Compartmentalized microfluidic platforms are an invaluable tool in neuroscience research. However, harnessing the full potential of this technology remains hindered by the lack of a simple fabrication approach for the creation of intricate device architectures with high‐aspect ratio features. Here, a hybrid additive manufacturing approach is presented for the fabrication of open‐well compartmentalized neural devices that provides larger freedom of device design, removes the need for manual postprocessing, and allows an increase in the biocompatibility of the system. Suitability of the method for multimaterial integration allows to tailor the device architecture for the long‐term maintenance of healthy human stem‐cell derived neurons and astrocytes, spanning at least 40 days. Leveraging fast‐prototyping capabilities at both micro and macroscale, a proof‐of‐principle human in vitro model of the nigrostriatal pathway is created. By presenting a route for novel materials and unique architectures in microfluidic systems, the method provides new possibilities in biological research beyond neuroscience applications.

cellular self-organization is the fundamental driving force behind the complex architectures of native tissue. Yet, attempts at replicating native tissue architectures in vitro often involve complex microfabrication methods and materials. While impressive progress has been made within engineered models of striated muscle, the wide adaptation of these models is held back by the need for specific tools and knowhow. In this report, we show that C2C12 myoblasts spontaneously organize into highly aligned myotube tissues on the mm to cm scale, when cultured on sufficiently soft yet fully isotropic gelatin hydrogel substrates. interestingly, we only observed this phenomenon for hydrogels with Young's modulus of 6 kPa and below. For slightly more rigid compositions, only local micrometerscale myotube organization was observed, similar to that seen in conventional polystyrene dishes. the hydrogel-supported myotubes could be cultured for multiple weeks and matured into highly contractile phenotypes with notable upregulation of myosin heavy chain, as compared to myotubes developed in conventional petri dishes. the procedure for casting the ultra-soft gelatin hydrogels is straight forward and compatible with standardized laboratory tools. it may thus serve as a simple, yet versatile, approach to generating skeletal muscle tissue of improved physiological relevance for applied and basic research. Skeletal muscle comprises the largest tissue in the human body, and plays an essential role in locomotion as well as in metabolism and homeostasis 1,2. The diseases associated with skeletal muscle are wide ranging and includes myopathies 3 , dystrophies as well as insulin resistance in diabetes mellitus type 2 4. Within in vitro research, traditional tissue culture polystyrene (TCPS) remains the most widespread substrate for culturing and studying skeletal muscle in health and disease. The use of TCPS is common, despite the general recognition that the practically incompressible and planar TCPS dishes constitute a very poor representation of the native cellular environment. Aiming to overcome this paradox, numerous advanced in vitro models of striated muscle have emerged in recent years. These models include freestanding micro tissues 5-10 , bio-printed constructs 11,12 , 3D cultures in fibrous scaffolds 13,14 and microphysiological systems 3,15,16. These novel approaches generally display highly unidirectional muscle tissues, and native function in terms of concerted contractile shortening. Nevertheless, there are several obstacles to the widespread adaptation of these models. For instance, many custom solutions are not readily compatible with standard laboratory tools and analyses, and their fabrication may require highly specific tools and detailed expertise. In the vast majority of engineered models of striated muscle, extracellular biochemical or mechanical cues are applied for guiding cellular organization into aligned tissues, for instance in the form of nanofibrous

Soft and stretchable electronic materials have a number of unique applications, not least within sensors for monitoring human health. Through development of appropriate inks, micro‐extrusion 3D printing offers an appealing route for integrating soft electronic materials within wearable garments. Toward this objective, here a series of conductive inks based on soft thermoplastic styrene–ethylene–butylene–styrene elastomers combined with silver micro‐flakes, carbon black nanoparticles, or poly(3,4‐ethylenedioxythiophene) (PEDOT) conducting polymer additives, is developed. Their electrical and mechanical properties are systematically compared and found to be highly dependent on additive amount and type. Thus, while silver composites offer the highest conductivity, their stretchability is far inferior to carbon black composites, which can maintain conductivity beyond 400% strain. The PEDOT composites are the least conductive and stretchable but display unique properties due to their propensity for ionic conductivity. To integrate these inks, as well as insulating counterparts, into functional designs, a multi‐material micro‐extrusion 3D printing routine for direct deposition onto stretchable, elastic fabrics is established. As demonstration, prototypes are produced for sensing common health markers including strain, physiological temperatures, and electrocardiograms. Collectively, this work demonstrates multi‐material 3D printing of soft styrene–ethylene–butylene–styrene elastomer composites as a versatile method for fabricating soft bio‐sensors.

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In the originally published article, some information was missing in the acknowledgements. Please find the correct acknowledgements here:

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