Structuration of zero-shrinkage LTCC using mineral sacrificial materials

Recently, LTCC (low-temperature co-fired ceramic) technology has increasingly found applications beyond pure electronics, in fields such as microfluidics, sensors and actuators, due to the ease of shaping the tapes in the green (unfired) state. Accurate control of hollow structures such as channels, membranes, cavities and gaps below cantilevers has remained difficult, however, although carbon-based sacrificial materials and adhesive/solvent-assisted low-pressure lamination techniques are adequate for several uses. Mineral sacrificial pastes (MSP), introduced by several groups including our laboratory, allow in principle much better control of open structures such as bridges and cantilevers, as they are removed only after the firing step. In practice, accurate dimensional control has been limited by deformation of the LTCC during sintering, due to shrinkage mismatch with the MSP. Attempts to eliminate this problem have met with limited success, as it is very difficult to perfectly match the shrinkage curve of the MSP (which must retain open porosity) to that of the LTCC substrate. Therefore, in this work, we endeavour to investigate MSP materials on self-constraining "zero- shrinkage" LTCC tape, which is therefore compatible with a low degree of sintering of the MSP. We present results of optimising the MSP formulation accordingly, to achieve reasonable consolidation, low deformation of LTCC and easy removal in weak acid solutions. Important topics such organic vehicle formulation and complete release processes (etching, rinsing and drying) of thin structures are also addressed

Structuration of thin bridge and cantilever structures in thick-film technology using mineral sacrificial materials

Thick-film and LTCC (Low Temperature Cofired Ceramic) technologies find increasing use in meso-scale sensors, actuators and related devices that feature excellent dimensional, thermal and chemical stability at moderate cost. While several materials and processes allow fabrication of structures such as channels, membranes and relatively short bridges, obtaining slender bridges and cantilevers with good shape control for applications such as microforce sensors has hitherto remained a challenging task. This work presents techniques based on mineral sacrificial materials that allow fabrication of such intricate structures in thick-film technology, and are also applicable to LTCC. Aspects such as optimal sacrificial materials, paste formulation, structure design and final chemical etching are addressed, with the aim of obtaining reproducible structures

The EPFL jumpglider: A hybrid jumping and gliding robot with rigid or folding wings

Recent work suggests that wings can be used to prolong the jumps of miniature jumping robots. However, no functional miniature jumping robot has been presented so far that can successfully apply this hybrid locomotion principle. In this publication, we present the development and characterization of the ’EPFL jumpglider’, a miniature robot that can prolong its jumps using steered hybrid jumping and gliding locomotion over varied terrain. For example, it can safely descend from elevated positions such as stairs and buildings and propagate on ground with small jumps. The publication presents a systematic evaluation of three biologically inspired wing folding mechanisms and a rigid wing design. Based on this evaluation, two wing designs are implemented and compared