Nanotechnology

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Nano drives improve displays

Display technology is currently realizing the benefits of nanotechnology in lighting support for the displays and the display construction itself.

One of the new display technologies is the Mirasol display from Qualcomm. This MEMS (microelectromechanical-system)-on-glass device targets low-power, daylight-readable color displays for portable-system applications.

Most LCD devices operating at low power, such as with mobile phones and tablet PCs, have issues with color representation. In varying light, the color accuracy of the display changes, altering the viewer’s perception of the image. The Mirasol display attempts to overcome these issues.

The display is a front-reflective display rather than a traditional backlit display. The properties of nanoscale materials combine with advanced MEMS-processing techniques, allowing the display to mimic naturally occurring phenomena. The display works by creating a color from an interference pattern on the reflected light that hits the top of the display. This process is the same one that makes a butterfly’s wing shimmer and display different colors.

The display uses red, green, and blue subpixels to create a single pixel measuring less than 1 micron. Each of the colored subpixels comprises cells, which form an array of devices. An applied voltage then switches these devices to “collapse” the MEMS device and turn off the reflective element (Figure 1).

The Mirasol display is just one example of the use of nanotechnology in a diverse range of applications. The area of nanomaterials—compounds, elements, and polymers that behave differently or exhibit new and unique properties at the nanoscale—is bringing many new support applications to electronics.

In the case of products from Cima NanoTech, the key nanomaterial is nanocrystalline silver. With its high conductive characteristics, silver has been in use as a standard material for more than 100 years. Cima formulates the silver and silver/copper into nanoparticle form and places these particles in suspensions and emulsions that designers can apply to various surfaces. Using self-assembly techniques, these nanoparticles form microscopic conductive networks that are transparent but that have properties similar to those of traditional opaque materials. Designers can apply the nanoparticle layer as a transparent film with an inexpensive, wet-rolling process in a large format, so it can become a low-cost, effective EMI (electromagnetic-interference) filter for plasma and other large displays. Designers can also pattern the material to form large-format resistive-touch-sensor overlays for LCD screens. In a new and growing application, the silver-and-copper particle solution can find use in conductive inks. Designers are able to print these inks on a surface using time-proven ink-jet technology.

This ability to print a conductor is drastically changing the RF- and PCB (printed-circuit-board)-prototyping flows by allowing, for example, the creation of one-time unique antenna designs that designers print and test on paper. Designers can similarly print a few fine-pitch prototypes on paper or mylar to test a design. The technique currently works in single-layer-system applications. However, multilayer-system applications are in progress.

Quantum dots are nanoparticles that have tunable optical characteristics. Companies including Nanosys and Zymera have turned these properties into commercial products. Nanosys has a series of quantum-dot lighting techniques that color-correct the wavelength of backlit LEDs in cell phones. Zymera is using the dots as bioluminescent particle tags for drugs to track the absorption and location of certain medications in the treatment of cancer, for example.