Chaehyun Lim

Direct patterning of carbon nanotube network devices by selective vacuum filtration

We report on a method which allows direct patterning of density controlled carbon nanotube network (NTN) devices during network formation. By lithographically patterning photoresist on the filter membrane, the nanotubes in suspension were guided to the exposed pattern areas of the filter surface during vacuum filtration allowing in situ device formation. The NTNs were transferred to an elastomer substrate by directly curing polydimethylsiloxane on its surface. We compared electrical characteristics of NTN patterns fabricated simultaneously using this method and found that the different NTNs with equal nanotube density showed reproducible characteristics.

A Highly Sensitive and Reliable Strain Sensor Using a Hierarchical 3D and Ordered Network of Carbon Nanotubes

A 3D network of single-walled carbon nanotubes embedded in poly-(dimethylsiloxane) is presented as a promising route to the fabrication of a flexible film with ordered and interconnected single-walled carbon nanotubes. This is possible using a simple transfer method of as-grown hierarchical single-walled carbon nanotubes on a Si pillar substrate. This film is used as a highly sensitive strain gauge sensor. This type of network embedded in a polymer film should be applicable to many fields involving mechanically stable and reliable strain sensors.

Nanoscale floating-gate characteristics of colloidal Au nanoparticles electrostatically assembled on Si nanowires

Nanoscale floating-gate characteristics of colloidal Au nanoparticles electrostatically assembled on Si nanowires have been investigated. Colloidal Au nanoparticles with ∼5nm diameters were selectively deposited onto the lithographically defined n-type Si nanowire surface by 2min electrophoresis between the channel and the side gates. The device transfer characteristics measured at room temperature showed hysteresis, with the depletion mode cutoff voltage applied by the side gates shifted by as much as 1.5V, with the source-drain bias at 1.4V. The results demonstrate that the electrostatic assembly of colloidal Au nanoparticles is a useful method for the fabrication of Si nanowire based nanoscale floating-gate nonvolatile memory structures.

Flexible and transparent touch sensor using single-wall carbon nanotube thin-films

Here we report on the fabrication and demonstration of flexible and transparent touch sensors using carbon nanotube thin film(CNTF). We fabricated two types of touch sensors. The first type was a compressively strained CNTF pressure sensor, and the second type was a 5-wire resistive CNTF touch sensor. The change in compressively strained CNTF conductivity depended on the strength of the applied vertical pressure and with 0.2 MPa applied vertical pressure, the CNTF sheet conductance increased rapidly by 10 %. We applied cyclic pressures (0.2 MPa) at 15 second intervals and found that the tactile pressure dependence was reproducible for several hundred cycles. In the case of 5-wire resistive CNTF touch sensors, the touch activation pressure of is 23 Pa. And it showed good repeatability over 105 times.