Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.

Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.

Abstract: Microfluidic devices are described that include a microfluidic channel, a first array of one or more magnets above the microfluidic channel, each magnet in the first array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the first array, and a second array of one or more magnets beneath the microfluidic channel, each magnet in the second array having a magnetic pole orientation opposite to a magnetic pole orientation of an adjacent magnet in the second array. The first array is aligned with respect to the second array such that magnetic fields emitted by the first array and second array generate a magnetic flux gradient profile extending through the channel. An absolute value of the profile includes a first maximum and a second maximum that bound a local minimum. The local minimum is located within the microfluidic channel or less than 5 mm away from a wall of the microfluidic channel. Methods of using the new devices are also described.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.

Abstract: This disclosure describes microfluidic devices that include one or more magnets, each magnet being operable to emit a magnetic field; and a magnetizable layer adjacent to the one or more magnets, in which the magnetizable layer is configured to induce a gradient in the magnetic field of at least one of the magnets. For example, the gradient can be at least 103 T/m at a position that is at least 20 ?m away from a surface of the magnetizable layer. The magnetizable layer includes a first high magnetic permeability material and a low magnetic permeability material arranged adjacent to the high magnetic permeability material. The devices also include a microfluidic channel arranged on a surface of the magnetizable layer, wherein a central longitudinal axis of the microfluidic channel is arranged at an angle to or laterally offset from an interface between the high magnetic permeability material and the low magnetic permeability material.