NEWS OF THE WEEK LAB O N A
CHIP
MICROFLUIDIC CIRCUITS Devices will have applications in various biological and chemical assays
T
HE MICROFLUIDIC EQUIVA-
lent of an integrated circuit has been made for the first time by researchers at the California Institute of Technology 'This is the first demonstration of such a complex microfluidic device with thousands of valves and hundreds of individually addressable chambers," says Stephen R. Quake, associate professor of applied physics at Caltech. "To put that all together on a 1-inch by 1inch chip is a notable achievement." The Caltech team also includes graduate students Todd Thorsen and SebastianJ. Maerkl. A"multiplexor," which is a combinatorial array of binary valve patterns, controls the fluid flow on the devices. The number of control channels is logarithmically related to the number of flow channels, allowing a large number offlowchannels while maintaining a small number of control channels. One device, for example, contains 1,000 chambers and 3,574 valves, but has only 22 inlets [5aence, published online Sept. 26, http:/Avwwsciencemag.org/cgi/co ntent/abstract/1076996]. The devices, made of polydimethylsiloxane (PDMS), are constructed in two layers, with the control layer stacked on top of the flow layer. The control channels have both narrow and wide sections; a valve is formed where a wide section crosses over a flow channel. These valves are opened and closed by applying pressure to the control channels, which deflects the PDMS membrane between the crossed channels, shutting off the flow channel. One such device functions as a memory device consisting of HTTP://PUBS.ACS.ORG/CEN
1,000 individually addressable compartments. "We can create arbitrary patterns in this array, just like you can in a regular memory," Quake says. "On the simplest level, it's analogous to RAM in that you can store bits of fluid and randomly pull them out." A second device allows reagents to be separately loaded, mixed, and recovered. Quake's team used this device in an assay to test for the expression of an enzyme. Quake plans to use these microfluidic devices for a variety of applications, including structural genomics, genetic analysis, environmental microbiology, and high-throughput screening. "We will design a chip specifically for each application, but we'll make use of components that have been useful in other circumstances," Quake says. DEBT
COMPLEX CIRCUIT An optical micrograph of a Caltech microfluidic chip loaded with colored food dyes. The devices do have shortcomings. "There is not a perfect material, and PDMS is no exception. There are always going to be issues such as permeability and nonspecific binding," Quake says. "But with clever design rules and device geometry, you can work within the limitations of any given material and still make very powerful devices."-CE LI A HENRY
R E D U C T I O N
ICI Sells Catalysts Unit To Johnson Matthey
I
CI is selling its catalysts division, Synetix, to precious-metals specialist Johnson Matthey for roughly $406 million in cash. ICI put Synetix up for sale in January. The unit's 2001 revenues were $228 million, with operating profits of $37 million. It provides catalysts and related services for end uses including edible oils, methanol, ammonia, oil and gas, chemicals, fine chemicals, and oleochemicals. "The acquisition is a significant step in growing our highly successful catalyst and chemicals business," Johnson Matthey CEO Christopher R. N. Clark says. "The combination of Synetix and our existing catalyst businesses will substantially enhance our market position in the worldwide catalyst industry." That's particularly true, the company predicts, in new growth segments such as gas-to-
liquids technology for the energy sector and chiral catalysis for the pharmaceuticals industry. Synetix is headquartered in Billingham, England, and has catalyst plants in the U.K., Germany, and India. Its 800 employees will transfer to Johnson Matthey. After taxes and other costs associated with the sale, ICI expects to pocket just under $300 million, which it will use to pay down debt. That is the main reason for the sale; Synetix otherwise neatly supports ICI's reshaped specialty focus. The sale, which requires regulatory clearance in Germany, is expected to close in the fourth quarter. And the sale of the part of Synetix businesses owned by ICI India Ltd. is subject to the approval of that company's shareholders.-PATRICIA SHORT
C&EN
/ SEPTEMBER
30, 2002
11
