Education

Research Description

Dr. Zhu is interested in mEMS/NEMS design, fabrication and characterization; mechanics and materials issues in nanostructures and thin films; and mechanics of soft materials (including polymers and biological cells) and interfaces. Dr. Zhu is currently 1) developing micro/nano electromechanical transducers (NEMS/MEMS), 2) studying mechanical, electrical, and thermal inter-relations at the nanoscale, and 3) studying mechanical behavior of biological cells, thin films, and adhesion.

Honors and Awards

• ASME Fellow, 2017
• Eshelby Mechanics Award, 2017
• University Faculty Scholar, 2015
• MAE Outstanding Research Award, 2015
• Alcoa Foundation Engineering Research Achievement Award (College of Engineering), 2015
• ASME Sia Nemat-Nasser Early Career Award, 2015
• Society of Experimental Mechanics Young Investigator Lecture Award, 2013
• Sigma Xi Faculty Research Award, 2012

Publications

Characterization and modeling of catalyst-free carbon-assisted synthesis of ZnO nanowires

Kong, X. C. and Wei, C. and Zhu, Y. and Cohen, P. and Dong, J. Y. (2018), Journal of Manufacturing Processes, 32(), 438-444.

Controlled bending and folding of a bilayer structure consisting of a thin stiff film and a heat shrinkable polymer sheet

Cui, J. X. and Adams, J. G. M. and Zhu, Y. (2018), Smart Materials & Structures, 27(5), .

Electrohydrodynamic printing of silver nanowires for flexible and stretchable electronics

Cui, Z. and Han, Y. W. and Huang, Q. J. and Dong, J. Y. and Zhu, Y. (2018), Nanoscale, 10(15), 6806-6811.

Evoked haptic sensations in the hand via non-invasive proximal nerve stimulation

Shin, H. and Watkins, Z. and Huang, H. and Zhu, Y. and Hu, X. G. (2018), Journal of Neural Engineering, 15(4), .

Gravure Printing of Water-based Silver Nanowire ink on Plastic Substrate for Flexible Electronics

Huang, Qijin and Zhu, Yong (2018), SCIENTIFIC REPORTS, 8(), .

Nanomaterial-enabled wearable sensors for healthcare

Yao, S. S. and Swetha, P. and Zhu, Y. (2018), Advanced Healthcare Materials, 7(1), .

A novel finger kinematic tracking method based on skin-like wearable strain sensors

Yao, S. S. and Vargas, L. and Hu, X. G. and Zhu, Y. (2018), IEEE Sensors Journal, 18(7), 3010-3015.

Anomalous tensile detwinning in twinned nanowires

Cheng, G. M. and Yin, S. and Chang, T. H. and Richter, G. and Gao, H. J. and Zhu, Y. (2017), Physical Review Letters, 19(25), .

Compact, highly efficient, and fully flexible circularly polarized antenna enabled by silver nanowires for wireless body-area networks

Jiang, Z. H. and Cui, Z. and Yue, T. W. and Zhu, Y. and Werner, D. H. (2017), IEEE Transactions on Biomedical Circuits and Systems, 11(4), 920-932.

Controlling the self-folding of a polymer sheet using a local heater: The effect of the polymer-heater interface

Cui, J. X. and Yao, S. S. and Huang, Q. J. and Adams, J. G. M. and Zhu, Y. (2017), Soft Matter, 13(21), 3863-3870.

Hypoxia and H2O2 dual-sensitive vesicles for enhanced glucose-responsive insulin delivery

Yu, J. C. and Qian, C. G. and Zhang, Y. Q. and Cui, Z. and Zhu, Y. and Shen, Q. D. and Ligler, F. S. and Buse, J. B. and Gu, Z. (2017), Nano Letters, 17(2), 733-739.

Large-area nanolattice film with enhanced modulus, hardness, and energy dissipation

Bagal, A. and Zhang, X. A. and Shahrin, R. and Dandley, E. C. and Zhao, J. J. and Poblete, F. R. and Oldham, C. J. and Zhu, Y. and Parsons, G. N. and Bobko, C. and Chang, C. H. (2017), Scientific Reports, 7(), .

Mechanics of crystalline nanowires: An experimental perspective

Zhu, Y. (2017), Applied Mechanics Reviews, 69(1), .

Piezoelectric floating element shear stress sensor for the wind tunnel flow measurement

Kim, T. and Saini, A. and Kim, J. and Gopalarathnam, A. and Zhu, Y. and Palmieri, F. L. and Wohl, C. J. and Jiang, X. N. (2017), IEEE Transactions on Industrial Electronics, 64(9), 7304-7312.

Pop-up assembly of 3D structures actuated by heat shrinkable polymers

Cui, J. X. and Adams, J. G. M. and Zhu, Y. (2017), Smart Materials & Structures, 26(12), .

Soft electrothermal actuators using silver nanowire heaters

Yao, S. S. and Cui, J. X. and Cui, Z. and Zhu, Y. (2017), Nanoscale, 9(11), 3797-3805.

Thrombin-responsive transcutaneous patch for auto-anticoagulant regulation

Zhang, Y. Q. and Yu, J. C. and Wang, J. Q. and Hanne, N. J. and Cui, Z. and Qian, C. G. and Wang, C. and Xin, H. L. and Cole, J. H. and Gallippi, C. M. and Zhu, Y. and Gu, Z. (2017), Advanced Materials, 29(4), .

A review on mechanics and mechanical properties of 2D materials-Graphene and beyond

Akinwande, D. and Brennan, C. J. and Bunch, J. S. and Egberts, P. and Felts, J. R. and Gao, H. J. and Huang, R. and Kim, J. S. and Li, T. and Li, Y. and Liechti, K. M. and Lu, N. S. and Park, H. S. and Reed, E. J. and Wang, P. and Yakobson, B. I. and Zhang, T. and Zhang, Y. W. and Zhou, Y. and Zhu, Y. (2017), Extreme Mechanics Letters, 13(), 42-77.

Bringing plos genetics editors to preprint servers

Barsh, G. S. and Bergman, C. M. and Brown, C. D. and Singh, N. D. and Copenhaver, G. P. (2016), PLoS Genetics, 12(12), .

Editorial for the focus issue on "Nanomechanics'' in Extreme Mechanics Letters

Zhu, Y. and Gianola, D. and Zhu, T. (2016), Extreme Mechanics Letters, 8(), 125-126.

Elastic drug delivery: could treatments be triggered by patient movement?

Zhang, Y. Q. and Yu, J. C. and Zhu, Y. and Gu, Z. (2016), Nanomedicine, 11(4), 323-325.

Evolution of irradiation-induced vacancy defects in boron nitride nanotubes

Cheng, G. M. and Yao, S. S. and Sang, X. H. and Hao, B. Y. and Zhang, D. Y. and Yap, Y. K. and Zhu, Y. (2016), Small (Weinheim An Der Bergstrasse, Germany), 12(6), 818-824.

Helical coil buckling mechanism for a stiff nanowire on an elastomeric substrate

Chen, Y. L. and Liu, Y. L. and Yan, Y. and Zhu, Y. and Chen, X. (2016), Journal of the Mechanics and Physics of Solids, 95(), 25-43.

In situ nanomechanical testing of crystalline nanowires in electron microscopes

Zhu, Y. (2016), JOM: the Journal of the Minerals, Metals & Materials Society, 68(1), 84-93.

Low-power wearable systems for continuous monitoring of environment and health for chronic respiratory disease

Dieffenderfer, J. and Goodell, H. and Mills, S. and McKnight, M. and Yao, S. S. and Lin, F. Y. and Beppler, E. and Bent, B. and Lee, B. and Misra, V. and Zhu, Y. and Oralkan, O. and Strohmaier, J. and Muth, J. and Peden, D. and Bozkurt, A. (2016), IEEE Journal of Biomedical and Health Informatics, 20(5), .

Mechanical force-triggered drug delivery

Zhang, Y. Q. and Yu, J. C. and Bomba, H. N. and Zhu, Y. and Gu, Z. (2016), Chemical Reviews, 116(19), 12536-12563.

Mechanism of the transition from in-plane buckling to helical buckling for a stiff nanowire on an elastomeric substrate

Chen, Y. L. and Zhu, Y. and Chen, X. and Liu, Y. L. (2016), Journal of Applied Mechanics: Transactions of the ASME, 83(4), .

Nanomaterial-enabled dry electrodes for electrophysiological sensing: A review

Yao, S. S. and Zhu, Y. (2016), JOM: the Journal of the Minerals, Metals & Materials Society, 68(4), 1145-1155.

On the size-dependent elasticity of penta-twinned silver nanowires

Chang, T. H. and Cheng, G. M. and Li, C. J. and Zhu, Y. (2016), Extreme Mechanics Letters, 8(), 177-183.

Silver nanowire based wearable sensors for multimodal sensing

Lin, F. Y. and Yao, S. S. and McKnight, M. and Zhu, Y. and Bozkurt, A. (2016), Sensing Systems, (), 55-58.

A piezoelectric shear stress sensor

Kim, T. and Saini, A. and Kim, J. and Gopalarathnam, A. and Zhu, Y. and Palmieri, F. L. and Wohl, C. J. and Jiang, X. N. (2016), Proceedings of SPIE-the International Society for Optical Engineering, 9803(), .

Cohesive-shear-lag modeling of interfacial stress transfer between a monolayer graphene and a polymer substrate

Guo, G. D. and Zhu, Y. (2015), Journal of Applied Mechanics: Transactions of the ASME, 82(3), .

Design and operation of silver nanowire based flexible and stretchable touch sensors

Cui, Z. and Poblete, F. R. and Cheng, G. M. and Yao, S. S. and Jiang, X. N. and Zhu, Y. (2015), Journal of Materials Research, 30(1), 79-85.

Flexible technologies for self-powered wearable health and environmental sensing

Misra, V. and Bozkurt, A. and Calhoun, B. and Jackson, T. and Jur, J. S. and Lach, J. and Lee, B. and Muth, J. and Oralkan, O. and Ozturk, M. and Trolier-McKinstry, S. and Vashaee, D. and Wentzloff, D. and Zhu, Y. (2015), Proceedings of the IEEE, 103(4), 665-681.

Large anelasticity and associated energy dissipation in single-crystalline nanowires

Cheng, G. M. and Miao, C. Y. and Qin, Q. Q. and Li, J. and Xu, F. and Haftbaradaran, H. and Dickey, E. C. and Gao, H. J. and Zhu, Y. (2015), Nature Nanotechnology, 10(8), 687-691.

Measuring graphene adhesion using atomic force microscopy with a microsphere tip

Jiang, T. and Zhu, Y. (2015), Nanoscale, 7(24), 10760-10766.

Nanomaterial-enabled stretchable conductors: Strategies, materials and devices

Yao, S. S. and Zhu, Y. (2015), Advanced Materials, 27(9), 1480-1511.

Recoverable plasticity in penta-twinned metallic nanowires governed by dislocation nucleation and retraction

Qin, Q. Q. and Yin, S. and Cheng, G. M. and Li, X. Y. and Chang, T. H. and Richter, G. and Zhu, Y. and Gao, H. J. (2015), Nature Communications, 6(), .

Silver nanowire strain sensors for wearable body motion tracking

Yao, S. S. and Lee, J. S. and James, K. and Miller, J. and Narasimhan, V. and Dickerson, A. J. and Zhu, X. and Zhu, Y. (2015), IEEE Sensors, (), 1823-1826.

Strain hardening and size effect in five-fold twinned Ag nanowires

Narayanan, S. and Cheng, G. M. and Zeng, Z. and Zhu, Y. and Zhu, T. (2015), Nano Letters, 15(6), 4037-4044.

Stretch-triggered drug delivery from wearable elastomer films containing therapeutic depots

Di, J. and Yao, S. S. and Ye, Y. Q. and Cui, Z. and Yu, J. C. and Ghosh, T. K. and Zhu, Y. and Gu, Z. (2015), ACS Nano, 9(9), 9407-9415.

Testing, measurement, and characterization of nanomaterials

Peng, B. and Ke, C. H. and Liu, Y. L. and Zhu, Y. (2015), Journal of Nanomaterials, (), .

Wearable silver nanowire dry electrodes for electrophysiological sensing

Myers, A. C. and Huang, H. and Zhu, Y. (2015), RSC Advances, 5(15), 11627-11632.

A review of microelectromechanical systems for nanoscale mechanical characterization

Zhu, Y. and Chang, T. H. (2015), Journal of Micromechanics and Microengineering, 25(9), .

Interfacial sliding and buckling of monolayer graphene on a stretchable substrate

Jiang, T. and Huang, R. and Zhu, Y. (2014), Advanced Functional Materials, 24(3), 396-402.

Mechanical properties of silicon carbide nanowires: effect of size-dependent defect density

Cheng, G. M. and Chang, T. H. and Qin, Q. Q. and Huang, H. C. and Zhu, Y. (2014), Nano Letters, 14(2), 754-758.

Novel wearable EMG sensors based on nanowire technology

Myers, A. and Du, L. and Huang, H. and Zhu, Y. (2014), IEEE Engineering in Medicine and Biology Society Conference Proceedings, (), 1674-1677.

Stretchable and reversibly deformable radio frequency antennas based on silver nanowires

Song, L. N. and Myers, A. C. and Adams, J. J. and Zhu, Y. (2014), ACS Applied Materials & Interfaces, 6(6), 4248-4253.

Surface-energy-assisted perfect transfer of centimeter-scale mono layer and few-layer MoS2 films onto Arbitrary Substrates

Gurarslan, A. and Yu, Y. F. and Su, L. Q. and Yu, Y. L. and Suarez, F. and Yao, S. and Zhu, Y. and Ozturk, M. and Zhang, Y. and Cao, L. Y. (2014), ACS Nano, 8(11), 11522-11528.

Wearable multifunctional sensors using printed stretchable conductors made of silver nanowires

Yao, S. S. and Zhu, Y. (2014), Nanoscale, 6(4), 2345-2352.

Fabrication of functional nanowire devices on unconventional substrates using strain-release assembly

Durham, J. W. and Zhu, Y. (2013), ACS Applied Materials & Interfaces, 5(2), 256-261.

Stress relaxation in carbon nanotube-based fibers for load-bearing applications

Zu, M. and Li, Q. W. and Zhu, Y. T. and Zhu, Y. and Wang, G. J. and Byun, J. H. and Chou, T. W. (2013), Carbon, 52(), 347-355.

Temperature control in thermal microactuators with applications to in-situ nanomechanical testing

Qin, Q. Q. and Zhu, Y. (2013), Applied Physics Letters, 102(1), .

Temperature-dependent material properties of Z-shaped MEMS thermal actuators made of single crystalline silicon

Ouyang, J. and McDonald, M. and Zhu, Y. (2013), Journal of Micromechanics and Microengineering, 23(12), .

A microelectromechanical system for thermomechanical testing of nanostructures

Chang, T. H. and Zhu, Y. (2013), Applied Physics Letters, 103(26), .

Highly conductive and stretchable silver nanowire conductors

Xu, F. and Zhu, Y. (2012), Advanced Materials, 24(37), 5117-5122.

Size effects on elasticity, yielding, and fracture of silver nanowires: In situ experiments

Zhu, Y. and Qin, Q. Q. and Xu, F. and Fan, F. R. and Ding, Y. and Zhang, T. and Wiley, B. J. and Wang, Z. L. (2012), Physical Review. B, Condensed Matter and Materials Physics, 85(4), .

Wavy ribbons of carbon nanotubes for stretchable conductors

Xu, F. and Wang, X. and Zhu, Y. T. and Zhu, Y. (2012), Advanced Functional Materials, 22(6), 1279-1283.

Z-shaped MEMS thermal actuators: Piezoresistive self-sensing and Preliminary Results for Feedback Control

Ouyang, J. and Zhu, Y. (2012), Journal of Microelectromechanical Systems, 21(3), 596-604.

A new electrothermal microactuator with Z-shaped beams: Design and operation

Zhu, Y. (2012), Proceedings of the ASME International Mechanical Engineering Congress and Exposition 2010, vol 12, (), 77-81.

Static friction between silicon nanowires and elastomeric substrates

Qin, Q. Q. and Zhu, Y. (2011), ACS Nano, 5(9), 7404-7410.

Strain-release assembly of nanowires on stretchable substrates

Xu, F. and Durham, J. W. and Wiley, B. J. and Zhu, Y. (2011), ACS Nano, 5(2), 1556-1563.

Controlled 3E buckling of silicon nanowires for stretchable electronics

Xu, F. and Lu, W. and Zhu, Y. (2010), ACS Nano, 5(1), 672-678.

Friction and shear strength at the nanowire-substrate interfaces

Zhu, Y. and Qin, Q. Q. and Gu, Y. and Wang, Z. L. (2010), Nanoscale Research Letters, 5(2), 291-295.

Mechanical properties of ZnO nanowires under different loading modes

Xu, F. and Qin, Q. Q. and Mishra, A. and Gu, Y. and Zhu, Y. (2010), Nano Research, 3(4), 271-280.

An electrothermal microactuator with Z-shaped beams

Guan, C. H. and Zhu, Y. (2010), Journal of Micromechanics and Microengineering, 20(8), .

Direct extraction of rate-dependent traction-separation laws for polyurea/steel interfaces

Zhu, Y. and Liechti, K. M. and Ravi-Chandar, K. (2009), International Journal of Solids and Structures, 46(1), 31-51.

Mechanical properties of vapor-liquid-solid synthesized silicon nanowires

Zhu, Y. and Xu, F. and Qin, Q. Q. and Fung, W. Y. and Lu, W. (2009), Nano Letters, 9(11), 3934-3939.

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Grants

Collaborative Research: Strength and Brittle-to-Ductile Transition of Silicon Nanowires at Elevated Temperatures

National Science Foundation (NSF)(9/01/18 - 8/31/21)

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Collaborative Research: Strength and Brittle-to-Ductile Transition of Silicon Nanowires at Elevated Temperatures

Sponsor: National Science Foundation (NSF)

Start Date: 9/01/18

End Date: 8/31/21

Abstract

The objective of this proposal is to develop and utilize novel in situ TEM nano-thermo-mechanical testing and atomistic modeling for elucidating the temperature, strain rate and sample size effects on the strength and brittle-to-ductile transition (BDT) in Si nanowires. While Si nanowires at room temperature have been measured with brittle fracture, our preliminary in situ testing inside transmission electron microscope (TEM) have shown that an increase of temperature can result in a fascinating BDT behavior in Si nanowires by activating the dislocation-mediated plastic deformation.

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SNM: Printing and Integration of Metal Nanowires and Organic Semiconductors for Large-Area Stretchable Electronics and Sensors

National Science Foundation (NSF)(7/01/17 - 6/30/21)

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SNM: Printing and Integration of Metal Nanowires and Organic Semiconductors for Large-Area Stretchable Electronics and Sensors

Sponsor: National Science Foundation (NSF)

Start Date: 7/01/17

End Date: 6/30/21

Abstract

The overarching goal of this project is to fabricate large-area, high-resolution, stretchable pressure sensor arrays for e-skin at low cost by integrating organic semiconductors, AgNW conductors, and elastomers. The devices will be fabricated using several scalable nanomanufacturing techniques including gravure printing, transfer printing, and electrohydrodynamic (EHD) printing.

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Towards Restoring Natural Sensation of Hand Amputees via Wearable Surface Grid Electrodes

National Science Foundation (NSF)(9/01/16 - 8/31/19)

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Towards Restoring Natural Sensation of Hand Amputees via Wearable Surface Grid Electrodes

Sponsor: National Science Foundation (NSF)

Start Date: 9/01/16

End Date: 8/31/19

Abstract

Hand amputation can severely limit the quality of life such as manipulating and sensing objects or expressing gestures. Attempt to replace the lost hand can be traced back 500 years ago, reflecting the strong desire of restoring hand functions. Currently, many robotic prosthetic hands have been developed, that have the dexterity capability approaching a human hand. However, very few state-of-art prosthetic hands have been successfully translated to end users. One key factor that limit the user acceptance is the lack of natural and reliable sensory communication to the user. Specifically, the sensory feedback to the user was substituted through un-natural stimuli, such as skin vibration, visual or audio cues. These stimuli can be implemented readily, but require user’s interpretation and conscious attention, imposing extra cognitive burden to the user. Alternatively, peripheral sensory nerves, transmitting haptic information to the central nervous system, can be activated electrically to provide natural haptic sensation. However, invasive open surgery procedures are typically required to implant electrodes interfacing with the nerves, and the resolution of elicited sensory regions is also typically low. To overcome these limitations, the objective of the current proposed project is to restore natural self-sensation of the missing hand via non-invasive grid electrodes, ultimately allowing arm amputees to explore and communicate with the world freely. The success of this project will completely transform the way for human being to communicate with robotic prostheses.

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Nanocellulose Microneedle Array for Intradermal ISF Extraction

NCSU Advanced Self Powered Systems of Sensors and Technologies (ASSIST) Center(9/01/15 - 8/31/16)

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Nanocellulose Microneedle Array for Intradermal ISF Extraction

Sponsor: NCSU Advanced Self Powered Systems of Sensors and Technologies (ASSIST) Center

Start Date: 9/01/15

End Date: 8/31/16

Abstract

Biomarker-based immunoassays are specific and quantitative; however, they depend on intradermal or subcutaneous extraction of fluid. One of the hurdles to intradermal extraction is the stratum corneum, the uppermost layer of “dead skin.” A method to bypass the stratum corneum and extract or probe ISF would be an invaluable tool for the development of real-time health monitors. Herein the design, fabrication and evaluation of a nanocellulose-coated microneedle array (NMA) to extract ISF is proposed. The underlying microneedles will be molded from soft, compliant materials and subsequently coated in nanocellulose. The nanocellulose-coating enables the extraction of ISF by capillary force and diffusion; it is also a mechanically tough coating which will protect the soft underlying microneedle and support long-term use. The proposed platform represents the first step towards the realization of a transdermal ISF sensor.

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Flexible and Stretchable Sensor Technology Research, Advanced Self Powered Systems of Sensors and Technologies Center, ASSIST Enhancement Project

Samsung Research America Inc.(4/01/15 - 12/31/16)

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Flexible and Stretchable Sensor Technology Research, Advanced Self Powered Systems of Sensors and Technologies Center, ASSIST Enhancement Project

Sponsor: Samsung Research America Inc.

Start Date: 4/01/15

End Date: 12/31/16

Abstract

The objective of this project is to investigate the electromechanical performances of the flexible and stretchable strain sensors under cyclic loading in order to improve the long-term reliability of the sensors. The strain sensors are built using the silver nanowire technology at NCSU. We specifically propose to improve the reliability at the interfaces (e.g., lead wire to the silver nanowires). We will work closely with the team at SRA-Dallas to identify the failure modes. If successful, this project will provide insights into the failure mechanisms of the strain sensors and develop new methods to improve the sensor reliability.

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Nanowire Synthesis for Gas and Bioelectronic Sensing

NCSU Advanced Self Powered Systems of Sensors and Technologies (ASSIST) Center(9/01/13 - 5/31/17)

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Nanowire Synthesis for Gas and Bioelectronic Sensing

Sponsor: NCSU Advanced Self Powered Systems of Sensors and Technologies (ASSIST) Center

Start Date: 9/01/13

End Date: 5/31/17

Abstract

A person’s water content is crucial to the body, as it regulates body temperature, blood pressure, heart rate and etc. An accepted way to obtain the body water level is through hydration testing. One common method to characterize skin hydration levels is measuring skin electrical impedance. The objective of this project is to develop wearable sensor system that can continuously monitor skin hydration level. Such continuous monitoring could help prevent the wearer from falling into a severely dehydrated state. A compliant and wearable electrode is the key to continuous hydration monitoring.

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Evaluation of Flexible Micropost Arrays for Shear Stress Measurement

National Aeronautics & Space Administration (NASA)(7/10/14 - 7/09/16)

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Evaluation of Flexible Micropost Arrays for Shear Stress Measurement

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 7/10/14

End Date: 7/09/16

Abstract

Micropillar arrays will be developed for shear stress measurement in NCSU subsonic wind tunnel. Micropillar array sensors will be characterized first, and then assembled into a test model and calibrated in the wind tunnel. Such a measurement device enables new aerodynamics research needed to design more fuel efficient, quieter aircraft with improved dynamics for smoother and safer flight.

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Poptube Technology, Enabling Multifunctional Hybrid Composites for Next Generation Aircrafts

National Aeronautics & Space Administration (NASA)(3/16/14 - 9/15/16)

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Poptube Technology, Enabling Multifunctional Hybrid Composites for Next Generation Aircrafts

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 3/16/14

End Date: 9/15/16

Abstract

Extraordinary mechanical, electrical, and thermal properties make carbon nanotubes (CNTs) ideal candidates to reinforce, toughen, and introduce multifunction to composite materials. As a response to this research need, this study proposes a novel, low-cost, continuous processing technique to directly grow CNTs on carbon fabrics to create high-performance, highly durable, multifunctional, hierarchical hybrid structural composites.

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Collaborative Research: Investigation of Deformation Mechanisms Governing the Tensile Ductility of Twinned Metal Nanowires

National Science Foundation (NSF)(9/01/14 - 8/31/18)

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Collaborative Research: Investigation of Deformation Mechanisms Governing the Tensile Ductility of Twinned Metal Nanowires

Sponsor: National Science Foundation (NSF)

Start Date: 9/01/14

End Date: 8/31/18

Abstract

The metallic nanostructures such as nanowires usually exhibit ultra-high strength, but low tensile ductility (i.e., tensile strain to fracture) owing to their limited strain hardening capability. The low ductility can severely affect the mechanical integrity of the constituent nanostructures in nanomechancial devices and other technological applications. The objective of this proposal is to synergistically integrate experiment and modeling to study the mechanical properties and deformation mechanisms governing the tensile ductility in twinned nanowires.

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MRI: Development of a Miniature, High Temperature, Multiaxial Testing System for Advanced Materials and Engineering Research

National Science Foundation (NSF)(8/15/13 - 7/31/18)

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MRI: Development of a Miniature, High Temperature, Multiaxial Testing System for Advanced Materials and Engineering Research

Sponsor: National Science Foundation (NSF)

Start Date: 8/15/13

End Date: 7/31/18

Abstract

A novel testing system will be designed and developed for mechanical testing of miniature tubular specimens under any combination of axial, torsional, and internal pressure monotonic and cyclic loading in the room to 1000oC temperature. The proposed test system size and orientation will be designed such that it can be set under an optical microscope (OM) and scanning electron microscope (SEM) for in-situ microstructural studies. With the emerging research in materials genome and integrated computational materials engineering, importance and significance in performing materials testing under realistic multiaxial loading and environmental (temperature, chemical and gas) conditions are in urgent need. For enhancing resilience of manufactured components, design of new materials should consider failure mechanisms at critical points (weld toe, stress concentration and hot spot) through testing miniature specimen under multiaxial loading. Such tests need to be performed at high temperatures for understanding premature failures of components in energy and aerospace industries. Manufacturing processes, welding, cold drawing, quenching, surface finishing etc. induce localized material heterogeneity whose influence on failure mechanism can only be studied through testing miniature coupons. Extreme service loading and environmental conditions alter local material properties, which can only be studied through miniature specimens in determining remaining life of critical components. Development of micro-fabrication techniques requires material properties and their evolutions which can only be determined accurately through miniature specimen testing under realistic loading. According to the investigators? knowledge, the proposed testing system currently is not commercially available anywhere in the world. Moreover, even a standard size axial-torsion mechanical testing machine with or without high temperature capability is not available at any universities in North Carolina or its neighboring states. The proposed miniature testing system will be shared by a large group of inter and intra university researchers in performing fundamental research on advanced material design and characterization, micro-forming, constitutive modeling, computational modeling, and failure-life prediction for the energy, aerospace, automobile, electronics, communication, biomedical, sensor and infrastructure industries. The proposed testing system will create research opportunities in material design and component manufacturing, integrated through constitutive and computational modeling research, as well as, meeting the research needs of material characterization usually obtained through standard testing systems. Development of the proposed testing system will performed by detailed thermo-mechanical analysis. Technologies of actuators, sensors, heating and pressurization, digital image correlation, water cooled grips and their controls will be critically evaluated in developing and integrating technologies needed for developing the proposed material testing system. Cooperation with the U.S. commercial partners will facilitate this process. The proposed system will impact design and development of new materials, high performance components, and micro-forming processes. Other important outcomes will be eliminating the long (10-20 years) trial & error methods of designing new materials for enhancing component life, and predicting failure life of components with much less uncertainty than today. Two Graduate and one undergraduate student will be trained on the novel testing system through designing and developing the proposed testing system. Many other students will be trained for use of the testing system in performing their research towards MS and PhD degrees. Undergraduate students through their research projects and K-12 teachers through The Engineering Place and Women in Engineering will perform experiments with the proposed system. Partnership with an US commercial testing system manufacturer will allow quick commercialization of the new system to other r

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