224 A 6.7 ACTUATOR 2004, 9th International Conference on New Actuators, 14 – 16 June 2004, Bremen, Germany Fig. 1: Working principle of the PipeJet dispenser. PipeJet™ - A SIMPLE DISPOSABLE DISPENSER FOR THE NANOLITER RANGE T. Lindemann, W. Streule, G. Birkle, R. Zengerle, P. Koltay IMTEK – Institute of Microsystem Technology, University of Freiburg, Germany Abstract: This paper reports for the first time on an unrivalled simple, disposable non-contact dispenser for the nanoliter range. In contrast to other known dispensers manufactured by silicon micromachining [1-4] the new device simply consists of an elastic polymer tube with circular cross section. Actuation is done by a piezostack driven piston, squeezing the tube at a defined position nearby the open end by a significant fraction of the cross section. In contrast to drop-on-demand devices based on an acoustic actuation principle [5] this leads to a significant mechanical displacement of the liquid. In our experiments we successfully tested ten media in the viscosity range from 1 mPas to 27 mPas and even up to approximately 200 mPas with a new actuation setup. Frequency characteristics showed an independent dosage volume for water up to a frequency of 15 Hz. Standard deviation within 1,000 shots resulted in an excellent CV of less than 2% of the dosage volume. With a print frequency of 340 Hz a flow rate up to 143 μl/s has been reached. Beyond the possibility to dispense highly viscous fluids also emulsion paints with particles of approximately 40 μm diameter have been printed successfully. Keywords: non-contact dispenser, nanoliter range, low-cost, drop-on-demand, high-viscous fluids Introduction The control of smallest amounts of fluid is of increasing interest in drug development, modern diagnostics and chemistry. Handling liquid volumes down to a few nanoliters with high reliability and high accuracy is very important for the reduction of the assay volumes especially in High Throughput Screening applications. Compared to the conventional pipetting systems, where the precision of the dosage volumes below 1 μl is limited by capillary and adhesive forces, dosage systems with free flying liquid jets or drops have the arbitrative advantage to avoid these surface interactions. Because of the variety of different fluids used in chemical and biochemical laboratories with very different properties it is essential that the dispenser provides a dosage volume nearly independent of fluid properties like viscosity, surface tension or density. So that it is not necessary to calibrate the system after every used liquid. For medical devices it is also recommended that all contaminated parts are disposable and therefore low-cost and easy to handle. Furthermore there is an increasing demand for dispensers which can dose fluids containing particles or beads. Applications like colour printing with emulsion paint or medical applications containing beads for medical detection require devices particularly insensitive against clogging. System Description Key element of the dispensing device termed “PipeJet™” is a clamped commercially available polymer tube. The rear end of the tube is connected to a reservoir and serves as a supply channel. The front end forms the nozzle for liquid ejection. By a fast displacement of a piston connected to a piezostack actuator, the tube is squeezed on an active area of approximately 5 mm length displacing the liquid towards both ends of the tube (figure 1). Due to the low fluidic resistance between the actuation area and the nozzle, most of the displaced volume is ejected as free liquid jet like shown in figure 2. By varying the dimension or the position of the active area compared to the nozzle outlet a