A syringe, especially for measuring microliter amounts, which comprises a barrel having over at least a part of its length an inner liner composed of a resilient plastics material surrounding a bore and a piston slidable within the liner bore, the maximum cross-sectional area of the piston being slightly greater than the cross-sectional area of the undeformed bore. The liner is preferably made of a polytetrafluoroethylene and the piston comprises a wire with a bead at one end. A method of attaching a needle to the syringe is also disclosed.
A method and a device are proposed for the injection of very small amounts of samples into cells (74) with the aid of a microcapillary (10). During the injection, a constant injection pressure of about 0.12 bar, provided by a pressurized cylinder (46) is applied to the microcapillary (10), which is reduced after the completion of the injection to a holding pressure of 0.02 bar until the next cell (64) is to be injected. A high-pressure (p.sub.1) supplied from another pressurized cylinder (44) serves for blowing out the microcapillary tip (12). A three-way valve (42) permits simple and rapid switching between the various pressures (p.sub.1, p.sub.2 and p.sub.3). Reproducible amounts of sample in the range from 10.sup.-11 ml to 10.sup.-13 ml can be injected reproducibly, simply and rapidly.
A method and a device are proposed for the injection of very small amounts of samples into cells (74) with the aid of a microcapillary (10). During the injection, a constant injection pressure of about 0.12 bar, provided by a pressurized cylinder (46) is applied ot the microcapillary (10), which is reduced after the completion of the injection to a holding pressure of 0.02 bar until the next cell (64) is to be injected. A high-pressure (p.sub.1) supplied from another pressurized cylinder (44) serves for blowing out the microcapillary tip (12). A three-way valve (42) permits simple and rapid switching between the various pressure (p.sub.1, p.sub.2 and p.sub.3). Reproducible amounts of sample in the range from 10.sup.-11 ml to 10.sup.-13 ml can be injected reprodicibly, simply and rapidly.
An operable syringe assembly comprises a barrel including a cylindrical coextruded body portion having a longitudinal axis. The body portion forms a side wall spaced from the axis defining a chamber for retaining fluid. The body portion includes an open proximal end and a distal end and further includes an inner portion of plastic material and a rigid portion of plastic material surrounding the inner portion. The rigid portion has a higher hardness than the inner portion. A plunger including an elongate shaft portion having a proximal end, a distal end and a rigid piston at the distal end is provided. The piston has an outside diameter greater than the inside diameter of the inner portion and a higher hardness than the inner portion. The piston portion is slidably positioned in fluid-tight engagement inside the barrel. The fluid-tight engagement is caused by the piston compressing the inner portion of the plastic material of the coextruded body portion. The proximal end of the plunger extends outwardly from the open proximal end of the barrel to facilitate moving the piston portion with respect to the barrel.
