Coil-Tac: Coiled Capacitor Mechanism with Liquid Metal for Tactile Sensing

George P Jenkinson; Andrew T Conn; Antonia Tzemanaki

doi:10.1109/LRA.2025.3558655

Coil-Tac: Coiled Capacitor Mechanism with Liquid Metal for Tactile Sensing

George P Jenkinson^*, Andrew T Conn, Antonia Tzemanaki

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

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Abstract

Exploiting the high conductivity and fluidity of liquid metal, Coil-Tac is a soft transduction mechanism based on measuring change in capacitance as a flowable liquid metal core moves within a conductive helical coil. Using finite difference methods, a model is derived that estimates the response of Coil-Tac with various coil pitches to within 0.0502 pF of our experimental results in the range of 0-2.5 pF, corresponding to a lateral liquid metal movement of up to 35 mm. The Coil-Tac mechanism is demonstrated to be capable of oscillatory tactile sensing at 5 Hz and touch location estimation when coupled to a soft interface. The mechanism coupled with the interface is sensitive enough to locate the centre of the contact to within 0.23 mm, and estimate the incident angle between the axis of the dome and a flat surface to within 0.53∘.

Original language	English
Pages (from-to)	5194-5200
Number of pages	7
Journal	IEEE Robotics and Automation Letters
Volume	10
Issue number	5
Early online date	7 Apr 2025
DOIs	https://doi.org/10.1109/LRA.2025.3558655
Publication status	Published - 1 May 2025

Bibliographical note

Publisher Copyright:
© 2025 IEEE.

Keywords

Force and Tactile Sensing
Soft Sensors and Actuators
Mechanism Design

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10.1109/LRA.2025.3558655

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Accepted author manuscript, 10.1 MBLicence: CC BY

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@article{a37c07a9b2784e689e2a0d21c7579e81,

title = "Coil-Tac: Coiled Capacitor Mechanism with Liquid Metal for Tactile Sensing",

abstract = "Exploiting the high conductivity and fluidity of liquid metal, Coil-Tac is a soft transduction mechanism based on measuring change in capacitance as a flowable liquid metal core moves within a conductive helical coil. Using finite difference methods, a model is derived that estimates the response of Coil-Tac with various coil pitches to within 0.0502 pF of our experimental results in the range of 0-2.5 pF, corresponding to a lateral liquid metal movement of up to 35 mm. The Coil-Tac mechanism is demonstrated to be capable of oscillatory tactile sensing at 5 Hz and touch location estimation when coupled to a soft interface. The mechanism coupled with the interface is sensitive enough to locate the centre of the contact to within 0.23 mm, and estimate the incident angle between the axis of the dome and a flat surface to within 0.53∘.",

keywords = "Force and Tactile Sensing, Soft Sensors and Actuators, Mechanism Design",

author = "Jenkinson, {George P} and Conn, {Andrew T} and Antonia Tzemanaki",

note = "Publisher Copyright: {\textcopyright} 2025 IEEE.",

year = "2025",

month = may,

day = "1",

doi = "10.1109/LRA.2025.3558655",

language = "English",

volume = "10",

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journal = "IEEE Robotics and Automation Letters",

issn = "2377-3766",

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}

TY - JOUR

T1 - Coil-Tac

T2 - Coiled Capacitor Mechanism with Liquid Metal for Tactile Sensing

AU - Jenkinson, George P

AU - Conn, Andrew T

AU - Tzemanaki, Antonia

PY - 2025/5/1

Y1 - 2025/5/1

N2 - Exploiting the high conductivity and fluidity of liquid metal, Coil-Tac is a soft transduction mechanism based on measuring change in capacitance as a flowable liquid metal core moves within a conductive helical coil. Using finite difference methods, a model is derived that estimates the response of Coil-Tac with various coil pitches to within 0.0502 pF of our experimental results in the range of 0-2.5 pF, corresponding to a lateral liquid metal movement of up to 35 mm. The Coil-Tac mechanism is demonstrated to be capable of oscillatory tactile sensing at 5 Hz and touch location estimation when coupled to a soft interface. The mechanism coupled with the interface is sensitive enough to locate the centre of the contact to within 0.23 mm, and estimate the incident angle between the axis of the dome and a flat surface to within 0.53∘.

AB - Exploiting the high conductivity and fluidity of liquid metal, Coil-Tac is a soft transduction mechanism based on measuring change in capacitance as a flowable liquid metal core moves within a conductive helical coil. Using finite difference methods, a model is derived that estimates the response of Coil-Tac with various coil pitches to within 0.0502 pF of our experimental results in the range of 0-2.5 pF, corresponding to a lateral liquid metal movement of up to 35 mm. The Coil-Tac mechanism is demonstrated to be capable of oscillatory tactile sensing at 5 Hz and touch location estimation when coupled to a soft interface. The mechanism coupled with the interface is sensitive enough to locate the centre of the contact to within 0.23 mm, and estimate the incident angle between the axis of the dome and a flat surface to within 0.53∘.

KW - Force and Tactile Sensing

KW - Soft Sensors and Actuators

KW - Mechanism Design

U2 - 10.1109/LRA.2025.3558655

DO - 10.1109/LRA.2025.3558655

M3 - Article (Academic Journal)

SN - 2377-3766

VL - 10

SP - 5194

EP - 5200

JO - IEEE Robotics and Automation Letters

JF - IEEE Robotics and Automation Letters

IS - 5

ER -

Coil-Tac: Coiled Capacitor Mechanism with Liquid Metal for Tactile Sensing

Abstract

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