Design, fabrication, and characterization of an SLA 3D printed nanocomposite electromagnetic microactuator

Here we demonstrate a 3D-printable microvalve that is transparent, built with a biocompatible resin, and has a simple architecture that can be easily scaled up into large arrays. Here we demonstrate a 3D-printable microvalve that is transparent, built with a biocompatible resin, and has a simple architecture that can be easily scaled up into large arrays. The open-at-rest valve design is derived from Quake's PDMS valve design. We used a stereolithographic (SL) 3D printer to print a thin (25 or 10 μm-thick) membrane (1200 or 500 μm-diam.) that is pneumatically pressed (∼3–6 psi) over a bowl-shaped seat to close the valve. We used poly(ethylene diacrylate) (MW = 258) (PEG-DA-258) as the resin because it yields transparent cytocompatible prints. Although the flexibility of PEG-DA-258 is inferior to that of other microvalve fabrication materials such as PDMS, the valve benefits from the bowl design and the membrane's high restoring force since it does not need a negative pressure to re-open. We also 3D-printed a micropump by combining three Quake-style valves in series. The micropump only requires positive pressure for its operation and profits from the fast return to the valves' open states. Moreover, we printed a 64-valve array constructed with 500 μm-diam. valves to demonstrate the reliability and scalability of the valves. Overall, we demonstrate the 3D-printing of compact microvalves and micropumps using a process that precludes the need for specialized, time-consuming labor.

As a 3D bioprinting technique, hydrogel stereolithography has historically been limited in its ability to capture the spatial heterogeneity that permeates mammalian tissues and dictates structure–function relationships. This limitation stems directly from the difficulty of preventing unwanted material mixing when switching between different liquid bioinks. Accordingly, we present the development, characterization, and application of a multi-material stereolithography bioprinter that provides controlled material selection, yields precise regional feature alignment, and minimizes bioink mixing. Fluorescent tracers were first used to highlight the broad design freedoms afforded by this fabrication strategy, complemented by morphometric image analysis to validate architectural fidelity. To evaluate the bioactivity of printed gels, 344SQ lung adenocarcinoma cells were printed in a 3D core/shell architecture. These cells exhibited native phenotypic behavior as evidenced by apparent proliferation and formation of spherical multicellular aggregates. Cells were also printed as pre-formed multicellular aggregates, which appropriately developed invasive protrusions in response to hTGF-β1. Finally, we constructed a simplified model of intratumoral heterogeneity with two separate sub-populations of 344SQ cells, which together grew over 14 days to form a dense regional interface. Together, these studies highlight the potential of multi-material stereolithography to probe heterotypic interactions between distinct cell types in tissue-specific microenvironments.