A Piezoactuated Droplet-Dispensing Microfluidic Chip

Abstract

A microfluidic dispensing device that is capable of generating droplets with volumes varying between 1 nL and 50 pL at an ejection frequency of up to 6 kHz is presented. In this device, a piezoactuator pushes onto an elastic membrane via piston tips; the mechanical bending of the membrane generates a pressure pulse pushing droplets out. An analytical model was developed solving bending characteristics of a plate-actuated fluidic dispensing system and used to calculate the displaced volume. The model was extended to perform stress analysis to find the optimum piston tip radius by minimizing design stresses. The optimum piston tip radius was found to be 67% of the chamber radius. The actuation force estimated using the analytical model was then used as input to a finite element model of the dispenser. A detailed numerical analysis was then performed to model the fluid flow and droplet ejection process and to find critical geometric and operating parameters. Results from both models were used together to find the best design parameters. The device contains three layers, a silicon layer sandwiched between two polydimethylsiloxane (PDMS) polymer layers. Silicon dry etching, together with PDMS soft lithography, was used to fabricate the chip. PDMS oxygen plasma bonding is used to bond the layers. Prototypes developed were successfully tested to dispense same-sized droplets repeatedly without unwanted droplets. The design allows easy expansion and simultaneous dispensing of fluids.

Biodegradable microsphere-mediated cell perforation in microfluidic channel using femtosecond laser

“…17,18 The microfluidic platform is one of the attractive systems for obtaining synergy with laser-based technology for cell manipulation, including optoinjection. Microfluidic chips have been used for dispensing, 19 cell analyzing, 20 and cell sorting 21 as well as drug delivery. 22,23 In 2010, Marchington et al 24 reported automated optoinjection into cells by using a microfluidic chip fabricated in polydimethylsiloxane.…”

Three-Dimensional Stem Cell Bioprinting

“…Stem cells can grow their own viable scaffold on their own if the tissue is epithelial and injected in situ [15]. In demonstration, this almost replicates the methods tissue engineers use to recreate epithelial tissue by simple micropipetting and drop-on-demand [33,34].…”

Dual-nozzle microfluidic droplet generator

“…Previously, this has been obtained by generating droplets using a pinched flow channel, followed by injecting the droplets into a stream of a carrier gas for analysis in ion coupled mass spectroscopy (ICPMS) [26]. Other groups have been able to achieve dispensing by either precise timing control of the dispensing process [27], or by the use of an active piezo-electric droplet generator [28]. Through the use of an active droplet generation method, the issue of droplet aggregation and merging can be prevented.…”