Mechanical Property Measurement of Carbon Infiltrated Carbon Nanotube Structures for Compliant Micromechanisms

Abstract

Carbon nanotubes (CNTs) can be grown in dense lithographically patterned forests to form framework structures that can be filled in via chemical vapor deposition to form solid structures. These solid structures can then be used in microelectromechanical systems (MEMS) applications. Initial testing with these structures suggests that when these frameworks are filled with carbon, the resulting material exhibits favorable properties for use in compliant MEMS. To better understand this material's properties, we conducted tests to measure its Young's modulus, failure stress, and stress relaxation in the direction perpendicular to the CNT growth, as well as the modulus and stress in the direction parallel to the CNTs. To determine the properties in the transverse direction, we applied vertical loads to the tips of simple cantilever beam samples, and recorded the force and deflection until failure. The results showed failure strain up to 2.48%. Cantilever samples prepared from the same pattern were also used to measure the stress relaxation of the material. The first test for each sample showed an average force relaxation of 3.72%, while successive tests only produced 1.23% after 24 h. To determine the properties in the direction parallel to the CNTs, we prepared simple rectangular beams and subjected them to 3-point bending tests. The average strain calculated in the parallel direction was 8.17%.[2013-0121] Index Terms-Micromechanical devices, carbon nanotubes, material properties.

High Aspect Ratio Carbon Nanotube Membranes Decorated with Pt Nanoparticle Urchins for Micro Underwater Vehicle PropulsionviaH2O2Decomposition

“…Figure f shows a representative carbon -infiltrated CNT-MM (CNT is herein taken to mean “carbon-infiltrated CNT”) with low-porosity sidewall surfaces. The precise patterning capabilities of photolithography and the macro-scale growth size of CNTs, in conjunction with the added structural versatility afforded by CNT-templated microfabrication, allows for the creation of a variety of high aspect ratio, nanocomposite materials of varying porosity/composition with enhanced structural integrity. , …”

Curvature-induced defects on carbon-infiltrated carbon nanotube forests

“…CNT height was controlled by the amount of time in the growth phase of the fabrication process. 20,26 The growth times in this study were 1 minute and 10 minutes, which corresponded to heights of 63 ± 14 μm and 389 ± 61 μm, respectively. The length of the substrate and CICNT infiltration time were held constant.…”

“…A carbon-infiltrated carbon nanotube (CICNT) forest is a CNT forest that has been subsequently infiltrated with amorphous pyrolytic carbon. 20 The structure maintains its shape and can still be rendered superhydrophobic like CNT forests with contact angles greater than 155°, 21 but it is more durable as a cohesive material because CNTs cannot be brushed off the substrate. Under bending loads, CICNT have shown a strength of 102 MPa and a modulus of elasticity of 4.1 GPa in the direction perpendicular to the forest ( i.e.…”

“…, pulling the nanotubes away from each other), and in the direction parallel to the nanotube axes, the achievable strength was 903 MPa with a modulus of elasticity of 11 GPa. 20 …”

High surface-area carbon microcantilevers

“…The interstices between the nanotubes were partially inltrated with a nanocrystalline carbon matrix material to form a cohesive structure. 8,9 Precisely dened CNT-M cantilevers (see Fig. 2) were microfabricated with a wide range of porosities by varying the inltration time.…”