Small, Smaller, and Nano
Editor’s Corner | Alfred A. Bove, MD, PhD, MACC, Editor-in-Chief, CardioSource WorldNews
As a budding electrical engineer, recently graduated and now enrolled in medical school, I was looking for a moonlighting job. I landed a part-time position in the school’s electronic design shop. There, researchers would request special devices to manage their measurements or to collect electrical signal data to be processed or plotted. The design shop was conveniently located four floors below the anatomy and physiology labs and the medical school classrooms. My first few jobs required designing and building special electrical circuits that processed research data.
That was the end of the vacuum tube era (you can read about them on Wikipedia), which was being replaced by the revolutionary development of circuits using discrete transistors. (Integrated circuits had been invented but still being perfected.) My vacuum tube devices were housed in a cabinet usually about a foot or so long and deep and eight inches high. Inside were vacuum tubes, resistors, capacitors—all of which could be connected in a way to process electrical signals. The front panel contained numerous 1- and 2-inch diameter knobs, toggle switches, and meters of various kinds with needles that pointed to the desired measurements.
Today, devices that perform those functions are incorporated in a small flat wafer about 2 x 2 mm square that can be placed in a small Band-Aid® type of surface sensor for ECG, EEG, oxygen saturation, temperature, and other measurements that are transmitted to a smart phone via Bluetooth signals. Similar integrated circuits are used in pacemakers and ICDs.
My student research involved early digital computers. A typical computer was five or six feet high, seven or eight feet long, and made up of several tall cabinets with large power cables to make them function. Many required large air conditioners to maintain a constant temperature in the “computer room.” A computer of that size usually had a 64 KB memory, one or two 250 KB hard drives, and several tape drives for long-term storage, and their processing speed was orders of magnitude slower than what we are accustomed to today. But it was a computer; it could be programmed to do complicated data processing and it saved enormous amounts of computation time. That behemoth in the computer room in 1968 had about 1/100,000th the capacity of the smartphone I carry on my belt today. The world of electronic gizmos has shrunk enormously, while the capacity of the gizmos has increased exponentially.
From Micro to Nano
Gordon Moore, a founder of Intel, predicted in 1965 that the number of transistors in an integrated circuit would double annually. His prediction (Moore’s law) was accurate for 15 years, and continues with doubling about every 3 years. We now talk about nanometer transistors, the smallest of which was just announced this summer by IBM; the prototype chip has transistors that are seven nanometers wide, meaning you could fit thousands of them inside a red blood cell.
One challenge: as chip components shrink, the copper wiring that connects them must shrink, too, and as these wires get thinner, they heat up tremendously. The solution may be graphene, made from single-atom-thick sheets of carbon that may help copper wires keep their cool. So we have the potential for billions of transistors and other circuit components in a single integrated circuit.
These advances have provided enormous capability in medical device technology. Some of these circuits can be used to create programmable microcomputers that presently operate the myriad functions in our smart phones. Others have circuits designed to provide a specific function such as heart rhythm detection and responses that might include pacing the heart, shocking the heart, or recording and storing a continuous ECG signal for later analysis.
We now have heart rhythm recorders implanted subcutaneously through a small skin incision that transmit data using Bluetooth technology to a nearby receiver that then sends the data to a central monitoring facility for analysis. These have contributed significantly to our understanding of syncope and of paroxysmal atrial fibrillation.
We see the development of subcutaneous miniature defibrillators, of pressure sensors implanted in the pulmonary artery to detect early changes leading to heart failure exacerbations, and of pacemakers that are essentially a small wireless bead that is deposited in the right ventricle. All of these devices are built around integrated microcircuits designed for a specific function, connected to unique signal sensors, microbatteries, and radio transmitters to produce a functioning, implantable device that both measures and records biologic information and makes therapeutic decisions based on the data it receives.
And we aren’t yet at the end of miniaturization. Circuits become denser, power consumption gets lower, and batteries are better designed, so that complex diagnostic and therapeutic functions can be incorporated into smaller physical devices that will function for a decade or more without needing replacement. Many of these advances have contributed to substantial improvements in health, while others are looking for applications. The continuing development of this technology will improve care for many of our patients in the future.
Alfred A. Bove, MD, PhD, MACC, is professor emeritus of medicine at Temple University School of Medicine in Philadelphia, and former president of the ACC.
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