Hansong Zeng

Fabrication of Skeletal Muscle Constructs by Topographic Activation of Cell Alignment

Skeletal muscle fiber construction for tissue‐engineered grafts requires assembly of unidirectionally aligned juxtaposed myotubes. To construct such a tissue, a polymer microchip with linearly aligned microgrooves was fabricated that could direct myoblast adaptation under stringent conditions. The closely spaced microgrooves fabricated by a modified replica molding process guided linear cellular alignment. Examination of the myoblasts by immunofluorescence microscopy demonstrated that the microgrooves with subcellular widths and appropriate height‐to‐width ratios were required for practically complete linear alignment of myoblasts. The topology‐dependent cell alignment encouraged differentiation of myoblasts into multinucleate, myosin heavy chain positive myotubes. The monolayer of myotubes formed on the microstructured chips allowed attachment, growth and differentiation of subsequent layers of linearly arranged myoblasts, parallel to the primary monolayer of myotubes. The consequent deposition of additional myoblasts on the previous layer of myotubes resulted in three‐dimensional multi‐layered structures of myotubes, typical of differentiated skeletal muscle tissue. The findings demonstrate that the on‐chip device holds promise for providing an efficient means for guided muscle tissue construction. Biotechnol. Bioeng. 2009;102: 624–631.

Sensing Movement: Microsensors for Body Motion Measurement

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.

Dynamic behavior of a liquid marble based accelerometer

This paper reports dynamic behavior of a liquid-state accelerometer prototype, which uses a liquid marble as the inertial proof mass. The governing equation is developed in comparison with the solid-state proof mass in a conventional accelerometer. Numerical analysis and experimental validation show that with appropriate parameters, resonance frequency of the sensor can be designed below 10 Hz, which falls into the range of low frequency body motion. The work provides the basis for development of a new paradigm of motion sensing with reduced fabrication and assembly complexity, which is promising for next generation accelerometers for low frequency motion detection.

Rotational Maneuver of Ferromagnetic Nanowires for Cell Manipulation

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.

A Mechatronic System for Quantitative Application and Assessment of Massage-Like Actions in Small Animals

Massage therapy has a long history and has been widely believed effective in restoring tissue function, relieving pain and stress, and promoting overall well-being. However, the application of massage-like actions and the efficacy of massage are largely based on anecdotal experiences that are difficult to define and measure. This leads to a somewhat limited evidence-based interface of massage therapy with modern medicine. In this study, we introduce a mechatronic device that delivers highly reproducible massage-like mechanical loads to the hind limbs of small animals (rats and rabbits), where various massage-like actions are quantified by the loading parameters (magnitude, frequency and duration) of the compressive and transverse forces on the subject tissues. The effect of massage is measured by the difference in passive viscoelastic properties of the subject tissues before and after mechanical loading, both obtained by the same device. Results show that this device is useful in identifying the loading parameters that are most conducive to a change in tissue mechanical properties, and can determine the range of loading parameters that result in sustained changes in tissue mechanical properties and function. This device presents the first step in our effort for quantifying the application of massage-like actions used clinically and measurement of their efficacy that can readily be combined with various quantitative measures (e.g., active mechanical properties and physiological assays) for determining the therapeutic and mechanistic effects of massage therapies.

An Engineering Approach for Quantitative Analysis of the Lengthwise Strokes in Massage Therapies

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.

On-Chip Blood Viscometer Towards Point-of-Care Hematological Diagnosis

Blood viscosity is an important hematological parameter which is widely used for the diagnosis of atherosclerosis, thrombosis and stroke. Currently used Couette rheometer drives the blood flow at a certain shear rate and measures the viscosity from the resistance toque towards the rotational shaft. Although effective, conventional rheometer is limited due to the complex configuration and the relatively large sample volume. More important, the rotating components hinder the miniaturization for point-of-care and unattended diagnosis. To address this, a microchip is reported for measuring the blood viscosity from the electrical impedances of the blood flowing inside a microchannel. This microdevice is advantageous over rotational viscometers in less sample consumption, rapid response and simple configuration. Considering the vital role of blood viscosity in cardiovascular disorders, this microchip provides a promising start point for on-chip hematological diagnosis.

Creating microstructures in electrospun nanofibers using a micropatterned collector chip

This paper reports a simple fabrication approach to create microstructures in electrospun polymer nanofibers. A collector chip with micropatterned electrodes generates electromechanical energy wells above the substrate, which induce selective patterning of polymer nanofibers on the collecting surface. This work provides a sound technology to interface electrospun nanomaterials to larger scaled structures. Particularly, it opens a door for developing MEMS components made of fibrous nanomaterials. It thus has immediate impacts in a broad array of biomedical and industrial applications including tissue engineering, drug delivery, and nanoelectronics.

Design and implementation of liquid droplet based motion sensing

This paper reports a liquid droplet based motion sensing system with advantages of simple fabrication, superior biocompatibility and binary signals. The sensor consists of a dielectric substrate and an array of microelectrodes patterned by surface micromachining techniques. In this sensing system, an ionic droplet behaves as the proof mass which responses to external applied acceleration. A lumped parameter model is built to compare the frequency response of such sensor with conventional solid proof mass accelerometers. Electrical signals detected by microelectrodes array are used to determine the applied acceleration based on droplet dynamics. Characterization of a prototype illustrates a good match between the predicted accelerations and the actual values.

Electrical Discharge based Microfabrication on Electrospun Nanofibers

This paper reports the use of electrical discharge for fabricating microstructures on electrospun polymer nanofibers. Microchips containing an array of conductive microelectrodes are fabricated. Electrical discharges are induced by applying high electrical voltage to these microelectrodes. The thermal energy generated by the micropatterned discharge arcs elevates the temperature in localized regions and melts polymer nanofibers in the close vicinity. Microstructures with the minimum line width as small as 20 ¿m are demonstrated. This method provides a promising start point to interface biodegradable nanofibrous materials to microstructures, which is significant for a broad array of biomedical and industrial applications.