A NIR-Light-Driven Twisted and Coiled Polymer Actuator with a PEDOT-Tos/Nylon-6 Composite for Durable and Remotely Controllable Artificial Muscle

Abstract

In this paper, we proposed a novel light-driven polymer actuator that could produce remotely controllable tensile stroke in response to near infrared (NIR) light. The light-driven polymer actuator was composed of a twisted and coiled nylon-6 fiber (TCN) and a thin poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonate (PEDOT-Tos) layer. By adopting dip-coating methodology with thermal polymerization process, we constructed a thin and uniform PEDOT-Tos layer on the surface of the three-dimensional TCN structure. Thanks to the PEDOT-Tos layer with excellent NIR light absorption characteristic, the NIR light illumination via a small LEDs array allowed the multiple PEDOT-Tos coated TCN actuators to be photo-thermally heated to a fairly consistent temperature and to simultaneously produce a contractile strain that could be modulated as high as 8.7% with light power. The actuation performance was reversible without any significant hysteresis and highly durable during 3000 cyclic operations via repetitive control of the LEDs. Together with its simple structure and facile fabrication, the light-driven actuator can lead to technical advances in artificial muscles due to its attractive benefits from remote controllability without complex coupled instruments and electromagnetic interference.

Keywords: NIR; TCN; contractile strain; photo-thermal.

Figure 1

(a) An illustrated stepwise fabrication process of TCN structure; (b) its optical microscope images taken before and after stretching.

Figure 2

(a) A stepwise DP process constructing a thin PEDOT-Tos coating on the surface of the TCN; (b) a photograph of the PEDOT-Tos coated TCN taken by optical microscope.

Figure 3

(a) Optical microscope images of the PT-TCN TCN prepared before UV/Ozone treatment (left) and after the treatment (right) (insets are low magnification photographs); (b) water contact angle at surface of a nylon-6 film before and after UV/Ozone treatment; (c) cross-section and surface SEM images of the PT-TCN.

Figure 4

(a) Surface temperature profile; (b) contractile strain with input light power; (c) contractile strain with maximum temperature for PEDOT-Tos coated TCPAs prepared by adopting a different number of the dip-coating process.

Figure 5

Effect of the spatial light power modulation to equalize vertical temperature distribution of the single PT-TCNA during photo-thermal heating using a 1 × 5 LEDs array: (a) Thermal images of a PT-TCNA radiated with a constant light power (left) and the modulated light power (right); (b) their vertical temperature distribution over central Y-axis; (c) hysteresis of the actuation performance during a heating/cooling cycle; (d) temporal change of temperature and displacement during a heating/cooling cycle.

Figure 6

(a) A photograph of performance measurement system; thermal image and actuation performance of the multiple PT-TCNAs during light illumination from the LEDs with modulated power; (b) thermal image of four PT-TCNs (left) and horizontal temperature profile averaged over vertical axis (right); (c) contractile strain profiles with light power; (d) change in contractile strain profile during 3000 repetitive actuations.