Mechanical Engineering Publications

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Lithium storage mechanisms in purpurin based organic lithium ion battery electrodes
(Nature Publishing Group, 2012) Reddy, Arava Leela Mohana; Nagarajan, Subbiah; Chumyim, Porramate; Gowda, Sanketh R.; Pradhan, Padmanava; Jadhav, Swapnil R.; Dubey, Madan; John, George; Ajayan, Pulickel M.
Current lithium batteries operate on inorganic insertion compounds to power a diverse range of applications, but recently there is a surging demand to develop environmentally friendly green electrode materials. To develop sustainable and eco-friendly lithium ion batteries, we report reversible lithium ion storage properties of a naturally occurring and abundant organic compound purpurin, which is non-toxic and derived from the plant madder. The carbonyl/hydroxyl groups present in purpurin molecules act as redox centers and reacts electrochemically with Li-ions during the charge/discharge process. The mechanism of lithiation of purpurin is fully elucidated using NMR, UV and FTIR spectral studies. The formation of the most favored six membered binding core of lithium ion with carbonyl groups of purpurin and hydroxyl groups at C-1 and C-4 positions respectively facilitated lithiation process, whereas hydroxyl group at C-2 position remains unaltered.
Paintable Battery
(Springer, 2012) Singh, Neelam; Galande, Charudatta; Miranda, Andrea; Mathkar, Akshay; Gao, Wei; Reddy, Arava Leela Mohana; Vlad, Alexandru; Ajayan, Pulickel M.
If the components of a battery, including electrodes, separator, electrolyte and the current collectors can be designed as paints and applied sequentially to build a complete battery, on any arbitrary surface, it would have significant impact on the design, implementation and integration of energy storage devices. Here, we establish a paradigm change in battery assembly by fabricating rechargeable Li-ion batteries solely by multi-step spray painting of its components on a variety of materials such as metals, glass, glazed ceramics and flexible polymer substrates. We also demonstrate the possibility of interconnected modular spray painted battery units to be coupled to energy conversion devices such as solar cells, with possibilities of building standalone energy capture-storage hybrid devices in different configurations.
Citrate-Capped Gold Nanoparticle Electrophoretic Heat Production in Response to a Time-Varying Radio-Frequency Electric Field
(American Chemical Society, 2012) Corr, Stuart J.; Raoof, Mustafa; Mackeyev, Yuri; Phounsavath, Sophia; Cheney, Matthew A.; Cisneros, Brandon T.; Shur, Michael; Gozin, Michael; McNally, Patrick J.; Wilson, Lon J.; Curley, Steven A.; Smalley Institute for Nanoscale Science and Technology
The evaluation of heat production from gold nanoparticles (AuNPs) irradiated with radio-frequency (RF) energy has been problematic due to Joule heating of their background ionic buffer suspensions. Insights into the physical heating mechanism of nanomaterials under RF excitations must be obtained if they are to have applications in fields such as nanoparticle-targeted hyperthermia for cancer therapy. By developing a purification protocol that allows for highly stable and concentrated solutions of citrate-capped AuNPs to be suspended in high-resistivity water, we show herein, for the first time, that heat production is only evident for AuNPs of diameters ≤10 nm, indicating a unique size-dependent heating behavior not previously observed. Heat production has also shown to be linearly dependent on both AuNP concentration and total surface area and was severely attenuated upon AuNP aggregation. These relationships have been further validated using permittivity analysis across a frequency range of 10 MHz–3 GHz as well as static conductivity measurements. Theoretical evaluations suggest that the heating mechanism can be modeled by the electrophoretic oscillation of charged AuNPs across finite length scales in response to a time-varying electric field. It is anticipated these results will assist future development of nanoparticle-assisted heat production by RF fields for applications such as targeted cancer hyperthermia.
Alumoxane/ferroxane nanoparticles for the removal of viral pathogens: the importance of surface functionality to nanoparticle activity
(The Royal Society of Chemistry, 2012) Maguire-Boyle, Samuel J.; Liga, Michael V.; Li, Qilin; Barron, Andrew R.; Richard E. Smalley Institute for Nanoscale Science and Technology
A bi-functional nano-composite coating has been created on a porous Nomex fabric support as a trap for aspirated virus contaminated water. Nomex fabric was successively dip-coated in solutions containing cysteic acid functionalized alumina (alumoxane) nanoparticles and cysteic acid functionalized iron oxide (ferroxane) nanoparticles to form a nanoparticle coated Nomex (NPN) fabric. From SEM and EDX the nanoparticle coating of the Nomex fibers is uniform, continuous, and conformal. The NPN was used as a filter for aspirated bacteriophage MS2 viruses using end-on filtration. All measurements were repeated to give statistical reliability. The NPN fabrics show a large decrease as compared to Nomex alone or alumoxane coated Nomex . An increase in the ferroxane content results in an equivalent increase in virus retention. This suggests that it is the ferroxane that has an active role in deactivating and/or binding the virus. Heating the NPN to 160 C results in the loss of cysteic acid functional groups (without loss of the iron nanoparticleﾒs core structure) and the resulting fabric behaves similar to that of untreated Nomex , showing that the surface functionalization of the nanoparticles is vital for the surface collapse of aspirated water droplets and the absorption and immobilization of the MS2 viruses. Thus, for virus immobilization, it is not sufficient to have iron oxide nanoparticles per se, but the surface functionality of a nanoparticle is vitally important in ensuring efficacy.
Hybrid 2D Nanomaterials as Dual-mode Contrast Agents in Cellular Imaging
(Wiley-VCH Verlag, 2012) Narayanan, Tharangattu N.; Gupta, Bipin K.; Vithayathil, Sajna A.; Aburto, Rebeca R.; Mani, Sendurai A.; Taha-Tijerina, Jaime; Xie, Bin; Kaipparettu, Benny A.; Torti, Suzy V.; Ajayan, Pulickel M.
RiceWrist Robotic Device for Upper Limb Training: Feasibility Study and Case Report of Two Tetraplegic Persons with Spinal Cord Injury
(Scientific & Academic Publishing, 2012) Kadivar, Z.; Sullivan, J.L.; Eng, D.P.; Pehlivan, A.U.; O'Malley, M.K.; Yozbatiran, N.; Berliner, J.DO.; Boake, C.; Francisco, G.E.
Regaining upper extremity function is the primary concern of persons with tetraplegia caused by spinal cord injury (SCI). Robotic rehabilitation has been inadequately tested and underutilized in rehabilitation of the upper extremity in the SCI population. Given the acceptance of robotic training in stroke rehabilitation and SCI gait training, coupled with recent evidence that the spinal cord, like the brain, demonstrates plasticity that can be enhanced by repetitive movement training such as that available with robotic devices, it is probable that robotic upper extremity training of persons with SCI could be clinically beneficial. The primary goal of this pilot study was to test the feasibility of using a novel robotic device –the RiceWrist Exoskeleton- for rehabilitation of the upper limbs (UL) of two tetraplegic persons with incomplete SCI. Two pilot experiments were conducted. Experiment 1was the first novel attempt to administer treatment with the RiceWrist. The left UL of a tetraplegic subject was treated during seven therapy sessions. The subject’s feedback and the investigator’s obser-vations were used to enhance the robotic device and the corresponding graphical-interface. In Experiment 2, a second tetra-plegic subject underwent 10 three-hour training sessions administered by a physical therapist. Smoothness factor (FS) –a new measure developed in Experiment 1- was used as the primary outcome to test the subject’s performance before and after the training. The RiceWrist was modified according to the feedback obtained in Experiment 1. Thereafter, the device was suc-cessfully administered for upper limb training of the tetraplegic individual. Noticeable improvements in FS were observed for the stronger arm of the subject who completed 10 sessions of training. Improvements were also observed in the subject’s hand according to the Jebsen-Taylor Hand Function Test. Results from this study suggest a potential application of the RiceWrist for rehabilitation of SCI individuals and offer valuable information regarding development of UL robotic devices for this population.
Roll up nanowire battery from silicon chips
(National Academy of Sciences, 2012) Vlad, Alexandru; Reddy, Arava Leela Mohana; Ajayan, Anakha; Singh, Neelam; Gohy, Jean-François; Melinte, Sorin; Ajayan, Pulickel M.
Here we report an approach to roll out Li-ion battery components from silicon chips by a continuous and repeatable etch-infiltratepeel cycle. Vertically aligned silicon nanowires etched from recycled silicon wafers are captured in a polymer matrix that operates as Liþ gel-electrolyte and electrode separator and peeled off to make multiple battery devices out of a single wafer. Porous, electrically interconnected copper nanoshells are conformally deposited around the silicon nanowires to stabilize the electrodes over extended cycles and provide efficient current collection. Using the above developed process we demonstrate an operational full cell 3.4 V lithium-polymer silicon nanowire (LIPOSIL) battery which is mechanically flexible and scalable to large dimensions.
Equilibrium at the edge and atomistic mechanisms of graphene growth
(National Academy of Sciences, 2012) Artyukhov, Vasilii I.; Liu, Yuanyue; Yakobson, Boris I.; Richard E. Smalley Institute for Nanoscale Science and Technology
The morphology of graphene is crucial for its applications, yet an adequate theory of its growth is lacking: It is either simplified to a phenomenological-continuum level or is overly detailed in atomistic simulations, which are often intractable. Here we put forward a comprehensive picture dubbed nanoreactor, which draws from ideas of step-flow crystal growth augmented by detailed first-principles calculations. As the carbon atoms migrate fromthe feedstock to catalyst to final graphene lattice, they go through a sequence of states whose energy levels can be computed and arranged into a step-by-step map. Analysis begins with the structure and energies of arbitrary edges to yield equilibrium island shapes. Then, it elucidates how the atoms dock at the edges and how they avoid forming defects. The sequence of atomic row assembly determines the kinetic anisotropy of growth, and consequently, graphene island morphology, explaining a number of experimental facts and suggesting how the growth product can further be improved. Finally, this analysis adds a useful perspective on the synthesis of carbon nanotubes and its essential distinction from graphene.
Derivation of response spectrum compatible non-stationary stochastic processes relying on Monte Carlo-based peak factor estimation
(Techno Press, 2012) Giaralis, Agathoklis; Spanos, Pol D.
In this paper a novel non-iterative approach is proposed to address the problem of deriving non-stationary stochastic processes which are compatible in the mean sense with a given (target) response (uniform hazard) spectrum (UHS) as commonly desired in the aseismic structural design regulated by contemporary codes of practice. This is accomplished by solving a standard over-determined minimization problem in conjunction with appropriate median peak factors. These factors are determined by a plethora of reported new Monte Carlo studies which on their own possess considerable stochastic dynamics merit. In the proposed approach, generation and treatment of samples of the processes individually on a deterministic basis is not required as is the case with the various approaches found in the literature addressing the herein considered task. The applicability and usefulness of the approach is demonstrated by furnishing extensive numerical data associated with the elastic design UHS of the current European (EC8) and the Chinese (GB 50011) aseismic code provisions. Purposely, simple and thus attractive from a practical viewpoint, uniformly modulated processes assuming either the Kanai-Tajimi (KT) or the Clough-Penzien (C-P) spectral form are employed. The Monte Carlo studies yield damping and duration dependent median peak factor spectra, given in a polynomial form, associated with the first passage problem for UHS compatible K-T and C-P uniformly modulated stochastic processes. Hopefully, the herein derived stochastic processes and median peak factor spectra can be used to facilitate the aseismic design of structures regulated by contemporary code provisions in a Monte Carlo simulation based or stochastic dynamics-based context of analysis.
Rapid fabrication of 3D terahertz split ring resonator arrays by novel single-shot direct write focused proximity field nanopatterning
(Optical Society of America, 2012) Singer, Jonathan P.; Lee, Jae-Hwang; Kooi, Steven E.; Thomas, Edwin L.
For the next generation of phoXonic, plasmonic, optomechanical and microfluidic devices, the capability to create 3D microstructures is highly desirable. Fabrication of such structures by conventional top-down techniques generally requires multiple timeconsuming steps and is limited in the ability to define features spanning multiple layers at prescribed angles. 3D direct write lithography (3DDW) has the capability to draw nearly arbitrary structures, but is an inherently slow serial writing process. Here we present a method, denoted focused proximity field nanopatterning (FPnP), that combines 3DDW with single or multiphoton interference lithography (IL). By exposing a thick photoresist layer having a phase mask pattern imprinted on its surface with a tightly focused laser beam, we produce locally unique complex structures. The morphology can be varied based on beam and mask parameters. Patterns may be written rapidly in a single shot mode with arbitrary positions defined by the direct write, thus exploiting the control of 3DDW with the enhanced speed of phase mask IL. Here we show the ability for this technique to rapidly produce arrays of “stand-up” far IR resonators.
Electrical performance of monolayer MoS2 field-effect transistors prepared by chemical vapor deposition
(American Institute of Physics, 2013) Amani, Matin; Chin, Matthew L.; Birdwell, A. Glen; O'Regan, Terrance P.; Najmaei, Sina; Liu, Zheng; Ajayan, Pulickel M.; Lou, Jun; Dubey, Madan
Molybdenum disulfide (MoS2) field effect transistors (FET) were fabricated on atomically smooth large-area single layers grown by chemical vapor deposition. The layer qualities and physical properties were characterized using high-resolution Raman and photoluminescence spectroscopy, scanning electron microscopy, and atomic force microscopy. Electronic performance of the FET devices was measured using field effect mobility measurements as a function of temperature. The back-gated devices had mobilities of 6.0 cm2/V s at 300K without a high-j dielectric overcoat and increased to 16.1 cm2/V s with a high-j dielectric overcoat. In addition the devices show on/off ratios ranging from 105 to 109.
Second harmonic microscopy of monolayer MoS2
(American Physical Society, 2013) Kumar, Nardeep; Najmaei, Sina; Cui, Qiannan; Ceballos, Frank; Ajayan, Pulickel M.; Lou, Jun; Zhao, Hui
We show that the lack of inversion symmetry in monolayer MoS2 allows strong optical second harmonic generation. The second harmonic of an 810-nm pulse is generated in a mechanically exfoliated monolayer, with a nonlinear susceptibility on the order of 10−7 m/V. The susceptibility reduces by a factor of seven in trilayers, and by about two orders ofmagnitude in even layers. A proof-of-principle second harmonicmicroscopymeasurement is performed on samples grown by chemical vapor deposition, which illustrates potential applications of this effect in the fast and noninvasive detection of crystalline orientation, thickness uniformity, layer stacking, and single-crystal domain size of atomically thin films of MoS2 and similar materials.
Blueshift of the A-exciton peak in folded monolayer 1H-MoS2
(American Physical Society, 2013) Crowne, Frank J.; Amani, Matin; Birdwell, A. Glen; Chin, Matthew L.; O'Regan, Terrance P.; Najmaei, Sina; Liu, Zheng; Ajayan, Pulickel M.; Lou, Jun; Dubey, Madan
Using the Plasmon Linewidth To Calculate the Time and Efficiency of Electron Transfer between Gold Nanorods and Graphene
(American Chemical Society, 2013) Hoggard, Anneli; Wang, Lin-Yung; Ma, Lulu; Fang, Ying; You, Ge; Olson, Jana; Liu, Zheng; Chang, Wei-Shun; Ajayan, Pulickel M.; Link, Stephan; Laboratory for Nanophotonics
We present a quantitative analysis of the electron transfer between single gold nanorods and monolayer graphene under no electrical bias. Using single-particle dark-field scattering and photoluminescence spectroscopy to access the homogeneous linewidth, we observe broadening of the surface plasmon resonance for gold nanorods on graphene compared to nanorods on a quartz substrate. Because of the absence of spectral plasmon shifts, dielectric interactions between the gold nanorods and graphene are not important and we instead assign the plasmon damping to charge transfer between plasmon-generated hot electrons and the graphene that acts as an efficient acceptor. Analysis of the plasmon linewidth yields an average electron transfer time of 160 ± 30 fs, which is otherwise difficult to measure directly in the time domain with single-particle sensitivity. In comparison to intrinsic hot electron decay and radiative relaxation, we furthermore calculate from the plasmon linewidth that charge transfer between the gold nanorods and the graphene support occurs with an efficiency of ∼10%. Our results are important for future applications of light harvesting with metal nanoparticle plasmons and efficient hot electron acceptors as well as for understanding hot electron transfer in plasmon-assisted chemical reactions.
Fluorinated Graphene Oxide: a New Multimodal Material for Biological Applications
(Wiley, 2013) Romero-Aburto, Rebeca; Narayanan, Tharangattu N.; Nagaoka, Yutaka; Hasumura, Takashi; Mitcham, Trevor M.; Fukuda, Takahiro; Cox, Paris J.; Bouchard, Richard R.; Maekawa, Toru; Kumar, Sakthi; Torti, Suzy V.; Mani, Sendurai A.; Ajayan, Pulickel M.
Fluorinated graphene oxide (FGO) is reported for the first time as a magnetically responsive drug carrier that can serve as a MRI and photoacoustic contrast agent, under pre-clinical settings, as well as a photothermal therapy Its hydrophilic nature facilitates biocompatibility. FGO as a broad wavelength absorber, with high charge transfer and strong nonlinear scattering is optimal for NIR laser-induced hyperthermia.
Systematic Construction of Higher Order Bases for the Finite Element Analysis of Multiscale Elliptic Problems
(Elsevier, 2013) Soghrati, Soheil; Stanciulescu, Ilinca
We introduce a new approach to deriving higher order basis functions implemented in the Multiscale Finite Element Method (MsFEM) for elliptic problems. MsFEM relies on capturing small scale features of the system through bases utilized in the coarse scale solution. The proposed technique for the derivation of such bases is completely systematic and the increase in the associated computational cost is insignificant. We also show that the implementation of higher order bases in MsFEM leads to similar advantages as using higher order Lagrangian shape functions in the conventional finite element method. Various numerical examples for heat transfer problems with periodic or heterogeneous thermal properties are given to demonstrate the efficiency and improved characteristics of the proposed higher order bases.
A Pre-Clinical Framework for Neural Control of a Therapeutic Upper-Limb Exoskeleton
(IEEE, 2013) Blank, Amy; O'Malley, Marcia K.; Francisco, Gerard E.; Contreras-Vidal, Jose L.
In this paper, we summarize a novel approach to robotic rehabilitation that capitalizes on the benefits of patient intent and real-time assessment of impairment. Specifically, an upper-limb, physical human-robot interface (the MAHI EXO-II robotic exoskeleton) is augmented with a noninvasive brain-machine interface (BMI) to include the patient in the control loop, thereby making the therapy “active” and engaging patients across a broad spectrum of impairment severity in the rehabilitation tasks. Robotic measures of motor impairment are derived from real-time sensor data from the MAHI EXO-II and the BMI. These measures can be validated through correlation with widely used clinical measures and used to drive patient-specific therapy sessions adapted to the capabilities of the individual, with the MAHI EXO-II providing assistance or challenging the participant as appropriate to maximize rehabilitation outcomes. This approach to robotic rehabilitation takes a step towards the seamless integration of BMIs and intelligent exoskeletons to create systems that can monitor and interface with brain activity and movement. Such systems will enable more focused study of various issues in development of devices and rehabilitation strategies, including interpretation of measurement data from a variety of sources, exploration of hypotheses regarding large scale brain function during robotic rehabilitation, and optimization of device design and training programs for restoring upper limb function after stroke.
Characterizing Effective d31 Values for PZT from the Nonlinear Oscillations of Clamped-Clamped Micro- Resonators
(Journal of Mechanical Engineering, 2013) Dick, Andrew J.; Nonlinear Phenomena Laboratory
In order to accurately predict the performance of micro-electromechanical systems which use piezoelectric material, precise knowledge of the piezoelectric coefficients is critical. Current material characterization methods rely on either simple structures restricted to small amplitude, linear oscillations or consider the piezoelectric material separate from the specific micro-scale device. A method is proposed for the characterization of the effective transverse piezoelectric coefficient d31 of lead zirconate titanate in a clamped-clamped micro-beam resonator experiencing nonlinear oscillations. Parameter trends identified by using a parametric identification scheme are analyzed and an approach is presented to calculate the linear piezoelectric coefficient. This method utilizes the relationship between a DC bias added to the excitation signal and the frequency shift experienced by the nonlinear response behavior. Through an additional numerical study, the sensitivity of the results to changes in the device length is identified and all data sets provide the same coefficient value when a length variation of less than 2% is allowed.
Super-stretchable, Transparent Carbon Nanotube-Based Capacitive Strain Sensors for Human Motion Detection
(Nature Publishing Group, 2013) Cai, Le; Song, Li; Luan, Pingshan; Zhang, Qiang; Zhang, Nan; Gao, Qingqing; Zhao, Duan; Zhang, Xiao; Tu, Min; Yang, Feng; Zhou, Wenbin; Fan, Qingxia; Luo, Jun; Zhou, Weiya; Ajayan, Pulickel M.; Xie, Sishen
Realization of advanced bio-interactive electronic devices requires mechanically compliant sensors with the ability to detect extremely large strain. Here, we design a new multifunctional carbon nanotube (CNT) based capacitive strain sensors which can detect strains up to 300% with excellent durability even after thousands of cycles. The CNT-based strain gauge devices exhibit deterministic and linear capacitive response throughout the whole strain range with a gauge factor very close to the predicted value (strictly 1), representing the highest sensitivity value. The strain tests reveal the presented strain gauge with excellent dynamic sensing ability without overshoot or relaxation, and ultrafast response at sub-second scale. Coupling these superior sensing capabilities to the high transparency, physical robustness and flexibility, we believe the designed stretchable multifunctional CNT-based strain gauge may have various potential applications in human friendly and wearable smart electronics, subsequently demonstrated by our prototypical data glove and respiration monitor.
Recent Advances in Optical Limiting Properties of Fluorinated Graphene Oxides
(SPIE, 2013) Chantharasupawong, Panit; Philip, Reji; Narayanan, Narayanan T.; Sudeep, Parambath M.; Mathkar, Akshay; Ajayan, Pulickel M.; Thomas, Jayan
There is a substantial interest in finding materials with high nonlinear optical (NLO) properties of materials because of its attractive applications in optical limiting for safety protections. In an effort to develop highly performing optical limiting materials, recently we have found that fluorination of graphene oxides leads to improvement in their NLO properties.

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