An integrated system for rapid PCR-based analysis on a microchip has been demonstrated. The system couples a compact thermal cycling assembly based on dual Peltier thermoelectric elements with a microchip gel electrophoresis platform. This configuration allows fast (approximately 1 min/ cycle) and efficient DNA amplification on-chip followed by electrophoretic sizing and detection on the same chip. An on-chip DNA concentration technique has been incorporated into the system to further reduce analysis time by decreasing the number of thermal cycles required. The concentration injection scheme enables detection of PCR products after performing as few as 10 thermal cycles, with a total analysis time of less than 20 min. The starting template copy number was less than 15 per injection volume.

Microfabricated devices for parallel and serial mixing of fluids are demonstrated. To simplify the voltage control hardware, electrokinetic mixing is effected using a single voltage source with the channels dimensioned to perform the desired voltage division. In addition, the number of fluid reservoirs is reduced by terminating multiple buffer, sample, or analysis channels in single reservoirs. The parallel mixing device is designed with a series of independent T-intersections, and the serial mixing device is based on an array of cross intersections and sample shunting. These devices were tested by mixing a sample with buffer in a dilution experiment. Sample fractions of 1.0, 0.84, 0.67, 0.51, 0.36, 0.19, and 0 were generated for the parallel mixing device, and sample fractions of 1.0, 0.36, 0.21, 0.12, and 0.06 for the serial mixing device.Microfabricated devices for performing chemical and biochemical assays have garnered increased attention over the last several years. 1-3 Considerable effort has been dedicated to developing functional elements to be incorporated into these labon-a-chip devices. A key issue is sample and reagent mixing. With electrokinetic material transport, reagents are mixed in proportions dictated by the applied potentials, the geometry of the channels, and the properties of the materials in those channels. To date, the proportioning of two or more fluids in different ratios has been accomplished by controlling the electric potentials applied to the fluidic reservoirs to effect dilution, 4 reactions, 5,6 and solvent programming. 7,8 These have required voltage control external to the microchip, e.g., programmable power supplies.Some simple integrated devices have combined precolumn 9 and postcolumn 10-12 derivatization reactions in conjunction with electrophoretic separations. In addition, restriction digestions 13 and competitive immunoassays 14 have been coupled to product analysis downstream. More features being integrated into a planar format have led to studying compact microchip designs, 15 fabricating arrays of channels for DNA analysis, 16,17 and multiple sample PCR with product analysis. 18 Coupled to this increased integration is the added complexity of the hardware needed to control microfluidic operations. One approach to simplify the control hardware for electrokinetic manipulations is to design the fluidic channels to perform the appropriate voltage division for reagent mixing and reactions.In this paper, we describe microfluidic designs that simplify the voltage control necessary to effect parallel and serial electrokinetic mixing on microchips. If the fluidic channels provide the appropriate voltage division, only a single fixed voltage source is required to transport and mix material. This minimizes the highvoltage hardware necessary to operate the microfluidic chip. In an effort to make the microchip architecture compact, multiple buffer, sample, or analysis channels terminate in single reservoirs. To test the parallel and serial mixing schemes, a sample was diluted with ...

We demonstrate the integration of vertically aligned carbon nanofiber (VACNF) elements with the intracellular domains of viable cells and controlled biochemical manipulation of cells using the nanofiber interface. Deterministically synthesized VACNFs were modified with either adsorbed or covalently-linked plasmid DNA and were subsequently inserted into cells. Post insertion viability of the cells was demonstrated by continued proliferation of the interfaced cells and long-term (> 22 day) expression of the introduced plasmid. Adsorbed plasmids were typically desorbed in the intracellular domain and segregated to progeny cells. Covalently bound plasmids remained tethered to nanofibers and were expressed in interfaced cells but were not partitioned into progeny, and gene expression ceased when the nanofiber was no longer retained. This provides a method for achieving a genetic modification that is non-inheritable and whose extent in time can be directly and precisely controlled. These results demonstrate the potential of VACNF arrays as an intracellular interface for monitoring and controlling subcellular and molecular phenomena within viable cells for applications including biosensors, in-vivo diagnostics, and in-vivo logic devices.

The penetration and residence of vertically aligned carbon nanofibers (VACNF) within live cell matrices is demonstrated upon substrates that incorporate spatially registered indices to facilitate temporal tracking of individual cells. Penetration of DNA-modified carbon nanofibers into live cells using this platform provides efficient delivery and expression of exogenous genes, similar to "microinjection"-styled methods, but on a massively parallel basis. Spatially registered indices on the substrate allow one to conveniently locate individual cells, facilitating temporal tracking of gene expression events. We describe fabrication and use of this gene delivery platform which consists of arrays of individual carbon nanofibers at 5-µm pitch within numerically indexed, 100-µm square grid patterns. Fabrication of these devices on silicon substrates enables mass production of 100 devices (5 mm 2 ) per wafer, with each device providing over 800,000 nanofiber-based "needles" for cellular impalement and gene delivery applications.