External material accession systems and methods

A method of reducing or eliminating spontaneous injection, the method comprising:

• (i) dipping an open end of an open ended fluid-filled capillary element into a source of a first fluid and applying a negative pressure to the first fluid, thus injecting the first fluid into the capillary element;
• and, (ii) changing the negative pressure to a positive pressure or a zero pressure, thereby reducing or eliminating spontaneous injection of the first fluid.

A method of screening one or more samples in a microfluidic enzyme inhibition assay, the method comprising:

• (i) introducing one or more samples into a microfluidic device;
• and,
• (ii) introducing at least one inactivating reagent before the one or more samples, after the one or more samples, or between at least two of the one or more samples.

A microfluidic device, comprising:

• a glass or quartz body structure having disposed therein an integrated channel structure than includes at least first and second intersecting microscale channels, at least the first channel terminating in a substantially rectangular opening in the body structure;
• a capillary element having a capillary channel disposed therethrough, and at least one end of the capillary element that is substantially rectangular, the substantially rectangular end of the capillary element being inserted into the substantially rectangular opening in the body structure and positioned such that the capillary channel in the capillary element is in fluid communication with at least first microscale channel in the body structure.

A microfluidic device comprising:

• a glass or quartz body structure having at least first and second channel segments disposed therein, the first and second channel segments each having first and second ends, the first end of the first channel being in fluid communication with the first end of the second channel at a first fluid junction;
• and
• a capillary element attached to and extending from the body structure, the capillary element comprising a capillary channel disposed therethrough, the capillary channel being in fluid communication at one end with the first and second channel segments at the first fluid junction.

A microfluidic system. comprising:

• a microfluidic device comprising a microscale channel disposed therein, the microscale channel containing varying volumes of first and second fluids over time, the first and second fluids having first and second conductives, respectively;
• an electrical controller operably coupled to the microscale channel for applying a variable electric field across a length of the microscale channel;
• a computer operably coupled to the electrical controller, and appropriately programmed to instruct the controller to vary the electric field to maintain a constant average electroosmotic flow rate within the channel, despite a change in total resistance across the length of the channel resulting from the varying volumes of first and second fluids over time.