Page 360 - Flexible Robotics in Medicine

352 Chapter 15

Figure 15.1
PEDOT:PSS/xylitol film (left), IL/PVDF-HFP 20 wt.% IL (middle), and IL/PVDF-HFP/PEDOT:PSS/
xylitol actuator (right).

15.2.3 Characterization of PEDOT:PSS/xylitol/Fe 3 O 4 composite films

The resistance of PEDOT:PSS/xylitol/Fe 3 O 4 composite films and the coated thread was
recorded using a 4-point probe method with Keithley 2400 SourceMeter. The load-
extension tensile test curves of the films were obtained with the Instron 5500 Series
Universal Instron tensile testing machine. The hysteresis loops and the magnetic properties
were characterized by the Lakeshore 7404 vibrating sample magnetometer (VSM).

15.2.4 Characterization of IL/PVDF-HFP/PEDOT:PSS/xylitol bending actuator

Similarly, the resistance of PEDOT:PSS/xylitol and IL/PVDF-HFP films were measured
with a 4-point probe method using the Keithley 2400 SourceMeter. The load-extension
curves of the films were obtained through tensile tests.

15.3 Results and discussion

In general, drop-casting onto glass substrates work better than into 3D printed molds.
Initially, the films were drop-cast into 3D printed molds. However, the films tend to
adhere firmly onto the edges of the molds, which makes the removal of films from the
molds difficult. The grooves and uneven surfaces exhibited by the layer by layer printing
method of 3D printing of the molds cause the films to crack during attempts to peel
them. Thus subsequent drop-casting was carried out using glass substrates instead.
Hence, the removal of films is now more straightforward, and the thickness of the film is
thinner as compared to when using the molds. The surface profile of the films is clearly
visible in Fig. 15.2.

The effect of the PEDOT loading ratio with respect to PSS in the solution affects the
stability of the fabricated films. Initially, PEDOT:PSS solution with different PSS