Department of Manufacturing Systems and Design Engineering, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea.
Graduate School of Nano IT Design Fusion, Seoul National University of Science and Technology, Seoul, 139-743, Republic of Korea.
J Nanosci Nanotechnol. 2021 May 1;21(5):2969-2979. doi: 10.1166/jnn.2021.19133.
In stretchable strain sensors, highly elastic elastomers such as polydimethylsiloxane (PDMS), Ecoflex, and polyurethane are commonly used for binder materials of the nanocomposite and substrates. However, the viscoelastic nature of the elastomers and the interfacial action between nanofillers and binders influence the critical sensor performances, such as repeatability, response, and hysteresis behavior. In this study, we developed a stretchable nanocomposite strain sensor composed of multiwalled carbon nanotubes and a silicone elastomer binder. The effects of binder and substrate materials on the repeatability, response, hysteresis behavior, and long-term endurance of the strain sensors were systematically investigated using stretching, bending, and repeated cyclic bending tests. Three different binder and substrate materials including PDMS, Ecoflex, and a mixture of PDMS/Ecoflex were tested. The stretchable strain sensors showed an excellent linearity and stretchability of more than 130%. Therefore, the long-term endurance of the strain sensors fabricated with Ecoflex binder should be improved. The strain sensors fabricated with Ecoflex binder showed a relatively large variation in electrical resistance during 10,000-cycle bending tests and repeatability errors at large bending angles. The strain sensors fabricated with PDMS binder showed repeatability errors at small bending angles and a slight response delay of 1 second. On the contrary, the strain sensors fabricated with a mixture of PDMS/Ecoflex binder showed excellent repeatability and response characteristics. The PDMS material showed hysteresis behavior; therefore, the strain sensors fabricated with PDMS binder on PDMS substrate exhibited a large hysteresis behavior in the first stretch-release cycle. It was found that the hysteresis behavior of the strain sensors was mainly dependent on substrate materials than on binder materials. The stretchable strain sensors made of the mixture of PDMS/Ecoflex exhibited excellent repeatability, response, hysteresis behavior, and excellent capability in detecting finger and wrist bending.
在可拉伸应变传感器中，通常使用高弹性弹性体，如聚二甲基硅氧烷（PDMS）、Ecoflex 和聚氨酯，作为纳米复合材料的粘结剂材料和基底。然而，弹性体的粘弹性和纳米填料与粘结剂之间的界面作用会影响关键的传感器性能，如重复性、响应和滞后行为。在这项研究中，我们开发了一种由多壁碳纳米管和硅酮弹性体粘结剂组成的可拉伸纳米复合应变传感器。通过拉伸、弯曲和重复循环弯曲测试，系统研究了粘结剂和基底材料对应变传感器的重复性、响应、滞后行为和长期耐久性的影响。测试了三种不同的粘结剂和基底材料，包括 PDMS、Ecoflex 和 PDMS/Ecoflex 的混合物。可拉伸应变传感器表现出超过 130%的优异线性度和可拉伸性。因此，Ecoflex 粘结剂制成的应变传感器的长期耐久性有待提高。用 Ecoflex 粘结剂制成的应变传感器在 10000 次弯曲测试过程中电阻变化较大，在大弯曲角度下重复性误差较大。用 PDMS 粘结剂制成的应变传感器在小弯曲角度下重复性误差较大，响应延迟约 1 秒。相反，用 PDMS/Ecoflex 混合物制成的应变传感器表现出优异的重复性和响应特性。PDMS 材料表现出滞后行为；因此，用 PDMS 粘结剂在 PDMS 基底上制成的应变传感器在第一次拉伸-释放循环中表现出较大的滞后行为。研究发现，应变传感器的滞后行为主要取决于基底材料，而不是粘结剂材料。由 PDMS/Ecoflex 混合物制成的可拉伸应变传感器表现出优异的重复性、响应、滞后行为以及对手指和手腕弯曲的出色检测能力。
