Method and apparatus for reducing sample dispersion in turns and junctions of microchannel systems

A low-dispersion device for turning the direction of transport of a moving sample that comprises:

• a microchannel system comprising at least one turning channel having an inlet end and an outlet end, an inner wall and an outer wall, and an included turn angle, wherein the turning channel comprises contraction and expansion regions such that a portion of the turning channel is constricted to a width that is smaller than the widths of the inlet and the outlet ends, and wherein the contraction and expansion regions define inner and outer walls of the turning channel that are substantially equal in length.

A low-dispersion device for turning the direction of transport of a moving sample that comprises:

• a microchannel system comprising at least one turning channel having an inlet end and an outlet end, an inner wall and an outer wall, and an included turn angle, wherein the turning channel comprises contraction and expansion regions such that a portion of the turning channel is constricted to a width that is smaller than the widths of the inlet and the outlet ends, and wherein the outer wall of the turning channel comprises linear segments at the inlet and outlet ends joined by an arc of fixed radius spanning the included turn angle and wherein the inner wall of the turning channel is configured to form the contraction and expansion regions.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end and wherein the branching junction has a cross-section that is rectangular, trapezoidal, or triangular.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end and wherein an included turn angle between the inlet end and at least one outlet end is about 22.5 degrees.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end and wherein an included turn angle between the inlet end and at least one outlet end is about 45 degrees.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end, and wherein the joining of adjacent junction walls interior of the outlet ends defines a cusp.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end, and wherein the contraction and expansion regions of the branching junction define a first distance of travel along one outer junction wall and a second distance of travel starting at the center of the inlet end and proceeding along the junction wall interior of one outlet end, and wherein the first and second distance of travel are substantially equal.

A low-dispersion device for dividing a sample that comprises:

• a microchannel system comprising first, second, and third branching junctions and at least two turning channels wherein each branching junction comprises one inlet end and at least two outlet ends, and the outlet ends of the first branching junction are joined by turning channels to the inlet ends of the second and third branching junctions and at least one of said first, second and third branching junctions comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one of its outlet ends.

A low-dispersion device for joining two or more samples that comprises:

• a microchannel system comprising at least one confluence junction having at least two inlet ends and one outlet end, wherein the confluence junction comprises contraction and expansion regions such that a portion of the confluence junction is constricted to a width that is smaller than the width of at least one inlet end and wherein the confluence junction has a cross-section that is rectangular, trapezoidal, or triangular.

A low-dispersion microchannel device for turning the direction of transport of a moving sample comprising:

• a turning channel having an inlet end and an outlet end, wherein the turning channel comprises a region in which the cross-sectional area is smaller than that of the inlet end and wherein the turning channel has a cross-section that is rectangular, trapezoidal, or triangular.

A low-dispersion device for turning the direction of transport of a moving sample that comprises:

• a microchannel system comprising at least one turning channel having an inlet end and an outlet end, an inner wall and an outer wall, and an included turn angle, wherein the turning channel comprises contraction and expansion regions such that a portion of the turning channel is constricted to a width that is smaller than the widths of the inlet and the outlet ends, and wherein the length of the inner wall along the contraction region is longer than the length of the outer wall along the contraction region.

A low-dispersion device for turning the direction of transport of a moving sample that comprises:

• a microchannel system comprising at least one turning channel having an inlet end and an outlet end, an inner wall and an outer wall, and an included turn angle, wherein the turning channel comprises contraction and expansion regions such that a portion of the turning channel is constricted to a width that is smaller than the widths of the inlet and the outlet ends, and wherein the length of the inner wall along the expansion region is longer than the length of the outer wall along the expansion region.

A low-dispersion device for turning the direction of transport of a moving sample that comprises:

• a microchannel system comprising at least one turning channel having an inlet end, an inner wall and an outer wall, and an included turn angle, wherein the turning channel comprises contraction and expansion regions such that a portion of the turning channel is constricted to a width that is smaller than the widths of the inlet and the outlet ends, and wherein the inner wall defines a path having at least one inflection point in the contraction region and having at least one inflection point in the expansion region, and expansion regions.

A low-dispersion device for dividing a sample that comprises:

• a planar substrate patterned to define a microchannel system comprising at least one branching junction having one inlet end and at least two outlet ends, wherein the sum of the widths of the two outlet ends is substantially equal to the width of the inlet end, and wherein the branching junction comprises contraction and expansion regions such that a portion of the branching junction is constricted to a width that is smaller than the width of at least one outlet end.

A low-dispersion device for joining two or more samples that comprises:

• a planar substrate patterned to define a microchannel system comprising at least one confluence junction having at least two inlet ends and one outlet end, wherein the confluence junction comprises contraction and expansion regions such that a portion of the confluence junction is constricted to a width that is smaller than the width of at least one inlet end.