Here we present a process for the fabrication of arrays of anisotropic flexible bonded micro-magnets attached to a transparent base. The micro-magnets are based on hard magnetic SmFeN or Sr-ferrite powders mixed with polydimethylsiloxane (PDMS). The size, shape and distribution of the micro-magnets are defined using a Si-mould fabricated by deep reactive ion etching (DRIE). The volume fraction of the magnetic powder was fixed at 30% while the thickness of the micro-magnets ranged from 50-300 μm and their in-plane dimensions from 20-400 µm. Powder alignment was achieved using a bulk NdFeB magnet. Arrays of micro-pillars of height 300 µm and width tapering from 300 µm at their base to 200 µm at their top were characterized using vibrating sample magnetometry (VSM) and Scanning Hall Probe Microscopy (SHPM) and the results of the latter were compared with analytical simulations. The homogeneous magnetic field produced by a 3-axis electromagnet was used to move the micro-pillars in a controlled fashion. The field induced in-plane displacement of the SmFeN-based pillars was more than three times greater than that of the Sr-ferrite-based ones, reaching 13 µm at the maximum applied field value of 100 mT.

Thermomagnetic generation is a promising technology for conversion of low-grade waste heat into electricity. Key requirements for the development of efficient thermomagnetic generators (TMGs) are tailored thermomagnetic materials as well as innovative designs enabling fast heat transfer. Recently, film-based thermomagnetic generators are developed that operate in the mode of resonant self-actuation enabling high frequency and stroke of a movable cantilever and, thus, efficient conversion of thermal energy into electrical energy. Here, the performance of a Gadolinium (Gd)-film-based TMG that is optimized for resonant self-actuation near room temperature is reported. The Gd-film TMG exhibits large oscillation frequencies up to 106 Hz and large strokes up to 2 mm corresponding to 38% of the oscillating cantilever's length. This performance occurs in a sharply bound range of ambient temperatures with an upper limit near the film's ferromagnetic to paramagnetic transition temperature T c of 20 °C and of heat source temperatures ranging between 40 and 75 °C. The maximum power per footprint is 23.8 µWcm −2 , at which the Gd film undergoes a temperature change of only 0.9 °C at ≈10 °C above T c .