Since the mid-80', when Binning and Roher made possible to "see" the atoms piece by piece, it has become more and more common, often necessary, to study and to develop structures with nanometric dimensions. In disciplines like material science, functional chemistry, molecular biology and optoelectronics the approach "atom-by-atom" or "molecule-by-molecule" has made devices with nanometric dimensions affordable, with original functionalities and often with stunning performance. Accessing the physical/chemical properties of these devices has therefore become essential and various techniques and methods (optical, chemical, mechanical etc.) have been developed to accomplish this task.
This course focuses on the method and the instrumentation to perform the electrical characterisation of the matter . The investigation of the electrical properties of nanoscopic samples (conductance, dielectric costant, charge density, impedance, charge trapping times, etc.) is not only essential when the samples are going to be used directly as a pure electronic device. Their knowledge is also often beneficial as a complementary information in conjiunction with other techniques (spectroscopic, morphological, etc.) to address the primary chemical/physical properties of the matter at the nanoscale.
On a more practical basis, monitoring the electrical properties of nanobiosamples and tracking their variations upon interaction with external forces is a powerfull way to build electronic nanobiosensors . The counting of cells by detecting conductance variations or the tracking of neuronal cell differentiation by cathecolamine exocitosys monitoring through amperometric measurements both demonstrate how electrical measurements on nanosamples, expecially in the biomolecular domain, have reached a high degree of sophistication. Not to mention how compact, flexible and cheap an electronic system can be when compared with other kind of measurement techniques.
The course aims to cover various aspects of electronic measurements, from the measurement techniques used to access the electrical properties of the nanoscopic systems to the specific circuits necessary to sense the tiny electric signals with the best possible resolution.
The course is thus intended for :
- all the nanobioscience scientists who desire to have a deep insight into the realm of electrical measurements on nanosamples and of the ultimate characteristics of instumentation integrated-on-chip;
- all the electronic designers of integrated circuits who desire to approach or to focus their realisations towards the vast and growing field of the instrumentation for the nanobioscience;
- all Ph-D students attracted by both fields who have not yet made up their minds, for them to continue to balance on both !
The program is structured to be a University-style course and not a collection of seminars. Topics are taken from the "basics" and developed untill examples of state-of-art realisations. A documentation will be provided at the beginning of each lesson. Time for discussions will be available at the end of each lesson.
In particular the course will focus on :
- How to design dedicated instrumentation for the measurement of currents, voltages, impedance and noise with the state-of-the-art sensitivity . The course will present the best circuit architectures, the design considerations for maximum resolution and their achievable performance together with the specific aspects to be taken into account when integrating the full instrument on a single chip.
- How to perform impedance spectroscopy measurements with sub-attofarad resolution and nanoscale position resolution .
The course will introduce capacitance measurements tecniques and impedance spectroscopy applications, eventually coupled with Atomic Force Microscopes to complement the electrical information with a position information of nanometric precision.
- How to perform electrical measurements on biomolecules in-vitro in the presence of physiological saline solution .
The course will present how to manage the electrical signals extracted from neutral molecules via electrochemical measurements with 3 electrodes, the electronic circuits to interface electrodes whose size can be as small as few tens of nanometer square and various applications in the biological domain from olfactory receptors, to cathecolamine exocitosis, to cell counting, etc.
- How to use electronic noise as a signal to access the physical properties of matter at the nanoscale .
The course will recall the most advanced methods to measure very low noise levels, even lower than the input noise of standard instrumentation. It will then highlight, through examples, the tecniques of noise characterisation to extract physical quantities: from telegraph noise to electron spin, from shot noise to dielectric relaxation times, showing the importance of adeguate instrumentation like the correlation spectum analyzer.