Dual-Conductive and Stiffness-Morphing Microneedle Patch Enables Continuous in Planta Monitoring of Electrophysiological Signal and Ion Fluctuation

The use of conductive microneedles presents a promising solution for achieving high-fidelity electrophysiological recordings with minimal impact on interfaced tissue. However, conventional metal-based microneedle suffers from high electrochemical impedance and mechanical mismatch. In this paper, we report a dual-conductive (i.e., both ionic and electronic conductive) and stiffness-morphing microneedle patch (DSMNP) for high-fidelity electrophysiological recordings with reduced tissue damage. The polymeric network of the DSMNP facilitates electrolyte absorption, and therefore allows the transition of stiffness from 6.82 N m-1 to 0.5139 N m-1. Furthermore, the nanoporous conductive polymer increased the specific electrochemical surface area after tissue penetration, resulting in ultralow specific impedance of 840 kΩ mm2 at 10 Hz. DSMNPs detected variation potential and action potential in real time and cation fluctuations in plants in response to environmental stimuli. After swelling, DSMNPs mechanically “lock” into biological tissues and prevent motion artifact by providing stable interface. These results demonstrate the potential of DSMNPs for various applications in the field of plant physiology research and smart agriculture.

导电微针（conductive microneedles）的应用为实现高保真电生理记录（high-fidelity electrophysiological recordings）提供了一种前景广阔的解决方案，且对界面组织（interfaced tissue）的影响极小。然而，传统金属基微针（metal-based microneedle）存在电化学阻抗（electrochemical impedance）高和力学失配（mechanical mismatch）的问题。本文报道了一种双导电（dual-conductive，即离子导电（ionic conductive）与电子导电（electronic conductive）兼具）且刚度可变（stiffness-morphing）的微针贴片（microneedle patch，DSMNP），可用于高保真电生理记录并减少组织损伤（tissue damage）。DSMNP的聚合物网络（polymeric network）有助于电解质吸收（electrolyte absorption），因此可实现刚度（stiffness）从6.82 N m⁻¹到0.5139 N m⁻¹的转变。此外，纳米多孔导电聚合物（nanoporous conductive polymer）在穿透组织后可增加比电化学表面积（specific electrochemical surface area），从而在10 Hz下实现840 kΩ mm²的超低比阻抗（specific impedance）。DSMNP可实时检测植物响应环境刺激（environmental stimuli）时的变异电位（variation potential）、动作电位（action potential）及阳离子波动（cation fluctuations）。肿胀后，DSMNP可通过提供稳定界面（stable interface）机械“锁定”于生物组织（biological tissues）中，从而防止运动伪影（motion artifact）。这些结果表明，DSMNP在植物生理学研究（plant physiology research）和智慧农业（smart agriculture）领域具有多种应用潜力。