Infineon described the Neuro-Chip development in a paper presented at the International Solid State Circuits Conference (ISSCC 2003), a highly respected global forum for new developments in semiconductors, held in San Francisco, California. The research findings include the first report on measurements of electrical signals from live neurons. Working with the renowned Max Planck Institute of Biochemistry, Infineon's project partner specialised in bioscience research, the researchers have recorded electrical signals from the neurons from snail brains.
Neurons are the specialised cells that make up the nervous systems of all living things. Nerve tissues, comprised of many associated nerve cells, are the principal component of the brain and spinal cord. Nerve cells communicate with each other through electrical pulses, so the ability to read these signals and record them in a computer system holds the promise of new insights into neurological processes.
"Concerning the signal-to-noise ratio, this chip operates close to elementary physical limits", stated Dr. Roland Thewes, the Senior Director responsible for biosensor chip activities within the Corporate Research Center at Infineon Technologies. "Infineon is able to draw on 50 years of knowledge in chip making to develop biochips that bring the advantages of silicon technology to biochemistry and new drug research. With the Neuro-Chip, we are laying the groundwork for advances in scientific understanding."
Infineon has collaborated since mid-2000 with researchers at the Max Planck Institute (MPI) for Biochemistry in Martinsried, near Munich, on development of the Neuro-Chip and the associated test system. Infineon is principally responsible for the semiconductor technology development, and the MPI provides its specialised know-how in the field of neuron-chip interfacing.
Professor Dr. Peter Fromherz, Director of the Max Planck Institute for Biochemistry in Martinsried, Germany, commented: "That our long-lasting basic research on neuron-semiconductor interfaces now sees a high-tech chip, is like a dream coming true. Infineon's development of cutting edge micro-electronics may be a pre-condition for unheard of applications in the field of biomedicine, biotechnology and brain research."
The Infineon Neuro-Chip integrates 128 x 128 sensors in an array pattern covering just one square millimeter. A sophisticated electronic circuit is integrated below each sensor, which amplifies and processes the extremely weak signals of neurons. Individual neurons are placed into a nutrient solution above the sensor array, which keeps the neurons alive and allows reconstruction of nerve tissue. Compared to classical methods of research, in which neurons are damaged in the preparation of study samples, undisturbed observation of nerve tissue over a period of several weeks offers scientists a continuous insight into the functionality of how the nervous system and brain learns, processes and stores its learnings.
The "Neuro-Chip" from Infineon Technologies is connected with a living nerve cell. The Neuro-Chip's 16.384 sensors read the electrical activity of the cell. The typical size of neurons is between 10 - 50 micrometers (1 µm, one thousandth of a millimeter).
Photo courtesy of Infineon Technologies, Max Planck Institute.
The sensor density of the Infineon Neuro-Chip is approximately 300 times greater than today's common methods for studying neurons, which use glass substrates with vapour-deposited metallic lanes to contact the neuron. Each sensor on the chip is separated by a distance of just eight micrometers, one thousandth of a millimeter. Since the typical size of neurons is between 10 - 50 micrometers, low-density sensors may not establish a reliable contact. The high-density sensor array of the Neuro-Chip assures that each neuron in a sample is contacted by at least one sensor.
Instead of sequentially checking every single neuron, the Infineon Neuro-Chip surveys several neurons at the same time. As a result, more statistically relevant data is available. Additionally, the Neuro-Chip enables recording of the operating sequence of electrical activity within nerve tissue over a defined time. Every second, the Neuro-Chip can record more than 2000 single values for each of its 16.384 sensors. The data can then be transformed into a colour picture for visual analysis. Researchers can detect from this data how complete nerve tissues react to electrical stimulation or certain chemical substances in a given period of time.
The total area of Infineon's Neuro-Chip measures five millimeter by six millimeter, including the circuitry required to amplify and process the neuron signals and transmit the data off-chip. The chip is based on a standard Complementary Metal Oxide Semiconductor (CMOS) technology extended with additional process steps to realise the capacitive sensors array.
Infineon's successful development of a complete integrated circuit enabling observation of the extremely low cell signals is a world technology breakthrough. The Neuro-Chips can detect and handle voltage changes with peaks ranging from 100 microvolt, one millionth of 1 Volt, to 5 millivolt, one thousandth of 1 Volt.
Infineon Technologies AG offers semiconductor and system solutions for the automotive and industrial sectors, for applications in the wired communications markets, secure mobile solutions as well as memory products. With a global presence, Infineon operates in the United States from San Jose, California, in the Asia-Pacific region from Singapore and in Japan from Tokyo. More Infineon news is available in this VMW issue's article Infineon supplies 3D biochips and complete analysis system for efficient drug development.