Aim: To assess several fabrication metrics of a 3D-printed smartphone-attachable continuous-flow magnetic focusing device for real-time separation and detection of different cell types based on their volumetric mass density in high-volume samples. Method: The smartphone apparatus has been designed and fabricated using three different 3D printing method. Several 3D printing metrics including cost, printing time, and resolution have been evaluated to propose a cost-efficient and high-performance platform for low-resource settings. Results: To apply the magnetic focusing technique on large sample volumes, a heterogeneous mixture of sample (e.g., containing blood cells and cancer cells) suspended in paramagnetic medium is pumped through a magnetic field at an optimum flow rate. The performance of the 3D-printed device has been investigated by demonstrating separation of microspheres, breast, lung, ovarian and prostate cancer cells mixed with blood cells. The separation distance of cancer and blood cells is around 100 μm, allowing the two cell types to be easily distinguished. Conclusion: This device could be useful for clinical centers in low-income countries where expensive infrastructure, equipment (e.g., FACS) and technical expertise are lacking. This device could ultimately be applied to rare cell separation and purification.

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Tunable piezoelectric metasurfaces have been proposed as a means of adaptively steering incident elastic waves for various applications in vibration mitigation and control. Bonding piezoelectric material to thin structures introduces electromechanical coupling, enabling structural dynamics to be altered via tunable electric shunts connected across each unit cell. For example, by carefully calibrating the inductive shunts, it is possible to implement the discrete phase shifts necessary for gradient-based waveguiding behaviors. However, experimental validations of localized phase shifting are challenging due to the narrow bandgap of local resonators, resulting in poor transmission of incident waves and high sensitivity to transient noise. These factors, in combination with the difficulties in experimental circuitry synthesis, can lead to significant variability of data acquired within the bandgap operating region. This paper presents a systematic approach for extracting localized phase shifts by taking advantage of the inherent correlation between the incident and transmitted wavefronts. During this procedure, matched filtering greatly reduces noise in the transmitted signal when operating in or near bandgap frequencies. Experimental results demonstrate phase shifts as large as −170° within the locally resonant bandgap, with an average 28% reduction in error relative to a direct time domain measurement of phase, enabling effective comparison of the dispersive behavior with corresponding analytical and finite element models. In addition to demonstrating the tunable waveguide characteristics of a piezoelectric metasurface, this technique can easily be extended to validate localized phase shifting of other elastic waveguiding metasurfaces.

Fault parameters in a structure can be identified by matching measurements with model predictions in the parametric space. As high frequency measurements are preferred to uncover small-size damage, piezoelectric impedance/admittance active interrogation has shown promising aspects. Nevertheless, the amount of useful measurement information is generally insufficient to pinpoint damage, and the inverse identification is underdetermined. In this research, we develop a combinatorial enhancement to tackle these challenges. A tunable piezoelectric impedance sensing procedure is developed in which an adaptive inductance element is integrated with the piezoelectric transducer, which will lead to enriched measurement data for the same damage. Subsequently, an intelligent multi-objective particle swarm optimization approach is synthesized to inversely identify the damage location and severity. Case studies are conducted to highlight the accuracy of the damage identification.

A tunable metasurface consisting of an array of piezoelectric unit cells is demonstrated to anomalously refract incident elastic wavefronts along a target direction. Each surface bonded transducer (PZT) is shunted with an individually calibrated synthetic inductor to form a local resonator, which is then tuned to modify the local dispersive characteristics of each unit cell and implement discrete phase shifts. The analog synthetic inductances are integrated with digital potentiometers to realize online tunability, allowing the metasurface to be recalibrated to accommodate different incident wave frequencies or target angles of refraction without requiring any physical alteration of the host structure. A microcontroller unit (MCU) then reads the stored empirical data and designates the appropriate settings for each digital potentiometer in order to realize the targeted waveguiding behavior for a specified incident wave frequency.