Abstract
We describe the mechanical properties of turbostratically graphitized carbon films obtained by carbon laser-patterning (CLaP) and their application as bending or mechanical pressure sensors. Stable conductive carbonized films were imprinted on a flexible polyethylene terephthalate (PET) substrate by laser-induced carbonization. After initial gentle bending, i.e. training, these sponge-like porous films show a quantitative and reversible change in resistance upon bending or application of pressure in normal loading direction. Maximum response values of ΔR/R0 = 388% upon positive bending (tensile stress) and −22.9% upon negative bending (compression) are implicit for their high sensitivity towards mechanical deformation. Normal mechanical loading in a range between 0 and 500 kPa causes a response between ΔR/R0 = 0 and −15%. The reversible increase or decrease in resistance is attributed to compression or tension of the turbostratically graphitized domains, respectively. This mechanism is supported by a detailed microstructural and chemical high-resolution transmission electron microscopic analysis of the cross-section of the laser-patterned carbon.
Highlights
With the advent of future applications in robotics, bionics, and smart textiles, flexible electronic devices are receiving an enormous scientific interest[1,2,3]
The mixture was gently stirred for 24 h to obtain a homogeneous viscous ink, which was applied on polyethylene terephthalate substrates (PET), polyurethane (PU), or nitrile gloves by doctor blading
These images in conjunction with corresponding selected-area electron diffraction (SAED) patterns in Fig. 4G confirm a high degree of crystallinity of turbostratic graphitic carbon in the upper laser-patterned carbon (LP-C) film regions while the lower regions still consist of predominantly amorphous pore walls and pockets
Summary
With the advent of future applications in robotics, bionics, and smart textiles, flexible electronic devices are receiving an enormous scientific interest[1,2,3]. The laser-patterned carbon (LP-C) was obtained from simple molecular precursors, namely citric acid and urea, and forms a composite with the flexible substrate, namely polyethylene terephthalate (PET) or polyurethane (PU).
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