Mika Suhonen

Contactless Electrical Sintering of Silver Nanoparticles on Flexible Substrates

Contactless rapid electrical sintering (RES) is demonstrated using microwave power. The method is implemented by coupling the near-field electric field of a sintering head across an underlying nanoparticle layer. We provide appropriate biasing conditions required for controlled power delivery and demonstrate real-time monitoring of the process by measuring the reflected power at 1.8 GHz. A small-scale sintering head is designed and fabricated on a printed circuit board (PCB). The PCB head is shown to provide a tenfold improvement in sintering efficiency when compared to a sintering head with a less focused electric field pattern. Finally, a high-power coaxial sintering head, with a narrow electrode spacing and biasing conditions similar to the PCB head, is used for demonstrating contactless RES over an air gap. Silver nanoparticle patterning inkjet printed on a temperature-sensitive flexible substrate is efficiently sintered in two passes with 50-W input power and 25-mm/s processing speed, when the vertical working distance to the constantly moving substrate is 1 mm. The demonstrated sintering technology can be applied to a number of printed electronics applications.

Scanning micromechanical mirror for fine-pointing units of intersatellite optical links

A light and fast two-axial fine-pointing mirror has a number of space applications, especially in intersatellite optical links. The fine pointing of laser beams in optical links is currently realized with electromagnetic or piezoelectric actuators, which are relatively large and heavy. Micro-electro-mechanical system technology bears a high potential in space applications, offering a reduction in device size, mass and power consumption. Microtechnology facilitates batch mode fabrication, yielding a low cost per unit. VTT Automation has designed and partially tested a silicon micromachined electrostatically actuated two-axial mirror, which can be controlled with microradian resolution and large bandwidth over the angular range of ±3 mrad.

MEMS-based AC voltage reference

An ac root-mean-square (RMS) voltage reference based on a microelectromechanical system (MEMS) component is presented. The device stability is investigated in various experiments. A time stability at a level of a few /spl mu/V/V in 24 h was measured using an accelerometer MEMS component at an operating frequency of 100 kHz.

Rapid Electrical Sintering of Nanoparticle Stuctures

A method for rapid electrical sintering (RES) of nanoparticle structures on temperaturesensitive substrates is presented. For an inkjetted silver nanoparticle conductor, a conductance increase of five orders of magnitude is demonstrated to occur in a timescale that typically varies between a few and one hundred milliseconds depending on process parameters. Furthermore, most of the conductance change takes only a few microseconds. The achievable final conductivities are within a factor of two from the bulk silver conductivity, as calculated using the external geometric dimensions of the structure ignoring porosity. The method is also applicable to other inorganic conductors such as indium-tin-oxide (ITO). More generally, the method offers a versatile tool in nanotechnology for electrical functionalization of nanoparticle structures. The method is also potentially suited for mass production.