Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion
In this paper, the effect of strain rate on the output signal of highly stretchable interdigitated capacitive (IDC) strain sensors is studied. IDC sensors fabricated with pristine Ecoflex and a composite based on 40 wt% of 200 nm barium titanate (BTO) dispersed in a silicone elastomer (Ecoflex 00-30...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-05-01
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| Series: | Robotics |
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| Online Access: | https://www.mdpi.com/2218-6581/10/2/69 |
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| author | Eshwar Reddy Cholleti Jonathan Stringer Piaras Kelly Chris Bowen Kean Aw |
| author_facet | Eshwar Reddy Cholleti Jonathan Stringer Piaras Kelly Chris Bowen Kean Aw |
| author_sort | Eshwar Reddy Cholleti |
| collection | DOAJ |
| description | In this paper, the effect of strain rate on the output signal of highly stretchable interdigitated capacitive (IDC) strain sensors is studied. IDC sensors fabricated with pristine Ecoflex and a composite based on 40 wt% of 200 nm barium titanate (BTO) dispersed in a silicone elastomer (Ecoflex 00-30<sup>TM</sup>) were subjected to 1000 stretch and relax cycles to study the effect of dynamic loading conditions on the output signal of the IDC sensor. It was observed that the strain rate has no effect on the output signal of IDC sensor. To study the non-linear elastic behaviour of pristine Ecoflex and composites based on 10, 20, 30, 40 wt% of 200 nm BTO filler dispersed in a silicone elastomer, we conducted uniaxial tensile testing to failure at strain rates of ~5, ~50, and ~500 mm/min. An Ogden second-order model was used to fit the uniaxial tensile test data to understand the non-linearity in the stress-strain responses of BTO-Ecoflex composite at different strain rates. The decrease in Ogden parameters (<i>α</i><sub>1</sub> and <i>α</i><sub>2</sub>) indicates the decrease in non-linearity of the stress-strain response of the composite with an increase in filler loading. Scanning electronic microscopy analysis was performed on the cryo-fractured pristine Ecoflex and 10, 20, 30, and 40 wt% of BTO-Ecoflex composites, where it was found that 200 nm BTO is more uniformly distributed in Ecoflex at a higher filler loading levels (40 wt% 200 nm BTO). Therefore, an IDC sensor was fabricated based on a 40 wt% 200 nm BTO-Ecoflex composite and mounted on an elastic elbow sleeve with supporting electronics, and successfully functioned as a reliable and robust flexible sensor, demonstrating an application to measure the bending angle of an elbow at slow and fast movement of the arm. A linear relationship with respect to the elbow bending angle was observed between the IDC sensor output signal under a 50% strain and the deflection of the elbow of hand indicating its potential as a stretchable, flexible, and wearable sensor. |
| first_indexed | 2024-03-10T11:42:29Z |
| format | Article |
| id | doaj.art-8319c729dff446d09bdc3267f56c0853 |
| institution | Directory Open Access Journal |
| issn | 2218-6581 |
| language | English |
| last_indexed | 2024-03-10T11:42:29Z |
| publishDate | 2021-05-01 |
| publisher | MDPI AG |
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| series | Robotics |
| spelling | doaj.art-8319c729dff446d09bdc3267f56c08532023-11-21T18:20:01ZengMDPI AGRobotics2218-65812021-05-011026910.3390/robotics10020069Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human MotionEshwar Reddy Cholleti0Jonathan Stringer1Piaras Kelly2Chris Bowen3Kean Aw4Department of Mechanical Engineering, University of Auckland, Auckland 1010, New ZealandDepartment of Mechanical Engineering, University of Auckland, Auckland 1010, New ZealandDepartment of Engineering Science, University of Auckland, Auckland 1010, New ZealandDepartment of Mechanical Engineering, University of Bath, Bath BA2 7AY, UKDepartment of Mechanical Engineering, University of Auckland, Auckland 1010, New ZealandIn this paper, the effect of strain rate on the output signal of highly stretchable interdigitated capacitive (IDC) strain sensors is studied. IDC sensors fabricated with pristine Ecoflex and a composite based on 40 wt% of 200 nm barium titanate (BTO) dispersed in a silicone elastomer (Ecoflex 00-30<sup>TM</sup>) were subjected to 1000 stretch and relax cycles to study the effect of dynamic loading conditions on the output signal of the IDC sensor. It was observed that the strain rate has no effect on the output signal of IDC sensor. To study the non-linear elastic behaviour of pristine Ecoflex and composites based on 10, 20, 30, 40 wt% of 200 nm BTO filler dispersed in a silicone elastomer, we conducted uniaxial tensile testing to failure at strain rates of ~5, ~50, and ~500 mm/min. An Ogden second-order model was used to fit the uniaxial tensile test data to understand the non-linearity in the stress-strain responses of BTO-Ecoflex composite at different strain rates. The decrease in Ogden parameters (<i>α</i><sub>1</sub> and <i>α</i><sub>2</sub>) indicates the decrease in non-linearity of the stress-strain response of the composite with an increase in filler loading. Scanning electronic microscopy analysis was performed on the cryo-fractured pristine Ecoflex and 10, 20, 30, and 40 wt% of BTO-Ecoflex composites, where it was found that 200 nm BTO is more uniformly distributed in Ecoflex at a higher filler loading levels (40 wt% 200 nm BTO). Therefore, an IDC sensor was fabricated based on a 40 wt% 200 nm BTO-Ecoflex composite and mounted on an elastic elbow sleeve with supporting electronics, and successfully functioned as a reliable and robust flexible sensor, demonstrating an application to measure the bending angle of an elbow at slow and fast movement of the arm. A linear relationship with respect to the elbow bending angle was observed between the IDC sensor output signal under a 50% strain and the deflection of the elbow of hand indicating its potential as a stretchable, flexible, and wearable sensor.https://www.mdpi.com/2218-6581/10/2/69barium titanateecoflexstrain rateogden modelnon-linearhighly stretchable printed strain sensor |
| spellingShingle | Eshwar Reddy Cholleti Jonathan Stringer Piaras Kelly Chris Bowen Kean Aw Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion Robotics barium titanate ecoflex strain rate ogden model non-linear highly stretchable printed strain sensor |
| title | Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion |
| title_full | Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion |
| title_fullStr | Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion |
| title_full_unstemmed | Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion |
| title_short | Mechanical Behaviour of Large Strain Capacitive Sensor with Barium Titanate Ecoflex Composite Used to Detect Human Motion |
| title_sort | mechanical behaviour of large strain capacitive sensor with barium titanate ecoflex composite used to detect human motion |
| topic | barium titanate ecoflex strain rate ogden model non-linear highly stretchable printed strain sensor |
| url | https://www.mdpi.com/2218-6581/10/2/69 |
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