Design of an interface to allow microfluidic electrophoresis chips to drink from the fire hose of the external environment

Abstract

An interface design is presented that facilitates automated sample introduction into an electrokinetic microchip, without perturbing the liquids within the microfluidic device. The design utilizes an interface flow channel with a volume flow resistance that is 0.54-4.1 x 10(6) times lower than the volume flow resistance of the electrokinetic fluid manifold used for mixing, reaction, separation, and analysis. A channel, 300 microm deep, 1 mm wide and 15-20 mm long, was etched in glass substrates to create the sample introduction channel (SIC) for a manifold of electrokinetic flow channels in the range of 10-13 microm depth and 36-275 microm width. Volume flow rates of up to 1 mL/min were pumped through the SIC without perturbing the solutions within the electrokinetic channel manifold. Calculations support this observation, suggesting a leakage flow to electroosmotic flow ratio of 0.1:1% in the electrokinetic channels, arising from 66-700 microL/min pressure-driven flow rates in the SIC. Peak heights for capillary electrophoresis separations in the electrokinetic flow manifold showed no dependence on whether the SIC pump was on or off. On-chip mixing, reaction and separation of anti-ovalbumin and ovalbumin could be performed with good quantitative results, independent of the SIC pump operation. Reproducibility of injection performance, estimated from peak height variations, ranged from 1.5-4%, depending upon the device design and the sample composition.

A fully integrated microfluidic genetic analysis system with sample-in–answer-out capability

“…With these valves open, flow is driven to the PCR domain as the more shallow elution waste path functions as a large fluidic resistor. Dominant flow (Ͼ99%) through the PCR domain is achieved by a combination of balanced flow resistance ratios (6) and elastomeric valving technology (7,8).…”

“…The MGA system described in this report brings together many advances in microfluidics over the last decade, exploiting differential channel flow resistances (6), elastomeric valves (7,8), laminar flow (9), and electrophoretic mobility within the device, in concert with external fluid flow control from a syringe pump for sample and reagent delivery. Nucleic acid purification through solid-phase extraction (SPE), followed by target sequence amplification by PCR and microchip electrophoretic (ME) amplicon separation and detection is completed in Ͻ30 min.…”

Real-Time Electrochemical Monitoring: Toward Green Analytical Chemistry

“…The high degree of integration offered by "lab-ona-chip" devices implies that the principles of green chemistry can be applied to all the steps of the analytical process. A recent contribution from Harrison's team 31 demonstrated a convenient interface of microfluidic devices to the external environment. Such ability to continuously introduce real samples into micrometer channels would make "lab-on-a-chip" devices compatible with reallife monitoring applications.…”

Biomedical applications of protein chips

“…in multidimensional separations. Many other electrophoretic and some chromatographic on-chip applications have been cited in the literature [12,13,[70][71][72][73]. Mass spectrometry is an important detection tool for protein chips.…”