Synthetic Mini Tree Utilizes Physical Capillary Action

In what may be an important advance in the field of microfluidics, researchers at Cornell replicated the capillary action of plants on a micro scale, and virtually reproduced the basic vessel grid of a tree. We think such technology might have implications for the development of lab-on-a-chip devices and other diagnostic medgadgets:
From Cornell:

In nature, trees use water in tubular tissues, called xylem, like ropes that pull more water out of the ground, delivering it to leaves. They manipulate the water in the xylem under negative pressure — what’s called a metastable liquid state — right on the verge of becoming a vapor.
Xylem-like capillaries are relatively easy to create by microfabrication, but the researchers’ choice of a material to act as membranes in the leaf and root to separate the liquid from the atmosphere and the soil was much trickier.

Stroock, assistant professor of chemical and biomolecular engineering, and Wheeler, a graduate student in his lab, used pHEMA hydrogel, or polyhydroxyethyl methacrylate, to form the plant membranes. The hydrogel is a solid embedded with water and has nanometer-scale pores. The material acts as a wick by holding liquid in the pores, through which capillary action creates tension in the water.
By building mimics of xylem capillaries within the gels, the scientists were able to create negative-pressures of the magnitude observed in trees, and to pump water against large resistances and out of subsaturated, or partially dry, sources.

Press release: World’s first synthetic tree is no giant redwood, but may lead to technologies for heat transfer, soil remediation
Images: (1) This optical micrograph of a synthetic tree shows a “trunk” channel entering from the left into a network of microchannels in the “leaf,” or “root,” network. The channels are approximately 100 micrometers wide, and total field of view is approximately 1.5 centimeters wide. (2) A transparent sheet of pHEMA, 1 millimeter thick, is etched with 80 parallel channels of varying lengths arranged to form a circle and connected by a single channel. The inset shows an optical micrograph of the cross-section of one microchannel.