The Microwave-Drill

Abstract

We present a drilling method that is based on the phenomenon of local hot spot generation by near-field microwave radiation. The microwave drill is implemented by a coaxial near-field radiator fed by a conventional microwave source. The near-field radiator induces the microwave energy into a small volume in the drilled material under its surface, and a hot spot evolves in a rapid thermalrunaway process. The center electrode of the coaxial radiator itself is then inserted into the softened material to form the hole. The method is applicable for drilling a variety of nonconductive materials. It does not require fast rotating parts, and its operation makes no dust or noise.

Microwaves and Electrochemistry

“…However, a much more dramatic microwave effect can be achieved by exploiting the ''antenna effect'' of smaller metal microelectrodes (see below), which can lead to energy focusing in the presence of microwave fields [35]. The microwave focusing effect at metal tips has also been reported for thermal drill systems, for example, for drilling concrete [36], and in thermal probes for medical applications [37].…”

Microwave Heating in Moist Materials

“…In most cases, thermal runaway is a problem becasue it usually leads to destruction of the material (Zielonka et al, 1997); however it has been very effectively used in some applications: Jerby et al (2002) have developed a microwave drill that can drill holes through glass and ceramics by super-heating a very small section of the material using microwave induced thermal runaway. The system works by creating very intense microwave fields immediately in front of a needle like probe that extends into the material as the drilling process proceeds.…”

“…Microwave energy has also been used to manage weeds and other soil born pathogens (Nelson, 1987;Bansal, 2006) and to treat various animal feeds to improve their digestibility (Sadeghi & Shawrang, 2006Brodie et al, 2010). Microwaves are commonly used to process ceramics (Takayama et al, 2005) and can be used to drill through ceramics and glass (Jerby et al, 2002).…”

The precise condition of thermal runaway in microwave heating on chemical reaction

“…Four kinds of imaginary part of effective permittivity in Table 2 are used in the following calculation as refs. [2,9]. …”

“…The temperature rising of the reaction system would cause the change of electrical characteristics, if this change makes the reaction system to absorb more electromagnetic energy, a positive feedback can be formed, and the temperature in the reaction system would rise rapidly to trigger thermal runaway. On the other hand, the industry may benefit from the thermal runaway, for example, it can be used to melt metal [2] , but usually it is harmful. In the application of microwave heating on organic reactions, thermal runaway may burn the reactants out and damage microwave chemistry reactors.…”