Untethered small-scale (from several millimetres down to a few micrometres in all dimensions) robots that can non-invasively access confined, enclosed spaces may enable applications in microfactories such as the construction of tissue scaffolds by robotic assembly, in bioengineering such as single-cell manipulation and biosensing, and in healthcare such as targeted drug delivery and minimally invasive surgery. Existing small-scale robots, however, have very limited mobility because they are unable to negotiate obstacles and changes in texture or material in unstructured environments. Of these small-scale robots, soft robots have greater potential to realize high mobility via multimodal locomotion, because such machines have higher degrees of freedom than their rigid counterparts. Here we demonstrate magneto-elastic soft millimetre-scale robots that can swim inside and on the surface of liquids, climb liquid menisci, roll and walk on solid surfaces, jump over obstacles, and crawl within narrow tunnels. These robots can transit reversibly between different liquid and solid terrains, as well as switch between locomotive modes. They can additionally execute pick-and-place and cargo-release tasks. We also present theoretical models to explain how the robots move. Like the large-scale robots that can be used to study locomotion, these soft small-scale robots could be used to study soft-bodied locomotion produced by small organisms.

Predetermined and selective placement of nanoparticles onto large-area substrates with nanometre-scale precision is essential to harness the unique properties of nanoparticle assemblies, in particular for functional optical and electro-optical nanodevices. Unfortunately, such high spatial organization is currently beyond the reach of top-down nanofabrication techniques alone. Here, we demonstrate that topographic features comprising lithographed funnelled traps and auxiliary sidewalls on a solid substrate can deterministically direct the capillary assembly of Au nanorods to attain simultaneous control of position, orientation and interparticle distance at the nanometre level. We report up to 100% assembly yield over centimetre-scale substrates. We achieve this by optimizing the three sequential stages of capillary nanoparticle assembly: insertion of nanorods into the traps, resilience against the receding suspension front and drying of the residual solvent. Finally, using electron energy-loss spectroscopy we characterize the spectral response and near-field properties of spatially programmable Au nanorod dimers, highlighting the opportunities for precise tunability of the plasmonic modes in larger assemblies.

The design and fabrication techniques for microelectromechanical systems (MEMS) and nanodevices are progressing rapidly. However, due to material and process flow incompatibilities in the fabrication of sensors, actuators and electronic circuitry, a final packaging step is often necessary to integrate all components of a heterogeneous microsystem on a common substrate. Robotic pick-and-place, although accurate and reliable at larger scales, is a serial process that downscales unfavorably due to stiction problems, fragility and sheer number of components. Self-assembly, on the other hand, is parallel and can be used for device sizes ranging from millimeters to nanometers. In this review, the state-of-the-art in methods and applications for self-assembly is reviewed. Methods for assembling three-dimensional (3D) MEMS structures out of two-dimensional (2D) ones are described. The use of capillary forces for folding 2D plates into 3D structures, as well as assembling parts onto a common substrate or aggregating parts to each other into 2D or 3D structures, is discussed. Shape matching and guided assembly by magnetic forces and electric fields are also reviewed. Finally, colloidal self-assembly and DNA-based self-assembly, mainly used at the nanoscale, are surveyed, and aspects of theoretical modeling of stochastic assembly processes are discussed.

other hazard risks of various substances under increasingly stringent regulatory requirements (Marx et al., 2016).Organ-on-Chip (OoC) is increasingly regarded as a potentially game-changing technology for these problems (Bahinski et al., 2015) and able to meet the needs of different stakeholders (Middelkamp et al., 2016). In spite of its promise (Zhang and Radisic, 2017), pharma has nevertheless remained cautious to invest in this new technology, presently awaiting evidence of its added cost-benefit value and whether it could represent a feasible route to precision medicine and improved patient stratification. It is thus necessary to bridge the gap between the potential of OoC systems and their worldwide acceptance. Defining the putative benefits of OoCs and how these can be proven and achieved is the preamble for an OoC roadmap -which is one of the aims of the ORCHID project.

Surface tension-driven self-alignment is a passive and highly-accurate positioning mechanism that can significantly simplify and enhance the construction of advanced microsystems. After years of research, demonstrations and developments, the surface engineering and manufacturing technology enabling capillary self-alignment has achieved a degree of maturity conducive to a successful transfer to industrial practice. In view of this transition, a broad and accessible review of the physics, material science and applications of capillary self-alignment is presented. Statics and dynamics of the self-aligning action of deformed liquid bridges are explained through simple models and experiments, and all fundamental aspects of surface patterning and conditioning, of choice, deposition and confinement of liquids, and of component feeding and interconnection to substrates are illustrated through relevant applications in micro- and nanotechnology. A final outline addresses remaining challenges and additional extensions envisioned to further spread the use and fully exploit the potential of the technique.

the stage of validation/qualification, which in general means that compounds and drugs already demonstrated as toxic or effective in treating disease in animals or patients show similar effects in OoC models. This is expected to encourage OoC adoption by industry, acceptance by regulatory bodies, and further development as animal alternatives. However, this outcome is still pending growth in confidence on OoC predictivity and utility.A comprehensive survey of the current OoC landscape in research, development, applications, and market opportunities was recently carried out by the Horizon 2020 FET-Open project Organ-on-Chip In Development (ORCHID 1 ). The goal of ORCHID is to create a roadmap for OoC technology, identify potential roadblocks and corresponding solutions, raise awareness and build ecosystems conducive to wide implementation and use of OoCs in science, R&D, and regulatory guidelines in Europe and elsewhere. ORCHID recently published a report (Mastrangeli et al., 2019) based on a bibliometric study, market analysis, interviews, and panel discussions with 31 experts at the ORCHID Vision workshop (Stuttgart, Germany, May 23, 2018). The report described current unmet needs (including evidence of added value, methods for automation and robustness), key challenges (structural materials, cell sourcing and culture media, long-term cell viability, real-time characterization, increasing complexity, qualification), barriers and perspectives (industrial acceptance, appropriate and timely dialogue among players) of this technology, as well as recommendations for defining a European OoC roadmap. The present document builds on this preliminary assessment and identifies potential solutions. The future strategy for Organ-on-Chip technologyFollowing up on the ORCHID Vision workshop, the ORCHID Strategy workshop was held in Leiden on January 17, 2019. 32 experts (see Appendix B) 2 from academia, innovation hubs, pharmaceutical and cosmetic industry, patient organizations, ethics schools, biotech companies, and regulatory agencies attended. They represented OoC developers, end users, and regulators in Europe. The aim of the workshop was to sketch an OoC landscape for future development of the technology by defining concrete goals and milestones that would form the roadmap strategy for moving forward. During two brainstorm sessions, expert groups focused on four application domains: personalized medicine, drug efficacy, drug toxicity, and disease mechanisms. The groups addressed domain-specific issues from the perspective of both developers and end users/regulators. IntroductionThis paper summarizes the outcome of the Organ-on-Chip (OoC) ORCHID Strategy workshop (Leiden, The Netherlands, January 17, 2019) intended to establish a European OoC roadmap through expert discussions, conclusions, and recommendations. The workshop identified six specific building blocks for the OoC roadmap: (1) application, (2) specification, (3) qualification, (4) standardization, (5) production and upscaling, and (6) adoption. Complementary a...

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We report experimental evidence for three sequential, distinct dynamic regimes in the capillary self-alignment of centimeter-sized foil dies released at large uniaxial offsets from equilibrium. We show that the initial transient wetting regime, along with inertia and wetting properties of the dies, significantly affect the alignment dynamics including the subsequent constant acceleration and damped oscillatory regimes. An analytical force model is proposed that accounts for die wetting and matches quasi-static numerical simulations. Discrepancies with experimental data point to the need for a comprehensive dynamical model to capture the full system dynamics.