Recently, the applications of ultrasound transducers expanded from high-end diagnostic tools to point of care diagnostic devices and wireless power receivers for implantable devices. These new applications additionally require that the transducer technology must comply to biocompatibility and manufacturing scalability. In this respect, Capacitive Micromachined Ultrasound Transducers (CMUTs) have a strong advantage compared to the conventional PZT based transducers. However, current CMUTs require a large DC bias voltage for their operation, which limits the miniaturizability of these devices. In this study, we propose a pre-charged collapse-mode CMUT for immersive applications that can operate without an external bias by means of a charge trapping Al2O3 layer embedded in the dielectrics between the top and bottom electrodes. The built-in charge layer was analytically modeled and four layer stack combinations were investigated and characterized. The measurement results of the CMUTs were then used to fit the model and to quantify the amount and type of trapped charge. It was found that these devices polarize due to the ferroelectric-like behavior of the Al2O3, and the amount of charge stored in the charge-trapping layer was estimated to be approximately 0.02 C/m2. Their acoustic performance shows a transmit and receive sensitivity of 8.8 kPa/V and 13.1 V/MPa respectively. In addition, we show that increasing the charging temperature, the charging duration, and the charging voltage results in a higher amount of stored charge. Finally, results of ALT tests showed that these devices have a lifetime of more than 2.5 years at body temperature.@en

Surface-modified silicon nanowire-based field-effect transistors
(SiNW-FETs) have proven to be a promising platform for molecular
recognition in miniature sensors. In this work, we present a novel nanoFET
device for the sensitive and selective detection of explosives based on affinity
layers of metal−organic polyhedra (MOPs). The judicious selection of the
geometric and electronic characteristics of the assembly units (organic ligands
and unsaturated metal site) embedded within the MOP cage allowed for the
formation of multiple charge-transfer (CT) interactions to facilitate the selective
explosive inclusion. Meanwhile, the host-stabilized CT complex inside the cage
acted as an effective molecular gating element to strongly modulate the electrical conductance of the silicon nanowires. By grafting the MOP cages onto a SiNWFET device, the resulting sensor showed a good electrical sensing capability to various explosives, especially 2,4,6-trinitrotoluene (TNT), with a detection limit below the nanomolar level. Importantly, coupling MOPswhich have tunable structures and propertiesto SiNW-based devices may open up new avenues for a wide range of sensing applications, addressing
various target analytes.@en