Chandrayaan-3 APXS elemental abundance measurements at lunar high latitude.

The elemental composition of the lunar surface provides insights into mechanisms of the formation and evolution of the Moon1,2. The chemical composition of lunar regolith have so far been precisely measured using the samples collected by the Apollo, Luna and Chang'e 5 missions, which are from equatorial to mid-latitude regions3,4; lunar meteorites, whose location of origin on the Moon is unknown5,6; and the in situ measurement from the Chang'e 3 and Chang'e 4 missions7-9, which are from the mid-latitude regions of the Moon. Here we report the first in situ measurements of the elemental abundances in the lunar southern high-latitude regions by the Alpha Particle X-ray Spectrometer (APXS) experiment10 aboard the Pragyan rover of India's Chandrayaan-3 mission. The 23 measurements in the vicinity of the Chandrayaan-3 landing site show that the local lunar terrain in this region is fairly uniform and primarily composed of ferroan anorthosite (FAN), a product of the lunar magma ocean (LMO) crystallization. However, observation of relatively higher magnesium abundance with respect to calcium in APXS measurements suggests the mixing of further mafic material. The compositional uniformity over a few tens of metres around the Chandrayaan-3 landing site provides an excellent ground truth for remote-sensing observations.

In Situ Observations of Nanofibril Nucleation and Growth during the Electrochemical Polymerization of Poly(3,4-ethylenedioxythiophene) Using Liquid-Phase Transmission Electron Microscopy.

The electrochemical deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) has been carried out previously in the presence of a variety of counterions. Previous studies have shown that elongated nanofibrillar structures of PEDOT would form reproducibly when certain counterions such as poly(acrylic acid) (PAA) were added to the reaction mixture. However, details of the nanofibril nucleation and growth stages were not yet clear. Here, we describe the structural evolution of PEDOT nanofibrils using liquid-phase transmission electron microscopy (LPTEM). We measured the growth velocities of nanofibrils in different directions at various stages of the process and their intensity profiles, and we have estimated the number of EDOT monomers involved. We observed that fibrils initially grew anisotropically in a direction nominally perpendicular to the local edge of the electrodes, with rates that were faster along their lengths as compared those along to their widths and thicknesses. These real-time observations have helped us elucidate the nucleation and growth of PEDOT nanofibrils during electrochemical deposition.

Printed flexible and transparent electronics: enhancing low-temperature processed metal oxides with 0D and 1D nanomaterials.

Metal oxides have broad multifunctionality and important applications to energy, sensing, and information display. Printed electronics have recently adopted metal oxides to push the limits of performance and stability for flexible thin film systems. However, a grand challenge in this field is to achieve these properties while balancing the thermal budget, which critically determines the applicability, flexibility, and cost of these systems. This paper presents a focused review of printed metal oxide electronics, highlighting our recent work developing high-performance, printed transistors processed at low temperatures via aqueous precursor chemistries, nanomaterial hybrid inks, and ultraviolet annealing. These results reveal the potential for printing uniquely high-performance active devices (electronic mobility >10 cm2 V-1 s-1) but also illustrates the utility of nanocomposites that integrate nanomaterials within a metal oxide matrix for improving device performance.

Principles of Moisturizer Product Design

Moisturizers provide significant benefit in dermatology ­ as adjuvant therapy for many clinical conditions, as a key player in anti-aging regimens, and as a core component in maintaining healthy skin barrier function. Although they have been a mainstay for decades, lotions and creams are no longer formulated with a one-size-fits-all approach, where thickness was the primary cue for efficacy. In fact, moisturizer design today has become an art as well as a science. Product efficacy, aesthetics, and packaging are all engineered in a variety of ways, to create an expansive market of products that meet many consumer needs. The addition of specific types of functional ingredients can make a noteworthy difference as well. This article will explore the myriad approaches for moisturizer development and debunk some of the long-standing myths that have pervaded the marketplace. J Drugs Dermatol. 2019;18(1 Suppl):s89-95

Chronic, wireless recordings of large-scale brain activity in freely moving rhesus monkeys.

Advances in techniques for recording large-scale brain activity contribute to both the elucidation of neurophysiological principles and the development of brain-machine interfaces (BMIs). Here we describe a neurophysiological paradigm for performing tethered and wireless large-scale recordings based on movable volumetric three-dimensional (3D) multielectrode implants. This approach allowed us to isolate up to 1,800 neurons (units) per animal and simultaneously record the extracellular activity of close to 500 cortical neurons, distributed across multiple cortical areas, in freely behaving rhesus monkeys. The method is expandable, in principle, to thousands of simultaneously recorded channels. It also allows increased recording longevity (5 consecutive years) and recording of a broad range of behaviors, such as social interactions, and BMI paradigms in freely moving primates. We propose that wireless large-scale recordings could have a profound impact on basic primate neurophysiology research while providing a framework for the development and testing of clinically relevant neuroprostheses.

High-performance inkjet-printed four-terminal microelectromechanical relays and inverters.

We report the first demonstration of inkjet-printed 4-terminal microelectromechanical (MEM) relays and inverters with hyper-abrupt switching that exhibit excellent electrical and mechanical characteristics. This first implementation of a printed 4-terminal device is critically important, since it allows for the realization of full complementary logic functions. The floated fourth terminal (body electrode), which allows the gate switching voltage to be adjusted, is bonded to movable channel beams via a printed epoxy layer in a planar structure, which can move downward together via the electrostatic force between the gate electrodes and body such that the channel can also actuate downward and touch the drain electrode. Because the body, channel, and drain electrodes are completely electrically separated, no detectable leakage or electrical interference between the electrodes is observed. The printed MEM relay exhibited an on-state resistance of only 3.48 Ω, immeasurable off-state leakage, subthreshold swing <1 mV/dec, and a stable operation over 10(4) cycles with a switching delay of 47 µs, and the relay inverter exhibits abrupt transitions between on/off states. The operation of the printed 4-terminal MEM relay was also verified against the results of a 3-dimensional (3D) finite element simulation.

Lubrication-related residue as a fundamental process scaling limit to gravure printed electronics.

In gravure printing, excess ink is removed from a patterned plate or roll by wiping with a doctor blade, leaving a thin lubrication film in the nonpatterned area. Reduction of this lubrication film is critical for gravure printing of electronics, since the resulting residue can lower device performance or even catastrophically impact circuit yield. We report on experiments and quantitative analysis of lubrication films in a highly scaled gravure printing process. We investigate the effects of ink viscosity, wiping speed, loading force, blade stiffness and blade angle on the lubrication film, and further, use the resulting data to investigate the relevant lubrication regimes associated with wiping during gravure printing. Based on this analysis, we are able to posit the lubrication regime associated with wiping during gravure printing, provide insight into the ultimate limits of residue reduction, and, furthermore, are able to provide process guidelines and design rules to achieve these limits.

Cell filling in gravure printing for printed electronics.

Highly scaled direct gravure is a promising printing technique for printed electronics due to its large throughput, high resolution, and simplicity. Gravure can print features in the single micron range at printing speeds of ∼1 m/s by using an optimized cell geometry and optimized printing conditions. The filling of the cells on the gravure cylinder is a critical process, since the amount of ink in the cells strongly impacts printed feature size and quality. Therefore, an understanding of cell filling is crucial to make highly scaled gravure printed electronics viable. In this work we report a novel experimental setup to investigate the filling process in real time, coupled with numerical simulations to gain insight into the experimental observations. By varying viscosity and filling speed, we ensure that the dimensionless capillary number is a good indicator of filling regime in real gravure printing. In addition, we also examine the effect of cell size on filling as this is important for increasing printing resolution. In the light of experimental and simulation results, we are able to rationalize the dominant failure in the filling process, i.e., air entrapment, which is caused by contact line pinning and interface deformation over the cell opening.

Systematic design of jettable nanoparticle-based inkjet inks: rheology, acoustics, and jettability.

Drop-on-demand inkjet printing of functional inks has received a great deal of attention for realizing printed electronics, rapidly prototyped structures, and large-area systems. Although this method of printing promises high processing speeds and minimal substrate contamination, the performance of this process is often limited by the rheological parameters of the ink itself. Effective ink design must address a myriad of issues, including suppression of the coffee-ring effect, proper drop pinning on the substrate, long-term ink reliability, and, most importantly, stable droplet formation, or jettability. In this work, by simultaneously considering optimal jetting conditions and ink rheology, we develop and experimentally validate a jettability window within the capillary number-Weber number space. Furthermore, we demonstrate the exploitation of this window to adjust nanoparticle-based ink rheology predictively to realize a jettable ink. Finally, we investigate the influence of mass loading on jettability to establish additional practical limitations on nanoparticle ink design.

Roll-to-roll gravure with nanomaterials for printing smart packaging.

Roll-to-roll (R2R) gravure is considered one of the highest throughput tools for manufacturing inexpensive and flexible ubiquitous IT devices called "smart packaging" in which NFC (near-field communication) transponder, sensors, ADC (analog-to-digital converter), simple processor and signage are all integrated on paper or plastic foils. In this review, we show R2R gravure can be employed to print smart packaging, starting from printing simple electrodes, dielectrics, capacitors, diodes and thin film transistors with appropriate nanomaterial-based inks on plastic foils.

A new switching device for printed electronics: inkjet-printed microelectromechanical relay.

Printed electronics employing solution-processed materials is considered to be the key to realizing low-cost large-area electronic systems, but the performance of printed transistors is generally inadequate for most of the intended applications due to limited performance of printable semiconductor materials. We propose an alternative approach for a printed switch, where the use of semiconductors can be avoided by building mechanical switches with printed metal nanoparticle-based inks. In this work, we detail the first demonstration of inkjet-printed microelectromechanical (MEM) switches with abrupt switching characteristics, very low on-state resistance (~10 Ω), and very low off-state leakage. The devices are fabricated using a novel process scheme to build three-dimensional cantilever structures from solution-processed metallic nanoparticles and sacrificial polymer layers. These printed MEM switches thus represent a uniquely attractive path for realizing printed electronics.

Printed Platinum Nanoparticle Thin-Film Structures for Use in Biology and Catalysis: Synthesis, Printing, and Application Demonstration.

This work describes the formulation of a stable platinum nanoparticle-based ink for drop-on-demand inkjet printing and fabrication of metallic platinum thin films. A highly conductive functional nanoink was formulated based on dodecanethiol platinum nanoparticles (3-5 nm) dispersed in a toluene-terpineol mixture with a loading of 15 wt %, compatible with inkjet printing. The reduced sintering temperatures (200 °C) make them interesting for integration in devices using flexible substrates and substrates that cannot tolerate high-temperature exposures. A resistive platinum heater was successfully printed as a demonstrator for integration of the platinum ink. The platinum nanoink developed herein will be, therefore, attractive for a range of applications in biology, chemistry, and printed electronics.

Femtoliter-scale patterning by high-speed, highly scaled inverse gravure printing.

Pattern printing techniques have advanced rapidly in the past decade, driven by their potential applications in printed electronics. Several printing techniques have realized printed features of 10 µm or smaller, but unfortunately, they suffer from disadvantages that prevent their deployment in real applications; in particular, process throughput is a significant concern. Direct gravure printing is promising in this regard. Gravure printing delivers high throughput and has a proven history of being manufacturing worthy. Unfortunately, it suffers from scalability challenges because of limitations in roll manufacturing and limited understanding of the relevant printing mechanisms. Gravure printing involves interactions between the ink, the patterned cylinder master, the doctor blade that wipes excess ink, and the substrate to which the pattern is transferred. As gravure-printed features are scaled, the associated complexities are increased, and a detailed study of the various processes involved is lacking. In this work, we report on various gravure-related fluidic mechanisms using a novel highly scaled inverse direct gravure printer. The printer allows the overall pattern formation process to be studied in detail by separating the entire printing process into three sequential steps: filling, wiping, and transferring. We found that pattern formation by highly scaled gravure printing is governed by the wettability of the ink to the printing plate, doctor blade, and substrate. These individual functions are linked by the apparent capillary number (Ca); the printed volume fraction (φ(p)) of a feature can be constructed by incorporating these basis functions. By relating Ca and φ(p), an optimized operating point can be specified, and the associated limiting phenomena can be identified. We used this relationship to find the optimized ink viscosity and printing speed to achieve printed polymer lines and line spacings as small as 2 µm at printing speeds as high as ∼1 m/s.

All printed edge-triggered register using single walled carbon nanotube-based thin film transistor.

We have studied the fabrication of Single Walled Carbon Nanotube (SWNT)-based Thin Film Transistors (TFTs) using Roll-to-Roll (R2R) gravure printer and inkjet printer on PET foils to show the possibility of printed electronics in point of mass production and low cost. In this paper, for realization of all printed multi-bits digital circuit, all printed positive-edge triggered master-slave D flip-flop (DFF) was fabricated on PET foil using printed SWNT TFTs. The printed DFF, consists of 8 NAND gates and 4 inverters, exhibit propagation delay of 75 ms at the input clock signal of 5 Hz.

AM radio circuit using printed electronic components.

In this paper, printing technologies have been employed to print the resonant circuit and detection circuit for an amplitude modulation system (AM radio), which consists of a printed inductor, capacitor, resistor and diode on plastic foils for using as an AM radio circuit. To test the printed inductor, capacitor, resistor and diode as components of AM radio, we selected 640 KHz, the strongest AM frequency in Sunchon City, Korea and monitored the audio signal by replacing each component by a corresponding printed one. As a result the 640 KHz AM radio signals were detected.

Hydrostatic optimization of inkjet-printed films.

In this work, we study the optimization of the geometry of inkjet-printed polymer films and develop a simple analytic framework to understand our results and establish limitations on inkjet-printed patterns. We show how drop spacing and ink concentration affect the thickness of a printed film and how hydrostatic conditions with contact angle hysteresis have to be considered to print optimized rectangular features. If advancing and receding contact angle are not taken into account, printed features will either bulge or break up into smaller beads. Thus, we provide a comprehensive analysis of the limits of film formation using regular assemblies of droplets.

Methodology for inkjet printing of partially wetting films.

Inkjet printing of precisely defined structures is critical for the realization of a range of printed electronics applications. We develop and demonstrate a methodology to optimize the inkjet printing of two-dimensional, partially wetting films. When printed inks have a positive retreating contact angle, we show that any fixed spacing is ineffective for printing two-dimensional features. With fixed spacing, the bead contact angle begins large, leading to a bulging overflow of its intended footprint. Each additional line reduces the bead contact angle, eventually leading to separation of the bead. We propose a printing scheme that adjusts the line-to-line spacing to maintain a bead's contact angle between its advancing and retreating values as it is printed. Implementing this approach requires an understanding of the two-dimensional bead surface and compensation for evaporation during the print. We derive an analytic equation for the bead's surface with pinned contact lines and use an empirical fit for mass loss due to evaporation. Finally, we demonstrate that enhanced contact angle hysteresis, achieved by preprinting a feature's border, leads to better corner definition.

Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector.

As thin films become increasingly popular (for solar cells, LEDs, microelectronics, batteries), quantitative morphological and crystallographic information is needed to predict and optimize the film's electrical, optical, and mechanical properties. This quantification can be obtained quickly and easily with X-ray diffraction using an area detector in two sample geometries. In this paper, we describe a methodology for constructing complete pole figures for thin films with fiber texture (isotropic in-plane orientation). We demonstrate this technique on semicrystalline polymer films, self-assembled nanoparticle semiconductor films, and randomly packed metallic nanoparticle films. This method can be immediately implemented to help understand the relationship between film processing and microstructure, enabling the development of better and less expensive electronic and optoelectronic devices.

First-principles studies of the dynamics of [2]rotaxane molecular switches.

Realization of controlled binary switching in individual molecules is of fundamental importance for nanoscale electronics where the use of molecular components promises the flexibility of engineering performance through controlled organic synthesis. The active component of the [2]rotaxane molecule consists of a cyclobis-(paraquat-p-phenylene) ring-shaped structure [(CBPQT(4+))(PF(6)(-))(4)], proposed to switch between two stations, tetrathiafulvalene (TTF) and 1,5-dioxynapthalene (DNP), that lie along a common molecular backbone. However, there are still several open questions regarding their operation and performance, particularly in a device geometry. In this work, the switching speed of crossbar array devices based on [2]rotaxane arrays is studied with first principles density functional theory (DFT). The energetics of a likely configurational pathway for the CBPQT-ring shuttling along the molecular backbone between stations is computed and analyzed, as are ionization potentials and electrostatic screening properties. From these quantities, a new switching mechanism is identified. The applied bias at the cathode alters the energy landscape, making the OFF-state configuration energetically unfavorable relative to the ON-state without involving charging, as previously suggested. (1) For a crossbar memory array of reasonable size, the calculations predict that the switching speed is dominated by the shuttling time of the CBPQT-ring, which is estimated to be a few microseconds. The applicability of this technology is discussed in light of this result.