• A Numerical Feasibility Study of Kinetic Energy Harvesting from Lower Limb Prosthetics

      Jia, Yu; orcid: 0000-0001-9640-1666; email: yu.jia.gb@ieee.org; Wei, Xueyong; orcid: 0000-0002-6443-4727; email: seanwei@mail.xjtu.edu.cn; Pu, Jie; email: 1821721@chester.ac.uk; Xie, Pengheng; email: 1821700@chester.ac.uk; Wen, Tao; orcid: 0000-0002-3216-6967; email: t.wen@chester.ac.uk; Wang, Congsi; email: congsiwang@163.com; Lian, Peiyuan; email: lian100fen@126.com; Xue, Song; email: sxue@xidian.edu.cn; Shi, Yu; orcid: 0000-0003-3891-7175; email: y.shi@chester.ac.uk (MDPI, 2019-10-10)
      With the advancement trend of lower limb prosthetics headed towards bionics (active ankle and knee) and smart prosthetics (gait and condition monitoring), there is an increasing integration of various sensors (micro-electromechanical system (MEMS) accelerometers, gyroscopes, magnetometers, strain gauges, pressure sensors, etc.), microcontrollers and wireless systems, and power drives including motors and actuators. All of these active elements require electrical power. However, inclusion of a heavy and bulky battery risks to undo the lightweight advancements achieved by the strong and flexible composite materials in the past decades. Kinetic energy harvesting holds the promise to recharge a small on-board battery in order to sustain the active systems without sacrificing weight and size. However, careful design is required in order not to over-burden the user from parasitic effects. This paper presents a feasibility study using measured gait data and numerical simulation in order to predict the available recoverable power. The numerical simulations suggest that, depending on the axis, up to 10s mW average electrical power is recoverable for a walking gait and up to 100s mW average electrical power is achievable during a running gait. This takes into account parasitic losses and only capturing a fraction of the gait cycle to not adversely burden the user. The predicted recoverable power levels are ample to self-sustain wireless communication and smart sensing functionalities to support smart prosthetics, as well as extend the battery life for active actuators in bionic systems. The results here serve as a theoretical foundation to design and develop towards regenerative smart bionic prosthetics.
    • An Analysis of Virtual Team Characteristics: A Model for Virtual Project Managers

      Cormican, Kathryn; Morley, Sandra; Folan, Paul; College of Engineering & Informatics, National University of Ireland, Galway. Ireland. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, Devon UK United Kingdom. (Facultad de Economía y Negocios, Universidad Alberto Hurtado, 2015-04)
      An integrated model, created to guide project managers, is outlined for the implementation and management of virtual teams. This model is developed by means of an exploratory literature review and an empirical investigation of virtual team utilization in a multinational medical device manufacturer, which examines several factors critical to their success. A TOWS matrix is used to structure the results of the analysis and to identify future virtual team strategies for the organization. The study demonstrates that a structured approach is essential to ensure that the benefits resulting from virtual teamwork are maximized.
    • Cantilevers-on-membrane design for broadband MEMS piezoelectric vibration energy harvesting

      Jia, Yu; Du, Sijun; Seshia, Ashwin A.; University of Chester; University of Cambridge (IOP Publishing, 2015-12-01)
      Most MEMS piezoelectric vibration energy harvesters involve either cantilever-based topologies, doubly-clamped beams or membrane structures. While these traditional designs offer simplicity, their frequency response for broadband excitation are typically inadequate. This paper presents a new integrated cantilever-on-membrane design that attempts to both optimise the strain distribution on a piezoelectric membrane resonator and improve the power responsiveness of the harvester for broadband excitation. While a classic membrane-based resonator has the potential to theoretically offer wider operational frequency bandwidth than its cantilever counterpart, the addition of a centred proof mass neutralises its otherwise high strain energy regions. The proposed topology addresses this issue by relocating the proof mass onto subsidiary cantilevers and integrates the merits of both the membrane and the cantilever designs. When experimentally subjected to a band-limited white noise excitation, up to approximately two folds of power enhancement was observed for the new membrane harvester compared to a classic plain membrane device.
    • Connection Configurations to Increase Operational Range and Output Power of Piezoelectric MEMS Vibration Energy Harvesters

      Du, Sijun; Chen, Shao-Tuan; Jia, Yu; Arroyo, Emmanuelle; Seshia, Ashwin A.; University of Cambridge; University of Chester (IOP Publishing, 2016-09-06)
      Among the various methods of extracting energy harvested by a piezoelectric vibration energy harvester, full-bridge rectifiers (FBR) are widely employed due to its simplicity and stability. However, its efficiency and operational range are limited due to a threshold voltage that the open-circuit voltage generated from the piezoelectric transducer (PT) must attain prior to any energy extraction. This voltage linearly depends on the output voltage of the FBR and the forward voltage drop of diodes and the nature of the interface can significantly limit the amount of extracted energy under low excitation levels. In this paper, a passive scheme is proposed to split the electrode of a micromachined PT into multiple (n) equal regions, which are electrically connected in series. The power output from such a series connected MEMS PT allows for the generated voltage to readily overcome the threshold set by the FBR. Theoretical calculations have been performed in this paper to assess the performance for different series stages (n values) and the theory has been experimentally validated. The results show that a PT with more series stages (high n values) improves the efficiency of energy extraction relative to the case with fewer series-connected stages under weak excitation levels.
    • Development of laser peening ceramics

      Shukla, Pratik; Lawrence, Jonathan; Waugh, David G.; University of Chester (2015-03)
    • Effect of laser treatment on the attachment and viability of mesenchymal stem cell responses on shape memory NiTi alloy

      Chan, Chi-Wai; Hussain, Issam; Waugh, David G.; Lawrence, Jonathan; Man, Hau-Chung; Queen's University, Belfast ; University of Lincoln ; University of Chester ; University of Chester ; Hong Kong Polytechnic University (Elsevier, 2014-05-22)
      The objectives of this study were to investigate the effect of laser-induced surface features on the morphology, attachment and viability of mesenchymal stem cells (MSCs) at different periods of time, and to evaluate the biocompatibility of different zones: laser-melted zone (MZ), heat-affected zone (HAZ) and base metal (BM) in laser-treated NiTi alloy.
    • An Efficient Inductor-less Dynamically Configured Interface Circuit for Piezoelectric Vibration Energy Harvesting

      Du, Sijun; Jia, Yu; Seshia, Ashwin A.; University of Cambridge; University of Chester (Institute of Electrical and Electronics Engineers, 2016-07-07)
      Vibration energy harvesting based on piezoelectric materials is of interest in several applications such as in powering remote distributed wireless sensor nodes for structural health monitoring. Synchronized Switch Harvesting on Inductor (SSHI) and Synchronous Electric Charge Extraction (SECE) circuits show good power efficiency among reported power management circuits; however, limitations exist due to inductors employed, adaption of response to varying excitation levels and the Synchronized Switch Damping (SSD) effect. In this paper, an inductor-less dynamically configured interface circuit is proposed, which is able to configure the connection of two piezoelectric materials in parallel or in series by periodically evaluating the ambient excitation level. The proposed circuit is designed and fabricated in a 0:35 μm HV CMOS process.The fabricated circuit is co-integrated with a piezoelectric bimorph energy harvester and the performance is experimentally validated. With a low power consumption (0:5 μW), the measured results show that the proposed rectifier can provide a 4.5 boost in harvested energy compared to the conventional full-bridge rectifier without employing an inductor. It also shows a high power efficiency over a wide range of excitation levels and is less susceptible to SSD.
    • An Efficient SSHI Interface With Increased Input Range for Piezoelectric Energy Harvesting Under Variable Conditions

      Du, Sijun; Jia, Yu; Do, Cuong D.; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2016-08-10)
      Piezoelectric vibration energy harvesters have been widely researched and are increasingly employed for powering wireless sensor nodes. The synchronized switch harvesting on inductor (SSHI) circuit is one of the most efficient interfaces for piezoelectric vibration energy harvesters. However, the traditional incarnation of this circuit suffers from a significant start-up issue that limits operation in low and variable amplitude vibration environments. This paper addresses this start-up issue for the SSHI rectifier by proposing a new architecture with SSHI startup circuitry. The startup circuitry monitors if the SSHI circuit is operating correctly and re-starts the SSHI interface if required. The proposed circuit is comprehensively analyzed and experimentally validated through tests conducted by integrating a commercial piezoelectric vibration energy harvester with the new interface circuit designed in a 0.35-μm HV CMOS process. Compared to conventional SSHI rectifiers, the proposed circuit significantly decreases the required minimum input excitation amplitude before energy can be harvested, making it possible to extract energy over an increased excitation range.
    • Eight parametric resonances in a multi-frequency wideband MEMS piezoelectric vibration energy harvester

      Jia, Yu; Du, Sijun; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2016-01-24)
      This paper presents a multi-order parametric resonant MEMS piezoelectric disk membrane, for the purpose of broadening the operational frequency bandwidth of a vibration energy harvester by employing the nonlinearity-induced bandwidth broadening associated with this phenomenon as well as the multi-frequency response associated with the higher orders. The fundamental mode -3dB bandwidth at 2.0 g recorded 55 Hz, while the first parametric resonant peak exhibited 365 Hz and the -3dB of the first 8 orders accumulated to 604 Hz. The membrane parametric resonator also experimentally demonstrated over 3-folds improvement in power density compared to a conventional direct resonator (cantilever), when subjected to band-limited white noise.
    • Enhancement in Interfacial Adhesion of Ti/Polyetheretherketone by Electrophoretic Deposition of Graphene Oxide

      Pan, Lei; Lv, Yunfei; Nipon, Roy; Wang, Yifan; Duan, Lixiang; Hu, Jingling; Ding, Wenye; Ma, Wenliang; Tao, Jie; Shi, Yu (Wiley, 2018-11-25)
    • Evaporation of liquid nitrogen droplets in superheated immiscible liquids

      Rebelo, Neville; Zhao, Huayong; Nadal, Francois; Garner, Colin; Williams, Andy; Loughborough University; University of Chester (Elsevier, 2019-08-22)
      Liquid nitrogen or other cryogenic liquids have the potential to replace or augment current energy sources in cooling and power applications. This can be done by the rapid evaporation and expansion processes that occur when liquid nitrogen is injected into hotter fluids in mechanical expander systems. In this study, the evaporation process of single liquid nitrogen droplets when submerged into n-propanol, methanol, n-hexane, and n-pentane maintained at 294 K has been investigated experimentally and numerically. The evaporation process is quantified by tracking the growth rate of the resulting nitrogen vapour bubble that has an interface with the bulk liquid. The experimental data suggest that the bubble volume growth is proportional to the time and the bubble growth rate is mainly determined by the initial droplet size. A comparison between the four different bulk liquids indicates that the evaporation rate in n-pentane is the highest, possibly due to its low surface tension. A scaling law based on the pure diffusion-controlled evaporation of droplet in open air environment has been successfully implemented to scale the experimental data. The deviation between the scaling law predictions and the experimental data for 2-propanol, methanol and n-hexane vary between 4% and 30% and the deviation for n-pentane was between 24% and 65%. The more detailed bubble growth rates have been modelled by a heuristic one-dimensional, spherically symmetric quasi-steady-state confined model, which can predict the growth trend well but consistently underestimate the growth rate. A fixed effective thermal conductivity is then introduced to account for the complex dynamics of the droplet inside the bubble and the subsequent convective processes in the surrounding vapour, which leads to a satisfactory quantitative prediction of the growth rate.
    • Evidence for the Perception of Time Distortion During Episodes of Alice in Wonderland Syndrome

      Jia, Yu; Miao. Ying; University of Chester; Aston University (Lippincott Williams & Wilkins, 2018-05-17)
      Alice in Wonderland syndrome (AIWS) is a rare perceptual disorder associated with sensation of one or several visual and/or auditory perceptual distortions including size of body parts, size of external objects, or passage of time (either speeding up or slowing down). Cause for AIWS is yet to be widely agreed, and the implications are widely varied. One of the research difficulties is the brevity of each episode, typically not exceeding few tens of minutes. This article presents a male adult in late 20s who has apparently experienced AIWS episodes since childhood, and infection has been ruled out. Reaction speed tests were conducted during and after AIWS episodes, across a span of 13 months. Statistically significant evidence is present for delayed response time during AIWS episodes when the patient claims to experience a sensation of time distortion: where events seem to move faster and people appear to speak quicker.
    • Experimental and theoretical study of a piezoelectric vibration energy harvester under high temperature

      Arroyo, Emmanuelle; Jia, Yu; Du, Sijun; Chen, Shao-Tuan; Seshia, Ashwin A.; University of Cambridge; University of Chester (IEEE, 2017-08-01)
      This paper focuses on studying the effect of increasing the ambient temperature up to 160 °C on the power harvested by an MEMS piezoelectric micro-cantilever manufactured using an aluminum nitride-on-silicon fabrication process. An experimental study shows that the peak output power decreases by 60% to 70% depending on the input acceleration. A theoretical study establishes the relationship of all important parameters with temperature and includes them into a temperature-dependent model. This model shows that around 50% of the power drop can be explained by a decreasing quality factor, and that thermal stresses account for around 30% of this decrease.
    • A finite element analysis of impact damage in composite laminates

      Shi, Yu; Soutis, Constantinos; University of Chester; University of Manchester (Cambridge University Press, 2012-12-01)
      In this work, stress-based and fracture mechanics criteria were developed to predict initiation and evolution, respectively, of intra- and inter-laminar cracking developed in composite laminates subjected to low velocity impact. The Soutis shear stress-strain semi-empirical model was used to describe the nonlinear shear behaviour of the composite. The damage model was implemented in the finite element (FE) code (Abaqus/Explicit) by a user-defined material subroutine (VUMAT). Delamination (or inter-laminar cracking) was modelled using interface cohesive elements and the splitting and transverse matrix cracks that appeared within individual plies were also simulated by inserting cohesive elements between neighbouring elements parallel to the fibre direction in each single layer. A good agreement was obtained when compared the numerically predicted results to experimentally obtained curves of impact force and absorbed energy versus time. A non-destructive technique (NDT), penetrant enhanced X-ray radiography, was used to observe the various damage mechanisms induced by impact. It has been shown that the proposed damage model can successfully capture the internal damage pattern and the extent to which it was developed in these carbon fibre/epoxy composite laminates.
    • High speed CO2 laser surface modification of iron/cobalt co-doped boroaluminosilicate glass

      Hodgson, Simon D.; Waugh, David G.; Gillett, Alice R.; Lawrence, Jonathan; University of Chester (IOP Publishing, 2016-06-10)
      A preliminary study into the impact of high speed laser processing on the surface of iron and cobalt co-doped glass substrates using a 60 W continuous wave (cw) CO2 laser. Two types of processing, termed fill-processing and line-processing, were trialled. In fill-processed samples the surface roughness of the glass was found to increase linearly with laser power from an Sa value of 20.8 nm–2.1 μm at a processing power of 54 W. With line processing, a more exponential-like increase was observed with a roughness of 4 μm at 54 W. The change in surface properties of the glass, such as gloss and wettability, have also been measured. The contact angle of water was found to increase after laser processing by up to 64°. The surface gloss was varied between 45 and 100 gloss units (GUs).
    • High temperature performance of a piezoelectric micro cantilever for vibration energy harvesting

      Arroyo, Emmanuelle; Jia, Yu; Du, Sijun; Chen, Shao-Tuan; Seshia, Ashwin A. (IOP Publishing, 2016-12-06)
      Energy harvesters withstanding high temperatures could provide potentially unlimited energy to sensor nodes placed in harsh environments, where manual maintenance is difficult and costly. Experimental results on a classical microcantilever show a 67% drop of the maximum power when the temperature is increased up to 160 °C. This decrease is investigated using a lumped-parameters model which takes into account variations in material parameters with temperature, damping increase and thermal stresses induced by mismatched thermal coefficients in a composite cantilever. The model allows a description of the maximum power evolution as a function of temperature and input acceleration. Simulation results further show that an increase in damping and the apparition of thermal stresses are contributing to the power drop at 59% and 13% respectively.
    • In vitro mesenchymal stem cell response to a CO2 laser modified polymeric material

      Waugh, David G.; Hussain, Issam; Lawrence, Jonathan; Smith, Graham C.; Toccaceli, Christina; University of Chester; University of Lincoln (Elsevier, 2016-05-16)
      With an ageing world population it is becoming significantly apparent that there is a need to produce implants and platforms to manipulate stem cell growth on a pharmaceutical scale. This is needed to meet the socio-economic demands of many countries worldwide. This paper details one of the first ever studies in to the manipulation of stem cell growth on CO2 laser surface treated nylon 6,6 highlighting its potential as an inexpensive platform to manipulate stem cell growth on a pharmaceutical scale. Through CO2 laser surface treatment discrete changes to the surfaces were made. That is, the surface roughness of the nylon 6,6 was increased by up to 4.3 µm, the contact angle was modulated by up to 5° and the surface oxygen content increased by up to 1 atom%. Following mesenchymal stem cell growth on the laser treated samples, it was identified that CO2 laser surface treatment gave rise to an enhanced response with an increase in viable cell count of up to 60,000 cells/ml when compared to the as-received sample. The effect of surface parameters modified by the CO2 laser surface treatment on the mesenchymal stem cell response is also discussed along with potential trends that could be identified to govern the mesenchymal stem cell response.
    • Influencing the attachment of bacteria through laser surface engineering

      Gillett, Alice R.; Waugh, David G.; Lawrence, Jonathan; University of Chester (Laser Institute of America, 2015-10)
      Bacteria have evolved to become proficient at adapting to both extracellular and environmental conditions, which has made it possible for them to attach and subsequently form biofilms on varying surfaces. This has resulted in major health concerns and economic burden in both hospital and industrial environments. Surfaces which prevent this bacterial fouling through their physical structure represent a key area of research for the development of antibacterial surfaces for many different environments. Laser surface treatment provides a potential candidate for the production of anti-biofouling surfaces for wide ranging surface applications within healthcare and industrial disciplines. In the present study, a KrF 248 nm Excimer laser was utilized to surface pattern Polyethylene terephthalate (PET). The surface topography and roughness were determined with the use of a Micromeasure 2, 3D profiler. Escherichia coli (E. coli) growth was analysed at high shear flow using a CDC Biofilm reactor for 48 hours, scanning electron microscopy was used to determine morphology and total viable counts were made. Through this work it has been shown that the surface modification significantly influenced the distribution and morphology of the attached E. coli cells. What is more, it has been evidenced that the laser-modified PET has been shown to prevent E. coli cells from attaching themselves within the laser-induced micro-surface-features.
    • Interface Cohesive Elements to Model Matrix Crack Evolution in Composite Laminates

      Shi, Yu; Pinna, Christophe; Soutis, Constantinos; University of Chester; University of Sheffield; University of Manchester (Springer, 2013-10-02)
      In this paper, the transverse matrix (resin) cracking developed in multidirectional composite laminates loaded in tension was numerically investigated by a finite element (FE) model implemented in the commercially available software Abaqus/Explicit 6.10. A theoretical solution using the equivalent constraint model (ECM) of the damaged laminate developed by Soutis et al. was employed to describe matrix cracking evolution and compared to the proposed numerical approach. In the numerical model, interface cohesive elements were inserted between neighbouring finite elements that run parallel to fibre orientation in each lamina to simulate matrix cracking with the assumption of equally spaced cracks (based on experimental measurements and observations). The stress based traction-separation law was introduced to simulate initiation of matrix cracking and propagation under mixed-mode loading. The numerically predicted crack density was found to depend on the mesh size of the model and the material fracture parameters defined for the cohesive elements. Numerical predictions of matrix crack density as a function of applied stress are in a good agreement to experimentally measured and theoretically (ECM) obtained values, but some further refinement will be required in near future work.
    • Laser melting of NiTi and its effects on in-vitro mesenchymal stem cell responses

      Waugh, David G.; Lawrence, Jonathan; Chan, Chi-Wai; Hussain, Issam; Man, Hau-Chung; University of Chester ; University of Chester ; University of Lincoln ; University of Lincoln ; Hong Kong Polytechnic University (Woodhead Publishing, 2015)