Fluidic self-assembly for MicroLED displays by controlled viscosity.

Displays in which arrays of microscopic 'particles', or chiplets, of inorganic light-emitting diodes (LEDs) constitute the pixels, termed MicroLED displays, have received considerable attention1,2 because they can potentially outperform commercially available displays based on organic LEDs3,4 in terms of power consumption, colour saturation, brightness and stability and without image burn-in issues1,2,5-7. To manufacture these displays, LED chiplets must be epitaxially grown on separate wafers for maximum device performance and then transferred onto the display substrate. Given that the number of LEDs needed for transfer is tremendous-for example, more than 24 million chiplets smaller than 100 µm are required for a 50-inch, ultra-high-definition display-a technique capable of assembling tens of millions of individual LEDs at low cost and high throughput is needed to commercialize MicroLED displays. Here we demonstrate a MicroLED lighting panel consisting of more than 19,000 disk-shaped GaN chiplets, 45 µm in diameter and 5 µm in thickness, assembled in 60 s by a simple agitation-based, surface-tension-driven fluidic self-assembly (FSA) technique with a yield of 99.88%. The creation of this level of large-scale, high-yield FSA of sub-100-µm chiplets was considered a significant challenge because of the low inertia of the chiplets. Our key finding in overcoming this difficulty is that the addition of a small amount of poloxamer to the assembly solution increases its viscosity which, in turn, increases liquid-to-chiplet momentum transfer. Our results represent significant progress towards the ultimate goal of low-cost, high-throughput manufacture of full-colour MicroLED displays by FSA.

Hepatic Stiffness Using Shear Wave Elastography and the Related Factors for a Fontan Circulation.

Hepatic problems related to a Fontan circulation have been highlighted and elastography using ultrasound is a non-invasive tool that can measure the severity of hepatic stiffness. We investigated the hepatic stiffness using shear wave elastography (SWE) and related factors in patients with a Fontan circulation. This study enrolled 64 patients with a Fontan circulation who underwent cardiac catheterization and abdominal ultrasound from 2011 to 2015. The correlation between the laboratory tests, hemodynamic factors by cardiac catheterization, and SWE was evaluated. The patients were classified into non-cirrhotic level (≥ 2.0 m/s) and cirrhotic level (< 2.0 m/s) groups by the SWE value. The mean age was 17.6 years and the mean duration after the Fontan operation was 12.1 years. The mean value of SWE in patients (1.95 m/s) was higher than the normal (< 1.3 m/s). The SWE was higher in patients without than those with a fenestration (2.03 vs. 1.75 m/s, P = 0.003). In a multiple regression analysis between SWE and other factors, the CVP, fenestration, and lipoprotein Apo B had a significant correlation. In a multivariate analysis of cirrhotic level group, the CVP was the only significant factor. The hepatic stiffness had significantly progressed in most patients with a Fontan circulation. A low CVP and Fontan circulation with a fenestration might reduce the progression of the hepatic stiffness.

Microspinning: Local Surface Mixing via Rotation of Magnetic Microparticles for Efficient Small-Volume Bioassays.

The need for high-throughput screening has led to the miniaturization of the reaction volume of the chamber in bioassays. As the reactor gets smaller, surface tension dominates the gravitational or inertial force, and mixing efficiency decreases in small-scale reactions. Because passive mixing by simple diffusion in tens of microliter-scale volumes takes a long time, active mixing is needed. Here, we report an efficient micromixing method using magnetically rotating microparticles with patterned magnetization induced by magnetic nanoparticle chains. Because the microparticles have magnetization patterning due to fabrication with magnetic nanoparticle chains, the microparticles can rotate along the external rotating magnetic field, causing micromixing. We validated the reaction efficiency by comparing this micromixing method with other mixing methods such as simple diffusion and the use of a rocking shaker at various working volumes. This method has the potential to be widely utilized in suspension assay technology as an efficient mixing strategy.

Hierarchical shape-by-shape assembly of microparticles for micrometer-scale viral delivery of two different genes.

Understanding tissue engineering using a bottom-up approach has been hindered by technical limitations because no platform can demonstrate the controlled formation of a heterogeneous population of cells in microscale. Here, we demonstrate hierarchical shape-by-shape assembly of virus-laden particles into larger ones to transfect two different genes on the seeded cells. We show that smaller daughter particles with different sizes and shapes can be assembled into the matching indentations of larger parent particles with different sizes and shapes. Then, we transfected a population of cells with two different gene-transfecting viruses, each of which was laden on the parent or daughter particles.

Flexible Electronics: An Epidermal Stimulation and Sensing Platform for Sensorimotor Prosthetic Control, Management of Lower Back Exertion, and Electrical Muscle Activation (Adv. Mater. 22/2016).

The design of an ultrathin, conformal electronic device that integrates electrotactile stimulation with electromyography, temperature, and strain sensing in a single, simple platform is reported by J. A. Rogers and co-workers on page 4462. Demonstrated application possibilities include prosthetic control with sensory feedback, monitors, and stimulation signals related to lower back exertion, and electrical muscle stimulation with feedback control.

An Epidermal Stimulation and Sensing Platform for Sensorimotor Prosthetic Control, Management of Lower Back Exertion, and Electrical Muscle Activation.

The design of an ultrathin, conformal electronic device that integrates electrotactile stimulation with electromyography, temperature, and strain sensing in a single, simple platform is reported. Experiments demonstrate simultaneous use of multiple modes of operation of this type of device in the sensorimotor control of robotic systems, in the monitoring of lower back exertion and in muscle stimulation.