Health and Medicine Technology

Gold Nanowires Electrochemically Grown for Biomedical Procedures


Electrodes that are implanted in human tissue and conventional surgical tools are relatively large on the cellular level. In areas such as neurosurgery, working at the individual cell level is becoming increasingly important.

A new device was developed by researchers from Kansas State University.  This device may benefit biomedical professionals during electrode and organ transplant procedures. Bret Flanders, associate professor of physics, and Govind Paneru, former graduate research assistant in physics, grew gold nanowires like a snowflake and sharpened these with a sewing machine.

The gold nanowires are 1,000 times thinner than a human hair and the device is used in medical procedures to manipulate and sense characteristics of individual cells. Flanders is of the opinion that their device is unique due to the size of the nanowires. Red blood cells are about 7 micrometers in diameter, while hair and skin cells measure approximately 10 to 20 micrometers. Each golden nanowire in the device is less than 100 nanometers in diameter. Biological cells can be pierced to stimulate the cell membrane and investigate its interior with these small wires.

The nanowires are electrochemically grown by accumulating particles from a solution into a new wire, rather than enlarging or lengthening an existing wire. In video footage, the nanowire can be seen to grow out of the micrometer thick electrode.

This process is similar to how a snowflake is assembled in the sky. Water vapor molecules in the air condense onto the surface of dust or pollen. The molecules continue to grow non uniformly until they turn into the familiar snowflake.

Flanders explained that the process is started on a microscope stage with a sharp microelectrode. The gold atoms condense onto the microelectrode sharp tip, similar to snowflake formation. The golden solution condenses onto the gold microelectrode as does water condensing onto the snowflake seed.

A sewing machine was used as an unconventional tool to develop the sharp electrodes. When the sewing machine crank is turned to sharpen the electrode, it works like putting the wire in a pencil sharpener. The process is however not mechanical like it is with a pencil sharpener, but uses a common salt solution and a sewing machine. This approach turned out to work the best.

The sewing machine is used to oscillate the microelectrode up and down in a beaker of potassium chloride solution, while the tip of the microelectrode is dissolved by applying a voltage. The electrode is sharpened because the tip is in the solution longer than any other part. If the wire were not oscillated, it would dissolve completely. Dipping the tip in and out of the solution causes it to dissolve the most, thereby sharpening it.

The nanowire is able to grow due to the sharpened electrode. The nanowire is finally removed from the electrode and then shipped to collaborators across the country for further manufacturing. To provide the invention with greater power, a nanofabrication company may incorporate it into a pre-existing device.

The research was published in the journals Applied Physics Letters and Nanotechnology.