Ultrafast High-pressure AC Electro-osmotic Pumps for Portable Biomedical Microfluidics

This paper details the development of an integrated AC electro-osmotic (ACEO) microfluidic pump for dilute electrolytes consisting of a long serpentine microchannel lined with three dimensional (3D) stepped electrode arrays. Using low AC voltage (1 Volt rms, 1 kHz), power (5 mW) and current (3.5 mA) in water, the pump is capable of generating a 1.4 kPa head pressure, a 100-fold increase over prior ACEO pumps, and a 1.37 mm/sec effective slip velocity over the electrodes without flow reversal. The integrated ACEO pump can utilize low ionic strength solutions such as distilled water as the working solution to pump physiological strength (100 mM) biological solutions in separate microfluidic devices, with potential applications in portable or implantable biomedical microfluidic devices. As a proof-of-concept experiment, the use of the ACEO pumps for DNA hybridization in a microfluidic microarray is demonstrated

Systematic {\em ab initio} study of the phase diagram of epitaxially strained SrTiO3_3

We use density-functional theory with the local-density approximation to study the structural and ferroelectric properties of SrTiO$_3$ under misfit strains. Both the antiferrodistortive (AFD) and ferroelectric (FE) instabilities are considered. The rotation of the oxygen octahedra and the movement of the atoms are fully relaxed within the constraint of a fixed in-plane lattice constant. We find a rich misfit strain-induced phase transition sequence and is obtained only when the AFD distortion is taken into account. We also find that compressive misfit strains induce ferroelectricity in the tetragonal low temperature phase only whilst tensile strains induce ferroelectricity in the orthorhombic phases only. The calculated FE polarization for both the tetragonal and orthorhombic phases increases monotonically with the magnitude of the strains. The AFD rotation angle of the oxygen octahedra in the tetragonal phase increases dramatically as the misfit strain goes from the tensile to compressive strain region whilst it decreases slightly in the orthorhombic (FO4) phase. This reveals why the polarization in the epitaxially strained SrTiO$_3$ would be larger when the tensile strain is applied, since the AFD distortion is found to reduce the FE instability and even to completely suppress it in the small strain region. Finally, our analysis of the average polar distortion and the charge density distribution suggests that both the Ti-O and Sr-O layers contribute significantly to the FE polarization

An Adaptive Controller Design for Flexible-joint Electrically-driven Robots With Consideration of Time-Varying Uncertainties

Almost all present control strategies for electrically-driven robots are under the rigid robot assumption. Few results can be found for the control of electrically driven robots with joint flexibility. This is because the presence of the joint flexibility greatly increases the complexity of the system dynamics. What is worse is when some system dynamics are not available and a good performance controller is required. In this paper, an adaptive design is proposed to this challenging problem. A backstepping-like procedure incorporating the model reference adaptive control is employed to circumvent the difficulty introduced by its cascade structure and various uncertainties. A Lyapunov-like analysis is used to justify the closed-loop stability and boundedness of internal signals. Moreover, the upper bounds of tracking errors in the transient state are also derived. Computer simulation results are presented to demonstrate the usefulness of the proposed scheme. Keywords: Adaptive control; Flexible-joint electrically-driven robot; FAT 2. Introduction Control of rigid robots has been well understood in recent years, but most of the schemes ignore the dynamics coming from electric motors and harmonic drivers that are widely implemented in the industrial robots. However, actuator dynamics constitute an important part of the complete robot dynamics, especially in the cases of high-velocity movement and highly varying loads[1],[2]. The main reason for using a reduced model is to simplify complexity of controller design. For each joint, consideration of the flexibility from the M. C. Chien was with the Department of Mechanical Engineering, National Taiwan University of Science and Technology. He is now with the Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, No. 195, Sec. 4, Chung-Hsing Rd., Chutung, Hsinchu, 310, Taiwan, R.O.C. (e-mail: [email protected]). 2 A. C. Huang is with the Department of Mechanical Engineering, National Taiwan University of Science and Technology. No. 43, Keelung Rd., Sec. 4, Taipei, Taiwan, ROC. (Tel:+886-2-27376490, Fax: +886-2-37376460, E-mail: [email protected]). (A. C. Huang provides phone number because he is the corresponding author.

Structure and piezoelectric properties of lead-free bismuth-based perovskite solid solutions

A new group of lead free piezoelectric perovskite solid solutions, (1-x)Bi(B'B")O₃-xABO₃, were obtained via solid-state processing techniques. The solubility of unstable perovskite Bi(B'B")O₃ compounds into stable perovskite compounds was found to be related to the tolerance factor of the ABO₃ perovskite endmembers. The morphotropic phase boundary (MBP) in perovskite solid solutions based on (1-x)Bi(Zn₁/₂Ti₁/₂)O₃-xBaTiO₃ has been measured at x≈0.9 by x-ray diffraction (XRD). Most of the work in this thesis was focused on the structure and electrical behavior of Bi(Zn₁/₂Ti₁/₂)O₃ (BZT) solid solutions with different ABO₃ end members. Dielectric characterization revealed that the trend of transition temperature Tm as a function of composition for BZT-ABO₃ solid solutions can be described by two types. In the first type, Tm decreased linearly or non-linearly until a second phase appeared, e.g. BZT-(Bi₁/₂K₁/₂)TiO₃. In the second type, Tm decreased to a minimum (usually below room temperature) and then increased as BZT content increased, e.g. BZT-BaTiO₃. In addition, with substitution of Li for Na in Bi(Zn₁/₂Ti₁/₂)O₃-NaNbO₃ the diffuseness of the transition peak decreased and transition temperature increased. Hysteresis measurements indicated that the ferroelectric state of NaNbO₃, (Bi₁/₂K₁/₂)TiO₃ and BaTiO₃ can be induced or enhanced with small amounts of BZT. However, added BZT content resulted in the transition from a normal ferroelectric state to quasi-relaxor state. The ternary system BiScO₃-Bi(Zn₁/₂Ti₁/₂)O₃-BaTiO₃ was also studied in terms of structure and dielectric behavior

Effects of Instructor Accent on Undergraduate Evaluations and Learning at a Catholic College

Catholic institutions of higher education are called to form citizens who fight against injustice, including persistent racial oppression. To do this, Catholic, public, and other private institutions must provide students opportunities to learn about and confront racism (Johnston, 2014). It is important that these institutions confront these issues because they employ faculty and staff who may experience systemic racism and can provide cultural knowledge to aid deconstructing racist ideologies. Undergraduate student evaluations of instructors or faculty, however, indicate discrimination against those perceived as non-white and with non-native English accents. This study focuses on one form of racism at a Catholic liberal arts college: bias against instructors who speak with a non-native English accent. This between-groups experimental study was guided by critical sociolinguistic theory and sociocultural theory to examine patterns in undergraduate engagement with material that varied only by instructor accent. Participants (n=98) completed a pre-assessment, a microlecture (randomized by accent), a post-assessment, and a microlecture evaluation. The study’s theoretical frameworks suggest that students would demonstrate bias against non-white presenters, despite the Catholic context and having no visual cues about the race or ethnicity of the presenter. Pre-and post-assessment results indicated that the microlecture had some limited effects on student learning regardless of instructor accent; however, instructors that were perceived as white had significantly higher ratings in terms of the student belief that they “showed enthusiasm about the subject matter” and that “watching this microlecture improved [their] score on the quiz.” These findings suggest continued work is needed to understand and confront issues of systemic racism in higher education