Summary Paragraph Sensory, motor, and cognitive operations involve the coordinated action of large neuronal populations across multiple brain regions in both superficial and deep structures1,2. Existing extracellular probes record neural activity with excellent spatial and temporal (sub-millisecond) resolution but from only a few dozen neurons per shank. Optical Ca2+ imaging3–5 offers more coverage but lacks the temporal resolution to reliably distinguish individual spikes and does not measure local field potentials. To date, no technology compatible with unrestrained animals has combined high spatiotemporal resolution with large volume coverage. To satisfy this need, we designed, fabricated, and tested a new silicon probe called Neuropixels. Each probe has 384 recording channels that can programmably address 960 CMOS processing-compatible low-impedance TiN6 sites that tile a single 10 mm long, 70x20 µm cross section shank. The 6x9 mm probe base is fabricated with the shank on a single chip. Voltage signals are filtered, amplified, multiplexed, and digitized on the base, allowing noise-free digital data transmission directly from the probe. The combination of dense recording sites and high channel count yielded well-isolated spiking activity from hundreds of neurons per probe implanted in mice and rats. Using two probes, more than 700 well-isolated single neurons were simultaneously recorded from five brain structures in an awake mouse. The fully integrated functionality and small size of Neuropixels probes allowed recording large populations of neurons from multiple brain structures in freely moving animals. This combination of high-performance electrode technology and scalable chip fabrication methods opens the path to record brain-wide neural activity during behavior.

The mammalian nervous system executes complex behaviors controlled by specialised, precisely positioned and interacting cell types. Here, we used RNA sequencing of half a million single cells to create a detailed census of cell types in the mouse nervous system. We mapped cell types spatially and derived a hierarchical, data-driven taxonomy. Neurons were the most diverse, and were grouped by developmental anatomical units, and by the expression of neurotransmitters and neuropeptides. Neuronal diversity was driven by genes encoding cell identity, synaptic connectivity, neurotransmission and membrane conductance. We discovered several distinct, regionally restricted, astrocytes types, which obeyed developmental boundaries and correlated with the spatial distribution of key glutamate and glycine neurotransmitters. In contrast, oligodendrocytes showed a loss of regional identity, followed by a secondary diversification. The resource presented here lays a solid foundation for understanding the molecular architecture of the mammalian nervous system, and enables genetic manipulation of specific cell types.

Measuring the dynamics of neural processing across time scales requires following the spiking of thousands of individual neurons over milliseconds and months. To address this need, we introduce the Neuropixels 2.0 probe together with newly designed analysis algorithms. The probe has more than 5000 sites and is miniaturized to facilitate chronic implants in small mammals and recording during unrestrained behavior. High-quality recordings over long time scales were reliably obtained in mice and rats in six laboratories. Improved site density and arrangement combined with newly created data processing methods enable automatic post hoc correction for brain movements, allowing recording from the same neurons for more than 2 months. These probes and algorithms enable stable recordings from thousands of sites during free behavior, even in small animals such as mice.

Well-defined gradients in molecular alignment have been used as tools to generate large amplitude, light-induced deformations in stiff polymer networks. These systems are reversible, monolithic and based on a simple one-step self-assembly process. To fabricate the actuators, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diacrylate hosts and photopolymerized in a twisted configuration. The resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa. Regardless of the temperature with respect to the glass transitions, subsequent exposure to UV radiation induced anisotropic expansion/contraction, and simple variations in geometry were used to generate uniaxial bending or helical coiling deformation modes. Because mechanical energy is directly related to elastic modulus, these systems are expected to provide significantly greater work output than contemporary polymer actuator materials.

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Films of liquid‐crystal networks with a splayed molecular alignment over their cross‐section display a well‐controlled deformation as a function of temperature. The deformation can be explained in terms of differences in thermal expansion depending on the average molecular orientation of the mesogenic centers of the monomeric units. The thermal expansion of the anisotropic polymers has been characterized as a function of their molecular structure and the polymerization conditions. As a reference, films with an in‐plane 90° twist have also been studied and compared with the splayed, out‐of‐plane molecular rotation. The twisted films show a complex macroscopic deformation owing to the formation of saddle‐like geometries, whereas the deformation of the splayed structured is smooth and well controlled. The deformation behavior is anticipated to be of relevance for polymer‐based microelectromechanical system (MEMS) technology.

Block copolymer self-assembly is an innovative technology capable of patterning technologically relevant substrates with nanoscale precision for a range of applications from integrated circuit fabrication to tissue interfacing, for example. In this article, we demonstrate a microwave-based method of rapidly inducing order in block copolymer structures. The technique involves the usage of a commercial microwave reactor to anneal block copolymer films in the presence of appropriate solvents, and we explore the effect of various parameters over the polymer assembly speed and defect density. The approach is applied to the commonly used poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) and poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) families of block copolymers, and it is found that the substrate resistivity, solvent environment, and anneal temperature all critically influence the self-assembly process. For selected systems, highly ordered patterns were achieved in less than 3 min. In addition, we establish the compatibility of the technique with directed assembly by graphoepitaxy.

In light-driven liquid-crystal network (LCN) actuators, large performance improvements are obtained by varying the orientation of the molecular director through the thickness of the film actuator. Experiments show that sub-millimeter bending radii are achieved using a splayed molecular orientation. Systems with a splayed or twisted nematic (TN) director profile drive greater amplitude and faster bending than uniaxial planar systems with the same chemical composition. The bending radii of these systems are predicted using a simple model including effects of light intensity, material composition and actuator thickness.