Michael D Gilchrist

Michael D Gilchrist
University College Dublin | UCD · School of Mechanical and Materials Engineering

PhD, DEng

About

345
Publications
110,529
Reads
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8,873
Citations
Additional affiliations
January 2011 - December 2013
University of Ottawa
Description
  • Visiting Professor
January 1998 - December 2013
University College Dublin
Description
  • Head of School

Publications

Publications (345)
Article
Full-text available
Head acceleration measurement sensors are now widely deployed in the field to monitor head kinematic exposure in contact sports. The wealth of impact kinematics data provides valuable, yet challenging, opportunities to study the biomechanical basis of mild traumatic brain injury (mTBI) and subconcussive kinematic exposure. Head impact kinematics ar...
Article
Full-text available
The risk of brain trauma has been associated with the rotational kinematics leading to the development of helmets with a variety rotational management technologies. The purpose of this paper was to employ a rotation specific test protocol to evaluate the effectiveness of two of these technologies. Dynamic response of the head was measured to assess...
Article
Full-text available
Electropolishing (EP) is most widely used as a metal finishing process. It is a non-contact electrochemical process that can clean, passivate, deburr, brighten, and improve the biocompatibility of surfaces. However, there is clear potential for it to be used to shape and form the topology of micro-scale surface features, such as those found on the...
Article
Point-Of-Care (POC) testing has advanced to more affordable and rapid alternatives by adapting conventional immunoassays and molecular assays (isothermal amplification, CRISPR, digital and real-time quantitative PCR) on polymeric and paper microfluidic platforms. However, commercialization of these POC devices often depends on tackling long-term ch...
Article
Full-text available
Direct contact with contaminated surfaces in frequently accessed areas is a confirmed transmission mode of SARS-CoV-2. To address this challenge, we have developed novel plastic films with enhanced effectiveness for deactivating the SARS-CoV-2 by means of nanomaterials combined with nanopatterns. Results prove that these functionalized films are ab...
Article
Full-text available
Head injuries are a major health concern for sport participants as 90% of emergency department visits for sport-related brain injuries are concussion related. ¹ Recently, reports have shown a higher incidence of sport-related concussion in female athletes compared to males. ³ Few studies have described the events by which concussions occur in women...
Article
The magnitude and number of head impacts experienced by young American football players are associated with negative brain health outcomes and may be affected by play-type strategies. The purpose of this research was to examine how play type affects the magnitude and number of head impacts in youth American tackle football. Head impacts were record...
Article
Repetitive head impacts are a growing concern for youth and adolescent contact sport athletes as they have been linked to long term negative brain health outcomes. Of all contact sports, tackle football and ice hockey have been reported to have the highest incidence of head or brain injury however, each sporting environment is unique with distinct...
Article
American football helmets used by youth players are currently designed and tested to the same standards as professionals. The National Operating Committee on Standard and Safety requested research aiming at understanding the differences in brain trauma in youth American football for players aged five to nine and nine to fourteen years old to inform...
Article
As a combination of conventional injection moulding and compression moulding, injection compression moulding is expected to deliver a more uniform distribution of cavity pressure and more precise replication of surface structures. However, processing defects such as flash and design constraints such as thin edges of a product can cause non-uniform...
Article
Mixed martial arts (MMA) is a sport where the fighters are at high risk of brain trauma, with characteristics, such as the frequency, magnitude, and interval of head impacts influencing the risk of developing short- and long-term negative brain health outcomes. These characteristics may be influenced by weight class as they may have unique fighting...
Article
Rugby league has been identified as a contact sport with a high incidence of concussion. Research has been conducted to describe incidence and mechanisms of concussion in rugby league, however the risks associated with injury events (shoulder, hip, head to head) are unknown. The purpose of this study was to describe the common injury events leading...
Article
Although ice hockey helmet standards mitigate the risk of catastrophic head injuries, the risk of concussion remains high. To improve protection, helmets need to be evaluated using impact conditions reflecting how concussions occur in ice hockey. The purpose of this research was to evaluate how three helmet impact tests represent three common concu...
Article
This study examined the effects and interaction of four primary impact parameters (impact velocity, angle of impact relative to the ground, ground compliance and helmet impact location) on head kinematics and brain tissue response for falls that are most commonly associated with equestrian sports. A helmeted headform was subject to parametric tests...
Article
Full-text available
Wormian (intrasutural) bones are small, irregular bones, that are found in the cranial sutures of the skull. The occurrence of Wormian bones in human skulls has been well documented but few studies have detected the presence of such bones in domestic animals. Although some research has linked the presence of Wormian bones to bone pathology, its ana...
Article
An in-depth analysis of 216 equestrian helmets involved in real-world accidents, with accompanying laboratory drop-test experiments has focussed on the crushing of energy absorbing liners. The mean measured residual crush (i.e., damage in the form of permanent deformation of helmet liner expressed as a percentage of the local undeformed thickness)...
Article
Understanding the relationship between head mass and neck stiffness during direct head impacts is especially concerning in youth sports where athletes have higher proportional head mass to neck strength. This study compared 2 neck stiffness conditions for peak linear and rotational acceleration and brain tissue deformations across 3 impact velociti...
Article
Injection moulding has shown its advantages and prevalence in the production of plastic optical components, the performance and functionality of which rely on the precision replication of surface forms and on minimizing residual stress. The present work constitutes a systematic and comprehensive analysis of practical microlens arrays that are desig...
Article
Full-text available
Bicycle helmets are shown to offer protection against head injuries. Rating methods and test standards are used to evaluate different helmet designs and safety performance. Both strain-based injury criteria obtained from finite element brain injury models and metrics derived from global kinematic responses can be used to evaluate helmet safety perf...
Article
Full-text available
Injection moulding is ubiquitous in the production of plastic optical components, the functionality of which depends on minimising residual stress and on precisely replicating surface forms. In this study, variotherm-assisted microinjection moulding is used to manufacture a practical microlens array designed for light-field applications in order to...
Article
Current helmet certification tests involve linear impacts on rigid anvils. The associated kinematics by which a jockey falls from a horse while riding are believed to be fundamentally different to those in the certification tests, i.e., they involve oblique falls (falls at an angle) to compliant surfaces. This paper provides primary data from real-...
Article
In elite ice hockey, concussions occur from a variety of impact sources with different compliances, such as player-to-player collisions, impacts on the ice, boards, and glass. The effectiveness of ice hockey helmets to manage an impact under varying compliance conditions is currently unknown. The objective of this research was to determine the effe...
Article
Acute and chronic neurological risks associated with brain trauma sustained in professional ice hockey has generated concern for youth participants. Minor hockey is a different game when compared to elite players presenting distinctive risk factors for each age division. Objective measures of brain trauma exposure were documented for six divisions...
Article
Full-text available
The regional dynamic mechanical properties of mouse, rat, pig, and human brain tissue were compared directly in this first-of-its-kind study. Our results suggest the use of pig or mouse brain tissue as suitable surrogates to characterise human brain tissue. The importance of this work is highlighted by the extensive use of constitutive data from an...
Article
Full-text available
Traumatic brain injury (TBI) is an important cause of mortality and morbidity worldwide. Finite element models of the human head are used widely to simulate TBI loading scenarios, to improve the understanding of the mechanical pathogenesis of head trauma. The reliability of such computational models depends strongly on the accuracy of the mechanica...
Article
Full-text available
Hard and brittle materials (HBMs) are promising materials for aerospace and astronomy applications, due to their excellent mechanical, optical, and chemical properties. However, they are difficult and costly to machine using conventional machining methods such as single point diamond turning. Laser assisted machining uses a focused laser beam to he...
Preprint
We show that porcine brain matter can be modelled accurately as a very soft rubber-like material using the Mooney-Rivlin strain energy function, up to strains as high as 60\%. This result followed from simple shear experiments performed on small rectangular fresh samples ($2.5$ cm$^3$ and $1.1$ cm$^3$) at quasi-static strain rates. They revealed a...
Preprint
Full-text available
Incompressible nonlinearly hyperelastic materials are rarely simulated in Finite Element numerical experiments as being perfectly incompressible because of the numerical difficulties associated with globally satisfying this constraint. Most commercial Finite Element packages therefore assume that the material is slightly compressible. It is then fu...
Article
Full-text available
The cerebral meninges, made up of the dura, arachnoid, and pia mater, is a tri-layer membrane that surrounds the brain and the spinal cord and has an important function in protecting the brain from injury. Understanding its mechanical behavior is important to ensure the accuracy of finite element (FE) head model simulations which are commonly used...
Preprint
Full-text available
The magnitude of force used in a stabbing incident can be difficult to quantify, although the estimate given by forensic pathologists is often seen as `critical' evidence in medico-legal situations. The main objective of this study is to develop a quantitative measure of the force associated with a knife stabbing biological tissue, using a combined...
Preprint
Full-text available
The aim was to investigate mechanical and functional failure of diffuse axonal injury (DAI) in nerve bundles following frontal head impacts, by finite element simulations. Anatomical changes following traumatic brain injury are simulated at the macroscale by using a 3D head model. Frontal head impacts at speeds of 2.5-7.5 m/s induce mild-to-moderat...
Preprint
Mechanical characterization of brain tissue at high loading velocities is crucial for modeling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences compression, tension and shear. Limited experimental data is available for brain tissue in extension at dynamic strain rates. In this research, a High Rate Tension Dev...
Preprint
During severe impact conditions, brain tissue experiences a rapid and complex deformation, which can be seen as a mixture of compression, tension and shear. Moreover, diffuse axonal injury (DAI) occurs in animals and humans when both the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue in...
Article
Objective The aim of this study was to measure the load on the lateral and medial aspects of the proximal radio-ulnar joint during extension of the carpus. Study Design This was an ex vivo biomechanical study. Sample Population Twenty-two cadaveric Greyhound thoracic limbs were used. Methods Twenty-two paired thoracic limbs were used. The olecranon...
Article
Full-text available
Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur in a multitude of different environments. Each event is composed of combinations of impact characteristics (striking velocity, impact mass, and surface compliance) that present unique loading conditions on the head and brain. The purpose of this study...
Article
Impact parameters used to design the American football helmet and the parameters associated with mechanisms of concussive injury are not consistent. Head impacts resulting in concussive injury in football are characterized as events creating rotational motion of the head that generate brain tissue strain. The extent of tissue strain influences the...
Article
The purpose of this research was to compare the frequency and magnitude of head impact events between Pee Wee and Bantam ice hockey players. Videos of Pee Wee and Bantam boys’ ice hockey were analysed to determine the frequency and type of head impact events. The head impact events were then reconstructed in the laboratory using physical and finite...
Article
The use of helmets in equestrian sports has reduced the occurrence of traumatic brain injuries although, despite improvements to helmets, concussion remains a common injury. Currently, equestrian helmets are designed to pass certification standards involving a linear drop test to a rigid surface, while most concussions in equestrian sports result f...
Article
Finite element head models represent a valuable tool to investigate brain injury due to head impacts. A biofidelic model is, therefore, necessary to obtain accurate and realistic results. Recent work has highlighted the importance of the scalp in head impact kinematics, particularly for oblique head impacts, where high rotational accelerations are...
Article
Ice hockey helmet standards have primarily been developed to reduce risk of traumatic brain injury (TBI). While severe TBI has become a rare event in ice hockey, concussion, a type of mild TBI, remains a common head injury. Concussions, in ice hockey result from a number of head impact events including, collisions, stick impacts, puck impacts, fall...
Article
Introduction Currently, biomechanics has not been able to effectively predict when a mild traumatic brain injury may occur as a result of head impact. To improve prediction of brain trauma and the development of protective innovations, it is important to create an understanding of the relationship between the biomechanics of the head impact event a...
Article
Full-text available
The aim of this study is to determine what loads are likely to be applied to the head in the event of a horse falling onto it and to determine by how much a typical equestrian helmet reduces these loads. An instrumented headform was designed and built to measure applied dynamic loads from a falling horse. Two differently weighted equine cadavers we...
Article
Compared to adults, it has been documented that children are at elevated risk for concussion, repeated concussions, and experience longer recovery times. What is unknown, is whether the developing brain may be injured at differing strain levels. This study examined peak and cumulative brain strain from 20 cases of concussion in both young children...
Article
Full-text available
American-style football participation poses a high risk of repetitive head impact (RHI) exposure leading to acute and chronic brain injury. The complex nature of symptom expression, human predisposition, and neurological consequences of RHI limits our understanding of what constitutes as an injurious impact affecting the integrity of brain tissue....
Article
Accidental falls occur to people of all ages, with some resulting in concussive injury. At present, it is unknown whether children and adolescents are at a comparable risk of sustaining a concussion compared to adults. This study reconstructed the impact kinematics of concussive falls for children, adolescents, and adults and simulated the associat...
Article
The performance of equestrian helmets to protect against brain injuries caused by fall impacts against compliant surfaces such as turf has not been studied widely. We characterise the kinematic response of simulated fall impacts to turf through field tests on horse racetracks and laboratory experiments. The kinematic response characteristics and gr...
Article
There is significant difference between the loading conditions used to certify equestrian helmets and the environment in which they are commonly used: this may affect their ability to provide adequate protection against head injury during a riding accident. The efficacy of helmet performance under real-world riding conditions can be judged by exami...
Article
Objectives: Equestrian helmets are designed to pass certification standards based on linear drop tests onto rigid steel surfaces. However, concussions in equestrian sports occur most commonly when a rider is thrown off a horse and obliquely impacts a compliant surface such as turf or sand. This paper seeks to elucidate the mechanics of such impact...
Article
In hockey, players experience different compliances during impacts to the head, from stiff ice to compliant collisions against other players. The objective of this study was to examine the effect of striking compliance in ice hockey impacts and its influence on dynamic response and brain tissue strain. Three striking caps of low, medium, and high c...
Article
Full-text available
A new method, a 3D printing technique, in particular, selective laser melting (SLM), has been used to fabricate moulds for the injection moulding of thermoplastic microfluidic chips that are suitable for prototyping and early stage scale-up. The micro metallic patterns are printed on to a pre-finished substrate to form a microstructured mould. The...
Article
Background Concussion is an injury that occurs in non-sporting and sporting environments. To determine improved clinical methods for identifying this injury, it is important to develop and understand how the impact event results in quantifiable differences in brain functioning—functioning that has been quantified in the past using saccadic measures...
Article
The purpose of this study was to test the effectiveness of a helmet to reduce maximum principal strain by decoupling the head–helmet interface in reconstructions of head-to-head concussive impacts in American football. The primary goal of the American football helmet has been protection of players against skull fractures and other traumatic brain i...
Article
The liver is the most commonly injured abdominal organ following either blunt or penetrating impact. Current mechanical properties available in the literature are typically only measured at low strain rates, low strains, or use linear viscoelastic models. There is also a dearth of high-rate, large strain, viscoelastic data available for liver tissu...
Article
Collisions are a common cause of concussions. The nature of a collision impact is governed by the velocity of the striking players and the body parts involved. The purpose of this study was to describe the effects of velocity, mass, surface stiffness and location on peak linear and angular acceleration and strain. A variable-mass pendulum fitted wi...
Article
In cycling, oblique head impacts from a fall cause rotational motion of a cyclist’s head and it is rotational kinematics that are most commonly associated with mild and severe brain injuries. This study aims to compare the head kinematics and brain strain response between two oblique test protocols for simulating fall impact events in cycling. (1)...
Article
Sporting helmets with linear attenuating strategies are proficient at reducing the risk of traumatic brain injury. However, the continued high incidence of concussion in American football, has led researchers to investigate novel helmet liner strategies. These strategies typically supplement existing technologies by adding or integrating head-helme...
Article
Full-text available
Objectives: To collect and analyse helmets from real-world equestrian accidents. To record reported head injuries associated with those accidents. To compare damage to helmets certified to different standards and the injuries associated with them. Methods: Two hundred sixteen equestrian helmets were collected in total. One hundred seventy-six he...
Article
Current equestrian standards employ a drop test to a rigid steel anvil. However, falls in equestrian sports often result in impacts with soft ground. The purpose of this study was to compare head kinematics and brain tissue response associated with surfaces impacted during equestrian accidents and corresponding helmet certification tests. A helmete...
Article
Full-text available
Commercial software for injection moulding is available to optimise the mould design for macroscale products, but such software cannot accurately simulate the moulding process and defects for micro features, which are critical for the performance of polymeric micro/nano devices. In the present work, essential micro features with an aspect ratio of...
Article
Full-text available
The aim was to investigate mechanical and functional failure of diffuse axonal injury (DAI) in nerve bundles following frontal head impacts, by finite element simulations. Anatomical changes following traumatic brain injury are simulated at the macroscale by using a 3D head model. Frontal head impacts at speeds of 2.5–7.5 m/s induce mild-to-moderat...
Article
Full-text available
Concussion can occur from a variety of events (falls to ice, collisions etc) in ice hockey, and as a result it is important to identify how these different impact sources affect the relationship between impact kinematics and strain that has been found to be associated to this injury. The purpose of this research was to examine the relationship betw...
Article
The purpose of this research was to conduct reconstructions of concussive and non-concussive impacts in ice hockey to determine the biomechanics and thresholds of concussive injury in ice hockey. Videos of concussive and non-concussive impacts in an elite professional ice hockey league in North America were reconstructed using physical and finite e...
Article
Despite young children being a high-risk population for sustaining concussive injuries in sport, few studies have investigated head impact biomechanics from sporting impacts using physical models and finite element models of the brain. Physical reconstructions are often used in concussive research, using the recorded kinematics to load finite eleme...
Article
Current standard headforms used for sport and automotive helmet certification have poor biofidelity in terms of their mass and moments of inertia (MOI) and may not be suitable for evaluating helmet performance in oblique impacts. In this study, a novel inertially correct headform is designed and built and is compared with the HIII 50th percentile m...