Optogenetic control of Drosophila using a red-shifted channelrhodopsin reveals experience-dependent influences on courtship

Optogenetics allows the manipulation of neural activity in freely moving animals with millisecond precision, but its application in Drosophila melanogaster has been limited. Here we show that a recently described red activatable channelrhodopsin (ReaChR) permits control of complex behavior in freely moving adult flies, at wavelengths that are not thought to interfere with normal visual function. This tool affords the opportunity to control neural activity over a broad dynamic range of stimulation intensities. Using time-resolved activation, we show that the neural control of male courtship song can be separated into (i) probabilistic, persistent and (ii) deterministic, command-like components. The former, but not the latter, neurons are subject to functional modulation by social experience, which supports the idea that they constitute a locus of state-dependent influence. This separation is not evident using thermogenetic tools, a result underscoring the importance of temporally precise control of neuronal activation in the functional dissection of neural circuits in Drosophila

Digital material aerospace structures

Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 71-76).This thesis explores the design, fabrication, and performance of digital materials in aerospace structures in three areas: (1) a morphing wing design that adjusts its form to respond to different behavioral requirements; (2) an automated assembly method for truss column structures; and (3) an analysis of the payload and structural performance requirements of space structure elements made from digital materials. Aerospace structures are among the most difficult to design, engineer, and manufacture. Digital materials are discrete building block parts, reversibly joined, with a discrete set of positions and orientations. Aerospace structures built from digital materials have high performance characteristics that can surpass current technology, while also offering potential for analysis simplification and assembly automation. First, this thesis presents a novel approach for the design, analysis, and manufacturing of composite aerostructures through the use of digital materials. This approach can be used to create morphing wing structures with customizable structural properties, and the simplified composite fabrication strategy results in rapid manufacturing time with future potential for automation. The presented approach combines aircraft structure with morphing technology to accomplish tuned global deformation with a single degree of freedom actuator. Guidelines are proposed to design a digital material morphing wing, a prototype is manufactured and assembled, and preliminary experimental wind tunnel testing is conducted. Seconds, automatic deployment of structures has been a focus of much academic and industrial work on infrastructure applications and robotics in general. This thesis presents a robotic truss assembler designed for space applications - the Space Robot Universal Truss System (SpRoUTS) - that reversibly assembles a truss column from a feedstock of flat-packed components, by folding the sides of each component up and locking onto the assembled structure. The thesis describes the design and implementation of the robot and shows that an assembled truss compares favorably with prior truss deployment systems. Thirds, space structures are limited by launch shroud mass and volume constraints. Digital material space structures can be reversibly assembled on orbit by autonomous relative robots using discrete, incremental parts. This will enable the on-orbit assembly of larger space structures than currently possible. The engineering of these structures, from macro scale to discrete part scale, is presented. Comparison with traditional structural elements is shown and favorable mechanical performance as well as the ability to efficiently transport the material in a medium to heavy launch vehicle. In summary, this thesis contributes the methodology and evaluation of novel applications of digital materials in aerospace structures.by Benjamin Jenett.S.M

Discrete mechanical metamaterials

Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, September, 2020Cataloged from the official PDF version of thesis.Includes bibliographical references (pages 127-136).Digital fabrication enables complex designs to be realized with improved speed, precision, and cost compared to manual techniques. Additive manufacturing, for example, is one of the leading methods for rapid prototyping and near net shape part production. Extension to full scale structures and systems, however, remains a challenge, as cost, speed and performance present orthogonal objectives that are inherently coupled to limited material options, stochastic process errors, and machine-based constraints. To address these issues, this thesis introduces new materials that physically embody attributes of digital systems, scalable methods for automating their assembly, and a portfolio of use cases with novel, full-scale structural and robotic platforms. First, I build on the topic of discrete materials, which showed a finite set of modular parts can be incrementally and reversibly assembled into larger functional structures.I introduce a new range of attainable properties, such as rigidity, compliance, chirality, and auxetic behavior, all within a consistent manufacturing and assembly framework. These discretely assembled mechanical metamaterials show global continuum properties based on local cellular architectures, resulting in a system with scalability, versatility, and reliability similar to digital communication and computation. Next, I present a new kind of material-robot system to enable methods of assembly automation. Rather than relying on global motion control systems for precision, mobile robots are designed to operate relative to their discrete material environment. By leveraging the embedded metrology of discrete materials, these relative robots have reduced complexity without sacrificing extensibility, enabling the robots to build structures larger and more precise than themselves.Multi-robot assembly is compared to stationary platforms to show system benefits for cost and throughput at larger scales. Finally, I show a range of discretely assembled systems that blur the boundary between structure and robotics. Full-scale demonstrations include statically reconfigurable bridges, supermileage racecars, and morphing aero and hydrodynamic vehicles. Performance scaling is projected to new regimes, using case studies of turbine blades, airships, and space structures. These discrete systems demonstrate new, disruptive capabilities not possible within the limits of traditional manufacturing.by Benjamin Eric Jenett.Ph. D.Ph.D. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Science

Building Block-Based Assembly of Scalable Metallic Lattices

© Copyright 2018 ASME. We describe a method for the manufacturing of metallic lattices with tunable properties through the reversible assembly of building block elements, which we call discrete metal lattice assembly (DMLA). These structures can have sub-millimeter scale features on millimeter scale parts used to assemble structures spanning tens of centimeters, comparable to those currently made with Direct Metal Laser Sintering (DMLS). However, unlike traditional additive manufacturing (AM) methods, the use of discrete assembly affords a number of benefits, such as extensible, incremental construction and being repairable and reconfigurable. We show this method results in large scale (tens of centimeters), ultralight (<10 kg/m3 effective density) lattices which are currently not possible with state of the art additive manufacturing techniques. The lattice geometry used here is a combination of two geometries with quadratic property scaling, resulting in a novel lattice with sub-quadratic scaling.NASA (Grants NNX14AM40H and NNX14AG47A

Hierarchical assembly of a self-replicating spacecraft

© 2017 IEEE. Extraterrestrial fabrication of spacecraft by current best-practice manufacturing methods is complicated by the need to integrate thousands of unique parts, each made using a diversity of processes and raw materials. Reducing this complexity could enable exponential space exploration via self-replicating spacecraft (known as Von Neumann probes). We propose a hierarchical model for machine design, based on 13 reversibly-assembled part types, reducing the complexity of machine self-replication and bridging prior work in the areas of in-situ resource utilization (ISRU) and modular robotics. Analogous to amino acids in biological systems, these parts form a basis set for the electronic and mechanical subsystems of an exploratory spacecraft. In simulation we validate representative subsystem designs and develop a hierarchical architecture for the design of mechanisms, actuation, and electronics. By standardizing and modularizing the parts, we drastically reduce the diversity of the required supply chain as well as the minimum viable payload mass. We estimate that a seed launch could contain approximately 105 parts, fit within the envelope of a 3U cubesat, and enable the assembly of over one hundred self-replicating assemblers.NSF (Award 1344222)NASA (Award NNX14AM40H)ARO (Award W911NF-16-1-0568

Digital Morphing Wing: Active Wing Shaping Concept Using Composite Lattice-Based Cellular Structures

We describe an approach for the discrete and reversible assembly of tunable and actively deformable structures using modular building block parts for robotic applications. The primary technical challenge addressed by this work is the use of this method to design and fabricate low density, highly compliant robotic structures with spatially tuned stiffness. This approach offers a number of potential advantages over more conventional methods for constructing compliant robots. The discrete assembly reduces manufacturing complexity, as relatively simple parts can be batch-produced and joined to make complex structures. Global mechanical properties can be tuned based on sub-part ordering and geometry, because local stiffness and density can be independently set to a wide range of values and varied spatially. The structure's intrinsic modularity can significantly simplify analysis and simulation. Simple analytical models for the behavior of each building block type can be calibrated with empirical testing and synthesized into a highly accurate and computationally efficient model of the full compliant system. As a case study, we describe a modular and reversibly assembled wing that performs continuous span-wise twist deformation. It exhibits high performance aerodynamic characteristics, is lightweight and simple to fabricate and repair. The wing is constructed from discrete lattice elements, wherein the geometric and mechanical attributes of the building blocks determine the global mechanical properties of the wing. We describe the mechanical design and structural performance of the digital morphing wing, including their relationship to wind tunnel tests that suggest the ability to increase roll efficiency compared to a conventional rigid aileron system. We focus here on describing the approach to design, modeling, and construction as a generalizable approach for robotics that require very lightweight, tunable, and actively deformable structures.United States. National Aeronautics and Space Administration (NNX14AG47A

A GAL4-Driver Line Resource for Drosophila Neurobiology

We established a collection of 7,000 transgenic lines of Drosophila melanogaster. Expression of GAL4 in each line is controlled by a different, defined fragment of genomic DNA that serves as a transcriptional enhancer. We used confocal microscopy of dissected nervous systems to determine the expression patterns driven by each fragment in the adult brain and ventral nerve cord. We present image data on 6,650 lines. Using both manual and machine-assisted annotation, we describe the expression patterns in the most useful lines. We illustrate the utility of these data for identifying novel neuronal cell types, revealing brain asymmetry, and describing the nature and extent of neuronal shape stereotypy. The GAL4 lines allow expression of exogenous genes in distinct, small subsets of the adult nervous system. The set of DNA fragments, each driving a documented expression pattern, will facilitate the generation of additional constructs for manipulating neuronal function