Eccentric Figure-Eight Coils for Transcranial Magnetic Stimulation

Previously we proposed an eccentric figure-eight coil that can cause threshold stimulation in the brain at lower driving currents. In this study, we performed numerical simulations and magnetic stimulations to healthy subjects for evaluating the advantages of the eccentric coil. The simulations were performed using a simplified spherical brain model and a realistic human brain model. We found that the eccentric coil required a driving current intensity of approximately 18% less than that required by the concentric coil to cause comparable eddy current densities within the brain. The eddy current localization of the eccentric coil was slightly higher than that of the concentric coil. A prototype eccentric coil was designed and fabricated. Instead of winding a wire around a bobbin, we cut eccentric-spiral slits on the insulator cases, and a wire was woven through the slits. The coils were used to deliver magnetic stimulation to healthy subjects; among our results, we found that the current slew rate corresponding to motor threshold values for the concentric and eccentric coils were 86 and 78 A/µs, respectively. The results indicate that the eccentric coil consistently requires a lower driving current to reach the motor threshold than the concentric coil. Future development of compact magnetic stimulators will enable the treatment of some intractable neurological diseases at home. Bioelectromagnetics. 35:55–65, 2015. © 2014 Wiley Periodicals, Inc.ArticleBIOELECTROMAGNETICS. 36(1):55-65 (2015)journal articl

Stepper microactuators driven by ultrasonic power transfer

Advances in miniature devices for biomedical applications are creating ever-increasing requirements for their continuous, long lasting, and reliable energy supply, particularly for implanted devices. As an alternative to bulky and cost inefficient batteries that require occasional recharging and replacement, energy harvesting and wireless power delivery are receiving increased attention. While the former is generally only suited for low-power diagnostic microdevices, the latter has greater potential to extend the functionality to include more energy demanding therapeutic actuation such as drug release, implant mechanical adjustment or microsurgery. This thesis presents a novel approach to delivering wireless power to remote medical microdevices with the aim of satisfying higher energy budgets required for therapeutic functions. The method is based on ultrasonic power delivery, the novelty being that actuation is powered by ultrasound directly rather than via piezoelectric conversion. The thesis describes a coupled mechanical system remotely excited by ultrasound and providing conversion of acoustic energy into motion of a MEMS mechanism using a receiving membrane coupled to a discrete oscillator. This motion is then converted into useful stepwise actuation through oblique mechanical impact. The problem of acoustic and mechanical impedance mismatch is addressed. Several analytical and numerical models of ultrasonic power delivery into the human body are developed. Major design challenges that have to be solved in order to obtain acceptable performance under specified operating conditions and with minimum wave reflections are discussed. A novel microfabrication process is described, and the resulting proof-of-concept devices are successfully characterized.Open Acces

Design and fabrication of flexible tactile sensing and feedback interface for communication by deafblind people

Humans generally interact and communicate using five basic sensory modalities and mainly through vision, touch and audio. However, this does not work for deafblind people as they have both impaired hearing and vision modalities, and hence rely on touch-sensing. This necessitates the development of alternative means that allows them to independently interact and communicate. To do this requires a solution which has the capability for tactile sensing and feedback. Therefore, tactile interface becomes a critical component of any assistive device usable by deafblind people for interaction and communication. Given that existing solutions mainly use rigid and commercial components, there is a need to tap into the advancements in flexible electronics in order develop more effective and conformable solutions. This research involves the development of flexible tactile communication interface usable in assistive communication devices for deafblind people. First, commercial sensors and actuators were utilised as a proof-of-concept and then four novel tactile interfaces were explored which include two similar touch-sensitive electromagnetic actuators, one capacitive tactile sensing array, and a facile flexible inductance-based pressure sensor. The two fabricated touch-sensitive electromagnetic actuators (Type 1 and 2) are both based on electromagnetic principle and capable of simultaneous tactile sensing and feedback. Each comprises of a tandem combination of two main modules - the touch-sensing and the actuation module, with both modules integrated as a single device in each case. The actuation module employs a flexible planar spiral coil and a Neodymium magnet assembled in a soft Polydimethylsiloxane (PDMS) structure, while the touch-sensing module is a planar capacitive metal- insulator-metal structure of copper. The flexible coil (~17µm thick and with 45 turns) was fabricated on a Polyimide sheet using Lithographie Galvanoformung Abformung (LIGA) process. The results of characterisation of these actuators at frequencies ranging from 10Hz to 200Hz, shows a maximum displacement (~ 190µm) around 40Hz. Evaluation of this by 40 (20 deafblind and 20 sighted and hearing) participants show that they can feel vibration at this range. Another tactile interface fabricated is an 8 x 8 capacitive tactile sensing array. The sensor was developed on a flexible Polyvinyl Chloride (PVC) sheet with column electrodes deposited on one side and row electrodes on the reverse side. It is intended for use as an assistive tactile communication interface for deafblind people who communicate using deafblind manual alphabets as well as the English block letters. An inductance-based pressure sensor was also designed, fabricated and characterised for use as an input interface for finger Braille as well as other tactile communication methods for deafblind people. It was realised with a soft ferromagnetic elastomer and a 17µm-thick coil fabricated on a flexible 50 µm-thick polyimide sheet. The ferromagnetic elastomer acts as the core of the coil, which when pressed, sees the metal particles moving closer to each other, leading to changes in the inductance. The coil, with 75µm conductor and 25µm pitch, was also realised using LIGA micromolding technique. Seven different sensors were fabricated using different ratios (1:1, 1:2, 1:3, 1:5, 2:1, 3:1, and 5:1) of Ecoflex to Iron particles. The performance of each sensor was investigated and generally, sensors with higher Iron particles gave better sensitivity, linear as well as dynamic range. In comparison with all other fabricated sensors, the sensor made with 1:5DD was recommended for application as a tactile interface

Studies on Spinal Fusion from Computational Modelling to ‘Smart’ Implants

Low back pain, the worldwide leading cause of disability, is commonly treated with lumbar interbody fusion surgery to address degeneration, instability, deformity, and trauma of the spine. Following fusion surgery, nearly 20% experience complications requiring reoperation while 1 in 3 do not experience a meaningful improvement in pain. Implant subsidence and pseudarthrosis in particular present a multifaceted challenge in the management of a patient’s painful symptoms. Given the diversity of fusion approaches, materials, and instrumentation, further inputs are required across the treatment spectrum to prevent and manage complications. This thesis comprises biomechanical studies on lumbar spinal fusion that provide new insights into spinal fusion surgery from preoperative planning to postoperative monitoring. A computational model, using the finite element method, is developed to quantify the biomechanical impact of temporal ossification on the spine, examining how the fusion mass stiffness affects loads on the implant and subsequent subsidence risk, while bony growth into the endplates affects load-distribution among the surrounding spinal structures. The computational modelling approach is extended to provide biomechanical inputs to surgical decisions regarding posterior fixation. Where a patient is not clinically pre-disposed to subsidence or pseudarthrosis, the results suggest unilateral fixation is a more economical choice than bilateral fixation to stabilise the joint. While finite element modelling can inform pre-surgical planning, effective postoperative monitoring currently remains a clinical challenge. Periodic radiological follow-up to assess bony fusion is subjective and unreliable. This thesis describes the development of a ‘smart’ interbody cage capable of taking direct measurements from the implant for monitoring fusion progression and complication risk. Biomechanical testing of the ‘smart’ implant demonstrated its ability to distinguish between graft and endplate stiffness states. The device is prepared for wireless actualisation by investigating sensor optimisation and telemetry. The results show that near-field communication is a feasible approach for wireless power and data transfer in this setting, notwithstanding further architectural optimisation required, while a combination of strain and pressure sensors will be more mechanically and clinically informative. Further work in computational modelling of the spine and ‘smart’ implants will enable personalised healthcare for low back pain, and the results presented in this thesis are a step in this direction

Advances in Bioengineering

The technological approach and the high level of innovation make bioengineering extremely dynamic and this forces researchers to continuous updating. It involves the publication of the results of the latest scientific research. This book covers a wide range of aspects and issues related to advances in bioengineering research with a particular focus on innovative technologies and applications. The book consists of 13 scientific contributions divided in four sections: Materials Science; Biosensors. Electronics and Telemetry; Light Therapy; Computing and Analysis Techniques

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Haptics: Science, Technology, Applications

This open access book constitutes the proceedings of the 13th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2022, held in Hamburg, Germany, in May 2022. The 36 regular papers included in this book were carefully reviewed and selected from 129 submissions. They were organized in topical sections as follows: haptic science; haptic technology; and haptic applications