Adhesive bonding of microfluidic chips: influence of process parameters

Abstract

In this note, the influence of process parameters for adhesive bonding as a versatile approach for the sealing of polymer microfluidic chips is investigated. Specifically, a process chain comprising pre-processing, adhesive transfer as well as post-processing is presented and parameter recommendations are provided. As a device for adhesive transfer, a modified laminator is utilized which transfers thin layers of adhesive onto the chip surface, only via a silicone roll. Using this device and a high temperature (T g > 100 • C) epoxy adhesive, adhesive layers in the range of 2-4 μm can be reproducibly transferred (CV < 4%). For best bonding results, it is recommended to provide 2.5 μm thin layers of adhesive in combination with a subsequent evacuation step at 10 mbar for 3 h. Further, it is proposed to integrate capture channels near large, featureless areas to compensate for variations in processing and thus prevent clogging of channels.

Thermoplastic Micromodel Investigation of Two-Phase Flows in a Fractured Porous Medium

“…Thermoplastic bonding is one of the most simple and straightforward thermoplastic processes [ 23 ]; however, it imparts a low bonding strength. Therefore, high-strength bonding techniques using materials such as solvents [ 27 ], adhesives [ 28 ], UV/Ozone [ 29 ], O 2 plasma [ 30 ], as well as welding [ 31 ] have been reported. Each polymer-replication or bonding technique presents specific advantages as well as process limitations for different applications.…”

Thermoplastic Micromodel Investigation of Two-Phase Flows in a Fractured Porous Medium

“…Thermoplastic bonding is one of the most simple and straightforward thermoplastic processes [23]; however, it imparts a low bonding strength. Therefore, high-strength bonding techniques using materials such as solvents [27], adhesives [28], UV/Ozone [29], O2 plasma [30], as well as welding [31] have been reported. Each polymer-replication or bonding technique presents specific advantages as well as process limitations for different applications.…”

Direct assembly of cyclic olefin copolymer microfluidic devices helped by dry photoresist

“…However, both the chip design [21] and the adhesive layer thickness [22] are major influence parameters for bonding, i.e., chips featuring large (>1 mm) and deep (>500 m) channels, only, will require less bonding process development due to the reduced risk of clogging than chips comprising small (500 m) and shallow (200 m) channels as well as isolated features. In addition, the bonding layer transferred has to form a thin and smooth layer on the microfluidic chip for a strong adhesive bonding.…”

“…Established materials for adhesive bonding in micro-machining are dry film photoresists [19][20][21]. Examples for dry film photoresists used in plastic LOC fabrication are ORDYL [22][23][24][25], e-NIT215 [26], Poly-ether-ether-ketone (PEEK) [27], TMMF [28] or self-made SU-8 foils [29,30].…”