Micromachined electrical field-flow fractionation system

A microchannel device for electrical field-flow fractionation of a fluid, comprising:

• a first substrate having a substantially planar inner surface;
• a first plurality of electrodes on the inner surface of the first substrate;
• a second substrate having a substantially planar inner surface and positioned over the first substrate;
• a second plurality of electrodes on the inner surface of the second substrate and facing the first plurality of electrodes;
• an intermediate layer interposed between the first substrate and the second substrate, the intermediate layer patterned so as to form opposing sidewalls of a plurality of microchannels, with the first and second plurality of electrodes each defining opposing continuous boundaries along the lengths of the microchannels, wherein the microchannels are dimensioned such that the distance between the first and second plurality of electrodes along the lengths of the microchannels is less than about 100 .mu.m;
• a plurality of inlet ports in the first or second substrate for allowing fluid flow into the microchannels;
• a plurality of outlet ports in the first or second substrate for allowing fluid flow out of the microchannels;
• and
• a plurality of detectors in operative communication with the microchannels for analyzing fluids in or from the microchannels, the detectors selected from one or more of the group consisting of electrical conductivity detectors and impedance detectors.

A micromachined system for electrical field-flow fractionation of a fluid, comprising:

• a first microchannel device comprising:
• a first substrate having a substantially planar inner surface;
• at least one first electrode on the inner surface of the first substrate;
• a second substrate having a substantially planar inner surface and positioned over the first substrate;
• at least one second electrode on the inner surface of the second substrate and facing the first electrode;
• and
• an insulating intermediate layer interposed between the first substrate and the second substrate, the intermediate layer patterned so as to form opposing sidewalls of at least one microchannel, with the first and second electrodes defining opposing continuous boundaries along the length of the microchannel, wherein the microchannel is dimensioned such that the distance between the first and second electrodes along the length of the microchannel is less than about 100 .mu.m;
• an inlet port in the first or second substrate for allowing fluid flow into the microchannel;
• and
• an outlet port in the first or second substrate for allowing fluid flow out of the microchannel;
• a reservoir means in fluid communication with the inlet port, for holding a fluid to be injected into the microchannel;
• and
• a first detector operatively connected with the first microchannel device for analyzing a fluid in the microchannel, wherein the first detector is an electrical conductivity detector or an impedance detector.

A micromachined system for electrical field-flow fractionation of a fluid, comprising:

• a first substrate having a substantially planar inner surface;
• a first plurality of electrodes on the inner surface of the first substrate;
• a second substrate having a substantially planar inner surface and positioned over the first substrate;
• a second plurality of electrodes on the inner surface of the second substrate and facing the first plurality of electrodes;
• an intermediate layer interposed between the first substrate and the second substrate, the intermediate layer patterned so as to form opposing sidewalls of a plurality of microchannels, with the first and second plurality of electrodes each defining opposing continuous boundaries along the lengths of the microchannels, wherein the microchannels are dimensioned such that the distance between the first and second plurality of electrodes along the lengths of the microchannels is less than about 100 .mu.m;
• a plurality of inlet ports in the first or second substrate for allowing fluid flow into the microchannels;
• a plurality of outlet ports in the first or second substrate for allowing fluid flow out of the microchannels;
• a buffer reservoir in fluid communication with the inlet ports;
• and
• a plurality of detectors operatively connected with the microchannels for multiple parallel processing of single or multiple test fluids in the microchannels, wherein the detectors are selected from one or more of the group consisting of electrical conductivity detectors, and impedance detectors.

A method of fabricating a microchannel device for electrical field-flow fractionation of a fluid, comprising the steps of:

• providing a first substrate having a substantially planar inner surface;
• providing a second substrate having a substantially planar inner surface;
• forming at least one inlet port and at least one outlet port in the first or second substrates;
• forming at least one first electrode layer on the inner surface of the first substrate;
• forming at least one second electrode layer on the inner surface of the second substrate;
• forming an insulating layer on the inner surface of the first substrate such that the insulating layer forms opposing sidewalls of at least one microchannel adjacent to the first electrode layer;
• attaching the second substrate to the insulating layer such that each of the first and second electrode layers define opposing continuous boundaries along the length of the microchannel, the distance between the first and second electrode layers along the length of the microchannel being less than about 100 .mu.m;
• and
• forming a detector in the microchannel, the detector configured to analyze a fluid in the microchannel.

An electrical field-flow fractionation process, comprising the steps of:

• providing a first microchannel device comprising:
• a first substrate having a substantially planar inner surface;
• at least one first electrode on the inner surface of the first substrate;
• a second substrate having a substantially planar inner surface and positioned over the first substrate;
• at least one second electrode on the inner surface of the second substrate and facing the first electrode;
• and
• an insulating intermediate layer interposed between the first substrate and the second substrate, the intermediate layer patterned so as to form opposing sidewalls of at least one microchannel, with the first and second electrodes defining opposing continuous boundaries along the length of the microchannel, wherein the microchannel is dimensioned such that the distance between the first and second electrodes along the length of the microchannel is less than about 100 .mu.m;
• applying a voltage differential to the first and second electrodes in order to induce an electric field across the microchannel;
• injecting a fluid through an inlet port in one of the substrates and into the microchannel;
• passing the fluid through the microchannel with the electric field therein in order to separate particles in the fluid;
• and
• monitoring the separated particles in the fluid with a first detector selected from the group consisting of an electrical conductivity detector and an impedance detector.