Page 300 - Carbon Nanotube Fibres and Yarns

Carbon nanotube yarn-based actuators 287

Fig. 11.9 Application examples of CNT yarn-based actuators. (A) Schemes and photo-
graphs of the smart window at closed and opened states. The HSF was twisted from ten
HPF fibers [50]; (B) schematic diagram of the automatically controlled device based on
condensation-driven contraction of the HYAMs [53]. (Source of (A): S. He, P. Chen, L. Qiu,
B. Wang, X. Sun, Y. Xu, H. Peng, A mechanically actuating carbon-nanotube fiber in response
to water and moisture, Angew. Chem. 127 (49) (2015) 15093–15097. Source of (B): S.H. Kim,
C.H. Kwon, K. Park, T.J. Mun, X. Lepró, R.H. Baughman, G.M. Spinks, S.J. Kim, Bio-inspired,
moisture- powered hybrid carbon nanotube yarn muscles, Sci. Rep. 6 (2016) 23016.)

rotary actuations, the windows were opened and subsequently closed
upon absorption and evaporation of water. The smart window could be
effectively operated in response to the change of weather: the window
is opened on a sunny day and automatically closed upon raining; and it
is opened again when the rain stops. Similarly, Kim et al. [53] demon-
strated a prototype of a coiled hydrophilic CNT yarn-based, autono-
mous, moisture-driven ventilation system (Fig. 11.9B). The upper baffle
is fixed on a top plate and the lower baffle is connected to the end of the
coiled yarn actuator. When either dew appears or the RH increases on
the surface of the yarn, the lower baffle moves up because of automatic
water-drive CNT yarn actuator contraction.
Lee et al. [60] demonstrated a biomolecule sensor driven by a CNT yarn-
based torsional actuator. Boronic acid, a reversible glucose-sensing material,
was conjugated to a nanogel derived from hyaluronic acid biopolymer and
used as guest material for the CNT yarn. The nanogel could generate revers-
ible swelling/deswelling depending on the surrounding glucose concentra-
tion (Fig. 11.10), which drove a torsional actuation to provide glucose sensing.
Combined with appropriate pumps and valves, organic solvent excitative
actuators could be used in various applications, such as robotics, prosthetics,
and medical devices [52]. Electrochemistry excitative actuators could also
be used as mechanical energy harvester to harvest wave energy from the
ocean by immersing the actuator into sea water [57].