A hand-held, power-free microfluidic device for monodisperse droplet generation.

Here we develop a microfluidic device to generate monodispersion sub-nanoliter size droplets. Our system reaches steady state within 3 s after the flow starts and generates 100,000 droplets in 28 s with high size consistency (CV < 8%). This low cost device is composed with a microfluidic chip, 2 tubings, a collection vial, a syringe and a station; and is in the size of an iPad Mini (4" × 6" × 3/4").

High-sensitivity electrochemical enzyme-linked assay on a microfluidic interdigitated microelectrode.

A novel enzyme-linked DNA hybridization assay on an interdigitated array (IDA) microelectrode integrated into a microfluidic channel is demonstrated with sub-nM detection limit. To improve the detection limit as compared to conventional electrochemical biosensors, a recyclable redox product, 4-aminophenol (PAP) is used with an IDA microelectrode. The IDA has a modest and easily fabricated inter-digit spacing of 10 μm, yet we were able to demonstrate 97% recycling efficiency of PAP due to the integration in a microfluidic channel.

Lab-on-chip flow injection analysis system without an external pump and valves and integrated with an in line electrochemical detector.

Surface energy in small droplets can be used to drive samples through microchannels. When a sample fluid is spontaneously driven through a solution filled microchannel with liquid droplets on its entry (sample) and exit (reservoir) ports, it is termed as a passive pumping device. A passive pump driven microfluidic system integrated with microfabricated planar electrodes or electrode arrays (e.

Computation of transient flow rates in passive pumping micro-fluidic systems.

Motion in micro-channels of passive flow micro-fluidic systems can be controlled by proper design and estimated by careful modeling. We report on methods to describe the flow rate as function of time in a passive pump driven micro-fluidic system. The model considers the surface energy present in small droplets, which prompts their shrinkage and induces flow.

The stability of radio-frequency plasma-treated polydimethylsiloxane surfaces.

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in microfluidic systems. To transform the hydrophobic PDMS surface to hydrophilic, it was treated with radio-frequency (RF) air plasma at 150, 300, and 500 mTorr pressures for up to 30 min.