When Cellulose Moves: Smart Sensors and Actuators Francisco Sousa, José F. Malta, Ana P. C. Almeida Advanced Materials Technologies, 2025 Cellulose, the most abundant biopolymer on Earth, has rapidly gained attention as a key component in the development of smart materials capable of dynamic and adaptive behavior. This review highlights the unique motion and actuation capabilities of cellulose‐based systems, focusing on their ability to convert external stimuli into mechanical movement. The recent progress in cellulose‐derived soft actuators that respond to moisture, electric fields, thermal and light input, and magnetic forces is detailed – enabling programmable shape changes, bending, twisting, and locomotion. Alongside these, cellulose‐based soft sensors that transduce environmental cues though magnetic, resistive and capacitive mechanisms are examined. Special emphasis is placed on the synergy between sensing and actuation in multifunctional devices that mimic natural movement and responsiveness. Applications in wearable devices, soft robotics, biomedical systems, energy harvesting, smart packaging, and bioinspired technologies are explored to demonstrate the practical potential of these materials. The challenges in achieving robust, reversible, and multi‐stimuli‐responsive motion are also addressed, and future directions for scaling up and integrating cellulose‐based smart systems into real‐world applications are proposed.
Reentrant Spin Glass and Magnetic Skyrmions in the Co7Zn7Mn6−xFex β-Mn-Type Alloys José F. Malta, Marta S. C. Henriques, José A. Paixão, António P. Gonçalves Magnetochemistry, 2024 Co7Zn7Mn6 is a β-Mn-type alloy belonging to the CoxZnyMnz (x+y+z=20) family that notoriously features a skyrmionic magnetic phase below the ferromagnetic ordering temperature and, in addition, a reentrant spin glass transition at low temperatures. In this work, we have studied the effect of partial substitution of Mn by Fe in the magnetic properties of this alloy. Samples of Co7Zn7Mn6−xFex, 0≤x≤1, were synthesised using the Bridgman–Stockbarger method, and their structure and composition were fully characterised by XRD and EDS. VSM and AC susceptibility measurements show that the partial substitution of Mn by Fe increases TC and the skyrmionic region of the magnetic phase diagram is suppressed for x>0.5. The AC susceptibility behaviour at low temperatures can be ascribed to the presence of a reentrant spin glass state observed for all compositions, with a spin glass freezing temperature, Tg, that shifts to lower temperatures as the Fe content increases.
Synthesis and Structural and Magnetic Properties of Polycrystalline GaMo4Se8 José F. Malta, Marta S. C. Henriques, José A. Paixão, António P. Gonçalves Magnetochemistry, 2023 GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). In this work, we have obtained pure GaMo4Se8 in polycrystalline form through an innovative two-step synthetic route. Phase purity and chemical composition were confirmed through the Rietveld refinement of the powder XRD pattern, the sample characterisation having been complemented with SEM analysis. The magnetic phase diagram was investigated using DC (VSM) and AC magnetometry, which disclosed the presence of cycloidal, skyrmionic and ferromagnetic phases in polycrystalline GaMo4Se8.
Thermoelectric Properties of Nickel and Selenium Co-Doped Tetrahedrite Duarte Moço, José F. Malta, Luís F. Santos, Elsa B. Lopes, António P. Gonçalves Materials, 2023 As the search continues for novel, cheaper, more sustainable, and environmentally friendly thermoelectric materials in order to expand the range of applications of thermoelectric devices, the tetrahedrite mineral (Cu12Sb4S13) stands out as a potential candidate due to its high abundance, low toxicity, and good thermoelectric performance. Unfortunately, as most current thermoelectric materials achieve zTs above 1.0, ternary tetrahedrite is not a suitable alternative. Still, improvement of its thermoelectric performance has been achieved to zTs ≈ 1 via isovalent doping and composition tuning, but most studies were limited to a single doping element. This project explores the effects of simultaneous doping with nickel and selenium in the thermoelectric properties of tetrahedrite. Simulated properties for different stoichiometric contents of these dopants, as well as the measured thermoelectric properties of the correspondent materials, are reported. One of the samples, Cu11.5Ni0.5Sb4S12.5Se0.5, stands out with a high power factor = 1279.99 µW/m·K2 at 300 K. After estimating the thermal conductivity, a zT = 0.325 at 300 K was obtained for this composition, which is the highest for tetrahedrites for this temperature. However, analysis of the weighted mobility shows the presence of detrimental factors, such as grain boundaries, disorder, or ionized impurity scattering, pointing to the possibility of further improvements.
