Reza Zandi Shafagh

Reaction injection molding and direct covalent bonding of OSTE+ polymer microfluidic devices

In this article, we present OSTE+RIM, a novel reaction injection molding (RIM) process that combines the merits of off-stoichiometric thiol–ene epoxy (OSTE+) thermosetting polymers with the fabrica ...

One step integration of gold coated sensors with OSTE polymer cartridges by low temperature dry bonding

We propose and demonstrate a novel one step method to integrate gold coated sensors with cartridges by dry covalent bonding. The cartridges are replica molded in an UV-curable off-stoichiometry thiol-ene (OSTE) polymer, featuring an excess of thiol functional groups that covalently bond to the surface of gold coated sensors upon contact. The method is demonstrated by the integration of a gold coated quartz crystal to a microfludic OSTE cartridge. The resulting bond interface is shown to be completely homogenous and void free and the package is tested successfully to a differential pressure of up to 2 bars. The performance of the biosensor chip is evaluated by measuring the unspecific binding of 0.5% albumin, resulting in a total frequency drop 205 Hz. This approach delivers a simple but rapid high quality integration aiming for the production of robust, low cost and disposable biosensor chips.

Single-Step Imprinting of Femtoliter Microwell Arrays Allows Digital Bioassays with Attomolar Limit of Detection

Bead-based microwell array technology is growing as an ultrasensitive analysis tool as exemplified by the successful commercial applications from Illumina and Quanterix for nucleic acid analysis and ultrasensitive protein measurements, respectively. High-efficiency seeding of magnetic beads is key for these applications and is enhanced by hydrophilic-in-hydrophobic microwell arrays, which are unfortunately often expensive or labor-intensive to manufacture. Here, we demonstrate a new single-step manufacturing approach for imprinting cheap and disposable hydrophilic-in-hydrophobic microwell arrays suitable for digital bioassays. Imprinting of arrays with hydrophilic-in-hydrophobic microwells is made possible using an innovative surface energy replication approach by means of a hydrophobic thiol-ene polymer formulation. In this polymer, hydrophobic-moiety-containing monomers self-assemble at the hydrophobic surface of the imprinting stamp, which results in a hydrophobic replica surface after polymerization. After removing the stamp, microwells with hydrophobic walls and a hydrophilic bottom are obtained. We demonstrate that the hydrophilic-in-hydrophobic imprinted microwell arrays enable successful and efficient self-assembly of individual water droplets and seeding of magnetic beads with loading efficiencies up to 96%. We also demonstrate the suitability of the microwell arrays for the isolation and digital counting of single molecules achieving a limit of detection of 17.4 aM when performing a streptavidin-biotin binding assay as model system. Since this approach is up-scalable through reaction injection molding, we expect it will contribute substantially to the translation of ultrasensitive digital microwell array technology toward diagnostic applications.

Flexible and Stretchable Microneedle Patches with Integrated Rigid Stainless Steel Microneedles for Transdermal Biointerfacing

This paper demonstrates flexible and stretchable microneedle patches that combine soft and flexible base substrates with hard and sharp stainless steel microneedles. An elastomeric polymer base enables conformal contact between the microneedle patch and the complex topography and texture of the underlying skin, while robust and sharp stainless steel microneedles reliably pierce the outer layers of the skin. The flexible microneedle patches have been realized by magnetically assembling short stainless steel microneedles into a flexible polymer supporting base. In our experimental investigation, the microneedle patches were applied to human skin and an excellent adaptation of the patch to the wrinkles and deformations of the skin was verified, while at the same time the microneedles reliably penetrate the surface of the skin. The unobtrusive flexible and stretchable microneedle patches have great potential for transdermal biointerfacing in a variety of emerging applications such as transdermal drug delivery, bioelectric treatments and wearable bio-electronics for health and fitness monitoring.