Multilayered microcoils are of great importance for the development of advanced electromagnetic microactuators and especially important to develop high-sensitivity microsensors and magnetic field neural stimulators for medical applications. A clean room-free procedure for manufacturing multilayered micrometric coils is presented in this article. The production of miniaturized multilayered coils from tens to hundreds of micrometres long is demonstrated. The microcoils have outer diameters ranging between 150 and 300 μm, arrangements of up to five consecutive layers, and an average fill factor of 85%. This means three times smaller diameters than the smallest diameter ever achieved by winding techniques while keeping a high fill factor and a large number of layers. Such small and highly performant microcoils have never been demonstrated neither by winding processes nor epitaxial growth techniques. These microcoils were tested inside different human body-like environments. Maximum current density versus temperature was measured in air, fat tissue, muscle tissue, and simulated body fluid at 36 °C. A maximum current density of 3600 A/m ² has been measured before coil failure. Experiments demonstrated that current densities of up to 610 A/m ² can safely be supplied to coils without risk of harm to internal tissues. These counterintuitive values are orders of magnitude larger than typical current densities used in macroscale actuators windings.

A miniaturized helical antenna is presented in this work. The antenna is flexible, it is 6100 μm long and it has a diameter of 352 μm. This antenna has such a small cross-section, that permits to be implanted in the human body with fine syringes and minimally invasive surgeries. The antenna can be used to receive power and/or send information in medical devices. The antenna is made of biocompatible materials: polytetrafluoroethylene (PFTE) and copper. The fundamental parameters of the antenna have been simulated and experimentally measured in animal human-like tissues, showing good agreement. The resonant frequency of the antenna is 4.7 GHz, with a reflection coefficient of -25.1 dB, and a gain of -4.7 dBi. As expected, the resonant frequency decreases inside biological tissues comparing to the free-space open-air measurement. Reducing the resonant frequency is an advantage because power signals can penetrate deeper into body tissues.

This work presents the results of the characterization of two 1 × 5 mm² miniaturized rectennas developed for medical applications. They have been designed for relatively high voltage and high-power applications, given the size of the rectennas. Both rectennas were tested in open-air conditions and surrounded by pork fat and muscle tissues, whose properties are similar to those of the human body. The resonant frequencies of the rectennas were found, and the incident electric field on the rectennas tests was increased. The first chip showed a maximum output voltage of 5.29 V and a maximum output power of 0.056 mW, at 1.446 GHz, under an incident field on the rectenna of 340 V/m, and the second chip, 4.62 V and 4.27 mW, at 1.175 GHz, under 535 V/m. The second rectenna can provide an output power greater than 5 mW. The rectennas presented in this article are beyond the state of the art, as they can deliver about three times more power and voltage than those of similar dimensions reported in the literature. Based on the test results, the efficiency of the rectennas was analyzed at different locations of the human body, considering different thicknesses of tissues with high and low water content. Finally, potential applications are described in which the rectennas could power implantable medical devices or microsurgery tools, for example, pulmonary artery pressure monitors.

The tribological characteristics of a below 1 mm micro ball bearing comprising steel disc and cages coated with thin copper and silver films were investigated. Electroplating and laser cutting were used to manufacture used elements. Friction was measured using a linear stage and an adapted version of a friction-loop method. The obtained results show an interesting relationship between the geometric properties of the micro scale thrust bearing and their performance and operational stability, which can be correlated to similar relationships observed in the macro scale. The most optimal design of the bearing showed stable operation, with the simplified rolling resistance coefficient in the range 0.002 to 0.003, independently of applied load, which was in range 150 mN to 1500 mN. The possibility of creating easily manufacturable micro ball bearings with a low rolling resistance coefficient comprised solely of cheap and sturdy elements was shown.

We present an innovative personal rapid transit technology compatible with current metro infrastructures, named OPTIMOTUS. The key of this technology is that passengers can travel without stops, thus multiplying several times the effective travel speed. In metro lines with shorter separation between stations (< 1000 m) and for long travels (> 5 stations), passengers travel speed could be up to 3.5 times faster with OPTIMOTUS than with conventional metro trains. In addition, its implementation costs would be relatively low since the vehicles are designed to be compatible with current metro railways. However, there are still many open issues to be engineered before claiming the full viability of the technology.