Periodic surface features generated during reciprocating diamond-wire sawing affect the surface morphology of monocrystalline silicon wafers, yet fluctuations within individual saw marks along the wire-running direction remain poorly understood. Here, wafers were sliced using electroplated diamond wires with carbon-steel and tungsten cores. Stylus profilometry and scanning electron microscopy were used to characterize groove-internal morphology and surface damage. Replacing the carbon-steel core with a tungsten core increased the estimated characteristic wavelength from approximately 44 to 70 mm and reduced the peak-to-valley (PV) height from approximately 17 to 6.5 μm. The tungsten-core wire also exhibited less pronounced brittle-fracture features and a more uniform surface morphology. The results indicate that core-wire material influences groove-internal surface modulation, which may be associated with changes in the dynamic response of the moving wire.
Thermoresponsive CNT/PNIPAm hydrogels exhibit resistivity changes during deswelling through two competing effects: water loss reduces ionic conduction and increases resistivity, whereas volume contraction densifies the CNT network and decreases resistivity. However, what determines the response direction remains unclear. Here, we investigate the effect of poly(vinylpyrrolidone) (PVP) molecular weight across twelve dispersion conditions.Heating from 25 to 50 °C produced predominantly opposite responses: resistivity decreased with low-molecular-weight PVP (K-15) and increased with high-molecular-weight PVP (K−30), reaching Δρ values of −1.82 and + 1.89 MΩ·mm, respectively, in the most responsive conditions. Raman spectra indicated comparable non-covalent PVP–CNT interactions for both molecular weights, suggesting that CNT surface interactions are unlikely to govern the response direction. Water loss and volume shrinkage correlated with response magnitude but did not explain its direction. Water loss consistently exceeded shrinkage, accompanied by a decrease in apparent density from 0.83 to 1.13 to 0.73–0.89 g cm−3. These results suggest that thermal resistivity response reflects competition between ionic conduction loss and CNT-network densification, with balance depending on PVP molecular weight. Thus, PVP molecular weight provides a practical design parameter for tuning thermal electrical response of CNT/PNIPAm hydrogels.
