Complex systems, soft matter and biophysics

Large infrastructural networks, telecommunications, “smart” sensors, Big Data, engineered materials place the study of complex systems among the most rapidly growing disciplines, including soft and active matter, and biophysics.  At international level, these areas, which also include fundamental physics (emerging quantum phenomena, such as high-temperature superconductivity) and interdisciplinary aspects like multilevel networks, epidemiology or the animal behaviour, are strengthening. Particularly important is the Human Brain Project (HBP). Goals are:

  • An integrated plan based on networks theory and Big Data, for controlling viral techno-social phenomena (biological, information, social) and cascade phenomena (technological breakdown, economic and financial crisis) and the optimization of infrastructures (electrical, transport and logistic networks).
  • Bio–eco–compatible, bio–mimetic, and granular materials for environment, medicine, agri–food, energy, cultural heritage, industry, brain information processing and synaptic transmission.
  • Devices based on surfaces and volumes intelligent control to realize robots for “smart factory”, for example for the growth of cell tissues or antibacterial surfaces.
  • Study of the interaction between organisms and environment for the impact of natural and anthropic perturbations, for studies on water and food quality and on the availability of fishing resources.
  • Study of complex biological systems (macromolecular, cellular and tissue, model organisms) with emphasis on biophysical mechanisms of pathology, for the development of new drugs, diagnostic and therapeutical approaches, based on nanosciences too.

In the frame of the HBP, the main goals are new methodological instruments for the study, the diagnosis and the treatment of illnesses and cerebral dysfunctions (autism, epilepsy, cognitive processes deficit, neurodegenerative pathologies), man-machine interfaces, neural modelling, low-consumption intelligent  technologies and brain–enabled robot.

Spotlights on research activity

Complex active optical networks as a new laser concept

We have investigated complex optical networks containing one or more gain sections, and we have reported the evidence of lasing action; the emission spectrum reflects the topological disorder induced by the connections. A theoretical description compares well with the measurements, mapping the networks to directed graphs and showing the analogies with the problem of quantum chaos on graphs. We have shown that the interplay of chaotic diffusion and amplification leads to an emission statistic with characteristic heavy tails: for different topologies, we have provided an unprecedented experimental demonstration of Lévy statistics, expected for random lasers, for a continuous–wave pumped system.

Contact person: Stefano Lepri, ISC-CNR Sesto Fiorentino
Complex systems, soft matter and biophysics

Local equilibrium in bird flocks

We have introduced a novel dynamical inference technique, based on the principle of maximum entropy, which accommodates network rearrangements and overcomes the problem of slow experimental sampling rates. We have used this method to infer the strength and range of alignment forces from data of starling flocks. We have found that local bird alignment occurs on a much faster timescale than neighbour rearrangement. Accordingly, equilibrium inference, which assumes a fixed interaction network, gives results consistent with dynamical inference. We conclude that bird orientations are in a state of local quasi–equilibrium over the interaction length scale, providing firm ground for the applicability of statistical physics in certain active systems.

Contact person: Massimiliano Viale, ISC–CNR Univ. Roma La Sapienza
Complex systems, soft matter and biophysics

Red blood cell as an adaptive optofluidic microlens

We have shown that a suspended red blood cell (RBC) behaves as an adaptive liquid–lens at microscale, thus demonstrating its imaging capability and tunable focal length. In fact, thanks to the intrinsic elastic properties, the RBC can swell up from disk volume of 90 fl up to a sphere reaching 150 fl, varying focal length from negative to positive values. These live optofluidic lenses can be fully controlled by triggering the liquid buffer’s chemistry. Real–time accurate measurement of tunable focus capability of RBCs is reported through dynamic wavefront characterization, showing agreement with numerical modelling. Moreover, in analogy to adaptive optics testing, blood diagnosis is demonstrated by screening abnormal cells through focal–spot analysis applied to an RBC ensemble as a microlens array.

Contact person: Lisa Miccio, ISASI–CNR Pozzuoli
Complex systems, soft matter and biophysics

Electrospun amplified fiber optics

We have reported on near–infrared polymer fiber amplifiers working over a band of about 20 nm. The fibers are cheap, spun with a process entirely carried out at room temperature, and shown to have amplified spontaneous emission with good gain coefficients and low levels of optical losses (a few cm–1). The amplification process is favored by high fiber quality and low self–absorption. The found performance metrics appear to be suitable for short–distance operations, and the large variety of commercially available doping dyes might allow for effective multi–wavelength operations by electrospun amplified fiber optics.

Contact person: Dario Pisignano, NANO–CNR Pisa
Complex systems, soft matter and biophysics