A mass manufacturable thermoplastic based microfluidic droplet generator on cyclic olefin copolymer

Abstract

The rapid progress of droplet microfluidics and its wide range of applications have created a high demand for the mass fabrication of low-cost, high throughput droplet generator chips aiding both biomedical research and commercial usage. Existing polymer or glass based droplet generators have failed to successfully meet this demand which generates the need for the development of an alternate prototyping technique. This work reports the design, fabrication and characterization of a mass manufacturable thermoplastic based microfluidic droplet generator on cyclic olefin copolymer (COC). COC chips with feature size as low as 20 µm have been efficiently fabricated using injection molding technology leading to a high production of inexpensive droplet generators. The novelty of this work lies in reoptimising surface treatment and solvent bonding methods to produce closed COC microchannels with sufficiently hydrophobic (contact angle of 120°) surfaces. These COC based droplet generators were shown to generate stable monodisperse droplets at a rate of 1300 droplets/second in the dripping regime. These new mass manufacturable, disposable and cheap COC droplet generators can be custom designed to cater to the rapidly increasing biomedical and clinical applications of droplet microfluidics.

A Review of Cyclic Olefin Copolymer Applications in Microfluidics and Microdevices

“…Following exposure, the microchannel swells and its features are defined where it is then bonded with a blank COC and washed in water to remove the ink. [194] Schelcher et al [70] combined thermal and solvent bonding by applying cyclohexane and hexadecane to a COC substrate before bonding it with another COC in a heated Thermal/plasma bonding High Medium Long High [ 153] Solvent bonding High Low Low Low [ 192,194] Solvent/thermal bonding High Low Medium Low-medium [ 70,193] Solvent/plasma bonding High Medium Medium Medium-high [ 106] PDMS-COC bonding method Bonding strength Process complexity Time Cost References Plasma bonding Low Medium Low Medium-high [ 184,186] Plasma/silane bonding Medium-high High Long Medium-high [ 170,177,183,[185][186][187] Solvent/thermal bonding Medium-high Low Medium Low-medium [90] hydraulic press at 110 °C and 600 kPa for 3 min. Table 5 compares the different bonding methods for COC-COC and PDMS-COC devices, and Table 6 summarizes the process for the bonding techniques in this review.…”

Microfluidics: Innovations in Materials and Their Fabrication and Functionalization

“…Microfluidic droplet reactors are an area of research with strong commercialization interest. Ghosh et al 72 showed that a COC bubble reactor could be mass produced and could generate 1 300 droplets per second, which is competitive with similar devices made by more involved processes, indicating potential for general applicability. A different system reported by Sahore et al 73 demonstrated COC reactors that could perform β-galactosidase enzymatic assays using both magnetic and flow manipulation.…”

Translational Opportunities for Microfluidic Technologies to Enable Precision Epigenomics

“…This microfluidic device showed the capability to tolerate different sample sizes, making it amenable toward future clinical practices with variable sample quantities; however, the approach has not yet demonstrated single cell resolution. Promisingly, these and related advances in droplet microfluidic technologies are being translated into mass-manufacturable thermoplastic materials, bringing them closer to at-scale manufacturing and fulfilling their promise for clinical distribution and implementation. − …”