Microanalysis of cellular function

1. A method for precise transport of at least one particle in a microchannel, comprising:

a) making available an inverted microwell system, the system comprising:

i) a microchannel having a first end and a second end, wherein the microchannel is configured to allow a liquid to flow in a liquid flow direction, the liquid flow direction being defined from the first end to the second end, and wherein the microchannel is defined between a first vertical wall disposed on a first side of the microchannel and a second vertical wall disposed on a second side of the microchannel, the first vertical wall comprising a first substrate portion, and the second vertical wall comprising a second substrate portion;

ii) a microwell having an open upper end and a lower end, the upper end open to the microchannel, the microchannel facilitating liquid transport to the microwell, the microwell comprising a third vertical wall extending between the upper end and the lower end, the third vertical wall comprising a third substrate portion; and

iii) a controlled electrode array, the electrode array comprising a first electrode, a second electrode, a third electrode, and a fourth electrode, wherein at least a portion of each of the first and third electrodes is embedded within the first substrate portion, and at least a portion of each of the second and fourth electrodes is embedded within the second substrate portion;

wherein the third and fourth electrodes are disposed adjacent an upper surface of the microchannel;

wherein the first and second electrodes are disposed below the third and fourth electrodes, respectively, such that the first substrate portion is disposed between the first and third electrodes and the second substrate portion is disposed between the second and fourth electrodes; and further

wherein the first and second electrodes are oriented along a first axis perpendicular to the liquid flow direction, and the third and fourth electrodes are disposed above the first and second electrodes, respectively,

the electrode array further comprising a fifth electrode at least partially embedded in the third substrate portion and at least partially extending around the microwell, and a sixth electrode at least partially embedded in the third substrate portion and at least partially extending around the microwell,

wherein the third electrode is disposed above the fifth electrode and the fourth electrode is disposed above the sixth electrode;

b) inserting a liquid containing at least one particle into the microchannel; and

c) creating, in the microchannel, a pattern of electric field strength to cause the at least one particle to move in a desired direction in the microchannel.

2. The method according to claim 1 , the controlled electrode array further comprising a seventh electrode, an eighth electrode, a ninth electrode, a tenth electrode, an eleventh electrode, and a twelfth electrode; wherein at least a portion of each of the seventh, ninth, and eleventh electrodes is embedded within the first substrate portion, and at least a portion of each of the eighth, tenth, and twelfth electrodes is embedded within the second substrate portion; and wherein the seventh and eighth electrodes are oriented along a second axis perpendicular to the liquid flow direction, the ninth and tenth electrodes are oriented along a third axis perpendicular to the liquid flow direction, and the eleventh and twelfth electrodes are oriented along a fourth axis perpendicular to the liquid flow direction, the method further comprising:

d) polarizing the first, seventh, and eleventh electrodes at a first voltage and a first phase;

e) polarizing the second, eighth, and twelfth electrodes at the first voltage and a second phase, the second phase being different than the first phase; and

f) grounding the ninth and tenth electrodes, thereby trapping said at least one particle in a location between the ninth and tenth electrodes.

3. The method according to claim 2 , further comprising, after said step f):

a) grounding the seventh and eighth electrodes;

b) polarizing the ninth electrode at the first voltage and the first phase; and

c) polarizing the tenth electrode at the first voltage and the second phase, thereby pushing said at least one particle toward a minimum of electric field between the seventh and eighth electrodes.

4. The method according to claim 1 , said inverted microwell system further comprising a detection structure configured to provide an output signal in response to passage of said at least one particle by the detection structure, the detection structure comprising a first detection electrode, a second detection electrode, a third detection electrode, and a fourth detection electrode, wherein the first and second detection electrodes are positioned opposite one another and on opposite sides of an axis parallel to the liquid flow direction such that a first gap is disposed between the first and second detection electrodes, wherein the third and fourth detection electrodes are positioned opposite one another and on opposite sides of the axis parallel to the liquid flow direction such that a second gap is disposed between the third and fourth detection electrodes, and wherein the first, second, third, and fourth detection electrodes are in contact with a bottom surface of said microchannel, wherein the controlled electrode array is configured to align the at least one particle along the axis parallel to the liquid flow direction, wherein a signal to noise ratio produced on the output signal by the passage of said at least one particle is at a maximum, and said method comprises:

a) connecting the second detection electrode and the fourth electrode to a voltage source for supplying an alternate voltage; and

b) connecting the first detection electrode and the third detection electrode to a readout circuit which amplifies a first output current and a second output current, the first and second output currents corresponding to the first and third detection electrodes, and wherein the readout circuit further provides a final output signal proportional to a difference between the first and second output currents or a ratio between the first and second output currents.

5. The method according to claim 1 , said inverted microwell system further comprising a detection structure configured to provide an output signal in response to detecting that the at least one particle is passing by the detection structure, the detection structure comprising a first detection electrode, a second detection electrode, and a third detection electrode, wherein the first, second and third detection electrodes each partially overlap an axis parallel to the liquid flow direction, and wherein the first, second, and third detection electrodes are in contact with a bottom surface of the microchannel, wherein the controlled electrode array is configured to align the at least one particle along the axis parallel to the liquid flow direction, wherein a signal to noise ratio produced on the output signal by the passage of said at least one particle is at a maximum, and said method comprises:

a) connecting the second detection electrode to a voltage source for supplying an alternate voltage; and

b) connecting the first and third detection electrodes to a readout circuit which amplifies a first output current and a second output current and provides a final output signal proportional to a difference between the first and second outputs or a ratio between the first and second output currents.

6. The method according to claim 1 , further comprising:

aligning, by the controlled electrode array, the at least one particle in the microchannel along an axis parallel to the liquid flow direction, and

detecting, by optical detection, the at least one particle after the controlled electrode array has aligned the at least one particle along the parallel axis.