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Mechatronics Systems Engineering, School of

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3D Origami Sensing Robots for Cooperative Healthcare Monitoring

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-01-25
Abstract: 

In this study, cooperative healthcare sensing robots that closely monitor and evaluate the patients’ muscle functions through gait analysis and electromyography (EMG) are developed. By integrating the biological sensors, the sensing robot can recognize the vital signs. The sensing robots are developed by the design and optimization of their architectures and materials using a green strategy. To achieve mechanically durable robot designs, 3D origami structures are used with specific optimum criteria. Different sensing robot applications are created through the 3D origami insole and humanoid hands for healthcare monitoring. The smart insole built with 3D origami monitors the foot pressure distribution for gait analysis of patients, and the humanoid hand equipped with the 3D origami‐structured EMG fingers cooperatively detects EMG signals. Such cooperative sensing robots hold considerable promise for healthcare monitoring with convenience for patients with quality of care, because the robots can derive empathetic adaptability with humans.

Document type: 
Article

Cortical Effects of Noisy Galvanic Vestibular Stimulation Using Functional Near-Infrared Spectroscopy

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-02-20
Abstract: 

Noisy galvanic vestibular stimulation (nGVS) can improve different motor, sensory, and cognitive behaviors. However, it is unclear how this stimulation affects brain activity to facilitate these improvements. Functional near-infrared spectroscopy (fNIRS) is inexpensive, portable, and less prone to motion artifacts than other neuroimaging technology. Thus, fNIRS has the potential to provide insight into how nGVS affects cortical activity during a variety of natural behaviors. Here we sought to: (1) determine if fNIRS can detect cortical changes in oxygenated (HbO) and deoxygenated (HbR) hemoglobin with application of subthreshold nGVS, and (2) determine how subthreshold nGVS affects this fNIRS-derived hemodynamic response. A total of twelve healthy participants received nGVS and sham stimulation during a seated, resting-state paradigm. To determine whether nGVS altered activity in select cortical regions of interest (BA40, BA39), we compared differences between nGVS and sham HbO and HbR concentrations. We found a greater HbR response during nGVS compared to sham stimulation in left BA40, a region previously associated with vestibular processing, and with all left hemisphere channels combined (p < 0.05). We did not detect differences in HbO responses for any region during nGVS (p > 0.05). Our results suggest that fNIRS may be suitable for understanding the cortical effects of nGVS.

Document type: 
Article
File(s): 

Endoscopic Optical Imaging Technologies and Devices for Medical Purposes: State of the Art

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-09-29
Abstract: 

The growth and development of optical components and, in particular, the miniaturization of micro-electro-mechanical systems (MEMSs), has motivated and enabled researchers to design smaller and smaller endoscopes. The overarching goal of this work has been to image smaller previously inaccessible luminal organs in real time, at high resolution, in a minimally invasive manner that does not compromise the comfort of the subject, nor introduce additional risk. Thus, an initial diagnosis can be made, or a small precancerous lesion may be detected, in a small-diameter luminal organ that would not have otherwise been possible. Continuous advancement in the field has enabled a wide range of optical scanners. Different scanning techniques, working principles, and the applications of endoscopic scanners are summarized in this review.

Document type: 
Article
File(s): 

Material Properties and Structure of Natural Graphite Sheet

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-10-29
Abstract: 

Natural graphite sheet (NGS) is compressible, porous, electrically and thermally conductive material that shows a potential to be used in fuel cells, fow batteries, electronics cooling systems, supercapacitors, adsorption air conditioning, and heat exchangers. We report the results of an extensive material characterization study that focuses on thermal conductivity, thermal difusivity, electrical conductivity, coefcient of thermal expansion (CTE), compression strain, and emissivity. All the properties are density-dependent and highly anisotropic. Increasing the compression from 100 to 1080 kPa causes the through-plane thermal and electrical conductivities to increase by up to 116% and 263%, respectively. The properties are independent of the sheet thickness. Thermal and electrical contact resistance between stacked NGS is negligible at pressures 100 to 1080 kPa. In the in-plane direction, NGS follows the Wiedemann-Franz law with Lorenz number 6.6 × 10−6 W  K−2. The in-plane CTE is low and negative (shrinkage with increasing temperature), while the through-plane CTE is high, increases with density, and reaches 33 × 10−6 K−1. Microscope images are used to study the structure and relate it to material properties. An easy-to-use graphical summary of the forming process and NGS properties are provided in Appendices A and B.

Document type: 
Article
File(s): 

Electrostatic Twisting of Core-Shell Nanofibers for Strain Sensing Applications

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-09-18
Abstract: 

Stretchable strain sensors are increasingly needed in emerging fields of wearable electronics and smart textiles for applications ranging from human motion detection to health monitoring. Nanofibers made from conductive materials or composites of polymers and conductive nanoparticles exhibit strong sensitivities but are difficult to utilize due to their small dimensions. Herein, we report on a technique for producing core-shell nanofibers and in-situ twisting of them to each other using a rotating electric field. The process produces sensitive threads that can be handled easily and used, for instance, in smart textile applications. The core-shell nanofibers utilized poly(vinylidene fluoride) as the structural polymer and multiwalled carbon nanotubes were used to make the core electrically conductive. The structure of nanofibers was studied through a set of analytical methods. The fibers exhibit strong piezoresistive responses and can be utilized in various strain sensing applications. Mechanical properties of fabricated submicron fiber yarns are compared with non-twisted fibers and improvement of their stretchability has been demonstrated. Furthermore, the sensitivity of fiber threads to different directions of stretching depended on the way of their knitting into fabric has been compared.

Document type: 
Article

Compressive Mechanical Characterization of Non-Human Primate Spinal Cord White Matter

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2018-07-01
Abstract: 

The goal of developing computational models of spinal cord injury (SCI) is to better understand the human injury condition. However, finite element models of human SCI have used rodent spinal cord tissue properties due to a lack of experimental data. Central nervous system tissues in non human primates (NHP) closely resemble that of humans and therefore, it is expected that material constitutive models obtained from NHPs will increase the fidelity and the accuracy of human SCI models. Human SCI most often results from compressive loading and spinal cord white matter properties affect FE predicted patterns of injury; therefore, the objectives of this study were to characterize the unconfined compressive response of NHP spinal cord white matter and present an experimentally derived, finite element tractable constitutive model for the tissue. Cervical spinal cords were harvested from nine male adult NHPs (Macaca mulatta). White matter biopsy samples (3 mm in diameter) were taken from both lateral columns of the spinal cord and were divided into four strain rate groups for unconfined dynamic compression and stress relaxation (post-mortem <1-hour). The NHP spinal cord white matter compressive response was sensitive to strain rate and showed substantial stress relaxation confirming the viscoelastic behavior of the material. An Ogden 1st order model best captured the non-linear behavior of NHP white matter in a quasi-linear viscoelastic material model with 4-term Prony series. This study is the first to characterize NHP spinal cord white matter at high (>10/sec) strain rates typical of traumatic injury. The finite element derived material constitutive model of this study will increase the fidelity of SCI computational models and provide important insights for transferring pre-clinical findings to clinical treatments.

Document type: 
Article
File(s): 

Buck-Plus-Unfolder as the Superior Active Power Decoupling Solution for 400 Vdc/kW-Level Applications

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-07-21
Abstract: 

In single-phase ac/dc applications where reliability and/or power-density are critical, active power decoupling (APD) circuits can be employed to reduce the required capacitance on the dc-link. Various APD circuits have been proposed so far, all with their advantages and disadvantages. However, many confusions still exist in the literature on this topic which is mainly attributed to a lack of unified and comprehensive assessment criteria. In this paper, first the decisive criteria for a modern APD circuit are established, and the buck APD is identified as the current state-of-the-art, based on them. Then the buck-plus-unfolder topology with triangular current mode (TCM) modulation is proposed as an improvement, and a simple, yet solid foundation is introduced to choose the superior decoupling solution at different specifications. The operation equations for the APD with TCM modulation are derived next, and the operation of the proposed solution is demonstrated using a hardware prototype.

Document type: 
Article
File(s): 

Buck-Plus-Unfolder as the Superior Active Power Decoupling Solution for 400 Vdc/kW-Level Applications

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-07-21
Abstract: 

In single-phase ac/dc applications where reliability and/or power-density are critical, active power decoupling (APD) circuits can be employed to reduce the required capacitance on the dc-link. Various APD circuits have been proposed so far, all with their advantages and disadvantages. However, many confusions still exist in the literature on this topic which is mainly attributed to a lack of unified and comprehensive assessment criteria. In this paper, first the decisive criteria for a modern APD circuit are established, and the buck APD is identified as the current state-of-the-art, based on them. Then the buck-plus-unfolder topology with triangular current mode (TCM) modulation is proposed as an improvement, and a simple, yet solid foundation is introduced to choose the superior decoupling solution at different specifications. The operation equations for the APD with TCM modulation are derived next, and the operation of the proposed solution is demonstrated using a hardware prototype.

Document type: 
Article
File(s): 

Highly-doped SiC Resonator with Ultra-Large Tuning Frequency Range by Joule Heating Effect

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-06-27
Abstract: 

Tuning the natural frequency of a resonator is an innovative approach for the implementation of mechanical resonators in a broad range of fields such as timing applications, filters or sensors. The conventional electrothermal technique is not favorable towards large tuning range because of its reliance on metallic heating elements. The use of metallic heaters could limit the tuning capability due to the mismatch in thermal expansion coefficients of materials forming the resonator. To solve this drawback, herein, the design, fabrication, and testing of a highly-doped SiC bridge resonator that excludes the use of metallic material as a heating element has been proposed. Instead, free-standing SiC structure functions as the mechanical resonant component as well as the heating element. Through the use of the Joule heating effect, a frequency tuning capability of almost ∆f/fo ≈ 80% has been demonstrated. The proposed device also exhibited a wide operating frequency range from 72.3 kHz to 14.5 kHz. Our SiC device enables the development of highly sensitive resonant-based sensors, especially in harsh environments.

Document type: 
Article

A Micromachined Vector Light Sensor

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-05-24
Abstract: 

We report the design, fabrication, and performance characteristics of a novel microfabricated light sensor designed to determine the intensity and direction of an incident light source. The device structure comprises several light sensors that are integrated onto a pyramid base. The direction to the light source is estimated using the ratios of the signals from the lights sensors that are facing different directions. We demonstrate that this “vector light sensor”, is capable of measuring both the intensity and the direction of light from a source. The three-dimensional structure of the sensor is created based on well-known silicon microfabrication techniques and uses photodiodes for the detection of visible light. The signals from the photodiodes were read and processed based on a simple algorithm to experimentally verify the device performance. In addition to the direction, the distance to a light source may be estimated by simple triangulation of data from two vector light sensors. The small size and low power consumption of the individual sensors make them suitable for applications where passive distance and direction estimation is required. Furthermore, it is envisioned that arrayed sensors can directly provide light-field information in a plane.

Document type: 
Article