Simplified Phenomenological Model for Ferroelectric Micro-Actuator.

As smart structures are becoming increasingly ubiquitous in our daily life, the need for efficient modeling electromechanical coupling devices is also rapidly advancing. Smart structures are often made of piezoelectric materials such as lead zirconate titanate (PZT), which exhibits strong nonlinear behavior known as hysteresis effect under a large applied electric field. There have been numerous modeling techniques that are able to capture such an effect; some techniques are suitable for obtaining physical insights into the micro-structure of the material, while other techniques are better-suited to practical structural analyses. In this paper, we aim to achieve the latter. We propose a simplified phenomenological macroscopic model of a nonlinear ferroelectric actuator. The assumption is based on the direct relation between the irreversible strain and irreversible electric field, and the consequently irreversible polarization. The proposed model is then implemented in a finite element framework, in which the main features such as local return mapping and the tangent moduli are derived. The outcomes of the model are compared and validated with experimental data. Therefore, the development presented in this paper can be a useful tool for the modeling of nonlinear ferroelectric actuators.

Rigorous analysis of the axial acoustic radiation force on a spherical object for single-beam acoustic tweezing applications.

Acoustic tweezers are increasingly utilized for the contactless manipulation of small particles. This paper provides a theoretical model demonstrating the acoustic manipulation capabilities of single-beam acoustic transducers. Analytical formulas are derived for the acoustic radiation force on an isotropic spherical object of arbitrary size, centered on a circular piston, simply supported and clamped radiator in an inviscid fluid. Using these results, the existence of a negative axial force pulling the object closer to the radiator is revealed and explored. These findings offer further insight into the feasibility of trapping objects in the near-field of a single-beam acoustic transducer. The calculations illustrate the trapping capabilities of the different emitters as a function of radiator size, particle size, and distance from the source and highlight the impact of radiator boundary conditions. Manipulation of a cell-like fluid sphere in water and an expanded polystyrene sphere in air are studied in more detail with results that are validated through finite element analysis. The developed theoretical model allows fast evaluation of acoustic radiation forces which could aid in the development of relatively simple and inexpensive contactless manipulation solutions.

Novel technology for microlenses for imaging applications.

Microlenses are an important functional element of a modern imaging device. Typically, they are fabricated from organic materials on top of individual pixels. Though they are widely used, they do exhibit a number of limitations. These are, but not limited to, thermal stability, radiation sensitivity, outgassing properties, additional topography, and difficulty in manufacturing asymmetrical, noncircular microlens designs using conventional manufacturing techniques. In this paper, we present a novel approach for the fabrication of microlenses. We report on the design, manufacturing, and characterization of microlenses fabricated from classical dielectric materials used in the manufacturing of CMOS semiconductor devices. These microlenses rely on a Fresnel optical design, provide functionality similar to the classical microlenses, and do not suffer from their limitations. We subjected these microlenses to several environmental reliability stress conditions, including pressure, temperature, humidity, and their variation. Moreover, we test their sensitivity to gamma rays and protons.

Time Multiplexed Active Neural Probe with 1356 Parallel Recording Sites.

We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated in-situ circuits for signal source amplification, which are directly located under each electrode. The probe supports the simultaneous recording of all 1356 electrodes with sufficient signal to noise ratio for typical neuroscience applications. For enhanced performance, further noise reduction can be achieved while using half of the electrodes (678). Both of these numbers considerably surpass the state-of-the art active neural probes in both electrode count and number of recording channels. The measured input referred noise in the action potential band is 12.4 µVrms, while using 678 electrodes, with just 3 µW power dissipation per pixel and 45 µW per read-out channel (including data transmission).

A Neural Probe With Up to 966 Electrodes and Up to 384 Configurable Channels in 0.13 $\mu$m SOI CMOS.

In vivo recording of neural action-potential and local-field-potential signals requires the use of high-resolution penetrating probes. Several international initiatives to better understand the brain are driving technology efforts towards maximizing the number of recording sites while minimizing the neural probe dimensions. We designed and fabricated (0.13- µm SOI Al CMOS) a 384-channel configurable neural probe for large-scale in vivo recording of neural signals. Up to 966 selectable active electrodes were integrated along an implantable shank (70 µm wide, 10 mm long, 20  µm thick), achieving a crosstalk of [Formula: see text] dB. The probe base (5 × 9 mm 2 ) implements dual-band recording and a 171.6 Mbps digital interface. Measurement results show a total input-referred noise of 6.4 µ V rms and a total power consumption of 49.1  µW/channel.