• Table of Contents • cen-chemjobs.org • Today's Headlines • Editor's Page • Business • Government & Policy • Science & Technology • ACS News • Calendars • Books • Career & Employment • Special Reports • Nanotechnology • What's That Stuff?          Back Issues 2003 2002 2001 2000 1999 1998  Safety Letters  Chemcyclopedia ACS Members can sign up to receive C&EN e-mail newsletter.   Join ACS			May 19, 2003 Volume 81, Number 20 CENEAR 81 20 p. 14 ISSN 0009-2347 SCIENCE & TECHNOLOGY NANOSCALE DEVICES Liposomes connected by membrane nanotubes form nanofluidic network CELIA HENRY Lipid membranes can be used to make nanoscale fluidic devices that can control single nanoparticles and molecules, according to Swedish scientists. Orwar PHOTO BY JAN-OLOF YXELL 10µm CONNECT THE DOTS This network contains six vesicles, each about 4 µm in diameter. COURTESY OF OWE ORWAR "We believe that these systems are suitable for a number of applications, ranging from studies of chemical reactions in confined biomimetic compartments and single-polymer dynamics to construction of complex nanoscale fluidic devices with applications in bioanalysis, sensors, and computation," says Owe Orwar, professor of biophysical chemistry at Chalmers University of Technology, Göteborg. "Today, we use the networks to perform studies on enzyme kinetics as a function of dimensionality, geometry, and surface properties as well as to construct complex sensor devices based on coupled chemical reactions and chemical kinetics." Orwar and his colleagues at Chalmers and Göteborg University use liposomes to create fluidic networks consisting of vesicles connected by nanotubes [Anal. Chem., 75, 2529 (2003)]. The main challenges are finding the right membrane materials and suitable surface properties to immobilize the networks, according to Orwar. The networks are made by immobilizing liposomes made of soybean lipids on a surface and then using a pipette and micromanipulator to divide them into daughter liposomes connected by thin tubes less than 100 to 300 nm in diameter. The resulting liposomes can be made as small as 3 or 4 µm in diameter. The liposome reactors can each support different chemical reactions. The nanotubes allow mass transport between the different microreactors. The fluid flow is controlled by deforming the surface-adhered vesicles, which changes their surface-to-volume ratio and increases the surface tension, inducing a flow of the membrane that constitutes the walls of the system. Samples are introduced either by direct injection into a vesicle using microelectroinjection or by nanotube-assisted injection of sample-filled daughter vesicles. The researchers use the nanodevice to transport single 30-nm fluorescent beads, which they detect using laser-induced fluorescence. "We have constructed a fully operational and integrated nanofluidic device that essentially has reached the limit of how small you can go in terms of channel and device dimension if you are working with single, large-biopolymer systems in biochemical physics, analysis, or synthesis," Orwar says. "This is probably the most flexible way that I know of making tubes with internal dimensions from 20 to 100 nm and studying properties of molecules or particles in them," says Harvard chemistry professor George M. Whitesides. "All one needs is surfactant, a good microscope, and a good micromanipulator." Nanotube vesicle networks videos, click on image Nanotube vesicle network being made. This movie shows a 2-µm-diameter particle being transported inside a nanotube between two vesicles. A membrane tension difference is created by pinching one of the vesicles with carbon fibers. Nanoparticles and single molecules are transported in the same way but are harder to visualize. Top Chemical & Engineering News Copyright © 2003 American Chemical Society			Advanced Options Related Stories Nanotechnology [C&EN Archive] Chemistry Highlights 2002 Nanotubes [C&EN, Dec. 16, 2002] Chemistry Highlights 2002 Nanoscience [C&EN, Dec. 16, 2002] Related Person Owe Orwar E-mail this article to a friend Print this article E-mail the editor
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