Mechanical Transduction of a Single Cell: Possible Applications for 3D Printed Lab-on-a-Chip

Mechanical signalling plays an important role in cell morphology, communication, migration, adhesion and differentiation. It is essential for the cell to translate mechanical forces into biochemical signals; known as mechanical transduction. This research offers a platform called 3D ‘lab-on-a-chip’ for investigating the effects of mechanical confinement in cells growth, gene expressions, motility, stress and diffusion. Lab-on-a-chip devices are miniature device that can shrink a conventional bench-top laboratory into a small chip. Compared to existing glass/semiconductor based platforms for cell mechanical transduction, our aim is to develop an alternate cost-effective platform using 3D printed lab-on-a-chip. Such a platform is reconfigurable, adaptable with rapid manufacturing and cost effective. The 3D microfluidic devices allow for mechanical transduction of a single cell within three dimensional micro channels designed specifically to the researchers needs. It is crucial to understand the mechanical transduction of the cell to be analyzed as the amount of stress exerted should be moderated to avoid destroying valuable cellular components. An application of this research is isolation of cancer cells. As cancer cells progress, cytoskeletal proteins transform leading to a change in deformability, contraction and elasticity as compared to a regular cell. By understanding the differences between different types of cell morphology and deformability, a 3D printable lab on a chip device can be designed to isolate the cell and mechanically transduce it to release its components for analysis. Our research utilizes finite element based analysis to design such a 3D lab-on-chip. Based on the amount of stress required to break the cell into components, the state of the cell can be determined. Understanding the kinetics and components of the cell cytoskeleton is important in the use of lab-on-a-chip devices which can also allow for a wide variety of other applications such as cell isolation, cell lysis, genomics, and cell state detection

Experimental Development of a Bat Inspired Obstacle Mapping System

This paper presents the development of an experimental method for obstacle detection using modified bat inspired navigation. Effective obstacle detection is vital to the efficient operation of many autonomous vehicles, mobile robotics and navigation systems. Varieties of sensors and sensor array combinations have been purposely developed to effectively detect and map obstacles and barriers during navigation [1][2]. Among these, ultrasonic sensors provide an inexpensive solution to distance and obstacle sensing. This is vital for industries such as automotive and transportation in which cost is a significant factor [3]. This work enhances the abilities of testing object classification capabilities of ultrasonic sensors through verification and proof of concept for bat-inspired, time of flight (TOF) based algorithms. Just as bats utilize acoustic echo to detect objects while navigating, this bat inspired system utilizes two static ultrasonic receivers and one central dynamic emitter. In our system, the electronic setup implemented was designed to activate a 40kHz emitter, capture the echo milliseconds later and incrementally move the emitter via the stepper motor. Upon activation of the emitter, the measurement device was triggered and the two distinct receiver signals were acquired. Receiver signals were then passed through a virtual low-pass filter and curve fitting algorithm in order to effectively and consistently determine the TOF values. Internal circuitry delays between trigger time and time of emission was accounted for through a test case with known orientation and speed of sound. Lastly the inherent nature of a diffuse detection surface permitted the detection of reflected signals from all emitter orientations. The experimental methodology developed in this research was successfully tested for detecting walls with a low cost ultrasonic emitter and receiver, setting a basis for analysis of future TOF based detection algorithms. The outcome of this research has the potential to provide effective barrier detection systems for autonomous navigation systems

Modeling Of Structural And Environmental Effects On Microelectromechanical (Mems) Vibratory Gyroscopes

In this paper we investigate the effects of stiffness, damping and temperature on the performance of a MEMS vibratory gyroscope. The stiffness and damping parameters are chosen because they can be appropriately designed to synchronize the drive and sense mode resonance to enhance the sensitivity and stability of MEMS gyroscope. Our results show that increasing the drive axis stiffness by 50% reduces the sense mode amplitude by ~27% and augments the resonance frequency by ~21%. The stiffness and damping are mildly sensitive to typical variations in operating temperature. The stiffness increases by 1.25%, while the damping decreases by 3.81%, when the temperature is raised from 0C to 45C. Doubling the damping reduces the oscillation amplitude by 80%, but ~1% change in the frequency. The predicted effects of stiffness, damping and temperature can be utilized to design a gyroscope for the desired operating condition

Development of a robust real-time filtering algorithm for inertial sensor based navigation systems with zero velocity update

Currently many GPS (Global Positioning System) satellites orbit the Earth providing users with information on position anywhere in the world and in all weather conditions. Information is gathered from the orbiting satellites and is merged with information from base towers on earth to locate a person’s position. Although GPS is leading the navigation system industry it does suffer in that GPS signals are unable to pass through solid structures. This means GPS is unable to accurately work in dense urban areas or indoor environments. This research aims to develop a sensor based standalone indoor navigation system using a robust real-time filtering algorithm to accurately provide a person’s positions and movement. Despite the numerous research and development on indoor navigation systems, little work has been done on maximizing the accuracy of the indoor navigation systems for achieving pin-point localization. The system proposed within utilizes a foot mounted IMU (inertial measurement unit) comprised of several inertial sensors capable of tracking a wearer’s movements without satellite signals. IMU based systems, as with most other indoor navigation technologies, suffer from sensor “drift” during longtime navigation, which can cripple the system. This research aims to filter sensory data collected by an IMU system through an EKF (extended Kalman filter) to correct drift. An EKF is an optimal estimation algorithm capable of estimating dynamic variables of indirect and uncertain measurements. In the team’s endeavor to maximize the accuracy and efficiency of the algorithm they have found the integration of an EKF to be largely efficacious in mitigating drift error. As of right now, major drift error is still observed which overtime accumulates into false mapping, but solutions are in the process to mitigate this error. We feel that inertial based navigation systems, when paired with a real-time filtering algorithm, offer an alternative to GPS navigation far more conducive to indoor environment

A Comparative Analysis of Capacitive Based Flexible Pressure Sensors

A Comparative Analysis of Capacitive Based Flexible Pressure Sensors Julia Pignanelli1, Dr. Simon Rondeau-Gagne2 and Dr. Jalal Ahamed3 Department of Biology, University of Windsor Department of Chemistry & Biochemistry, University of Windsor Mechanical, Automotive and Materials Engineering Department, University of Windsor This paper presents the material characterization of a flexible polymer for potential biomedical pressure sensing applications. The emergence of flexible, capacitive based pressure sensors with similar tactile sensing properties as human skin are highly desirable in many applications such as continuous cardiovascular monitoring, electronic skin and rehabilitation technologies [2,3]. Most of these sensors require high sensitivity, fast response time, flexibility and low cost. Due to flexible and foldable nature of the sensor, it can be integrated to artificial skin or imposed on the body surface. Among different sensing technologies, one promising method is through the use of micro-structured, flexible, dielectric polymers, for example PDMS (Polydimethylsiloxane). Micro-structures increase the sensitivity of the device. Current methods for constructing micro-patterns into the PDMS requires expensive and labor intensive methods such as photolithographic techniques and chemical etching, which lack low-cost and large-area compatible alternatives. The objective of this work is to construct and characterize a flexible capacitor pressure sensing device by using a simple, cost effective method of PDMS microstructuring as described by previously by Grzybowki et al. [1]. The PDMS was prepared by mixing 20 parts elastomer and 1 part curing agent. The rough structured PDMS is prepared by simply curing the polymer within an epoxy mold that incorporates a micro – pattern like design found within a commercially available tape [1]. The sample was placed in a vacuum for one hour at room temperature and then cured for another 24 hours at room temperature. Flexibility of the sensors is a key parameter related to sensor sensitivity. Flexibility can be measured by measuring the modulus of elasticity. Our test reveals the rough structured 20:1 PDMS modulus to be 1.29 MPa whereas the non-structured 20:1 PDMS modulus was found to be 2.90 MPa. The difference in moduli was not determined to be significant as expected since the structures are not changing the material property of PDMS. Through characterization and preparation of rough structured capacitive based PDMS pressure sensors, we hope to produce a capacitive sensing device with excellent detection sensitivity at a low cost and with a simple method of production. Refrences: Grzybowski, B., Qin, D., Haag, R., & Whitesides, G. (2000). Elastomeric optical elements with deformable surface topographies: applications to force measurements, tunable light transmission and light focusing. Sensors And Actuators A: Physical, 86(1-2), 81-85. Boutry, C., Nguyen, A., Lawal, Q., Chortos, A., Rondeau-Gagné, S., & Bao, Z. (2015). A Sensitive and Biodegradable Pressure Sensor Array for Cardiovascular Monitoring. Advanced Materials, 27(43), 6954-6961. Mannsfeld, S., Tee, B., Sltengerg, R, Chen, C.,,, Barman, S., Muir, B., Sokiloy, A., Reese, C. and Bao, Z. (2010). Highly sensitive flexible pressure sensors with microstrucutred rubber dielectric layers. Nature Materials, 9(10), 859-864

Optimization of Interaural Intensity Difference based Binaural Sonar Sensing System for Object Detection

Interaural Intensity Difference (IID) in binaural sonar systems is used for echolocation and obstacle sensing. In this article, we show by simulation the optimized system’s parameters in terms of frequency, sensor separation distance and the working range for an IID based binaural sonar sensing system. Our result shows that the best performances with a frequency range between 100 to 300 kHz and a separation distance, depending on the size of the microphone, in our case between 2 cm to 5 cm within the working range of 1 m. The approach developed in this paper could be useful for mobile localization and mapping, particularly in compact size mobile devices

Fabrication of an autonomously self-healing flexible thin-film capacitor by slot-die coating

Flexible pressure sensors with self-healing abilities for wearable electronics are being developed, but generally either lack autonomous self-healing properties or require sophisticated material processing methods. To address this challenge, we developed flexible, low-cost and autonomously self-healing capacitive sensors using a crosslinked poly(dimethylsiloxane) through metal-ligand interactions processed into thin films via slot-die coating. These films have excellent self-healing properties, approximately 1.34 × 105 μm3 per hour at room temperature and 2.87 × 105 μm3 per hour at body temperature (37 °C). Similarly, no significant change in capacitance under bending strain was observed on these flexible thin-films when assembled on poly(ethyleneterephthalate) (PET) substrates; capacitors showed good sensitivity at low pressure regimes. More importantly, the devices fully recovered their sensitivity after being damaged and healed, which is directly attributed to the rapid and autonomous self-healing of the dielectric materials

Design of a Microfluidic Based Lab-on-a-chip for Integrated Sample Manipulation and Dispensing

Microfluidic based miniature lab-on-a-chip devices integrate different laboratory functionality in microscale. Microarray technology is evolving as a powerful tool for biomedical and pharmaceutical applications to identify gene sequences or to determine gene expression levels. Preparation of samples and spotting the arrays are the two major steps required for making microarrays. The microfluidic components developed in this research would facilitate performing the above-mentioned steps by a single lab-on-a-chip. Three microfluidic modules were developed: a non-contact microdispenser, an interface connecting the microdispenser with planar Electrowetting on Dielectric (EWOD) sample manipulator and a microvalve that controls the flow at the interface. An electrostatically actuated non-contact type drop-on-demand based microdispenser was developed. The dispenser was designed using finite element modeling technique that solved electrostatically actuated dispensing process. Prototypes were fabricated and tested verifying stable droplet dispensing with error in subsequent droplet generation was less than 15% between each droplet. The frequency of stable generation was 20 Hz and the average volume of dispensed droplet was 1 nL. A closed-channel EWOD actuated interface was developed that allowed a series of droplets to merge inside at the interface converting droplet flow to a continuous flow. An innovative design modification allowed series of droplet merging inside closed-channel. The interface allows integration of pressure driven devices such as: pumps, dispensers, and valves with droplet based planar EWOD devices. A novel EWOD based microvalve was developed that utilizes a thermo-responsive polymer to block and unblock a pressurized continuous flow. EWOD actuation was used to control the positioning of the valving polymer at location of interest. The valve also isolated a pressurized flow from an integrated planar EWOD device. Valves with zero leak rates were demonstrated. Such a valve will be useful in controlling microflows in EWOD to pressure driven flows such as dispensers.Ph

Driving performance in exporter-importer exchange relationships: The efficacy of interorganizational trust as a response to exchange risks

AbstractDrawing on the transaction cost analysis perspective, this study examines how three types of exchange risks influence performance in exporter-importer exchange relationships. These risks include cultural distance, which gives rise to behavioral uncertainty and its associated measurement problem; market turbulence, a dimension of environmental uncertainty that gives rise to an adaptation problem; and transaction-specific assets, representing a safeguarding problem. The conceptual model assesses how an informal governance mechanism, inter-organizational trust, responds to these three exchange risks and, in doing so, fosters relational and export performance. Based on a structural equation model conducted in PLS, our findings indicate that cultural distance relates positively to inter-organizational trust, and market turbulence positively relates to exporter-specific assets. Exporter-specific assets and inter-organizational trust were found to have a reciprocal relationship. This research also confirms the mediating role of relational performance concerning the effects of exporter-specific assets and inter-organizational trust on financial export performance