verification of the performance of this integrated piezoelectric module. First, finite element analysis and laser Doppler vibrometry were used to assess the vibration performance of the module, confirming that it can generate significant axial micro-vibrations at a resonant frequency of 4652 Hz. In vibration experiments, the module achieved an axial displacement of ±9.6 μm at a frequency of 4.6 kHz, with minimal deviation in the vibration direction, demonstrating excellent axial vibration capabilities. In terms of force sensing, static and dynamic calibration tests were conducted. Compared to a commercial force sensor, the module showed a strong linear relationship in static loading, with a correlation coefficient of 0.9998 and a sensitivity of 9.3 mV/mN. During dynamic tests, the module accurately tracked force changes under sinusoidal and square wave loading, with error kept within ±0.2 mN, indicating high precision and good repeatability. Furthermore, the practical performance of the module was validated through gelatin phantom and in vivo mouse brain penetration experiments. Gelatin tests showed that with vibration activated, the maximum puncture force was reduced by about 13%, and the penetration process was smoother. In the mouse brain experiments, the puncture force was reduced by 33% when vibration was applied, and the extraction process was smoother, demonstrating the module's effectiveness in reducing puncture forces while maintaining high precision. Overall, the module demonstrated excellent performance in vibration, force sensing accuracy, and practical applications, highlighting its potential for minimally invasive surgery and biomedical applications, particularly in brain-machine interfaces and microsurgical neural implantations.
Despite the module's outstanding performance in vibration-assisted penetration and force sensing, there are several limitations. First, the electrical noise in dynamic loading conditions may affect its precision, particularly in noisy surgical environments, which may require more advanced noise filtering techniques. Second, variations in temperature and humidity could affect the performance of the piezoelectric material, especially under extreme conditions. Furthermore, while the module's resonant frequency is optimized for soft tissues, adjustments may be needed for harder tissues (e.g., cornea) due to impedance mismatch. Additionally, the module's response time may lag during high-speed insertions, requiring further optimization. "Lastly, while the module performs well in single-point penetration, its application in more complex scenarios, such as multi-channel or array electrode implantation, still requires further validation." said Bingze He.
Authors of the paper include Bingze He, Yao Guo, and Guangzhong Yang.
This work was supported by Shanghai Municipal Science and Technology Major Project 2021SHZDZX.
The paper, "Integrated Piezoelectric Vibration and In Situ Force Sensing for Low-Trauma Tissue Penetration" was published in the journal Cyborg and Bionic Systems on Oct. 21, 2025, at DOI: 10.34133/cbsystems.0417.
