Click‐and‐Bond: Room‐Temperature and Solvent‐Free Bonding of Polymer‐Based Microfluidic Devices

Abstract

The numerous advances in the field of microfluidics have enabled the successful implementation of microfluidic devices in (bio)sensing for a wide range of applications, including medical diagnostics. [3] In particular, the coupling of microfluidic devices with sensing modules or sample-pre-treatment modules have led to major advances in the realization of microfluidic devices for both point-of-care (POC) and portable usage. [4] Rigid thermoplastic polymers are nowadays widely explored as innovative materials for the fabrication of microfluidic devices, due to the cost-effective and high-volume production alternatives that they offer compared to the more traditionally used materials such as glass and silicon. [5][6][7] Polycarbonate, poly(methyl methacrylate), polystyrene, and cyclic olefin copolymer (COC) have emerged as particularly attractive substrate materials for this type of applications owing to their beneficial physico-chemical properties. Among several properties, their high transparency and low autofluorescence enable, for example, the use of widespread and advantageous optical techniques, such as fluorescence detection, for biosensing applications. [8] Current focus on personalized healthcare has sparked the expansion of the functionalities of microfluidic devices, particularly in the use of chemically specific coatings. Among the aforementioned innovative polymeric materials, COC has emerged as a suitable material for a large range of applications owing to multiple beneficial properties. Its good chemical resistance, biocompatibility, excellent transparency, and high glass transition temperature (T g ) represent the most interesting characteristics for the production of devices. [9] In particular, the high resistance of COC toward common solvents favors the use of such materials over the so far largely employed polydimethylsiloxane (PDMS)-based materials. [7,10] PDMS presents, in fact, a major disadvantage of swelling in contact with solvents such as chloroform, benzene, acetone, and ethanol. Additionally, surface chemical treatments of PDMS have been reported to be unstable over time. [11,12] However, the intrinsically hydrophobic nature of COC substrates promotes non-specific binding of biomolecules and prevents the flow of aqueous solutions through the channels. [13]

Interface Engineering of “Clickable” Organic Electrochemical Transistors toward Biosensing Devices

“…30,31 In addition, the strain-promoted alkyne−azide cycloaddition (SPAAC) reaction between ring-strained cycloalkynes and azides has also been widely applied for the catalyst-free modification of surfaces. 32,33 This reaction does not require the use of the copper, which is known to be cytotoxic, and can fully proceed under physiological conditions, increasing the possibilities for the engineering of surfaces though click chemistry. 34 In this context, researchers have employed CuAAC and SPAAC in order to develop several interfacial architectures that function as electrochemical and optical biosensing platforms.…”

“…42 Very recently, the incorporation of both OEG and "clickable" dibenzocyclooctyne (DBCO) units to PLL was reported, allowing the SPAAC between these groups and probes that bear the complementary azide functionality and therefore endowing the controlled immobilization of DNA molecules to produce biosensing interfaces with antifouling features. 32,43 In this work, we report the interface engineering of "clickable" OECTs in order to develop transistor-based biosensing devices. We first investigate different channel structures for PEDOT-N 3 -based transistors.…”

“…Furthermore, the addition of functional moieties to PLL has been recently explored, including different recognition elements such as biotin, maleimide, and RGD peptide. , In addition, oligo- and poly-ethylene glycol (OEG and PEG, respectively) chains have also been grafted to PLL, yielding a hydrogel-like brush structure while incorporating antifouling properties . Very recently, the incorporation of both OEG and “clickable” dibenzocyclooctyne (DBCO) units to PLL was reported, allowing the SPAAC between these groups and probes that bear the complementary azide functionality and therefore endowing the controlled immobilization of DNA molecules to produce biosensing interfaces with antifouling features. , …”

“…The incorporation of the Cu­(I) catalyst activates the alkyne moieties, facilitating the kinetics of the alkyne–azide condensation and also organizing the reacting groups, exclusively providing the 1,4-disubstituted 1,2,3-triazole . These features have driven the application of CuAAC in a wide range of fields, and particularly toward the fabrication of interfacial architectures for the design of biosensing devices. , In addition, the strain-promoted alkyne–azide cycloaddition (SPAAC) reaction between ring-strained cycloalkynes and azides has also been widely applied for the catalyst-free modification of surfaces. , This reaction does not require the use of the copper, which is known to be cytotoxic, and can fully proceed under physiological conditions, increasing the possibilities for the engineering of surfaces though click chemistry . In this context, researchers have employed CuAAC and SPAAC in order to develop several interfacial architectures that function as electrochemical and optical biosensing platforms. ,, …”