Cornell Engineering : Self Assembling Materials

With inspiration from nature and techniques from nanoscale chemistry, the Wiesner Research Group developed a new class of hybrid materials— flexible ceramics—that are transparent and bendable but quite strong and not likely to shatter. Silica shells of single-celled microorganisms were the inspiration. In them, organic components of the microorganism direct the growth of inorganic materials to form perfect, symmetrical shapes.

New classes of hybrid materials with nanoscale structures developed by Uli Wiesner, professor in Materials Science and Engineering, combine the flexibility of organic molecules with the functionality of solid-state inorganic materials for applications in areas ranging from the microelectronic industry to the life sciences.

A new class of macromolecules discovered by Wiesner and his research team, referred to as extended amphiphilic dendrons, self-assembles into structures with dimensions on the order of 10 nanometers, an unusual process that mimics nature’s most fundamental system of organizing living tissue.

“We can encode information about the selfassembly behavior into their molecular architecture,” Wiesner says. “This is an exciting direction known as molecular engineering.”

Doped with inorganic lithium salts, ion transport can be observed along nanometer-sized channels that could prove relevant for applications such as battery electrolytes, fuel cells, and solar cells.

By surrounding fluorescent dyes with a protective silica shell, Wiesner and his group have created fluorescent nanoparticles, with possible applications in displays, biological imaging, optical computing, sensors, and microarrays such as DNA chips. These so-called Cornell dots, with their unique core-shell architecture, are as small as 25 nanometers in diameter and have advantages over existing fluorescent dye markers: they are about 30 times brighter and more photostable. Silica is benign and cheap in its production and compatible with silicon manufacturing technology, thus opening enormous opportunities in the life sciences and information technology.

3D structures produced by means of two-photon lithography to test new concepts in microfluidics

In Materials Science and Engineering, Professor Christopher Ober leads a team of Cornell researchers who are developing polymer surfaces for environmentally friendly marine coatings designed using self-assembly processes to provide structures with nanometer-scale precision.

Working with other researchers supported by the Office of Naval Research, the group is developing coatings that resist fouling (the accumulation of plants and marine organisms on the coating surface) and achieve this without toxic metals that might leach into the environment. These materials, based on fluorinated liquid crystalline block copolymers, form complex nanoscopic structures that aid fouling release and stabilize the coating structure. The use of block co-polymers, Ober says, offers remarkable possibilities for size and structure control on much smaller length scales than currently possible and with intricate geometries and functions unattainable in conventional coatings.

The group is exploring similar strategies for biomedical surfaces. Their goal is biocompatible surface structures with elements on length scales ranging from the nanometer to the micron at the twoand three-dimensional levels alike.