Mechanical Engineering ETDs

Publication Date



I report on the study of the electrical and mechanical effects of the inclusion of a thin layer of multiwalled carbon nanotubes (MWCNT) into the surface of polydimethylsiloxane (PDMS) as a method of creating an electrically actuated, flexible microfluidic valve. Samples of PDMS loaded with various surface loadings of MWCNT on the surface are prepared and tested using a uniaxial tension tester, combined with a four point probe electrical test. In contrast with other works reporting inclusion of MWCNT in the bulk of the material, I have found that inclusion of the MWCNT on the surface only has no discernable effect on the mechanical properties of the PDMS samples, but causes a significant and repeatable change in the electrical performance. I have also found that a loading of 4.16 g/m2 results in an electrical resistivity of 7.31\u038710-4 ohms\u0387cm, which is 200% lower than that previously reported for bulk inclusion samples. The microstructure of the MWCNTs was found to consist of both individual fibers and spherical clumps of fibers. I suggest that, due to the microstructure of the MWCNTs used in this study, the mechanical properties can be modeled as a thin layer of particulates, while the electrical properties can be modeled as a thin bed of bulk MWCNTs.


Microfluidic devices--Materials, Nanocomposites (Materials), Nanotubes, Polydimethylsiloxane.

Degree Name

Mechanical Engineering

Level of Degree


Department Name

Mechanical Engineering

First Committee Member (Chair)

Khraishi, Tariq

Second Committee Member

Apblett, Christopher

Third Committee Member

Shen, Yu-Lin


Sandia National Laboratories

Document Type