Fabrication and mechanical characterization of LCVD-deposited carbon micro-springs

Carbon micro-springs were fabricated using laser-assisted chemical vapor deposition (LCVD) at laser powers and ethylene pressures ranging between 200 and 700 mW and 400 and 900 mbar, respectively. A scanning electron microscope was used to determine geometrical parameters such as wire diameter, outside coil diameter, spacing, and pitch. The spring rates for nine batches of springs – chosen from the extremes and middle of the processing ranges – were determined with values ranging between 0.0294 and 0.0604 mN/μ m. With the spring rate values, trends regarding the shear modulus and the modulus elasticity of the carbon material as a function of laser power and precursor pressure were deduced. The shear moduli of the chosen batches had values between 13.6 and 733.5 MPa, and using a Poisson’s ratio value of 0.3 the moduli of elasticity ranged from 0.0353 to 1.9071 MPa.