Most babies born in 1900 died before the age of 50; 100 years later life expectancy in the UK now exceeds 80 years, with the number of over-65s expected to double by 2030. This trend is radically changing the age demographics of the population and creating a new set of challenges for engineers. One of the most significant of these is to give people a higher quality of life in their old age.

Significant progress has been made; 300,000 hip replacements are now performed annually worldwide, releasing people from pain, and extending the active period of their lives by 20 years or more. The success of these implants has led scientists to develop a new type of biomaterial that is promising to do for medicine what silicon did for computing.

Historically the function of biomaterials has been to replace diseased or damaged tissues. These biomaterials were selected to be as inert as possible while fulfilling mechanical roles such as teeth filling and hip replacement. Metals such as titanium and mercury amalgam have been remarkably successful in repairing hard tissues like bones and teeth respectively because they are chemically inert and so don’t decay inside the body, and are strong enough to last tens of years. Applying this approach to softer tissues has proved less easy because designing soft materials with the required flexibility that can also maintain their integrity is tricky. The proposed solution is to create implants that grow and repair themselves.

Take the knee for instance, its function relies on cartilage, a soft material in which elasticity is vital to its role of transmitting forces that are produced when we walk, jump and generally lark about. It needs to do this while being hard enough to allow the knee joint to smoothly rotate and twist as you change direction. Being hard but elastic is not an easy combination for a material, and cartilage performs this by having cells living within it, the job of which is to continually maintain a three-dimensional internal skeleton of collagen fibres that give the material its properties. These cells are called chondroblast cells, and cartilage is their habitat. It is possible to grow chondroblast cells from a patient’s own stem cells. However, the injection of these into an existing joint does not result in the repair of the cartilage because it is not just that the cells are missing, but that their habitat is damaged or destroyed.

What is required is the erection of a temporary structure within the joint that mimics some of the basic internal architecture of cartilage but also protects the cells from mechanical stress. Introducing chondroblast cells into such a scaffold, as it is called, allows them to grow and divide, to increase their population, and in doing so gives them time and space to rebuild their habitat, and so regrow cartilage. The neat thing about this is that the scaffold can be designed to dissolve once the cells finish rebuilding their habitat.

This idea was pioneered in the 1960s by Professor Larry Hench in response to the huge number of amputees produced by the Vietnam war. Hench and his team discovered a material called hydroxylapatite, a mineral that occurs in the body and bonds very strongly to bone. They experimented with many formulations and in the end found that when it was made in the form of a glass, it had extraordinary properties: bone cells, called osteoblasts, like to live on it, and when they did that they created new healthy bone. When this bioactive glass was made in a porous form it had tiny channels into which the osteoblast cell could grow and by doing so they replaced it with fully functioning bone.

Such tissue engineering has been very successfully used in clinical practice to provide synthetic bone grafts and to rebuild the bones of the skull and face. It is not yet in clinical use for cartilage regeneration, but is being successfully used in laboratories. In this case the cells are nurtured in a bioreactor that mimics the temperature and humidity of the human body while also providing the cells with nutrients.

The potential of scaffolding technology has opened up the future possibility of building replacement organs for the human body such as livers and kidneys. The first steps in this direction have already been taken with the development of a human windpipe grown in a laboratory and implanted into a patient. One of the major problems for such tissue engineering is creating and maintaining a blood supply to the artificially grown tissues so that they can survive and function when they are implanted inside the body. If synthetic organs become a reality, they will radically change the world of medicine. Such a fundamental change is going to be needed to allow an aging population to work for longer before taking their pensions, and to live to be a centenarian while being fit and healthy. I certainly hope to be one of these.

This is the last column in my series on stuff. Over the last year it has been my pleasure and privilege to select a different material every month with the aim to uncover the human needs and desires that brought it into being, and decode the materials, science and engineering behind it. I hope you’ve enjoyed it as much as I have. The full list of columns is on the Guardian/Observer website.