Methods for microfluidic aspirating and dispensing

A method for aspirating a fluid from a source, comprising the steps of:

• reducing the hydraulic pressure within an aspirate-dispense system by withdrawing a predetermined quantity of system fluid from a feedline of said system;
• dipping a tube of said system in said fluid source;
• and
• adjusting positive displacement means of said system so that a reduced pressure is created in said system to aspirate a quantity of said fluid of said source into said tube of said system.

A method for dispensing a fluid onto a target using an aspirate-dispense system including a drop-on-demand valve in fluid communication with a direct current fluid source, comprising the steps of:

• pressurizing said system by adjusting said direct current fluid source of said system while maintaining said valve of said system in a closed position to build hydraulic pressure within said system to a generally steady state and/or predetermined value;
• selecting a desired flow rate of fluid to be dispensed from a tube of said system onto said target;
• and
• operating said direct current fluid source and said valve of said system to dispense precise and/or predetermined quantities of said fluid onto said target.

A method for aspirating fluid from a source and dispensing said fluid onto a target using an aspirate-dispense system including a drop-on-demand valve in hydraulic communication with a direct current fluid source, comprising the steps of:

• adjusting said system by opening said valve of said system to dispense system liquid into a non-target position so that the hydraulic pressure within said system is reduced;
• dipping a tube of said system in said fluid source;
• creating a reduced pressure in said system by operating said direct current fluid source to aspirate a quantity of said fluid of said source into said tube of said system;
• pressurizing said system by adjusting said direct current fluid source of said system while maintaining said valve in a closed position to build hydraulic pressure within said system to a generally steady state value;
• and
• actuating said direct current fluid source and said valve of said system to dispense precise and/or predetermined quantities of said fluid onto said target.

An apparatus for aspirating and/or dispensing predetermined quantities of a fluid, comprising:

• a dispenser including a drop-on-demand valve adapted to be opened and closed at a predetermined frequency and/or duty cycle;
• a direct current fluid source in fluid communication with said dispenser for metering predetermined quantities of said fluid to or from said dispenser;
• one or more pressure sensors placed intermediate said dispenser and said direct current fluid source and/or at said dispenser for monitoring the hydraulic pressure within said apparatus;
• whereby, actuations of said valve and/or said direct current fluid source provide pressure compensation prior to aspirate and/or dispense functions by reducing or raising the hydraulic pressure within said apparatus to a predetermined and/or generally steady state pressure.

A hydraulic system for dispensing precise quantities of a fluid, comprising:

• a dispenser including a drop-on-demand valve adapted to be opened and closed at a predetermined frequency and/or duty cycle;
• a direct current fluid source in fluid communication with said dispenser for metering predetermined quantities of said fluid to said dispenser;
• the output fluid flow rate (Qn) of said hydraulic system being substantially in accordance with a transfer function having the form:
• 27 Q n Q t = K s ⁡ ( s + 1 τ ) 1 + K s ⁡ ( s + 1 τ ) = 1 1 + 1 K ⁢ s ⁡ ( s + 1 τ )
• with a characteristic equation given by:
• 28 1 + K s ⁡ ( s + 1 τ ) = 0
• and a gain K given by:
• 29 K = 1 R t ⁢ C ⁢ ⁢ τ
• where, Qt is the input fluid flow rate provided by said direct current fluid source, Rt is the flow resistance, C is the elastic capacitance, τ is the inertial or inductive time constant, and s is the Laplacian variable.