Hansong Zeng - Academia.edu (original) (raw)

Papers by Hansong Zeng

A simulation approach for predicting wear coefficient of Ultra High Molecular Weight PolyEthylene... more A simulation approach for predicting wear coefficient of Ultra High Molecular Weight PolyEthylene (UHMWPE) rubbing against CoCr alloy is proposed, which considers the combined contributions of mixed lubrication, crosslink density, plowing and adhesive wear. Mixed lubrication model is used to calculate the relative contribution of fluid and asperity contact. Discrete bead-spring element method is used to obtain the indentation depth under an asperity contact load, while the plowing is computed by molecular dynamic algorithms using LAMMPS. The adhesive wear is determined using energy method coupled with Hertz contact theory. The new approach is validated by comparing predicted wear rate with that measured from experiment in literature.

Volume 2: Biomedical and Biotechnology Engineering, 2008

ABSTRACT

Lab on a chip, Jan 21, 2014

Insect compound eyes and human camera eyes are two exquisite optical systems created by nature. T... more Insect compound eyes and human camera eyes are two exquisite optical systems created by nature. The compound eye boasts an angle of view (AOV) up to 180° thanks to its hemispherical arrangement of hundreds of prime microscale lenses. The camera eye, on the other hand, can change shape to focus on objects at various depths, yet accepts light within a smaller AOV. Imitations of either imaging system have been abundant but with limited success. Here, we describe a reconfigurable polymeric optofluidic device that combines the architectural merits of both vision mechanisms, featuring a large AOV (up to 120°) with adaptive focusing capabilities (from 0 to 275 diopter (D)). This device consists of bi-layered microfluidics: an array of millimeter-sized fluidic lenses is integrated into the top layer and arranged on an elastomeric membrane embedded within the bottom layer. The membrane can be deformed from a planar surface into a series of dome-shaped geometries, rearranging individual fluid...

Journal of Medical Devices, 2008

Massage therapies are widely used for improving and restoring the function of human tissues. It i... more Massage therapies are widely used for improving and restoring the function of human tissues. It is generally accepted that such therapies promote human health and well-being by several possible mechanisms, including increase in blood flow and parasympathetic activity, release of relaxation hormones, and inhibition of muscle tension, neuromuscular excitability, and stress hormones. Nonetheless, most of the purported beneficial/adverse effects of massage are based on anecdotal experiences, providing little insight on its effectiveness or the mechanisms underlying its usefulness. Furthermore, most studies to date have not quantitatively demonstrated the efficacy of massage on human health. This might be due to the lack of appropriate tools necessary for the application of quantitatively controlled loading and for the evaluation of the subsequent responses. To address this issue, we developed a device that applies compression in lengthwise strokes to the soft tissues of the New Zealand white rabbit, thereby mimicking the rubbing and effleurage techniques of massage. This device permits control of the magnitude and frequency of mechanical load applied to the rabbit's hind limb for various durations. The measurement of tissue compliance and the viscoelastic properties as a function of loading parameters was also demonstrated. Findings of this study suggest that this device offers a quantitative analysis of the applied loads on the tissue to determine an optimal range of loading conditions required for the safe and effective use of massage therapies. Downloaded From: http://medicaldevices.asmedigitalcollection.asme.org/ on 03/03/2015 Terms of Use: http://asme.org/terms Journal of Medical Devices DECEMBER 2008, Vol. 2 / 041003-3 Downloaded From: http://medicaldevices.asmedigitalcollection.asme.org/ on 03/03/2015 Terms of Use: http://asme.org/terms Journal of Medical Devices DECEMBER 2008, Vol. 2 / 041003-7 Downloaded From: http://medicaldevices.asmedigitalcollection.asme.org/ on 03/03/2015 Terms of Use: http://asme.org/terms

Sensors and Actuators B: Chemical, 2009

Fabrication of non-photodefinable polymer materials into microstructures is one of the major chal... more Fabrication of non-photodefinable polymer materials into microstructures is one of the major challenges for development of functional biomedical microchips. In this paper, we describe a vacuum-assisted microfluidic approach for patterning polydimethylsiloxane (PDMS) microstructures on a solid substrate of a different material. The results show that liquid prepolymer driven by the vacuum-induced differential pressure can fill microchannels at a greatly enhanced rate than that driven by capillary forces. This allows fast patterning of liquid prepolymer into small structures before the polymer becomes too viscous to flow. This approach also eliminates the diffusion of liquid prepolymer into undesired regions. Discrete polymer microstructures can thus be successfully fabricated on a solid substrate. The effectiveness of the fabrication method is demonstrated by creating helical structures, suspended microbridges, and doublelayered structures. The characteristic dimensions of the demonstrated structures are less than 10 m. This approach is expected to facilitate the use of these non-photodefinable polymer microstructures, into miniaturized systems for micro-total-analysis.

Sensors and Actuators B: Chemical, 2011

This paper demonstrates a liquid droplet-based motion sensing system which has the advantages of ... more This paper demonstrates a liquid droplet-based motion sensing system which has the advantages of simple fabrication, low power consumption and digital signal processing. The sensor consists of a dielectric substrate patterned with an array of microelectrodes, and a saline droplet as the proof mass. Once an external linear acceleration is applied, the inertial force moves the droplet on the micropatterned substrate. The acceleration is determined from the movement profile detected by the microelectrodes. In order to enhance the threshold and the sensitivity of motion sensing, two surface treatment approaches are utilized to create superhydrophobic surfaces. The result shows that the minimal sliding angle that can move a 20 l droplet on the superhydrophobic surface is lower than 1 • , corresponding to a threshold of lower than 0.017 g. A lumped-parameter model is developed to estimate the dynamic behavior of the proposed system. The result shows that the frequency response of the droplet-based sensor is more significant at low frequencies than at high frequencies, which is distinct from solid-state accelerometers. Measurement under a constant acceleration shows that the predicted value derived from the measurement has a good match with the actual applied acceleration, validating the proposed system as a viable alternative for motion sensing.

Sensors, 2011

Recognition of body posture and motion is an important physiological function that can keep the b... more Recognition of body posture and motion is an important physiological function that can keep the body in balance. Man-made motion sensors have also been widely applied for a broad array of biomedical applications including diagnosis of balance disorders and evaluation of energy expenditure. This paper reviews the state-of-the-art sensing components utilized for body motion measurement. The anatomy and working principles of a natural body motion sensor, the human vestibular system, are first described. Various man-made inertial sensors are then elaborated based on their distinctive sensing mechanisms. In particular, both the conventional solid-state motion sensors and the emerging non solid-state motion sensors are depicted. With their lower cost and increased intelligence, man-made motion sensors are expected to play an increasingly important role in biomedical systems for basic research as well as clinical diagnostics.

IEEE Transactions on NanoBioscience, 2000

1-D magnetic nanowires provide a powerful tool for investigating biological systems because such ... more 1-D magnetic nanowires provide a powerful tool for investigating biological systems because such nanomaterials possess unique magnetic properties, which allow effective manipulation of cellular and subcellular objects. In this study, we report the rotational maneuver of ferromagnetic nanowires and their applications in cell manipulation. The rotational maneuver is studied under two different suspension conditions. The rotation of nanowires in the fluid is analyzed using Stokes flow assumption. Experimental results show that when the nanowires develop contacts with the bottom surfaces, the rotational maneuver under a modest external magnetic field can generate rapid lateral motion. The floating nanowires, on the other hand, do not exhibit substantial lateral displacements. Cell manipulation using skeletal myoblasts C2C12 shows that living cells can be manipulated efficiently on the bottom surface by the rotational maneuver of the attached nanowires. We also demonstrate the use of rotational maneuver of nanowires for creating 3-D nanowire clusters and multicellular clusters. This study is expected to add to the knowledge of nanowire-based cell manipulation and contribute to a full spectrum of control strategies for efficient use of nanowires for micro-total-analysis. It may also facilitate mechanobiological studies at cellular level, and provide useful insights for development of 3-D in vivo-like multicellular models for various applications in tissue engineering.

Applied Surface Science, 2013

ABSTRACT Silica nanoparticles coating and sintering is a widely-used approach for creating hydrop... more ABSTRACT Silica nanoparticles coating and sintering is a widely-used approach for creating hydrophobic and superhydrophobic surfaces. The role of substrate material in this process, however, has not been thoroughly investigated. In this work, the role of substrate material is examined by measuring surface wettability of three different substrate materials (glass, polyimide and copper) under systematically varied conditions. These surfaces are modulated from hydrophilic (water contact angle (WCA) < 90°) to superhydrophobic (WCA > 150°) by coating and sintering silica nanoparticles, followed by assembling a layer of fluorine compound. Static WCA characterization shows that surface wettability is not solely dependent on the concentration of the coating colloidal, but is also on the substrate material. In particular, copper substrate exhibits a larger WCA than glass and polyimide substrates. Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and Atomic Force Microscopy (AFM) characterizations show that the substrate material-dependent wettability is attributed to thermal-induced nanostructures on the copper surface, which contributes to the hierarchical micro-/nano- topography. This finding is important for designing hydrophobic/superhydrophobic surfaces comprised of different materials, especially those that would experience thermal cycles in surface functionalization and subsequent use.