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Antonia Georgopoulou received her degree (M.Eng.) in Chemical Engineering with distinction from the University of Patras in 2017. She received her degree (M.S.) in Biomedical Engineering from ETH Zürich in 2019. During her Masters studies, her work focused in bioprinting and material development for tissue engineering applications. Since 2019, she is a Doctoral Student at Empa - Materials Science and Technology in the department of Functional Materials, working on the topic of sensor development for soft robotics. Her research focuses on composite materials, additive manufacturing, elastomer-based sensors, and materials for soft robotics.
In recent years, soft pneumatic actuators have come into the spotlight because of their simple control and the wide range of complex motions. To monitor the deformation of soft robotic systems, elastomer-based sensors are being used. However, the embedding of sensors into soft actuator modules by polymer casting is time consuming and difficult to upscale. In this study, it is shown how a pneumatic bending actuator with an integrated sensing element can be produced using an extrusion-based additive manufacturing method, e.g., fused deposition modeling (FDM). The advantage of FDM against direct printing or robocasting is the significantly higher resolution and the ability to print large objectives in a short amount of time. New, commercial launched, pellet-based FDM printers are able to 3D print thermoplastic elastomers of low shore hardness that are required for soft robotic applications, to avoid high pressure for activation. A soft pneumatic actuator with the in situ integrated piezoresistive sensor element was successfully printed using a commercial styrene-based thermoplastic elastomer (TPS) and a developed TPS/carbon black (CB) sensor composite. It has been demonstrated that the integrated sensing elements could monitor the deformation of the pneumatic soft robotic actuator. The findings of this study contribute to extending the applicability of additive manufacturing for integrated soft sensors in large soft robotic systems.
Antonia Georgopoulou; Lukas Egloff; Bram Vanderborght; Frank Clemens. A Soft Pneumatic Actuator with Integrated Deformation Sensing Elements Produced Exclusively with Extrusion Based Additive Manufacturing. Engineering Proceedings 2021, 6, 11 .
AMA StyleAntonia Georgopoulou, Lukas Egloff, Bram Vanderborght, Frank Clemens. A Soft Pneumatic Actuator with Integrated Deformation Sensing Elements Produced Exclusively with Extrusion Based Additive Manufacturing. Engineering Proceedings. 2021; 6 (1):11.
Chicago/Turabian StyleAntonia Georgopoulou; Lukas Egloff; Bram Vanderborght; Frank Clemens. 2021. "A Soft Pneumatic Actuator with Integrated Deformation Sensing Elements Produced Exclusively with Extrusion Based Additive Manufacturing." Engineering Proceedings 6, no. 1: 11.
Soft pneumatic actuators with a channel network (pneu-net) based on thermoplastic elastomers are compatible with fused deposition modeling (FDM). However, conventional filament-based fused deposition modeling (FDM) printers are not well suited for thermoplastic elastomers with a shore hardness (Sh < 70A). Therefore, in this study, a pellet-based FDM printer was used to print pneumatic actuators with a shore hardness of Sh18A. Additionally, the method allowed the in situ integration of soft piezoresistive sensing elements during the fabrication. The integrated piezoresistive elements were based on conductive composites made of three different styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomers, each with a carbon black (CB) filler with a ratio of 1:1. The best sensor behavior was achieved by the SEBS material with a shore hardness of Sh50A. The dynamic and quasi-static sensor behavior were investigated on SEBS strips with integrated piezoresistive sensor composite material, and the results were compared with TPU strips from a previous study. Finally, the piezoresistive composite was used for the FDM printing of soft pneumatic actuators with a shore hardness of 18 A. It is worth mentioning that 3 h were needed for the fabrication of the soft pneumatic actuator with an integrated strain sensing element. In comparison to classical mold casting method, this is faster, since curing post-processing is not required and will help the industrialization of pneumatic actuator-based soft robotics.
Antonia Georgopoulou; Lukas Egloff; Bram Vanderborght; Frank Clemens. A Sensorized Soft Pneumatic Actuator Fabricated with Extrusion-Based Additive Manufacturing. Actuators 2021, 10, 102 .
AMA StyleAntonia Georgopoulou, Lukas Egloff, Bram Vanderborght, Frank Clemens. A Sensorized Soft Pneumatic Actuator Fabricated with Extrusion-Based Additive Manufacturing. Actuators. 2021; 10 (5):102.
Chicago/Turabian StyleAntonia Georgopoulou; Lukas Egloff; Bram Vanderborght; Frank Clemens. 2021. "A Sensorized Soft Pneumatic Actuator Fabricated with Extrusion-Based Additive Manufacturing." Actuators 10, no. 5: 102.
Soft robotics and flexible electronics are rising in popularity and can be used in many applications. However, there is still a need for processing routes that allow the upscaling in production for functional soft robotic parts in an industrial scale. In this study, injection molding of liquid silicone is suggested as a fabrication method for sensorized robotic skin based on sensor fiber composites. Sensor fibers based on thermoplastic elastomers with two different shore hardness (50A and 70A) are combined with different silicone materials. A mathematical model is used to predict the mechanical load transfer from the silicone matrix to the fiber and shows that the matrix of the lowest shore hardness should not be combined with the stiffer fiber. The sensor fiber composites are fixed on a 3D printed robotic finger. The sensorized robotic skin based on the composite with the 50A fiber in combination with pre-straining gives good sensor performance as well as a large elasticity. It is proposed that a miss-match in the mechanical properties between fiber sensor and matrix should be avoided in order to achieve low drift and relaxation. These findings can be used as guidelines for material selection for future sensor integrated soft robotic systems.
Antonia Georgopoulou; Silvain Michel; Frank Clemens. Sensorized Robotic Skin Based on Piezoresistive Sensor Fiber Composites Produced with Injection Molding of Liquid Silicone. Polymers 2021, 13, 1226 .
AMA StyleAntonia Georgopoulou, Silvain Michel, Frank Clemens. Sensorized Robotic Skin Based on Piezoresistive Sensor Fiber Composites Produced with Injection Molding of Liquid Silicone. Polymers. 2021; 13 (8):1226.
Chicago/Turabian StyleAntonia Georgopoulou; Silvain Michel; Frank Clemens. 2021. "Sensorized Robotic Skin Based on Piezoresistive Sensor Fiber Composites Produced with Injection Molding of Liquid Silicone." Polymers 13, no. 8: 1226.
In this letter, we developed a piezoresistive auxetic sensor structure based on a silicone elastomer and carbon-based conductive thermoplastic elastomer fiber sensor (CTPE fiber). Liquid silicone has been used as the matrix material. In addition silicone has been mixed with silica filler to tailor the stiffness of an auxetic elastic structure that improved the sensor behavior of silicone-based CTPE fiber composites. The 2D auxetic structures with and without silica fillers have been successfully printed with the direct ink writing method. The piezoresistive fiber was integrated and the auxetic structure were embedded in the silicone matrix in a second step, via casting method. To detect the electrical signal behavior of the integrated fiber sensor, the hybrid manufactured auxetic fiber sensor composite was investigated using dynamic cycle testing between 0 and 20% strain. Using silicone with silica filler for the printing of the auxetic structure, the sensor behavior of the piezoresistive fiber elastomer composite was improved and a secondary peak of the sensor signal could be avoided at low strains. Unfortunately, a constant gauge factor between 0 and 20% strain could not be obtained by implementing the auxetic structure element inside the CTPE fiber composite. However, this structure can already be integrated into a watchband and used for gesture-controlled applications.
Frank Clemens; Mark Melnykowycz; Forian Bar; Daniel Goldenstein; Antonia Georgopoulou. 2D Printing of Piezoresistive Auxetic Silicone Sensor Structures. IEEE Robotics and Automation Letters 2021, 6, 2541 -2546.
AMA StyleFrank Clemens, Mark Melnykowycz, Forian Bar, Daniel Goldenstein, Antonia Georgopoulou. 2D Printing of Piezoresistive Auxetic Silicone Sensor Structures. IEEE Robotics and Automation Letters. 2021; 6 (2):2541-2546.
Chicago/Turabian StyleFrank Clemens; Mark Melnykowycz; Forian Bar; Daniel Goldenstein; Antonia Georgopoulou. 2021. "2D Printing of Piezoresistive Auxetic Silicone Sensor Structures." IEEE Robotics and Automation Letters 6, no. 2: 2541-2546.
Soft robotic sensors have been limited in their applications due to their highly nonlinear time variant behavior. Current studies are either looking into techniques to improve the mechano-electrical properties of these sensors or into modelling algorithms that account for the history of each sensor. Here, we present a method for combining multi-material soft strain sensors to obtain equivalent higher quality sensors; better than each of the individual strain sensors. The core idea behind this work is to use a combination of redundant and disjoint strain sensors to compensate for the time-variant hidden states of a soft-bodied system, to finally obtain the true strain state in a static manner using a learning-based approach. We provide methods to develop these variable sensors and metrics to estimate their dissimilarity and efficacy of each sensor combinations, which can double down as a benchmarking tool for soft robotic sensors. The proposed approach is experimentally validated on a pneumatic actuator with embedded soft strain sensors. Our results show that static data from a combination of nonlinear time variant strain sensors is sufficient to accurately estimate the strain state of a system.
Thomas George Thuruthel; Josie Hughes; Antonia Georgopoulou; Frank Clemens; Fumiya Iida. Using Redundant and Disjoint Time-Variant Soft Robotic Sensors for Accurate Static State Estimation. IEEE Robotics and Automation Letters 2021, 6, 2099 -2105.
AMA StyleThomas George Thuruthel, Josie Hughes, Antonia Georgopoulou, Frank Clemens, Fumiya Iida. Using Redundant and Disjoint Time-Variant Soft Robotic Sensors for Accurate Static State Estimation. IEEE Robotics and Automation Letters. 2021; 6 (2):2099-2105.
Chicago/Turabian StyleThomas George Thuruthel; Josie Hughes; Antonia Georgopoulou; Frank Clemens; Fumiya Iida. 2021. "Using Redundant and Disjoint Time-Variant Soft Robotic Sensors for Accurate Static State Estimation." IEEE Robotics and Automation Letters 6, no. 2: 2099-2105.
Combining conductive fillers like carbon black with elastomers allows the development of soft elastomer strain sensors that can reach very large elongations, an important requirement for many robotic applications. However, when the conductive filler is introduced in the polymer, significant stiffening occurs, affecting the mechanical properties, e.g. Young’s Modulus, of the soft structure. In this attempt, single piezoresistive fiber composites were successfully fabricated, without drastically increasing the stiffness. Two silicone elastomers that are widely used in robotic applications were examined as matrix materials. Furthermore, modeling the stresses exerted on the fiber inside the composite was successfully used to predict the detachment of fiber inside the matrix, observed by visual inspection. For the PDMS based composite, pre-straining improved sensor properties, which could be confirmed for the monitoring of the movement of the crane robot. The results showed that the pre-strained piezoresistive sensor fiber-matrix composites positions of the robot crane can be monitored even at low strains.
Antonia Georgopoulou; Silvain Michel; Bram Vanderborght; Frank Clemens. Piezoresistive sensor fiber composites based on silicone elastomers for the monitoring of the position of a robot arm. Sensors and Actuators A: Physical 2020, 318, 112433 .
AMA StyleAntonia Georgopoulou, Silvain Michel, Bram Vanderborght, Frank Clemens. Piezoresistive sensor fiber composites based on silicone elastomers for the monitoring of the position of a robot arm. Sensors and Actuators A: Physical. 2020; 318 ():112433.
Chicago/Turabian StyleAntonia Georgopoulou; Silvain Michel; Bram Vanderborght; Frank Clemens. 2020. "Piezoresistive sensor fiber composites based on silicone elastomers for the monitoring of the position of a robot arm." Sensors and Actuators A: Physical 318, no. : 112433.
Embedded sensing can benefit soft robots with the ability to interact with their environment but producing embedded soft sensors can be challenging. Multi-material Fused Deposition Modeling (FDM) additive manufacturing allows producing complex structures, by combining more than one kind of polymeric material. For multi-material FDM, conductive thermoplastic elastomer filaments have been developed. This allows the printing of flexible functional structures, based on thermoplastic elastomer structures with conductive paths that are of great interest for stretchable electronics and soft robotic applications. In this study, stretchable piezoresistive elastomer strain sensor composites were successfully produced by using multi-material FDM. A piezoresistive thermoplastic elastomer was printed on the top of a nonconductive, flexible thermoplastic elastomer strip using FDM multi-material 3D printer. FDM elastomer filaments with different shore hardness as substrate materials for the gripper structure were used. The hardness of the elastomer affected the printability and the adhesion to the conductive elastomer material, which was used as a strain sensor material. The hardness affected the strain sensor properties too. The piezoresistive response, dynamic behavior, drift, relaxation and sensitivity of the printed multi-material strips were investigated by tensile tests. Soft robotic grippers with integrated sensing elements to detect deformation while touching the objective were selected as a case study. The soft grippers with the integrated sensors exhibited intelligent response by recognizing when they were griping a small or big object and when an obstacle was inhibiting their function.
Antonia Georgopoulou; Bram VanderBorght; Frank Clemens. Multi-material 3D Printing of Thermoplastic Elastomers for Development of Soft Robotic Structures with Integrated Sensor Elements. Industrializing Additive Manufacturing 2020, 67 -81.
AMA StyleAntonia Georgopoulou, Bram VanderBorght, Frank Clemens. Multi-material 3D Printing of Thermoplastic Elastomers for Development of Soft Robotic Structures with Integrated Sensor Elements. Industrializing Additive Manufacturing. 2020; ():67-81.
Chicago/Turabian StyleAntonia Georgopoulou; Bram VanderBorght; Frank Clemens. 2020. "Multi-material 3D Printing of Thermoplastic Elastomers for Development of Soft Robotic Structures with Integrated Sensor Elements." Industrializing Additive Manufacturing , no. : 67-81.
Antonia Georgopoulou; Tutu Sebastian; Frank Clemens. Thermoplastic elastomer composite filaments for strain sensing applications extruded with a fused deposition modelling 3D printer. Flexible and Printed Electronics 2020, 5, 035002 .
AMA StyleAntonia Georgopoulou, Tutu Sebastian, Frank Clemens. Thermoplastic elastomer composite filaments for strain sensing applications extruded with a fused deposition modelling 3D printer. Flexible and Printed Electronics. 2020; 5 (3):035002.
Chicago/Turabian StyleAntonia Georgopoulou; Tutu Sebastian; Frank Clemens. 2020. "Thermoplastic elastomer composite filaments for strain sensing applications extruded with a fused deposition modelling 3D printer." Flexible and Printed Electronics 5, no. 3: 035002.
Piezoresistive strain sensors dominate the field of soft elastomer sensors, with many interesting findings and applications. Nevertheless, the methods of characterizing the performance of the sensor differ in each study, leading to different conclusions and making comparison of the different sensor systems challenging. In this Review, the most important methods for characterization of the sensor response are being presented and some cases of elastomer strain sensors are being highlighted. Furthermore, the different materials options for elastomer strain sensors are shown, with special sections for the rapidly growing fields of additive manufacturing and 3D printing. In addition to the material choices and testing methods, different applications of strain sensors are presented. From the biomedical field, these soft sensors find applications in wearable devices, vital sign monitoring, and rehabilitation assistive devices. In soft robotics, they can be used in monitoring and controlling the function of soft robot and actuation systems, a function that can aid with feedback control, increasing the efficiency of the robot’s function. Last but not least, in combination with the emerging self-healing materials, elastomer strain sensors can be used for monitoring the integrity of materials and structures.
Antonia Georgopoulou; Frank Clemens. Piezoresistive Elastomer-Based Composite Strain Sensors and Their Applications. ACS Applied Electronic Materials 2020, 2, 1826 -1842.
AMA StyleAntonia Georgopoulou, Frank Clemens. Piezoresistive Elastomer-Based Composite Strain Sensors and Their Applications. ACS Applied Electronic Materials. 2020; 2 (7):1826-1842.
Chicago/Turabian StyleAntonia Georgopoulou; Frank Clemens. 2020. "Piezoresistive Elastomer-Based Composite Strain Sensors and Their Applications." ACS Applied Electronic Materials 2, no. 7: 1826-1842.
In this study, a thermoplastic elastomer sensor fiber was embedded in an elastomer matrix. The effect of the matrix material on the sensor properties and the piezoresistive behavior of the single fiber-matrix composite system was investigated. For all composites, cycling test (dynamic test) and the relaxation behavior at different strains (quasi-static test) were investigated. In all cases, dynamic properties and quasi-static significantly changed after embedding, compared to the pure fiber. The composite with the silicone elastomer PDMS (Polydimethylsiloxane) as matrix material exhibited deviation from linear response of the resistivity at low strains and proved an unsuitable choice compared to natural rubber. The addition of a spring construct in the embedded sensor fiber natural rubber composite improved the linearity at low strains but increased the mechanical and electrical hysteresis of the soft matter sensor composite. Using pre-vulcanized natural rubber improved linearity at low strains and reduced significantly the stress and relative resistance relaxation as well as the resistance hysteresis, especially if the resistance remained low. In both cases of the pre-vulcanized rubber and the spring structure, the piezoresistive behavior was improved, and at the same time, the stiffness of the system was increased indicating that using a stiffer matrix can be a strategy for improving the sensor properties.
Antonia Georgopoulou; Claudia Kummerlöwe; Frank Clemens. Effect of the Elastomer Matrix on Thermoplastic Elastomer-Based Strain Sensor Fiber Composites. Sensors 2020, 20, 2399 .
AMA StyleAntonia Georgopoulou, Claudia Kummerlöwe, Frank Clemens. Effect of the Elastomer Matrix on Thermoplastic Elastomer-Based Strain Sensor Fiber Composites. Sensors. 2020; 20 (8):2399.
Chicago/Turabian StyleAntonia Georgopoulou; Claudia Kummerlöwe; Frank Clemens. 2020. "Effect of the Elastomer Matrix on Thermoplastic Elastomer-Based Strain Sensor Fiber Composites." Sensors 20, no. 8: 2399.