Alexander Vastesson

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 ...

A polymer neural probe with tunable flexibility

A novel polymeric material, off-stoichiometry thiol-ene-epoxy (OSTE+), has been evaluated for the fabrication of neural implants. OSTE+ is easily photo-structurable and exhibits mechanical properties suitable for stable implantation of the probe into brain tissue, while being sufficiently soft at physiological temperatures to reduce living tissue damage. The facile processing of OSTE+ allows use in applications where SU-8 or polyimide currently are the materials of choice. Uniquely, OSTE+ has a Youngs modulus of 1.9 GPa at 10 °C decreasing almost two orders of magnitude to 30 MPa at 40 °C, which can be compared to the Youngs modulus of 2.1 GPa for SU-8. We show a probe, with nine gold electrode sites, implanted into 0.5% agar at 40 °C using active cooling during the implantation.

Off-stoichiometry improves the photostructuring of thiol–enes through diffusion-induced monomer depletion

Thiol–enes are a group of alternating copolymers with highly ordered networks and are used in a wide range of applications. Here, “click” chemistry photostructuring in off-stoichiometric thiol–enes is shown to induce microscale polymeric compositional gradients due to species diffusion between non-illuminated and illuminated regions, creating two narrow zones with distinct compositions on either side of the photomask feature boundary: a densely cross-linked zone in the illuminated region and a zone with an unpolymerized highly off-stoichiometric monomer composition in the non-illuminated region. Using confocal Raman microscopy, it is here explained how species diffusion causes such intricate compositional gradients in the polymer and how off-stoichiometry results in improved image transfer accuracy in thiol–ene photostructuring. Furthermore, increasing the functional group off-stoichiometry and decreasing the photomask feature size is shown to amplify the induced gradients, which potentially leads to a new methodology for microstructuring.