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While there is a steady growth in the number of microfluidics applications, the search for an optimal material that delivers the diverse characteristics needed for the numerous tasks is still nowhere close to being settled. Often overlooked and still underrepresented, the thiol-ene family of polymer materials has an enormous potential for applications in organs-on-a-chip, droplet productions, microanalytics, and point of care testing. In this review, the main characteristics of the thiol-ene materials are given, and advantages and drawbacks with respect to their potential in microfluidic chip fabrication are critically assessed. Select applications, which exploit the versatility of the thiol-ene polymers, are presented and discussed. It is concluded that, in particular, the rapid prototyping possibility combined with the material's resulting mechanical strength, solvent resistance, and biocompatibility, as well as the inherently easy surface functionalization, are strong factors to make thiol-ene polymers strong contenders for promising future materials for many biological, clinical, and technical lab-on-a-chip applications.

Fluorescent, DNA-stabilized silver nanoclusters (DNA-AgNCs) are applied in a range of applications within nanoscience and nanotechnology. However, their diverse optical properties, mechanism of formation, and aspects of their composition remain unexplored, making the rational design of nanocluster probes challenging. Here, a synthetic procedure is described for obtaining a high yield of emissive DNA-AgNCs with a C-loop hairpin DNA sequence, with subsequent purification by size-exclusion chromatography (SEC). Through a combination of optical spectroscopy, gel electrophoresis, ICP-MS, and small-angle X-ray scattering (SAXS) in conjunction with the systematic study of various DNA sequences, the low-resolution structure and mechanism of the formation of AgNCs were investigated. Data indicate that fluorescent DNA-AgNCs self-assemble via a head-to-head binding of two DNA hairpins, bridged by a silver nanocluster, resulting in the modelling of a dimeric structure harboring an Ag 12 cluster.

Polymeric microfluidic chips offer a number of benefits compared to their glass equivalents, including lower material costs and ease and flexibility of fabrication. However, the main drawback of polymeric materials is often their limited resistance to (organic) solvents. Previously, thiol-ene materials were shown to be more solvent resistant than most other commonly used polymers; however, they still fall short in “harsh” chemical environments, such as when chlorinated solvents are present. Here, we show that a simple yet effective treatment of thiol-ene materials results in exceptional solvent compatibility, even for very challenging chemical environments. Our approach, based on a temperature treatment, results in a 50-fold increase in the chloroform compatibility of thiol-enes (in terms of longevity). We show that prolonged heat exposure allows for the operation of the microfluidic chips in chloroform for several days with no discernable deformation or solvent-induced swelling. The method is applicable to many different thiol-ene-based materials, including commercially available formulations, and also when using other commonly considered “harsh” solvents. To demonstrate the utility of the solvent compatible thiol-enes for applications where chloroform is frequently employed, we show the continuous and uniform production of polymeric microspheres for drug delivery purposes over a period of 8 hours. The material thus holds great promise as an alternative choice for microfluidic applications requiring harsh chemical environments, a domain so far mainly restricted to glass chips.

The scaffolding DNA sequence and the size of silver nanoclusters (AgNCs), confined in a DNA template are the key parameters in determining the fluorescent properties of DNA-stabilized silver nanoclusters (DNA/AgNCs). In addition, we suggest here that the structural shift of a DNA hairpin-dimer is as important as the DNA sequence in determining the emission wavelength of DNA/AgNCs. Furthermore, we show that the structural shift post AgNC formation can be triggered by incubation time and pre-AgNC formation under salt conditions. As an important factor in predicting the emission properties of DNA/AgNCs, the modulation of DNA secondary structures with either sequence changes or ionic conditions can be applied for the dual-color detection system of a target molecule. Particularly, the dual-color detection method may increase the reliability of DNA/AgNC sensors for miRNAs.