Application Example for heatable Dispensers
Adhesives often have high viscosities. There are two ways to dispense them: the design of the microdispenser can be optimized for higher viscosities or the viscosity is reduced by heating. GeSiM microdispensers should not be heated to more than 120 °C, i.e., the viscosity of the liquid should not exceed 5 mPa·s at 120 °C.
The UV-curable adhesives OG169 and UVO-114 (Epoxy Technologies) could be dispensed (viscosities at room temperature: 82 mPas and 300 – 700 mPas, resp.) The left image depicts the dependence of droplet velocity and diameter on the excitation voltage for UVO-114; the inset of Fig. 1 shows a picture of a single droplet of adhesive in front of the dispenser nozzle.
The right side picture shows an array of single epoxy spots on glass, made by the Nano-Plotter. The spot size is about 200 µm and can be varied using different piezo settings. Although the viscosity of OG169 is much lower than that of UVO-114, it needs a higher temperature for dispensing.
A number of liquids (e.g. glycerol) were successfully tested. Inthe case of two-component epoxies, the individual components must be dispensed using two different microdispensers. Mixing and curing of the epoxy then takes place on the substrate, one example being 301-2 from Epoxy Technologies.