Miniaturized flowthrough microdispenser with piezoceramic tripod actuation

Abstract

In this paper, the further development of a silicon flowthrough microdispenser is described. Previously reported designs of the dispenser used bimorph, and later multilayered, piezoelectric actuator elements for the generation of droplets. The introduction of a multilayered actuator significantly reduced the voltage amplitude needed to dispense droplets. Dispenser properties relevant for chemical analysis systems, e.g., reduced sample volume, internal surface area, and dispersion, were improved by miniaturization of the device. In this paper, a new actuator design, the tripod, is presented to enable further dispenser miniaturization and to facilitate device assembly. Tripod actuators were manufactured using a prototyping process, based on micromilling, for multilayer piezoceramic components. A building technique for miniaturized electrical interconnects, based on microstructured flexible printed circuits, is also suggested in line with the prospect of future miniaturization. The microfluidic properties of the tripod-actuated dispenser were evaluated. Stable droplet generation in the frequency range from 0 to 3 kHz was demonstrated, providing a maximum dispensed flow rate of 7.8 L min.[1210]

Microdroplet generation in gaseous and liquid environments

“…7a, the direct linear displacement of a piezoceramic element generates a droplet. This displacement can cause a diaphragm (Kim and Park 2008;Steger et al 2002), tripod (Bergkvist et al 2005) or piston (Ben-Tzvi et al 2007) to change the volume in a chamber or capillary, generate pressure waves and eject a droplet from an orifice.…”

“…Once the droplet reaches the terrace edge, it drains off and begins forming a new droplet on the well's wall, seen in Fig. 17c, d. Once the droplet reaches a critical size, it will Table 1 Comparison of minimum droplet size and actuation cycle times for selected liquid-in-air actuation mechanisms (Bergkvist et al 2005;Wu et al 2005;Laurell et al 1999;Demirci et al 2005;Lee and Lal 2004;Tan et al 2008;Tseng et al 2002b;Dadvand et al 2009;Hirata et al 1996;Castrejón-Pita et al 2008;Amirzadeh Goghari and Chandra 2008;Kamisuki et al 2000;Kim et al 2006;Jones et al 2001 break off and the remaining fluid will recede back onto the terrace, starting the process over again (Sugiura et al 2001).…”

“…Table 2 Comparison of minimum droplet size for selected liquid-inliquid actuation mechanisms (Wu et al 2006;Kim et al 2009;Sugiura et al 2001;Nisisako et al 2002;Ward et al 2005;Bransky et al 2009;Forget et al 2008;Ozen et al 2006 Electrowetting 418 a If generated droplets were not spherical, the diameter was found by approximating the volume as a sphere Bergkvist et al described a situation where resonance was detrimental: in a DoD piezoelectric droplet generator, in frequency ranges affected by resonance, the sizes of droplets had higher variability. This led to the categorization of the generator's frequency spectrum: the frequency range before resonance affected generation was the ''primary stable frequency region,'' the frequency immediately before resonance affected generation was the ''primary stable frequency,'' the frequency range after the primary stable frequency but before generation halted or completely randomized was the ''secondary stable region'' and the highest frequency in the set of ranges beyond the secondary stable region capable of producing stable droplets was the ''maximum dispensing frequency'' (Bergkvist et al 2005).…”

“…In DoD pressure-based droplet generation, pulse duration and amplitude determine droplet size (for a fixed nozzle size) (Castrejón-Pita et al 2008;Bergkvist et al 2005).…”

Implementation of a protein profiling platform developed as an academic‐pharmaceutical industry collaborative effort

“…The fundamental microchip building blocks, including the SMEC and the microdispenser unit (1 and 2 in Fig. 3, respectively), were initially developed, characterized, and reported individually [19,[26][27][28]. In the protein profiling platform an integrated microfluidic system for stand-alone sample processing and interfacing to MALDI-TOF MS was designed to combine these microchip functions.…”