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Abstract In this study, the frequency selectivity phenomenon in the mammalian cochlea is replicated in a simulated environment. Frequency selectivity is found to be of crucial importance in the accurate perception of environmental noise. Previous studies have found that mammalian cochlea consists of basilar membrane which varies in width and stiffness along its length. This results in a gradient in mechanical properties and in turn results in a place-coding mechanism, where different frequencies of sound cause maximum displacement of the basilar membrane at specific locations along its length. The basilar membrane consists of multiple hair cells located along its length. The displacement of the basilar membrane due to sound waves causes hair cells to bend. This bending of hair cells activates ion channels, leading to the generation of electrical signals. Leveraging the principles of cochlear processing, a Kalimba-key-based broadband vibroacoustic device is developed in this study having potential implications for sensory technology and human perception enhancement. Dynamic vibration resonators (DVRs) are employed in this research to emulate the frequency-selective behavior of the mammalian cochlea where the DVRs act as hair cells. A beam structure, acting as a platform for 136 strategically placed DVRs, each corresponding to a Kalimba instrument key is considered. Upon stimulation, these Kalimba keys replicate the vibrations of the cochlear basilar membrane, enabling the recreation of frequency selectivity across a broad spectrum. To simulate the system, a Timoshenko beam is considered to consist of spatially attached Kalimba keys modeled as a Single-Degree Of Freedom (SDOF) systems. A Finite Element (FE) model of this system is developed to calculate the response of the system. Frequency selectivity for different combinations of Kalimba keys is explored in this study. This study shows promising results having potential implications extending beyond healthcare, encompassing fields such as robotics where the integration of biological cochlear principles could enhance robots’ sensory perception and interaction capabilities in diverse environments. 

Controlled but explosive growth in vaporization rates is made feasible by ultrasonic acoustothermal heating of the microlayers associated with microscale nucleating bubbles within the microstructured boiling surface/region of a millimeter-scale heat exchanger (HX). The HX is 5 cm long and has a 1 cm × 5 mm rectangular cross section that uses saturated partial flow-boiling operations of HFE-7000. Experiments use layers of woven copper mesh to form a microstructured boiling surface/region and its nano/microscale amplitude ultrasonic (~1-6 MHz) and sonic (< 2 kHz, typically) vibrations induced by a pair of very thin ultrasonic piezoelectric-transducers (termed piezos) that are placed and actuated from outside the heat-sink. The ultrasonic frequencies are for substructural microvibrations whereas the lower sonic frequencies are for suitable resonant structural microvibrations that assist in bubble removal and liquid filling processes. The flow and the piezos' actuation control allow an approximately 5-fold increase in heat transfer coefficient value, going from about 9000 W/m²-°C associated with microstructured no-piezos cases to 50,000 W/ m²-°C at a representative heat flux of about 25 W/cm². The partial boiling approach is enabled by one inlet and two exit ports. Further, significant increases to current critical heat flux values (~70 W/cm²) are possible and are being reported elsewhere. The electrical energy consumed (in W) for generating nano/micrometer amplitude vibrations is a small percentage (currently < 3%, eventually < 1% by design) of the total heat removed (in W), which is a heat removal rate of 125 W for the case reported here.