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Background: Low-intensity transcranial focused ultrasound stimulation is a promising candidate for noninvasive brain stimulation and accurate targeting of brain circuits because of its focusing capability and long penetration depth. However, achieving a sufficiently high spatial resolution to target small animal sub-regions is still challenging, especially in the axial direction. Objective: To achieve high axial resolution, we designed a dual-crossed transducer system that achieved high spatial resolution in the axial direction without complex microfabrication, beamforming circuitry, and signal processing. Methods: High axial resolution was achieved by crossing two ultrasound beams of commercially available piezoelectric curved transducers at the focal length of each transducer. After implementation of the fixture for the dual-crossed transducer system, three sets of in vivo animal experiments were conducted to demonstrate high target specificity of ultrasound neuromodulation using the dual-crossed transducer system (n ¼ 38). Results: The full-width at half maximum (FWHM) focal volume of our dual-crossed transducer system was under 0.52 mm 3 . We report a focal diameter in both lateral and axial directions of 1 mm. To demonstrate successful in vivo brain stimulation of wild-type mice, we observed the movement of the forepaws. In addition, we targeted the habenula and verified the high spatial specificity of our dualcrossed transducer system. Conclusions: Our results demonstrate the ability of the dual-crossed transducer system to target highly specific regions of mice brains using ultrasound stimulation. The proposed system is a valuable tool to study the complex neurological circuitry of the brain noninvasively.

Owing to their simple and low-cost architecture, extended-gate biosensors based on the combination of a disposable sensing part and a reusable transducer have been widely utilized for the label-free electrical detection of chemical and biological species. Previous studies have demonstrated that sensitive and selective detection of ions and biomolecules can be achieved by controlled modification of the sensing part with an ion-selective membrane and receptors of interest. However, no systematic studies have been performed on the impact of the transducer on sensing performance. In this paper, we introduce the concept of a nanoscale field-effect transistor (FET) as a reusable and sensitive transducer for extended-gate biosensors. The capacitive effect from the external sensing part can degrade the sensing performance, but the nanoscale FET can reduce this effect. The nanoscale FET with a gate-all-around (GAA) structure exhibits a higher pH sensitivity than a commercially available FET, which is widely used in conventional extended-gate biosensors. A sensitivity reduction is observed for the commercial FET, whereas the pH sensitivity is insensitive to the area of the sensing region in the nanoscale FET, thus allowing the scaling of the detection area. Our analysis based on a capacitive model suggests that the high pH sensitivity in the compact sensing area originates from the small input capacitance of the nanoscale FET transducer. Moreover, a decrease in the nanowire width of the GAA FET leads to an improvement in the pH sensitivity. The extended-gate approach with the nanoscale FET-based transduction can pave the way for a highly sensitive analysis of chemical and biological species with a small sample volume.

A physical unclonable function (PUF) device using a nano-electromechanical (NEM) switch was demonstrated. The most important feature of the NEM-switch-based PUF is its use of stiction. Stiction is one of the chronic problems associated with micro- and nano-electromechanical system (MEMS/NEMS) devices; however, here, it was utilized to intentionally implement a PUF for hardware-based security. The stiction is caused by capillary and van der Waals forces, producing strong adhesion, which can be utilized to design a highly robust and stable PUF. The probability that stiction will occur on either of two gates in the NEM switch is the same, and consequently, the occurrence of the stiction is random and unique, which is critical to its PUF performance. This uniqueness was evaluated by measuring the interchip Hamming distance (interchip HD), which characterizes how different responses are made when the same challenge is applied. Uniformity was also evaluated by the proportion of "1" or "0" in the response bit-string. The reliability of the proposed PUF device was assessed by stress tests under harsh environments such as high temperature, high dose radiation, and microwaves.