Abstract: The invention provides particle compositions having applications in nucleic acid analysis. Nucleic acid polymer particles of the invention allow polynucleotides to be attached throughout their volumes for higher loading capacities than those achievable solely with surface attachment. In one aspect, nucleic acid polymer particles of the invention comprise polyacrylamide particles with uniform size distributions having low coefficients of variations, which result in reduced particle-to-particle variation in analytical assays. Such particle compositions are used in various amplification reactions to make amplicon libraries from nucleic acid fragment libraries.

Abstract: The invention provides a passive fluidics circuit for directing different fluids to a common volume, such as a reaction chamber or flow cell, without intermixing or cross contamination. The direction and rate of flow through junctions, nodes and passages of the fluidics circuit are controlled by the states of upstream valves (e.g. opened or closed), differential fluid pressures at circuit inlets or upstream reservoirs, flow path resistances, and the like. Free diffusion or leakage of fluids from unselected inlets into the common outlet or other inlets at junctions or nodes is prevented by the flow of the selected inlet fluid, a portion of which sweeps by the inlets of unselected fluids and exits the fluidics circuit by waste ports, thereby creating a barrier against undesired intermixing with the outlet flow through leakage or diffusion. The invention is particularly advantageous in apparatus for performing sensitive multistep reactions, such as pH-based DNA sequencing reactions.

Abstract: The invention is directed to apparatus and methods for delivering multiple reagents to, and monitoring, a plurality of analytical reactions carried out on a large-scale array of electronic sensors underminimal noise conditions. In one aspect, the invention provides method of improving signal-to-noise ratios of output signals from the electronic sensors sensing analytes or reaction byproducts by subtracting an average of output signals measured from neighboring sensors where analyte or reaction byproducts are absent. In other aspects, the invention provides an array of electronic sensors integrated with a microwell array for confining analytes and/or particles for analytical reactions and a method for identifying microwells containing analytes and/or particles by passing a sensor-active reagent over the array and correlating sensor response times to the presence or absence of analytes or particles.