Author: Prof David Taylor, chartered engineer, MA PhD FIEI MRIA, Professor of Materials Engineering and Head of Department of Mechanical and Manufacturing Engineering in Trinity College Dublin
The following article is based on a talk which I gave to the Engineers Ireland Heritage Society on 15 April 2013. I am very grateful to the Heritage Society for asking me to talk on the topic of bioengineering, because it has given me the opportunity to reflect on this subject, to ask myself what bioengineering actually is and to think about how this subject has developed historically in this country and elsewhere. Bioengineering consists of two different but related activities: the use of engineering principles to understand the human body and the development of new medical products such as implants, diagnostic tools and imaging equipment. In recent years, the subject has come to prominence in this country, thanks to the large number of medical device and pharmaceutical companies established here. But in fact bioengineering is a very old subject, just as old as engineering itself. We can see this by looking at some of the very earliest developments in the engineering sciences. For example, in 1505 Leonardo da Vinci made studies of the action of the wind on the wings of birds: his elegant sketches and notes have been passed down to us today. Working from this basic understanding or aerodynamics, he designed one of the first-ever flying machines, an example of what we now call biomimetics, or bio-inspired design. Galileo (1564-1642) is best known for his work on astronomy, but engineers are well aware that he also wrote Dialogues Concerning Two New Sciences: Mechanics and Local Motion, which is the first systematic treatise on mechanics. In this book, he frequently draws on nature to illustrate examples of mechanical principles such as the strength of materials, hydraulics and impact forces. A similar approach was also taken by other pioneers such as Borelli and Galvani and this should come as no surprise – in their times, animals, plants and the human body were the best available examples of complex machines.
In one memorable passage, Galileo discusses the effects of size and scale in the strengths of beams, a complex problem which is still being researched today. He realises that simple linear scaling does not work because volume (and therefore mass) increases more rapidly than linear or areal dimensions; he illustrates the principle very elegantly by comparing the bones of small and large animals (see Fig 1, right) and speculates that a size limit will be reached where an animal’s bones could not support its own weight. Thus, even at the very start of the development of engineering as a discipline, we see the appearance of bioengineering as a means of understanding engineering principles and as an inspiration for engineering inventions.
Moving now to the 19th century, Irishman Samuel Haughton (1821-1897) was a great pioneer of bioengineering. Here, again, we find the two parallel activities of understanding the human body and using this understanding to do something useful. Haughton had a very broad understanding of science and engineering, including geology, the medical sciences and mechanics, which he was able to integrate very successfully to produce Animal Mechanics, arguably the first book on what we now call biomechanics. Drawing on his observations of living animals and fossils, Haughton developed a great understanding of the mechanics and kinematics of joints and other body parts. He corresponded with Charles Darwin and Haughton’s expertise could have been very useful to Darwin, but sadly there was a fundamental disagreement. Haughton rejected the concept of evolution, arguing that animals had been designed and made by God in the forms in which then now exist. He supported his argument with many examples aimed at showing that the designs of body parts are perfect, unable to be improved upon and therefore clearly the work of God, the great designer. This is an interesting example of how two people looking at the same physical evidence, and both using sound scientific principles, can nevertheless come to very different conclusions. Haughton used his understanding of biomechanics in a very practical way, to calculate the ideal ‘drop’ distance to be used when executing a person by hanging. It may seem surprising to us that a medical man, and one in holy orders as well, should devote himself to this grisly subject. But for Haughton, it was a humanitarian act, given that capital punishment existed and was very common (7,000 public hangings occurred in Britain between 1770 and 1830). This research aimed to minimise the suffering of the condemned person, bringing death as swiftly and painlessly as possible. Haughton’s approach was based on potential energy, calculated by multiplying the drop distance by the person’s weight, an approach which is still common today in studies of impact fracture.
THE MODERN PERIOD
Moving to the 20th century, two developments were very important in the establishment of the modern subject of bioengineering. The first of these is the invention of the artificial hip joint. A number of different inventions were tried, but the implant developed by John Charnley (1911-1982) turned out to be by far the most successful, and is in many respects identical to those used today (see Figs 2, 3 and 4)).
The enormous success of this device (these days approximately three quarters of a million hip joints are implanted annually) gave prominence to bioengineering and encouraged many engineers, myself included, to get involved with medical devices. The other major factor was the Whitacker Foundation, whose mission was to stimulate the development of bioengineering in the USA. Between 1975 and 2006, it donated over $700 million and created 30 academic programmes in biomedical engineering in US universities. Within a few decades, bioengineering grew from being a niche activity in which a few engineers spent time helping doctors, to a mature discipline in its own right.
I would like to finish this article by reflecting on that process, drawing on my own experience. I first became involved with bioengineering in 1985, shortly after arriving to work in Trinity College Dublin, as a result of meeting James Sheehan, a prominent orthopaedic surgeon who had recently been involved in starting up the Blackrock Clinic. Mr Sheehan was an engineer as well as a doctor, having designed a hip implant and a knee implant himself (see Fig 3), and he recognised the value of bringing engineers into the hospital, showing them operations in progress and discussing problems that surgeons were experiencing. Myself and another engineer, Brendan McCormack, worked with Mr Sheehan for many years and developed a Bioengineering Centre in Trinity College Dublin (TCD) and University College Dublin (UCD). There were only a few other such groups in Ireland at the time, notably Edward Little in the University of Limerick and Annraoi de Paor in UCD’s Electronic Engineering Department. There was a great pioneering spirit at that time, and what I most remember is that we did not really know what we were doing! The subject was only just starting and we were prepared to try anything – most of the time, we were bluffing and just about getting away with it. Over the following decade, IDA Ireland operated a strong policy of attracting high-technology companies into Ireland, and the medical device industry was of particular interest. We had many meetings with companies during that time; I think that the existence of bioengineering research activities in our universities, albeit at a fledgling stage, was a factor in the decision of these companies to come to Ireland. We also set up an annual national conference, Bioengineering in Ireland, which continues to this day as a focus for the discussion of current research. Over the last 30 years in which I have been lucky enough to work in this field, the nature of bioengineering, and of the person that we call a bioengineer, has changed significantly. In 1990, I would have described a bioengineer as a person who was first and foremost an engineer, skilled in his/her own branch of engineering, who had picked up enough medical knowledge to work with doctors.
INTERFACE BETWEEN MEDICINE AND BIOLOGY
By 2000, a new type of person was emerging, one who was capable of working on the interface between medicine and biology. One such person whom I was lucky enough to work with was Patrick Prendergast, currently Provost of TCD. Patrick’s great contribution was to take computer modelling techniques originally intended for engineering use, such as finite element analysis, and adapt them to allow simulation of the living system: modelling the behaviour of cells which react to our mechanical environment and make changes to adapt our bodies accordingly. Today, the bioengineer is a special and unique kind of engineer, as is recognised by the many undergraduate courses in this field in our universities. It is a challenging discipline, requiring knowledge in both the physical and biological sciences, and design skills which encompass engineering and medicine. Examples of current developments in this field are tissue engineering, whereby living cells are used to create tissues and organs for implantation, and biomimetics, the creation of new engineering materials and devices inspired by nature. It is a very rewarding subject to work in, constantly changing and growing, and one that I can recommend to any young engineer.
David Taylor, chartered engineer, MA PhD FIEI MRIA is Professor of Materials Engineering and Head of Department of Mechanical and Manufacturing Engineering in TCD. He works on the strength and fracture of biological materials and biomedical devices, in the Trinity Centre for Bioengineering.