Self-healing Cellular Architectures

Powerful and sophisticated systems, from computers, through control systems, to 'conventional' household appliances
have become a necessity in our modern way of life. In the modern world of digital electronics - virtually all of which is now
built using VLSI technology - we are quite accustomed to the idea that hundreds of thousands, often millions, of individual
components on a chip must work faultlessly over extended periods of time. Yet, it commonly requires only a single
transistor to fail to have catastrophic consequences for the entire system.
Imagine an automobile travelling at high speed in the fast line of a busy motorway. Suddenly, the electronic Engine
Management Unit (EMU) develops a malfunction, the engine cuts out; soon after this the servo-assisted brakes and
steering (that depend on the engine inlet manifold vacuum) both cease to function properly; a queue of stationary vehicles
is fast approaching. The outcome of this scenario is left to the reader's imagination. This is a somewhat dramatic thoughtexperiment,
but one that brings the safety-criticality and reliability aspects of some everyday digital electronic components
in our lives into stark focus.
The design of complex, but reliable, electronic systems and ensuring their long-term fault free operation is a major
challenge we face today. This demand is even more pronounced in the case of electronic systems where their correct
operation is imperative, e.g., anti-lock braking systems, fly-by-wire aircraft, space exploration, industrial control and
shutdown systems; they should be able to operate correctly in the presence of faults and be fault tolerant.
How can we design such reliable systems? Nature offers some remarkable examples dealing with complexity and
unreliability. Living organisms, and in particular the human body, is one of the most complex systems ever known. Yet
they possess an extremely high degree of reliability. Although local failures, due to harmful pathogens and environmental
conditions, are common, the overall function of the organism is highly reliable. Many of the cells and tissues die as a
result of damage, but because self-diagnostic and self-healing continues incessantly, full functional integrity of the body is
not compromised. It will carry on working properly because the body's defence mechanism, comprising numerous
immune responses, will try to restore its full functionality. We could therefore justly ask ourselves the question; "would it
be more efficient and less costly to draw inspiration from nature in how it deals with the complexity vs. unreliability issue
with such a remarkable degree of efficiency?"
The challenge we propose to take on, therefore, is to adapt biological processes found in living beings in our pursuit of
designing reliable electronic systems that demand an ever increasing level of complexity. Although a great deal has
already been achieved in these areas, much of this progress having been made by the two collaborators in this proposal,
there remains still a vast amount to be done.
The objective of this proposal is to evaluate and apply novel, biologically inspired, processes and algorithms for building
reliable VLSI systems on silicon that possess self-diagnostic and self-healing properties. Inspired by nature, our research
will adapt properties of biological systems, such as their multi-cellular organisation and evolutionary development, to
create efficient electronic systems. It will also apply biological processes and the characteristics of both the innate and the
acquired immune system to help solve the reliability and fault tolerant issues of artificial systems at cell, tissue
(subsystem) and also at organism (system) levels. Our research will aim to pave the way for a biologically inspired unique
design approach for electronics systems across a wide range of applications; from communication, through computing
and control, to systems operating in hostile environments.