Figure 1.
PEDOT-PSS silk thread observation with a conventional microscope and a scanning electron microscope (SEM).
A. Macroscopic image of pristine silk thread (left) and PEDOT-PSS combined silk thread (right). B. C. Cross-section of pristine silk (B) and PEDOT-PSS silk thread (C) observed with a transmitted light optical microscope (scale bar 50 µm). D–F. Scanning electron micrograph of pristine silk (D) and PEDOT-PSS silk thread (E, Higher magnification view F). Arrows indicate fine filaments of silk fiber (D) coated with PEDOT-PSS (E). Arrowheads indicate PEDOT-PSS webbing between silk fibers. (F, Scale bar 20 µm). Pristine silk shows charge up and has a blurred image because of its insulation properties (D).
Table 1.
Electrical conductivity of PEDOT-PSS silk thread; comparison of fixation and chemical additives.
Figure 2.
Mechanical properties of PEDOT-PSS silk thread.
A. Tensile strength of pristine PEDOT-PSS film in dry (left) and wet (right) states (n = 10, error bar: 1 S.D.). B. Stress-elongation curves of pristine silk thread (blue lines 1, 1′), PEDOT-PSS silk thread (red lines 2, 2′), and glycerol treated PEDOT-PSS silk thread (green lines 3, 3′), in dry (1, 2, 3) and wet states (1′, 2′, 3′). The average data of 10 samples are plotted on the graph. Inset: Enlarged view of stress-elongation curves of the 3 groups in a dry condition in a lower strength range, pristine silk thread 1) PEDOT-PSS silk thread 2) and glycerol treated PEDOT-PSS silk thread 3). Glycerol treatment improved the elasticity of PEDOT-PSS silk thread.
Figure 3.
Glycerol enhanced water sturdiness of PEDOT-PSS silk thread.
A. Photograph of the threads soaked in water for three days. 1) Pristine silk thread. 2) PEDOT-PSS silk thread without glycerol. 3) PEDOT-PSS silk thread with glycerol. 4) PEDOT-PSS silk thread without water soaking. B. Repeated cycles of washing with water and drying impaired the electrical conductivity of the PEDOT-PSS silk thread. The conductance of PEDOT-PSS silk thread (red line) and glycerol treated PEDOT-PSS silk thread (green line) after every washing cycle are shown (measured at dry state, averaged data from 10 samples are plotted). The conductance of thread that were not treated with glycerol fell to less than 1% that of the control. Glycerol treated thread retained its conductance after the third washing.
Figure 4.
Electrophysiological recordings obtained using electrodes made with PEDOT-PSS silk glycerol thread.
A. Structure of skin surface electrodes using PEDOT-PSS glycerol silk thread. a. String shaped electrode for electrocardiograph (ECG). b. Flat electrode for electroencephalogram (EEG). B. ECG recordings obtained from an experimental rat with bipolar deviation. Inset shows the position of the three electrodes. C. EEG recorded from a rat in an anesthetized condition. Inset shows the position of six different electrodes (flat PEDOT-PSS silk glycerol electrode, Fig. 4A, image b) on scalp and reference electrodes (Ag AgCl) on bilateral auricle. D. Sensory evoked potential (SEP) recorded from a rat parietal area with a flat PEDOT-PSS silk glycerol electrode induced by left posterior leg stimulations via (string shape PEDOT-PSS silk glycerol electrode, Fig. 4A, image a). Averaged data for 200 recorded signals are shown.
Figure 5.
Comparison of ECG signals recorded from conventional, PEDOT-PSS silk thread and textile electrodes.
Simultaneously recorded rat ECG signals from conventional medical electrodes (a), PEDOT-PSS silk glycerol thread electrodes (b), textile electrodes (c) pressure contact with skin by elastic band wrapping (pressure contact, left) or medical adhesive tape fixation without body movement (middle) and with body movement (right) are shown. ECGs recorded with PEDOT-PSS silk glycerol thread electrodes are comparable to ECGs obtained with conventional medical electrodes (a,b) under all conditions. The tape fixed textile electrode produced a hum (c, middle) and baseline drift (c, right) without and with body movement, respectively.
Table 2.
Combined resistance of conventional, PEDOT-PSS silk glycerol thread and textile electrodes on rat skin.