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CoFe₂O₄–BaTiO₃core–shell nanowires with tunable magnetic anisotropy and magnetoelectric coupling are generated using a template-assisted synthetic procedure providing composition control. 

In this work, a composite of barium ferrite (BaM) and multiwalled carbon nanotubes (CNTs) in a polymer matrix of polydimethylsiloxane (PDMS) are reported for the purpose of suppressing electromagnetic interference (EMI). Shielding is accomplished primarily through absorption, which arises from a combination of the ferromagnetic resonance (FMR) from the BaM and conductive losses from the CNTs. The composite is fabricated by mixing commercially available BaM nanoparticles and CNTs into PDMS, screen printing the mixture into molds, then curing at 80 °C in a DC magnetic field. Characterization involves placing the composite in the cross‐section of a rectangular waveguide, then using a vector network analyzer (VNA) to measure scattering (S) parameters from 33–50 GHz. Using the measured S parameters, power reflected and absorbed can be calculated and used to characterize the composite's shielding effectiveness (SE), and the complex permittivity and permeability can be determined. The resulting 2.4 mm thick composite shows a peak absorption of 26.9 dB at the FMR frequency of 47.4 GHz. When normalized for thickness, the composite, on average, absorbs 11.3 dB mm⁻¹and operates at a higher frequency than other shielding composites found in the literature. 

Nanomaterials have unique properties, functionalities, and excellent performance, and as a result have gained significant interest across disciplines and industries. However, currently, there is a lack of techniques that can assemble as-synthesized nanomaterials in a scalable manner. Electrophoretic deposition (EPD) is a promising method for the scalable assembly of colloidally stable nanomaterials into thick films and arrays. In EPD, an electric field is used to assemble charged colloidal particles onto an oppositely charged substrate. However, in constant voltage EPD the deposition rate decreases with increasing deposition time, which has been attributed in part to the fact that the electric field in the suspension decreases with time. This decreasing electric field has been attributed to two probable causes, (i) increased resistance of the particle film and/or (ii) the growth of an ion-depletion region at the substrate. Here, to increase EPD yield and scalability we sought to distinguish between these two effects and found that the growth of the ion-depletion region plays the most significant role in the increase of the deposit resistance. Here, we also demonstrate a method to maintain constant deposit resistance in EPD by periodic replenishing of suspension, thereby improving EPD’s scalability. 

Stiffness and forces are two fundamental quantities essential to living cells and tissues. However, it has been a challenge to quantify both 3D traction forces and stiffness (or modulus) using the same probe in vivo. Here, we describe an approach that overcomes this challenge by creating a magnetic microrobot probe with controllable functionality. Biocompatible ferromagnetic cobalt-platinum microcrosses were fabricated, and each microcross (about 30 micrometers) was trapped inside an arginine–glycine–aspartic acid–conjugated stiff poly(ethylene glycol) (PEG) round microgel (about 50 micrometers) using a microfluidic device. The stiff magnetic microrobot was seeded inside a cell colony and acted as a stiffness probe by rigidly rotating in response to an oscillatory magnetic field. Then, brief episodes of ultraviolet light exposure were applied to dynamically photodegrade and soften the fluorescent nanoparticle–embedded PEG microgel, whose deformation and 3D traction forces were quantified. Using the microrobot probe, we show that malignant tumor–repopulating cell colonies altered their modulus but not traction forces in response to different 3D substrate elasticities. Stiffness and 3D traction forces were measured, and both normal and shear traction force oscillations were observed in zebrafish embryos from blastula to gastrula. Mouse embryos generated larger tensile and compressive traction force oscillations than shear traction force oscillations during blastocyst. The microrobot probe with controllable functionality via magnetic fields could potentially be useful for studying the mechanoregulation of cells, tissues, and embryos. 

Algorithmic decision-making can lead to discrimination against legally protected groups, but measuring such discrimination is often hampered by a fundamental selection challenge. We develop new quasi-experimental tools to overcome this challenge and measure algorithmic discrimination in pretrial bail decisions. We show that the selection challenge reduces to the challenge of measuring four moments, which can be estimated by extrapolating quasi-experimental variation across as-good-as-randomly assigned decision-makers. Estimates from New York City show that both a sophisticated machine learning algorithm and a simpler regression model discriminate against Black defendants even though defendant race and ethnicity are not included in the training data. 

We report the design, fabrication, and characterization of a prototype that meets the form, fit, and function of a household 1.5 V AA battery, but which can be wirelessly recharged without removal from the host device. The prototype system comprises a low-frequency electrodynamic wireless power transmission (EWPT) receiver, a lithium polymer energy storage cell, and a power management circuit (PMC), all contained within a 3D-printed package. The EWPT receiver and overall system are experimentally characterized using a 238 Hz sinusoidal magnetic charging field and either a 1000 µF electrolytic capacitor or a lithium polymer (LiPo) cell as the storage cell. The system demonstrates a minimal operating field as low as 50 µTrms (similar in magnitude to Earth’s magnetic field). At this minimum charging field, the prototype transfers a maximum dc current of 50 µA to the capacitor, corresponding to a power delivery of 118 µW. The power effectiveness of the power management system is approximately 49%; with power effectiveness defined as the ratio between actual output power and the maximum possible power the EWPT receiver can transfer to a pure resistive load at a given field strength. 

This paper presents the design, fabrication and experimental characterization of a chip-sized wireless power receiver for low-frequency electrodynamic wireless power transmission (EWPT). Utilizing a laser micro-machined meandering suspension, one NdFeB magnet, and two PZT-SA piezoelectric patches, this 0.08 cm 3 micro-receiver operates at its torsion mode mechanical resonance of 724 Hz. The device generates 360 μW average power (4.2 mWcm -3 power density) at 1 cm distance from a transmitter coil operating at 724 Hz and safely within allowable human exposure limits of 2 mTrms field. Compared to a previously reported macro-scale prototype, this volume-efficient micro-receiver is 31x smaller and offers 3.2x higher power density within a low-profile, compact footprint for wirelessly charging wearable and bio-implantable devices.