3D printable piezoresistive tactile sensing technologies for soft robotics
Topic(s) : Multifunctional and smart composites
Co-authors :
Christopher BASCUCCI (SWITZERLAND), Josie HUGHES , Frank CLEMENSAbstract :
Soft robotics is an important branch in the field of automated systems, distinguishing itself for the use of highly compliant materials. This characteristic enables soft robots to provide effective automation in several applications like healthcare [1], gripping systems [2], animal-ecosystem exploration [3], and hazardous rescue missions [4][5].
All the robotic typologies require a closed-loop control system based on actuation and sensing to effectively communicate with the surrounding environment. Tactile sensing is crucial to assess object localization and force detection, and, for this aim, several technologies like capacitive, piezoresistive, piezoelectric, optical, and triboelectric can be employed [6]. Unfortunately, despite the increasing recent research interest, reliable applications in this field are still at an early stage due to the lack of accuracy and long-term durability [6]. In this study, three different piezoresistive approaches based on 3D printable thermoplastic styrene block copolymers (TPS) will be extensively evaluated and compared, highlighting points of strength and limitations of each of them:
1. Architected 3D porous structures composed of conductive TPS materials
2. Architected 3D porous structures composed of non-conductive TPS materials, dip-coated with conductive TPS ink
3. Architected 3D porous structures composed of non-conductive TPS materials, covered with a skin (~ 0.1 mm) composed of conductive TPS material
The three systems will be investigated via dynamic and quasi-static electro-mechanical compressive tests. The focus will be on the mechanical shape recovery of the samples and electric signal phenomena like drift, hysteresis, relaxation, and Maxwell-Wagner interfacial polarization [7][8]. In particular, leveraging the piezoresistive technology, the variable contact between robotic systems and objects will be correlated to a resistivity change of the sensor material. By increasing the conductivity of the TPS material, a lower drift, hysteresis and relaxation could be achieved. Higher conductivity resulted in a lower Maxwell-Wagner interfacial polarization, too. Unfortunately, the mechanical shape recovery of the 3D porous structures of conductive TPS materials significantly decreased. Therefore, using the second and third approaches looks more promising for the integration of piezoresistive sensors into tactile robotic applications.
In addition to compression experiments, a 3D printed conductive skin was used to localize the touch locally using electrical impedance tomography (EIT). EIT has recently gained a lot of attention for the development of biomimetic skins due to its accuracy [9]. In this work, the EIT technique will be applied to 3D printed skins with different electrode patterns, addressing the influence of their design on the measurement sensitivity.
All the robotic typologies require a closed-loop control system based on actuation and sensing to effectively communicate with the surrounding environment. Tactile sensing is crucial to assess object localization and force detection, and, for this aim, several technologies like capacitive, piezoresistive, piezoelectric, optical, and triboelectric can be employed [6]. Unfortunately, despite the increasing recent research interest, reliable applications in this field are still at an early stage due to the lack of accuracy and long-term durability [6]. In this study, three different piezoresistive approaches based on 3D printable thermoplastic styrene block copolymers (TPS) will be extensively evaluated and compared, highlighting points of strength and limitations of each of them:
1. Architected 3D porous structures composed of conductive TPS materials
2. Architected 3D porous structures composed of non-conductive TPS materials, dip-coated with conductive TPS ink
3. Architected 3D porous structures composed of non-conductive TPS materials, covered with a skin (~ 0.1 mm) composed of conductive TPS material
The three systems will be investigated via dynamic and quasi-static electro-mechanical compressive tests. The focus will be on the mechanical shape recovery of the samples and electric signal phenomena like drift, hysteresis, relaxation, and Maxwell-Wagner interfacial polarization [7][8]. In particular, leveraging the piezoresistive technology, the variable contact between robotic systems and objects will be correlated to a resistivity change of the sensor material. By increasing the conductivity of the TPS material, a lower drift, hysteresis and relaxation could be achieved. Higher conductivity resulted in a lower Maxwell-Wagner interfacial polarization, too. Unfortunately, the mechanical shape recovery of the 3D porous structures of conductive TPS materials significantly decreased. Therefore, using the second and third approaches looks more promising for the integration of piezoresistive sensors into tactile robotic applications.
In addition to compression experiments, a 3D printed conductive skin was used to localize the touch locally using electrical impedance tomography (EIT). EIT has recently gained a lot of attention for the development of biomimetic skins due to its accuracy [9]. In this work, the EIT technique will be applied to 3D printed skins with different electrode patterns, addressing the influence of their design on the measurement sensitivity.