Eli Jerby

Eliahu (Eli) Jerby (Hebrew: אלי ג'רבי; born June 22, 1957) is a full professor at the Iby and Aladar Fleischman Faculty of Engineering at Tel Aviv University.

His studies deal with localized interactions between electromagnetic (EM) radiation and materials in various phases, and with the development of their applications in the microwave regime.

Jerby was graduated in 1979 with bachelor's and master's degrees in electrical engineering at Tel Aviv University.

In 1988 he completed his PhD in physical electronics, on 3D linear theory of free-electrons lasers (FEL’s).

He was awarded then post-doctoral fellowships from Fulbright and Rothschild Foundations, and studied as a research fellow in the laboratory of Prof. George Bekefi at the Massachusetts Institute of Technology (MIT).

In 1990 he was appointed as a faculty member at the Faculty of Engineering of Tel Aviv University.

He established there research and teaching laboratories in various aspects of microwaves, where he has been leading research and development activities, teaching, and mentoring of research students.

The studies of Prof. Jerby and his team deal with various interactions between EM waves and materials in phase transitions, and in particular between microwave radiation and solids in melting processes, powders and dusty plasma generation.

He is also developing potential applications for these phenomena.

Jerby’s early research dealt with excitation and amplification mechanisms of EM radiation using electron beams in vacuum, in fast-wave interactions (such as cyclotron-resonance masers (gyrotrons) and FEL’s).

Later he combined these mechanisms synergistically with slow-wave interactions in periodic structures of 1, 2 and 3 dimensions (similarly to structures now known as metamaterials).

In this study, a FEL device operating at low voltages, and accordingly in the UHF range (with a one-meter wavelength, the longest achieved in FEL devices), was demonstrated for the first time.

Additional innovations were also presented in these studies, such as the use of ferroelectric cathodes to produce electron beams for these devices, two- and three-dimensional gyrotron arrays, a carbon-dioxide laser excited by microwaves, FEL-antenna array, and more.

Another branch of Jerby’s studies with his team deals with the effect of creating hotspots by localized microwave-heating (LMH), including a theoretical analysis of this phenomenon, and its applications.

LMH experiments have been conducted in Jerby’s laboratory on various solids, such as ceramics, concrete, glass, silicon, etc..

These experiments and their models showed the feasibility of accelerated local microwave heating, up to transition temepratures of melting, vaporization and plasma ejection.

In these LMH processes, the hotspots evolves within a few seconds of EM irradiation (in the order of ~100 watts).

The local temperature exceeds over 1,000 degrees Celsius at the hotspot, typically of ~2 mm in diameter (about two orders of magnitude smaller than the ~12-cm EM wavelength).

This finding, apparently seems as a violation of the diffraction limit, is explained by the temperature dependence of the material's properties, so that initial non-uniform heating causes the hotter area to heat up faster (and dissipate less heat) than its surroundings.

This phenomenon of local instability was also described by Jerby in analogy to the Matthew effect, which exists in general in diverse fields, such as society, economics, academia, etc. (also known as the accumulative effect of advantages and disadvantages, or as the theological question of why the rich get richer and the poor become poorer).

The phenomenon of intentional LMH provides the basis for the microwave-drill invention (see upper figure).

This discovery, presented in 2002, aroused the media interest worldwide at the time.

Microwave drills have since been successfully tested in various materials and for a variety of applications, such as delicate drilling in glass [18], as well as in bones for medical purposes, drilling in rocks for mining purposes, and the like.

Microwave drills for concrete demonstrated silent operation in relatively deep drilling (e.g. to ~26-cm depth in a ~1.2 cm diameter).

Microwave cutting of concrete was also demonstrated.

Recently, a similar capability was also shown for iron cutting, by means of LMH combined with direct current (DC).

The LMH studies showed that operating a device similar to the microwave drill in the inverse direction (that is, by pulling instead of pushing the electrode) causes the molten hotspot to detach from the substrate material.

Further irradiation of the melt by localized microwaves causes its vaporization in a form of a plasma column.

In certain operating conditions, this plasma is further converging to a form of a plasma ball floating in the air (see lower figure).

This plasma contains, in addition to ions and electrons, also larger charged particles, on a nanometric and micrometric scale, which originate from the substrate material, and is therefore defined as dusty plasma.

The similarity between these laboratory-made plasma balls and the relatively rare phenomenon of ball lightning in nature enables to some extent the simulation the natural atmospheric phenomenon in the laboratory.

A similar experiment also demonstrates various volcanic phenomena, such as the flow of hot lava from the molten core of a basalt rock.

Later in this study, it was also proposed to use the DC-LMH mechanism to create dusty plasma for the purpose of extracting minerals from rocks, directly by electrical means, without the need for mechanical operations to crush the rock.

Additional studies examined novel applications for the LMH phenomenon, such as igniting thermite mixtures, and 3D-printing of metal powders.

The thermite mixture contains two powders, one of a metal and the other of another metal oxide.

It was discovered in this study that the ignition of this metallic fuel using LMH is highly efficient.

This inherently oxygen-balanced combustion is also possible in vacuum and empty spaces, as well as in aqueous media (due to the "Bubble marble" phenomenon, also discovered in this study).

The LMH implementation for 3D printing is based on melting small batches of metal powder, and adding them incrementally to each other in the desired structural shape (i.e. in an additive manufacturing approach).

These LMH applications also coincide with the current trend of using transistor-based microwave applicators (instead of magnetrons) for energetic uses, and in particular for heating, a trend that Jerby and his group pioneered since 2006.

Jerby's research has received multi-year funding from the Israel Science Foundation (ISF), the Binational Science Foundation (BSF), the Israeli ministries of energy and science, and more.