# Epoxy/Glass Fiber Nanostructured p- and n-Type Thermoelectric Enabled Model Composite Interphases
## 2 Materials and Methods
### Characterization Techniques  
Contact angle measurements were acquired via a commercial automated contact angle goniometer system manufactured by Ossila Ltd (Sheffield, UK).  
The morphology of the hierarchical GFs, as well as the reference GFs were evaluated via SEM using the JEOL JSM 6510 LV SEM (JEOL Ltd., Akishima, Japan) with an operating voltage of 3.5 KV.  
Thermogravimetric measurements were carried out in the STA 449C analyzer Netzsch-Gerateau GmbH, Selb, Germany. The experimental procedure included a dynamic step from 25 to 1000 \({}^{\circ}\)C with a heating rate of 10 \({}^{\circ}\)C/min at ambient conditions to examine the reference and the nanocoated GFs mass loss.  
The Labram HR-Horiba scientific micro-Raman system was used. The 514.5 nm line of an Ar + ion laser operating at a power of 1.5 mW at the focal plane was employed for the Raman excitation. An optical microscope equipped with a 50\(\times\) long working distance objective served both for delivering the excitation light and collecting the back-scattered Raman light. Raman spectra in the range of 90-3500 cm\({}^{-1}\) were collected.  
In order to determine the basic electrical characteristics, p and n-type bucky paper films were prepared by overnight vacuum filtering of the respective SWCNTs dispersions and four probe sheet resistance measurements were conducted (Table 1). A typical 4-probe technique (Four-Point Probe commercial system manufactured by Ossila Ltd.) was used to calculate the electrical conductivity based on the following formula: \(\sigma=1/R\times L/S\times(\ln 2/\pi)\), where \(R\) is the measured 4 probe sheet resistance, \(L\) is the length, and \(S\) is the cross section of each sample. It should be mentioned that the employed four-point probe system with four equally-spaced, co-linear probes to the material (interelectrode probe distance/spacing: 1 mm) is capable of delivering currents between 10 nA and 150 mA, and can measure voltages from as low as 100 \(\mu\)V up to 10 V, which results in a sheet resistance measurement range of 3 mOhm/\(\square\) to 10 MOhm/\(\square\). The values reported are mean values of at least four measurements performed on different samples.  
The DC measurements were conducted with a standard two-probe method using the Agilent 34401A multimeter with 6\(\frac{1}{2}\) digits resolution. Model composites were placed and measured at 25 mm electrode-electrode distance at room temperature and 25% relative humidity (RH).  
The voltage output of the model composites was determined using a custom-made setup. The samples were mounted on two metal blocks, which enabled the generation of a temperature difference. For all measurements, the one aluminum block (\(T_{\text{cold}}\)) was kept at room temperature (\(\sim\)24 \({}^{\circ}\)C) via mild water circulation, while the other one (\(T_{\text{hot}}\)) was heated until 125 \({}^{\circ}\)C via calibrated temperature-controlled resistors, allowing for the generation of a temperature gradients. The generated thermovoltage (\(\Delta V\)) was measured across the electrodes by a multimeter-voltmeter. The temperature of the two blocks was measured with an IR-thermometer (OMEGA OS-VIR50 Dual Laser Video IR Video Thermometer) to verify the temperature difference (\(\Delta T\)), and the Seebeck coefficient (S) was derived from the ratio \(\Delta V/\Delta T\).