Page 359 - Flexible Robotics in Medicine

Electromechanical characterization of magnetic responsive and conductive 351

to PEDOT. Another solution of PEDOT:PSS was purchased from Sigma-Aldrich with
0.5 wt.% PEDOT, 0.8 wt.% PSS. Xylitol in powder form and Fe 3 O 4 NPs of 50 100 nm
particle size were also obtained from Sigma-Aldrich.

Firstly, PEDOT:PSS was doped with 5 vol.% DMSO to increase its conductivity. By doing
so, the PSS strands are wrapped around, exposing the PEDOT chains. After this, 0.75 wt.% of
xylitol was dispersed in PEDOT:PSS to increase the plasticity of the resulting films. Then,
different amounts of Fe 3 O 4 NPs were dispersed into the resulting solution through sonication
to form different ratios of PEDOT:PSS/xylitol/Fe 3 O 4 solutions. The different solutions were
then drop-cast onto clean glass substrates. While drop-casting onto 3D printed molds allows
the formation of thicker films, the removal of films from these molds is more complicated.

The films were left to dry at 60 C for 40 minutes to form PEDOT:PSS/xylitol/Fe 3 O 4
composite films.
To fabricate PEDOT:PSS/xylitol/Fe 3 O 4 -coated cotton thread, two pieces of the cotton
thread was immersed in the PEDOT:PSS/xylitol/Fe 3 O 4 solution of ratios 1:1 and 1:5 for
30 minutes at room temperature. After this, the coated cotton thread was placed into the

oven at 70 C for 30 minutes to dry.

15.2.2 Preparation of IL/PVDF-HFP/PEDOT:PSS/xylitol bending actuator

Xylitol and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI)
are obtained from Sigma-Aldrich. 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)
imide (EMI-TFSI) was used as an IL. Poly(vinylidene fluoride-co-hexafluoropropylene)
(PVDF-HFP) was obtained from Sigma-Aldrich as well, and it adopts a translucent pellet
form.

IL/PVDF-HFP films are fabricated by first dissolving PVDF-HFP in dimethylformamide

(DMF) with a ratio of 1:9 for PVDF-HFP:DMF. The mixture was left at 40 C for 90 minutes
and stirred continually using a magnetic stirrer to dissolve PVDF-HFP in DMF completely.
20 and 30 wt.% of (EMI-TFSI) as IL is then added to the resulting solution. The different
solutions were then drop-cast into small glass Petri dishes. Aluminum foil was wrapped to
cover the opening around the dishes, and small openings were made on top to control the rate
of evaporation. The samples were left overnight, and the resultant IL/PVDF-HFP film was
then removed from the Petri dish.
The 0.75 wt.% of xylitol was dispersed in PEDOT:PSS solution doped with 5 vol.% DMSO.
This resultant solution was drop-cast onto clean glass substrates to form uniform thin films
after drying at 60 C for 40 minutes. The IL/PVDF-HFP film was sandwiched between two

PEDOT:PSS/xylitol film electrodes and heated at 50 C for 5 hours for constructing an EAP
actuator (Fig, 15.1).