Doctoral Researcher

Current Research Interests

Carbon Nanotube Nanoneedles

They are made out of Single-wall or multi-wall carbon nanotubes, as an assembly of tubes into needle shape structures. Following figure (right) shows SEM image of a carbon nanotube nanoneedle made out of single-wall carbon nanotubes. By applying a voltage across two microelectrodes within a water solution, the carbon nanotubes get aligned by the electric field. As it is schematically shown in the figure bellow (left), by slowly pulling the two microprobes apart from each other, the surface tension of the liquid and the hydrophobicity of the carbon nanotubes coerce the tubes into a needle-like structure. The diameter, length and quality of such nanoneedles depend on voltages applied and the concentration of carbon nanotubes in the solution.

Nanoneedle manufacturing


Single Protein Measurements

As it is illustrated here, by using nanoneedles the protein immobilization and an effective background-free isolation of a single or a few molecules at the needle tip can be simultaneously accomplished.

Immobilization and isolation

Shown in the schematic is the near “point contact” surface that can keep the proteins in their natural conformation. Also, unlike immobilization schemes on a planar surface with only top-entry access of limited ‘solid-angle’, substrates can access the enzymes immobilized on a nanoneedle tip within a solid-angle twice as large. While planar-surface immobilization reduces enzyme activity, believe this is not the case for the proteins immobilized on the nanoneedle tip.


Electrochemical Sensing:

Carbon nanotube nanoneedles can be used as electrochemical sensors. While they can be considered nano electrodes made far easier and simpler than current methods reported in the literature, they are made out of carbon nanotubes which have been proven through varies investigations to enhance the electrochemical sensing. Natural carboxylic groups which are presented at the tip of the nanoneedles make them suitable to detect different kinds of bio-materials using the same functionalization procedure. The small diameter and high aspect ratio of the nanoneedles help to push not only for the detection limits (low concentration) but also the size limits (low detection volume) which in turn make them a unique new tool to investigate in the realms that have never studied before. The following figure shows a schematic of the setup for electrochemical sensing using carbon nanotube nanoneedles.

Electrochemical detection

Cell transfection:

With Diameters as small as tens of nanometers, best aspect ratio available in the word, already existent carboxylic groups and the high conductivity and mechanical flexibility, carbon nanotube nanoneedles can uniquely be used for cell transfection and drug delivery. These nanoneedles can be the only tips that can deliver into small cells and specific organelles with in the cells. Considering the minimal stress that is exerted on the cells by inserting the nanoneedles with in them (due to small diameter and high aspect ratio), insertion of multiple nanoneedles with in a cell is possible. All these, make the nanoneedles an ideal candidate for delivery, detection and manipulation in a single cell. Figure bellow shows transfection of a single cell with DAPI dye using nanoneedle.

Cell probing


•Ph.D. in Physics (2003-2007), Brown University, Providence, RI, USA

•Sc. M. in Physics (2001-2003), Brown University, Providence, RI, USA

•B.S. in Physics (1997-2001), Sharif University, Tehran, Iran


• Maryam Jouzi, Matthew B. Kerby, Anubhav Tripathi, Jimmy Xu,”A nanoneedle method for high-sensitivity low-background monitoring of protein activity”, under review in Nano Lett. 2007

• J. F. Waters, P. R. Guduru, M. Jouzi, and J. M. Xu, T. Hanlon, S. Suresh, “Shell buckling of individual multiwalled carbon nanotubes using nanoindentation ”, App. Phys. Lett87, 103109, 2005

• J. F. Waters, L. Riester, M. Jouzi, P. R. Guduru,a) and J. M. Xu, “Buckling instabilities in multiwalled carbon nanotubesunder uniaxial compression”, App. Phys. Lett85(10),1787, 2004

• A. Hartman, M. Jouzi, R. Bennett, and J.M. Xu, “Theoretical and Experimental Studies of Carbon Nanotube Electro-mechanical couplings”, Phys. Rev. Lett.92(23), 236804, 2004