Well-less capillary array electrophoresis chip using hydrophilic sample bridges.

An innovative sample introduction method that facilitates extreme simplification of the layout of a capillary array electrophoresis (CAE) chip is described. Multiple samples were directly injected onto CAE channels from sample loaders using hydrophilic sample bridges, thus obviating auxiliary components of sample wells and sampling channels of a typical CAE chip. Hydrophilic sample bridges were spontaneously formed in hydrophobic surroundings to connect sample loaders to corresponding CAE channels, through which electrosample injections were effectively made. Sample dispersion was intrinsically avoided due to the "sticky" nature of the bridges. Utilizing hydrophilic interactions, target spots for formation of sample bridges can be expanded from the actual openings of CAE channels, which reduces the burden of precise positioning of samples toward CAE channels. In this work, simultaneous introduction of multiple samples onto well-less CAE channels arranged with 1-mm gaps was successfully demonstrated. Well-less CAE chips, feasible now due to the hydrophilic sample bridges, would bring unprecedented advantages in both production and operation because of their extreme simplicity.