However, systematic studies on the expandability of the proposed mechanism to other metals and the crack generation behaviors dependent on the magnitude of applied strain were missing. In this work, we investigated the effect of applied strain and film thickness on nanocrack generation

using titanium (Ti) films on PDMS substrates. Ti was chosen as the film material because of its several advantages such as good adhesion to diverse materials, high strength-to-weight ratio, good resistance to corrosion, and high biocompatibility even though it is a poor conductor [19–22]. Differing patterns of cracks in the Ti film created under varying strains resulted in a change in electrical resistance that corresponded to the applied strain, providing an opportunity that the cracked Ti film on PDMS substrate could be used for a flexible strain sensor covering a wide range of strain. The suggested strain sensor is very easy to fabricate and handle, BV-6 cost which ultimately allows for low-cost, Selleckchem SRT2104 portable strain sensors. It is also transparent, thereby expanding its potential use to monitoring deformations in various transparent bodies such as fragile structures, flexible electronics, and health-monitoring appliances. Methods A schematic procedure to fabricate a cracked Ti film on a PDMS substrate

is illustrated in Figure 1. To prepare an elastomeric PDMS sheet, a PDMS base resin (Sylgard 184, Dow Corning, Midland, MI, USA) was first mixed with a curing agent (Dow Corning) in a vial at a fixed weight ratio (10:1), and the mixture was poured onto a petri dish followed by degassing for more than 1 h [16, 23]. It was then cured at 70°C for 3 h [16], and the sheet thickness was 0.4 mm after curing. The cured PDMS sheet was sliced into a size of

28 mm (length) × 8 mm (width) rectangular samples. Ti films were deposited on the PDMS substrates Niclosamide by radio-frequency (RF) sputtering using a 2-in. Ti target (purity 99.99%). The base pressure was kept below 10-6 Torr. Film EPZ5676 molecular weight deposition was performed in an Ar gas flow of 9 sccm (process pressure approximately 1 × 10-3 Torr) at a RF power of 50 W. In this condition, the film growth rate was approximately 4 nm/s, and Ti films of varying thicknesses (80, 180, and 250 nm) were grown on the PDMS substrates with controlled deposition time. The Ti film area was constrained to 10 mm (length) × 8 mm (width) by masking both ends of the PDMS substrates during deposition. In the next step, the Ti films on PDMS substrates were uniaxially elongated to induce cracks in the Ti films. Here, the magnitude of applied strain was modulated in the range of 0% to 80%. Figure 1 Schematic process to fabricate a cracked Ti film on a PDMS substrate. Step 1: preparation of a PDMS sheet, step 2: slicing of the PDMS sheet into 26 mm × 8 mm-sized samples, step 3: deposition of a Ti thin film on the PDMS substrate, and step 4: generation of cracks by mechanical stretching.