The microwave-drill principle ͓Jerby et al., Science 298, 587 ͑2002͔͒ is based on a localized hot-spot effect induced by a near-field coaxial applicator. The microwave drill melts the nonmetallic material locally and penetrates mechanically into it to shape the hole. This paper presents a theoretical analysis of the thermal-runaway effect induced in front of the microwave drill. The model couples the Maxwell's and heat equations including the material's temperature-dependent properties. A finite-difference time-domain algorithm is applied in a two-timescale numerical model. The simulation is demonstrated for mullite, and benchmarked in simplified cases. The results show a temperature rise of ϳ10 3 K / s up to 1300 K within a hot spot confined to a ϳ4-mm width ͑ϳ0.1 wavelength͒. The input-port response to this near-field effect is modeled by equivalent time-varying lumped-circuit elements. Besides the physical insight, this theoretical study provides computational tools for design and analysis of microwave drills and for their real-time monitoring and adaptive impedance matching.

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 thermal-runaway 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.

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.

This paper presents a method for heating silicon wafers locally by open-end coaxial microwave applicators, with optical techniques employed for measuring the temperature. Silicon samples of ∼2 × 2 cm 2 area were radiated in air atmosphere by a microwave drill operating at 2.45 GHz in the range of 20-450 W. The rate of temperature variation was measured by the Fabry-Pérot etalon effect in samples illuminated by InGaAs lasers. The steady-state temperatures were measured by the changes in the absorption index of an InGaAs laser beam. The experimental results indicate heating rates of ∼150 K s −1 and a temperature range of 300-900 K across the silicon sample during the microwave heating process. Further operation of the microwave drill caused local melting of the silicon samples. This paper presents the experimental setup and results, as well as numerical simulations of the microwave heating process.

The paper introduces a method for drilling into hard non-conductive materials by localized microwave radiation (US patent 6,114,676). The microwave drill utilizes a conventional microwave source (2.45-GHz magnetron) to form a portable and relatively simple drilling tool. The drilling head consists of a coaxial feed with a near-field concentrator. The latter focuses the microwave radiation into a small volume under the drilled-material surface. The concentrator itself penetrates into the hot spot created in a fast thermal runaway process. The drilling debris is removed mechanically. This microwave device can be used to drill into concrete, silicon, ceramic, rocks, glass, plastic, and even wood. Hole diameters obtained so far range from 0.5 mm to 13 mm. The larger holes are produced with a slight mechanical assistance. The paper presents recent experimental results of the microwave-drill in various ceramics.