TopSpot Vario: New Method for Parallel Nanoliter Dosing by Direct Liquid Displacement

Inhalt:
TopSpot(r) printheads are used for the highly parallel nanoliter dispensing of bio-chemical substances at a pitch of typically 500 µm [1,2] . This paper reports on a new and improved way of operating the printheads, using an incompressible material between the piezo actuator and the dispensing medium [3,4]. The advantage of an incompressible medium is the direct relation between the amplitude of the piezo-stack actuation and the ejected liquid volume. Earlier reports stated that the filling of the printheads is a key issue. In this paper we report on the implementation of an already reported microchannel design for bubble free priming of blind channels [5] into the printhead design. The evaluation of the 24 channel TopSpot Vario printheads revealed that droplet volume can be freely tuned between 250 pl and 1600 pl for aqueous solutions. Best printing performance with an inter and intra nozzle reproducibility of droplet volumes of 7.5 % respectively 1.9 % was found for droplet volumes of 270 pl. Stable printing could be provided up to printing frequencies of 400 Hz and for liquids with viscosities up to 11 mPa.s.