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The ability to manufacture biodegradable structures at small scales is integral to a variety of applications in biological, medical, and pharmaceutical fields. Recent developments in additive manufacturing (or "three-dimensional (3D) printing") allow for biodegradable materials to be printed with high resolution; however, there is typically a limit with respect to a resolvable feature size (e.g., layer height) that dictates the minimum increments for tuning distinct degradation-mediated functionalities via print geometry. Here we investigate the potential to 3D print designs that afford additional degrees of control during intermediate stages between the complete biodegradation of microstructures that differ by a single layer height. Preliminary fabrication results revealed effective printing of tubular 3D biodegradable gelatin methacryloyl (GelMA) structures with outer diameters of 100 μm and wall thicknesses of 35 μm using two-photon direct laser writing (DLW)-based additive manufacturing. Simulation results for varying designs suggest that both the total degradation time as well as the diffusion dynamics through a microstructure during the final stage of biodegradation can be modulated via geometric means. Thus, the concepts presented in this work could open new avenues in areas including drug delivery and biomaterials. 

The emergence of soft robots has presented new challenges associated with controlling the underlying fluidics of such systems. Here, we introduce a strategy for additively manufacturing unified soft robots comprising fully integrated fluidic circuitry in a single print run via PolyJet three-dimensional (3D) printing. We explore the efficacy of this approach for soft robots designed to leverage novel 3D fluidic circuit elements—e.g., fluidic diodes, “normally closed” transistors, and “normally open” transistors with geometrically tunable pressure-gain functionalities—to operate in response to fluidic analogs of conventional electronic signals, including constant-flow [“direct current (DC)”], “alternating current (AC)”–inspired, and preprogrammed aperiodic (“variable current”) input conditions. By enabling fully integrated soft robotic entities (composed of soft actuators, fluidic circuitry, and body features) to be rapidly disseminated, modified on demand, and 3D-printed in a single run, the presented design and additive manufacturing strategy offers unique promise to catalyze new classes of soft robots. 

Additive manufacturing (or "three-dimensional (3D) printing") technologies offer unique means to expand the architectural versatility with which microfluidic systems can be designed and constructed. In particular, "direct laser writing (DLW)" supports submicron-scale 3D printing via two-photon (or multi-photon) polymerization; however, such high resolutions are poorly suited for fabricating the macro-to-micro interfaces (i.e., fluidic access ports) critical to microfluidic applications. To bypass this issue, here we present a novel strategy for using DLW to 3D print architecturally complex microfluidic structures directly onto-and notably, fully integrated with-macroscale fused silica tubes. Fabrication and experimental results for this "ex situ DLW (esDLW)" approach revealed effective structure-to-tube sealing, with fluidic integrity maintained during fluid transport from macroscale tubing, into and through demonstrative 3D printed microfluidic structures, and then out of designed outlets. These results suggest that the presented DLW-based printing approach for externally coupling microfluidic structures to macroscale fluidic systems holds promise for emerging applications spanning chemical, biomedical, and soft robotics fields. 

In situ direct laser writing ( is DLW) strategies that facilitate the printing of three-dimensional (3D) nanostructured components directly inside of, and fully sealed to, enclosed microchannels are uniquely suited for manufacturing geometrically complex microfluidic technologies. Recent efforts have demonstrated the benefits of using micromolding and bonding protocols for is DLW; however, the reliance on polydimethylsiloxane (PDMS) leads to limited fluidic sealing ( e.g. , operational pressures <50–75 kPa) and poor compatibility with standard organic solvent-based developers. To bypass these issues, here we explore the use of cyclic olefin polymer (COP) as an enabling microchannel material for is DLW by investigating three fundamental classes of microfluidic systems corresponding to increasing degrees of sophistication: (i) “2.5D” functionally static fluidic barriers (10–100 μm in height), which supported uncompromised structure-to-channel sealing under applied input pressures of up to 500 kPa; (ii) 3D static interwoven microvessel-inspired structures (inner diameters < 10 μm) that exhibited effective isolation of distinct fluorescently labelled microfluidic flow streams; and (iii) 3D dynamically actuated microfluidic transistors, which comprised bellowed sealing elements (wall thickness = 500 nm) that could be actively deformed via an applied gate pressure to fully obstruct source-to-drain fluid flow. In combination, these results suggest that COP-based is DLW offers a promising pathway to wide-ranging fluidic applications that demand significant architectural versatility at submicron scales with invariable sealing integrity, such as for biomimetic organ-on-a-chip systems and integrated microfluidic circuits.