179 research outputs found
Dynamic Performance of Nonlinear 100X Displacement Amplification Piezoelectric Actuator
No full textThe dynamic frequency response of a nonlinear piezoelectric amplification mechanism capable of over 150 fold displacement amplification is presented. Research to amplify the displacement of piezoelectric actuators has included flexure based approaches that utilize geometric configuration, and has included frequency based approaches that utilize resonance and small steps to contribute to a full motion. The dynamic operation of the actuator presented here utilizes the benefits from both of these methods. The geometry allows for great displacement amplification, and operation within a specific frequency band allows for the exploitation of a nonlinear singularity. The actuator has three distinct modes of dynamic operation, one of which achieves significant displacement by utilizing momentum to pass through a singular configuration. A nonlinear model, linear models for each frequency response mode, and multiple prototypes are presented. This actuator operating in the high displacement frequency band is promising as an input actuator for stepping mechanisms. Copyright © 2010 by ASME
A PZT Array Actuator Using Buckling Strain Amplification and Preload Mechanisms
No full textDisplacement amplification mechanisms have been a topic of research for piezoelectric actuators for decades to overcome their significantly small strain, but still utilize their high power density, force, and efficiency This paper further analyzes a nonlinear buckling mechanism to improve its efficiency, defined as the ratio of mechanical work output of the buckling actuator to the mechanical work output of the PZT actuator, as well as, employing two methods, preload and loading conditions, that improve its work output per cycle. This is accomplished by running a numerical analysis of the geometry of the flexure joints in the buckling mechanism which found a maximum mechanical efficiency of 48%. The preload is applied using shape memory alloy wire to exploit the low stiffness of the super elastic regime; which in turn allows a larger work output due to a loading condition supplied by a novel gear design. Finally a prototype was fabricated to provide a baseline of comparison against these concepts. Topics: Actuators, Buckling, Mechanism
Nonlinear, large-strain PZT actuators using controlled structural buckling
No full textBuckling is a highly nonlinear and singular phenomenon in thin beams, and is usually an undesired characteristic that must be prevented from occurring in engineered systems. Buckling, however, can be a useful mechanism for gaining extremely large displacement amplification, since a tiny displacement in the axial direction of the beam may lead to a large defection in the middle of the beam. This paper presents a novel large-strain piezoelectric actuator exploiting the buckling of a structure with imbedded PZT stacks. Although the free displacement of a PZT stack is only 0.1% of the stack length, the buckling mechanism, controlled with an effective algorithm and strategically placed redirecting stiffness, can produce a large bi-polar displacement that is approximately 150 times larger than the original PZT displacement. Furthermore, the structural buckling produces a pronounced nonlinearity in output impedance; the effective stiffness viewed from the output port varies as a function of output displacement, which can be a useful property for those applications where actuator stiffness needs to vary
Towards the Development of Optogenetically-Controlled Skeletal Muscle Actuators
No full textEngineered skeletal muscle tissue has the potential to be used as dual use actuator and stress-bearing material providing numerous degrees of freedom and with significant active stress generation. To exploit the potential features, however, technologies must be established to generate mature muscle strips that can be controlled with high fidelity. Here, we present a method for creating mature 3-D skeletal muscle tissues that contract in response to optical activation stimuli. The muscle strips are fascicle-like, consisting of several mm-long multinucleate muscle cells bundled together. We have found that applying a tension to the fascicle-like muscle tissue promotes maturation of the muscle. The fascicle-like muscle tissue is controlled with high spatiotemporal resolution based on optogenetic coding. The mouse myoblasts C2C12 were transfected with Channelrhodopsin-2 to enable light (∼470 nm) to control muscle contraction. The 3D muscle tissue not only twitches in response to an impulse light beam, but also exhibits a type of tetanus, a prolonged contraction of continuous stimuli, for the first time. In the following, the materials and culturing method used for 3D muscle generation is presented, followed by experimental results of muscle constructs and optogenetic control of the 3D muscle tissue.National Science Foundation (U.S.)National Science Foundation (U.S.). Science and Technology Center. Emergent Behaviors of Integrated Cellular Systems (grant no. NSF STC-0902396)Singapore-MIT Alliance. BioSystems and Micromechanics (BioSyM) Inter-Disciplinary Research Grou
Distributed Live Muscle Actuators Controlled by Optical Stimuli
No full textA multi degree of freedom skeletal muscle system stimulated via optical control is presented. These millimeter-scale, optically excitable 3D skeletal muscle bio-actuators are created by culturing genetically modified precursory muscle cells that are activated with light: optogenetics. These muscle bio-actuators are networked together to create a distributed muscle system. Muscle systems can manipulate loads having no fixed joint. These types of loads include shoulders, the mouth, and the jaw. Topics: Actuators , Muscl
Bioengineered Fascicle-Like Skeletal Muscle Tissue Constructs
No full textTissue engineered skeletal muscle constructs have and will continue to be valuable in treating, and testing various muscle injuries and diseases. However a significant drawback to numerous methods of producing 3D skeletal muscle constructs grown in vitro is that muscle cell density as a fraction of total volume or mass, is often significantly lower than muscle found in vivo. Therefore a method to increase muscle cell density within a construct is needed. Topics: Biological tissues, MuscleNational Science Foundation (U.S.). Center on Emergent Behaviors of Integrated Cellular Systems (Grant CBET-0939511
Design Method for Buckling Amplified Piezoelectric Actuator Using Flexure Joint and its Application to an Energy Efficient Brake System
No full textThis paper shows a practical design method for a displacement amplification mechanism for a piezoelectric actuator which employs a buckling-like phenomenon. This mechanical singularity realizes a substantial displacement magnification, at least 50 times, within a simple structure. An SMA preload mechanism essentially provides potential for full range push-pull actuation to the piezoelectric actuator. This integrated actuator performs a high energy transfer ratio and is suitable for brake mechanisms due to their requirement of high force, specific displacement and energy efficiency. A practical design method is shown and is evaluated by comparing the analytical model with finite element analysis and experimental hardware performance. The actuator properties obtained by these methods fit well each other with errors less than 13%. The experimental actuators are applied to a brake for a commercial motor and its properties are evaluated. The brake can produce more than 2.5Nm in the displacement range of 0.5mm. These experimental results suggest that this novel piezoelectric actuator has potential for use in a wide range of applications. Topics: Bending (Stress), Design methodology, Buckling, Piezoelectric actuators, Brake
Mechanical Characterization and Shape Optimization of Fascicle-Like 3D Skeletal Muscle Tissues Contracted with Electrical and Optical Stimuli
No full textHere we present a quantitative approach to constructing effective 3D muscle tissues through shape optimization and load impedance matching with electrical and optical stimulation. We have constructed long, thin, fascicle-like skeletal muscle tissue and optimized their form factor through mechanical characterization. A new apparatus was designed and built which allowed us to measure force-displacement characteristics with diverse load stiffnesses. We have found that a) there is an optimal form factor that maximizes the muscle stress, b) the energy transmitted to the load can be maximized with matched load stiffness, and c) optical stimulation using channelrhodopsin2 in the muscle tissue can generate twitch force as large as its electrical counterpart for well developed muscle tissue. Using our tissue construct method we found an optimal initial diameter of 500 microns outperformed tissues using 250 microns by more than 60% and tissues using 760 microns by 105%. Using an optimal load stiffness, our tissues have generated 12 pJ of energy at a peak generated stress of 1.28 kPa. Additionally, the difference in optically stimulated twitch performance vs. electrically stimulated is a function of how well the overall tissue performs, with average or better performing strips having less than 10% difference. The unique mechanical characterization method used is generalizable to diverse load conditions and will be used to match load impedance to muscle tissue impedance for a wide variety of applications.National Science Foundation (U.S.) (Grant No. CBET-0939511)Singapore-MIT Alliance for Research and Technology (BioSyM IRG)National Science Foundation (U.S.). Emergent Behaviors of Integrated Cellular System
Supplementary Tables1-43 for 'Transposon mutagenesis identifies cooperating genetic drivers during keratinocyte transformation and cutaneous squamous cell carcinoma progression'
No full textSupplementary Tables for manuscript: Transposon mutagenesis identifies cooperating genetic drivers during keratinocyte transformation and cutaneous squamous cell carcinoma progression. Aziz Aiderus, Justin Y. Newberg, Liliana Guzman-Rojas, Ana M. Contreras-Sandoval, Amanda L. Meshey, Devin J. Jones, Felipe Amaya-Manzanares, Roberto Rangel, Jerrold M. Ward, Song-Choon Lee, Kenneth Hon-Kim Ban, Keith Rogers, Susan M. Rogers, Luxmanan Selvanesan, Leslie A. McNoe, Neal G. Copeland, Nancy A. Jenkins, Kenneth Y. Tsai, Michael A. Black, Karen M. Mann, and Michael B. Man
SBCapSeq Protocol manuscript files for 'Quantifying tumor heterogeneity, clonal dynamics, and cancer driver gene evolution from Sleeping Beauty transposon mutagenesis models using SBCapSeq'
No full textSupplementary datasets and other information accompanying manuscript: Quantifying tumor heterogeneity, clonal dynamics, and cancer driver gene evolution from Sleeping Beauty transposon mutagenesis models using SBCapSeq by Karen M. Mann Ana M. Contreras-Sandoval, Liliana Guzman-Rojas, Justin Y. Newberg, Amanda L. Meshey, Devin J. Jones, Felipe Amaya-Manzanares, Neal G. Copeland, Nancy A. Jenkins, and Michael B. Mann.SBCapSeq is a transposon-based liquid-phase capture experimental and bioinformatic workflow optimized for Ion Torrent sequencing. SBCaptureSeq permits selective, semi-quantitative, and scalable deep sequencing of Sleeping Beauty transposon insertion sites from adaptor-ligated, barcoded Ion Torrent libraries created from populations of cells (bulk specimens) and single cells from both tumor and non-tumor genomes. This protocol includes detailed procedures for genomic DNA isolation, library preparation, capture hybridization, target sequence enrichment, sequencing, and data analysis. The SBCapSeq method, which takes about 7–10 days to perform, permits semi-quantitative sequencing and has been specifically optimized for Sleeping Beauty transposon mutagenesis genetic studies.</div
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