Abstract: Apparatus and methods have been developed to deliver automatically a sample to a reaction vessel, an analytical device or any location where sample introduction or deposition is desired. A sample delivery system of the invention generally includes a housing defining a channel, e.g., a capillary, and a volume controller, which is a temperature control device, in thermal communication with the channel. The channel preferably is closed at one end, and contains an opening for introduction of a sample. The closed end of the channel is associated thermally with the temperature control device. The temperature control device heats and cools a thermally expandable fluid in the channel which controls movement of a sample into, within and out of the channel.