Biocompatible bonding of a rigid off-stoichiometry thiol-ene-epoxy polymer microfluidic cartridge to a biofunctionalized silicon biosensor

Abstract

Attachment of biorecognition molecules prior to microfluidic packaging is advantageous for many silicon biosensor-based lab-on-a-chip devices. This necessitates biocompatible bonding of the microfluidic cartridge, which, due to thermal or chemical incompatibility, excludes standard microfabrication bonding techniques. Here, we demonstrate a novel processing approach for a commercially available, two-step curable polymer to obtain biocompatible UVA-bonding of polymer microfluidics to silicon biosensors. Biocompatibility is assessed by UVA-bonding to antibody-functionalized ring resonator sensors and performing antigen capture assays while optically monitoring the sensor response. The assessments indicate normal biological function of the antibodies after UVA-bonding with selective binding to the target antigen. The bonding strength between polymer and silicon chips (non-biofunctionalized and biofunctionalized) is determined in terms of static liquid pressure. Polymer microfluidic cartridges are stored for more than 18 weeks between cartridge molding and cartridge-to-silicon bonding. All bonded devices withstand more than 2500 mbar pressure, far exceeding the typical requirements for lab-on-a-chip applications, while they may also be de-bonded after use. We suggest that these characteristics arise from bonding mainly through intermolecular forces, with a large extent of hydrogen bonds. Dimensional fidelity assessed by microscopy imaging shows less than 2% shrinkage through the molding process and the water contact angle is approximately 80°. As there is generally little absorption of UVA light (365 nm) in proteins and nucleic acids, this UVA-bonding procedure should be applicable for packaging a wide variety of biosensors into lab-on-a-chip systems.

Performance and biocompatibility of OSTEMER 322 in cell-based microfluidic applications

“…2C). The measured angle exceeds the reported values of 67°for standard cured oste322 as published by Sandström et al 71 and 73 ± 2°(for oste327) and 70 ± 3°(for oste322) reported by Zhou et al 37 For reverse cured oste322, 72 the CA was found to be approximately 80°(ranging from 73°to 85°) and 96°for OSTE-80. 41 The increase in the contact angle measured in this study could be attributed to the alteration in the fabrication process of the oste322 inserts, which were subjected to a heating procedure before their removal from the PDMS mould.…”

“…For reverse cured oste322, 72 the CA was found to be approximately 80° (ranging from 73° to 85°) and 96° for OSTE-80. 41 The increase in the contact angle measured in this study could be attributed to the alteration in the fabrication process of the oste322 inserts, which were subjected to a heating procedure before their removal from the PDMS mould.…”

Microfluidic devices for photo-and spectroelectrochemical applications

“…Reversible bonding techniques for access to electrodes may therefore be used. Recently, alternative room temperature bonding methods, which can also be applied to EC devices, have been demonstrated [35]. For size critical applications, the total footprint including contact pads can be an issue.…”

High‐Resolution 3D Printing of Dual‐Curing Thiol‐Ene/Epoxy System for Fabrication of Microfluidic Devices for Bioassays

“…Due to their controllable mechanical properties, and their ability for reshaping surface functionalization, and dry-bonding, dualcuring materials have become an interesting class of materials for advanced applications such as shape memory materials, [1,2] essential element for the detection of specific analytes in microfluidic analysis. The bio-functionalization of channel surfaces can be carried out by bonding of the open channel to a readyfor-use biosensor [17,18] or by direct biofunctionalization of the microchip material. [19] For successful biofunctionalization, the channel material often needs an additional treatment such as coating of a linker with sufficient interaction or direct immobilization of the biomolecule onto the surface.…”