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Wang et al. Soft Sci 2024;4:41 https://dx.doi.org/10.20517/ss.2024.53 Page 27 of 43

Figure 12. Principle application of micro-cylindrical sensors for surgical robots and microfiberbots. (A) Schematic design of the micro
EIS-on-a-needle for depth profiling (µEoN-DP); (B) Photograph of the IDE fabricated on the curved surface of the needle; (C) Images of
experimental setup. Reproduced with permission [51] . Copyright 2016, MDPI; (D) Schematic of the overall system of the sRFA-needle; (E)
Schematic of the operating principles of contact resistance-based P-sensor and resistance-based T-sensor; (F) P-sensor at hydrostatic
pressure. Reproduced with permission [211] . Copyright 2021, John Wiley and Sons; (G) A schematic representation of the FSCR,
comprising a soft polymer matrix embedded with hard magnetic particles and reinforced with a PLA mesh. Reproduced with
permission [214] . Copyright 2021, Springer Nature; (H) Schematic of fiber cantilever bending driven by thermal expansion; (I) Six tip
displacement patterns captured using the slow shutter speed function of a mirrorless camera while moving a 500-μm optical fiber
connected to a 650-nm LED. Reproduced with permission [112] . Copyright 2024, American Association for the Advancement of Science.
EIS: Electrical impedance spectroscopy; IDE: interdigitated electrode; sFRA: sensor-integrated radiofrequency ablation; FSCR:
ferromagnetic soft catheter robot; PLA: polylactide; LED: light-emitting diode.

[24]
acoustic impedance , and medical needles with integrated acoustic impedance sensors are widely utilized
for this purpose. Additionally, in radiofrequency (RF) ablation, heat-induced steam popping may occur,
causing tissue necrosis. To mitigate this risk, Jeong et al. developed a flexible pressure sensor that operates
based on the variation in contact resistance between an electrode and a three-dimensional microstructured
PI/CNT composite film [211,212] [Figure 12D and E]. By integrating both pressure and temperature sensors into
the surface of an ablation needle, real-time monitoring of temperature and pressure is possible during
procedures [Figure 12F]. During needle insertion, mechanical deformation occurs due to tissue reaction
forces. This deformation can be assessed by integrating strain sensors, enabling more precise needle