On the design and fabrication of nanoliter-volume hanging drop networks.

Hanging drop cultures provide a favorable environment for the gentle, gel-free formation of highly uniform three-dimensional cell cultures often used in drug screening applications. Initial cell numbers can be limited, as with primary cells provided by minimally invasive biopsies. Therefore, it can be beneficial to divide cells into miniaturized arrays of hanging drops to supply a larger number of samples.

Electrochemical direct writing and erasing of silver nanostructures on phosphate glass using atomic force microscopy.

This paper reports a liquid-free, mask-less electrochemical direct-write lithographic technique using an atomic force microscopy (AFM) probe for writing silver nanostructures in minutes on an optically transparent substrate. Under ambient conditions, silver is locally and controllably extracted to the surface of superionic (AgI) (AgPO) glass by bringing a conductive AFM probe tip in contact with it, biasing the probe with a negative voltage, and regulating the resulting current. The growth mechanism of the resulting nanostructure is explored by extracting silver with a stationary AFM tip on the surface of the silver.

Nano-fabrication with a flexible array of nano-apertures.

We report fabrication and use of a flexible array of nano-apertures for photolithography on curved surfaces. The batch-fabricated apertures are formed of metal-coated silicone tips. The apertures are formed at the end of the silicone tips by either electrochemical etching of the metal or plasma etching of a protective mask followed by wet chemical etching.

Double transfer printing of small volumes of liquids.

We report here a technique to print small volumes of liquid on a hydrophobic substrate. This process is based on the control of the critical parameters that govern a quasi-equilibrium liquid transfer process from one surface to another. We present a qualitative model that describes the physics of a transfer printing process between hydrophobic surfaces, and we use the parameters outlined in this model to manipulate the amount of liquid transferred between surfaces.

Hydrodynamic microfabrication via"on the fly" photopolymerization of microscale fibers and tubes.

A microfluidic apparatus capable of creating continuous microscale cylindrical polymeric structures has been developed. This system is able to produce microstructures (e.g.

An externally driven magnetic microstirrer.

In this paper, an inexpensive, easy-to-fabricate active magnetic mixer is presented. This mixer functions on top of a common magnetic stir plate and is capable of mixing two streams, each at flow rates up to 5 ml min(-1). A liquid-phase photopolymerization technique is used to fabricate the device.

Microfluidic tectonics platform: A colorimetric, disposable botulinum toxin enzyme-linked immunosorbent assay system.

A fabrication platform for realizing integrated microfluidic devices is discussed. The platform allows for creating specific microsystems for multistep assays in an ad hoc manner as the components that perform the assay steps can be created at any location inside the device via in situ fabrication. The platform was utilized to create a prototype microsystem for detecting botulinum neurotoxin directly from whole blood.

Ultra rapid prototyping of microfluidic systems using liquid phase photopolymerization.

We present a method for the ultra rapid prototyping of microfluidic systems using liquid phase photopolymerization, requiring less than 5 min from design to prototype. Microfluidic device fabrication is demonstrated in a universal plastic or glass cartridge. The method consists of the following steps: introduction of liquid prepolymer into the cartridge, UV exposure through a mask to define the channel geometry, removal of unpolymerized prepolymer, and a final rinse.

Physics and applications of microfluidics in biology.

Fluid flow at the microscale exhibits unique phenomena that can be leveraged to fabricate devices and components capable of performing functions useful for biological studies. The physics of importance to microfluidics are reviewed. Common methods of fabricating microfluidic devices and systems are described.