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Elastic and viscoelastic characterization of microcapsules for drug delivery using a force-feedback MEMS microgripper

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BIOMEDICAL MICRODEVICES 2009年第2期11卷 421-427页

作者： Kim, Keekyoung Liu, Xinyu Zhang, Yong Cheng, Ji Yu Wu, Xiao Sun, Yu Univ Toronto Adv Micro & Nanosyst Lab Toronto ON M5S 3G8 Canada Univ Toronto Leslie Dan Fac Pharm Toronto ON M5S 3M2 Canada

This paper reports a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper and its application to micro-scale compression testing of swollen hydrogel microcapsules at wet state during manipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5 nN) and the other for gripping force measurements (force resolution: 19.9 nN). With the capability of resolving gripping forces down to 19.9 nN and material deformations with a 20.5 nm resolution, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules (15-25 mu m), demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials.

关键词： MEMS microgripper Micro-scale compression testing Hydrogel microcapsule Young's modulus viscoelastic parameters

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Manipulation at the NanoNewton Level: Micrograpsing for Mechanical Characterization of Biomaterials

Manipulation at the NanoNewton Level: Micrograpsing for Mech...

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IEEE International Conference on Robotics and Automation

作者： Kim, Keekyoung Liu, Xinyu Zhang, Yong Cheng, Ji Wu, Xiao Yu Sun, Yu Univ Toronto Adv Micro & Nanosyst Lab 5 Kings Coll Rd Toronto ON M5S 3G8 Canada Univ Toronto Leslie Dan Fac Pharm Toronto ON M5S 3G8 Canada

ISBN: (纸本)9781424427888

This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15-25 mu m) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials.

关键词： Micromanipulation MEMS microgripper micrograsping force feedback hydrogel microcapsule Young's modulus viscoelastic parameters

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Optofluidic stretching of RBCs using single optical tweezers

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JOURNAL OF BIOPHOTONICS 2008年第6期1卷 522-525页

作者： Mohanty, Samarendra K. Uppal, Abha Gupta, Pradeep K. Raja Ramanna Ctr Adv Technol Laser Biomed Applicat & Instrumentat Div Indore 452013 India Univ Calif Irvine Beckman Laser Inst Irvine CA 92612 USA

Our previous studies demonstrated a huge difference in rotational speed of trapped red blood cells under diseased condition. which was presumably attributed to change in viscoclastic properties. Here, we report use of single optical tweezers combined with viscous drag for stretching of the trapped cell. Significant differences were observed in the measured viscoclastic parameters of fresh and aged/malaria-infected RBCs under hypotonic condition. The technique was also found to provide information about adhesion properties of RBCs. [GRAPHICS] One end of RBC being held by optical tweezes (clotted arrows), while subjected to microfluiclic flow (solid arrow). (c) 2008 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词： Optical tweezers red blood cell viscoelastic parameters disease diagnosis

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Cytomechanics of oscillatory contractions. 1. Measuring active mechanical properties of the Physarum polycephalum plasmodial strands

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Biophysics 2008年第6期53卷 580-585页

作者： Morozov, M.A. Teplov, V.A. Institute of Theoretical and Experimental Biophysics Russian Academy of Sciences Pushchino Moscow oblast 142290 Russian Federation

An experimental device with an inexpensive electronic-mechanical measurement system was designed to clarify the role of mechanical tensions in cell activation. This device provides for maintaining a specified kinetics of either the object's length or applied load to measure its tension force or deformation. The experiments were performed with the plasmodium of Physarum polycephalum, a giant unicellular organism, which is a classical object for studying a nonmuscle motility. Several examples of the longitudinal dynamics of the plasmodial strand and its activation in response to periodic switching at certain phases of the contraction- relaxation cycle are described. © 2008 Pleiades Publishing, Ltd.

关键词： Biomechanics Cell motility Plasmodium of Physarum polycephalum Self-oscillations viscoelastic parameters

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Rheological analysis of asphalt tested by Bending Beam Rheometer

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Wuhan Ligong Daxue Xuebao (Jiaotong Kexue Yu Gongcheng Ban)/Journal of Wuhan University of Technology (Transportation Science and Engineering) 2006年第2期30卷 205-208页

作者： Feng, Jiliang Transportation College South East University Nanjing 210096 China

Based on the theory of viscoelasticity, Burgers model is constructed to represent the relationship between stress and strain, and to deduce the creep rule of asphalt in BBR. Then DPS statistical software is applied to obtain the viscoelastic parameters of asphalt with the nonlinear regression model. Moreover, the basic principle of SHRP assessing method of BBR test is discussed in this paper. The BBR test of Shell 70# asphalt is selected as an example to verify the rheological model, as well as the viscoelastic parameters are imposed to predict DTT stress at the same temperature. The results demonstrate that Burgers model can be used to assess properties of asphalt binders.

关键词： Bending Beam Rheometer Burgers Model Rheology viscoelastic parameters

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A new unified method for determining viscoelastic parameters (η₀, Ψ₁₀,G⁰_N and J⁰_e), topologically constrained dimension numbers (n′, a and (v)over-tilde) and molecular weight (Me, Mc and Mn) of polymers from single shear flow measurements

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POLYMER TESTING 2002年第7期21卷 823-831页

作者： Song, MS Zhang, C Hu, GX Li, XY Beijing Univ Chem Technol Sch Mat Sci & Engn Minst Educ Key Lab Sci & Technol Controllable Chem React Beijing 100029 Peoples R China

Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated. The theoretical relations of eta((gamma) over dot) and Psi(10)((gamma) over dot) to shear rate ((gamma) over dot) and topologically constrained dimension number n' and a were derived. Then, dependence of linear viscoelastic parameters (eta(0) and G(N)(0)) and topologically constrained dimension numbers (n', a and (v) over tilde) on the primary molecular weight (Mn), molecular weight between entanglements (Mc) and the entanglement sites sequence distribution on polymer chain are obtained. A new method for determination of viscoelastic parameters (eta(0),Psi(10),G(N)(0) and J(e)(0)), topologically constrained dimension number (n', a and (v) over tilde) and molecular weight (Mn, Mc and Me) from the simple shear flow measurements was proposed. It was used to determine those parameters and structure of HDPE, and good agreement between these values with those obtained by other methods was found. The agreement provides a quantitative verification for the molecular theory of non-linear viscoelasticity with constrained entanglement in polymer melts. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： material function constrained entanglements viscoelastic parameters topologically constrained dimension determining molecular weights non-linear viscoealsticity

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Constitutive equations of viscoelasticity and estimation of viscoelastic parameters of unidirectional fibrous polymeric composites

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JOURNAL OF COMPOSITE MATERIALS 2000年第19期34卷 1624-1639页

作者： Klasztorny, M Wilczynski, AP Warsaw Univ Technol Inst Mech & Design PL-02524 Warsaw Poland

A method for modelling viscoelastic properties of fibre reinforced polymeric composites, based on the original reinforcement theory as well as original description of viscoelasticity of the matrix [4], is developed in the paper. The composite material consists of a viscoelastic isotropic polymer matrix and elastic monotropic fibres. In order to model arbitrary shear/bulk creep in the matrix, the Mittag-Leffler fractional exponential functions are used as the generating functions. Hence, the viscoelastic model of the polymer matrix is described with 2 elastic constants and 6 viscoelastic constants, while the elastic properties of the fibres are described with 5 well-known elastic constants. Both groups of the material constants can be estimated experimentally relatively easy. Coupled constitutive equations of linear viscoelasticity of a unidirectional fibrous polymeric composite, modeled as a homogeneous monotropic material are formulated in the study. The viscoelastic model of the composite is described using 5 elastic constants and 27 viscoelastic constants, i.e., 9 long-lasting compliance ratios, 9 retardation times, and 9 fractions defining an order of the fractional exponential functions. The elastic-viscoelastic analogy is used to predict theoretically the complex compliances of the composite [4]. An iterative optimization procedure for theoretical prediction of the viscoelastic constants of the composite is formulated, computerised and positively tested on the selected composite materials.

关键词： unidirectional fibrous composite isotropic viscoelastic matrix monotropic elastic fibres homogenisation constitutive equations of linear viscoelasticity viscoelastic parameters optimisation procedure

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Dynamic mechanical analyses and flexural fatigue of PVC foams

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COMPOSITE STRUCTURES 2002年第2期58卷 175-183页

作者： Kanny, K Mahfuz, H Carlsson, LA Thomas, T Jeelani, S Tuskegee Univ TCAM Tuskegee AL 36088 USA Florida Atlantic Univ Dept Mech Engn Boca Raton FL 33431 USA

Flexural fatigue tests were performed on cross-linked PVC foams of densities in the range from 75 to 300 kg/m(3) at a frequency of 3 Hz and at a stress ratio, R = 0.1. S-N diagrams were generated, and the failure mechanisms were examined. The fatigue behavior was found to be similar to structural materials with a fatigue strength that increased with increased foam density. The final failure event was catastrophic due to crack propagation initiating at the tension side of the specimen. SEM analyses performed on the R300 foam specimen revealed cell wall cracking and densification of the foam during the earlier part of the fatigue life. This densification contributed to stiffening of foam specimens. viscoelastic parameters of the foams were determined using a dynamic mechanical analyzer over a frequency range of 1-10 Hz. For the virgin specimens it was found that the viscoelastic moduli and damping ratio were quite independent of frequency over this range of frequencies. viscoelastic parameters were also extracted at intermediate stages of fatigue life and the residual properties were studied with respect to the number of fatigue cycles. It was observed that the variation of dynamic mechanical analysis (DMA) parameters with the number of fatigue cycles was consistent with the variation of residual global stiffness of the material. Experimental details and the analyses of fatigue behavior are presented in this paper. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： fatigue viscoelastic parameters foam cores DMA

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Validating the generality and predictive ability of unified rheological curves for unmodified paving asphalts

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CONSTRUCTION AND BUILDING MATERIALS 2000年第6-7期14卷 325-339页

作者： Shenoy, A Turner Fairbank Highway Res Ctr Mclean VA 22101 USA

Fundamental rheological properties of unmodified paving asphalts have been shown to form unified curves when the material's volumetric flow rate MVR (in cm(3)/10 min) is used as a normalizing factor. The generality of the unification technique is shown by analyzing rheological data for a wide variety of unmodified core asphalts under different temperature conditions. Based on a broad spectrum of covered data, it is concluded that the unified curves are applicable to all unmodified paving asphalts. The predictive ability of the unified curves is then checked and found to give reasonably reliable information. Thus, using a simple parameter like MVR which is determined quite accurately on a relatively inexpensive, easy-to-use flow measurement device (FMD), all fundamental rheological parameters of unmodified paving asphalts can be calculated from the unified curves without the actual data generation of viscoelastic properties through the dynamic shear rheometer. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： asphalt rheology unified curves viscoelastic parameters flow measurement device material's volumetric-flow rate

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Measurement of viscoelastic properties of root cell walls affected by low pH in lateral roots of Pisum sativum L.

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PLANT AND SOIL 2000年第1期226卷 21-28页

作者： Tanimoto, E Fujii, S Yamamoto, R Inanaga, S Nagoya City Univ Inst Nat Sci Div Biomol Sci Nagoya Aichi 4678501 Japan Tezukayama Coll Biol & Chem Lab Nara 6310034 Japan Tottori Univ Arid Land Res Ctr Tottori 6800001 Japan

Mechanical extensibility of the cell wall limits the elongation growth of roots. Low pH, ranging from pH 3-4.5, induces rapid elongation of excised roots, a phenomenon known as acid growth. The creep-extension analysis was carried out to measure and elucidate the viscoelastic properties of root cell walls in the acidic environment in vitro. The viscoelastic properties were determined at the elongation zone of the lateral roots of pea ( Pisum sativum L. cv. Alaska) and described by the physical parameters of three elastic (E-0, E-1, E-2) and three viscosity (eta (0), eta (1), eta (2)) parameters using a Kelvin-Voigt-Burgers' model. The present method could measure the viscoelasticity of 1-mm long root zones from 2 to 9 mm behind the tip. Among the parameters, E-0 and eta (0) were the most significant parameters to represent the whole extensibility of the roots. The parameter eta (0) markedly declined in response to the environmental low pH (acid growth), whereas other parameters were not much affected by low pH. Relationship between the change in these physical parameters and the change in cell wall extensibility under low pH was discussed in order to elucidate the rheological processes taking place in the elongating cell walls.

关键词： acid pH cell wall creep extension lateral roots Pisum sativum viscoelastic parameters

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