Nozzle-Free Printing of CNT Electronics Using Laser-Generated Focused Ultrasound.

Printed electronics have made remarkable progress in recent years and inkjet printing (IJP) has emerged as one of the leading methods for fabricating printed electronic devices. However, challenges such as nozzle clogging, and strict ink formulation constraints have limited their widespread use. To address this issue, a novel nozzle-free printing technology is explored, which is enabled by laser-generated focused ultrasound, as a potential alternative printing modality called Shock-wave Jet Printing (SJP).

Multijet Gold Nanoparticle Inks for Additive Manufacturing of Printed and Wearable Electronics.

Conductive and biofriendly gold nanomaterial inks are highly desirable for printed electronics, biosensors, wearable electronics, and electrochemical sensor applications. Here, we demonstrate the scalable synthesis of stable gold nanoparticle inks with low-temperature sintering using simple chemical processing steps. Multiprinter compatible aqueous gold nanomaterial inks were formulated, achieving resistivity as low as ∼10 Ω m for 400 nm thick films sintered at 250 °C.

Correlative Imaging of Three-Dimensional Cell Culture on Opaque Bioscaffolds for Tissue Engineering Applications.

Three-dimensional (3D) tissue engineering (TE) is a prospective treatment that can be used to restore or replace damaged musculoskeletal tissues, such as articular cartilage. However, current challenges in TE include identifying materials that are biocompatible and have properties that closely match the mechanical properties and cellular microenvironment of the target tissue. Visualization and analysis of potential 3D porous scaffolds as well as the associated cell growth and proliferation characteristics present additional problems.

Structure-Property-Processing Correlations of Graphene Bioscaffolds for Proliferation and Differentiation of C2C12 Cells.

Graphene - an atomically thin layer of carbon atoms arranged in a hexagonal lattice - has gained interest as a bioscaffold for tissue engineering due to its exceptional mechanical, electrical, and thermal properties. Graphene's structure and properties are tightly coupled to synthesis and processing conditions, yet their influence on biomolecular interactions at the graphene-cell interface remains unclear. In this study, C2C12 cells were grown on graphene bioscaffolds with specific structure-property- processing-performance (SP3) correlations.

Aerosol jet printing of piezoelectric surface acoustic wave thermometer.

Surface acoustic wave (SAW) devices are a subclass of micro-electromechanical systems (MEMS) that generate an acoustic emission when electrically stimulated. These transducers also work as detectors, converting surface strain into readable electrical signals. Physical properties of the generated SAW are material dependent and influenced by external factors like temperature.

Correlative Imaging of 3D Cell Culture on Opaque Bioscaffolds for Tissue Engineering Applications.

Three-dimensional (3D) tissue engineering (TE) is a prospective treatment that can be used to restore or replace damaged musculoskeletal tissues such as articular cartilage. However, current challenges in TE include identifying materials that are biocompatible and have properties that closely match the mechanical properties and cellular environment of the target tissue, while allowing for 3D tomography of porous scaffolds as well as their cell growth and proliferation characterization. This is particularly challenging for opaque scaffolds.

Plasma-jet printing of colloidal thermoelectric BiTe nanoflakes for flexible energy harvesting.

Thermoelectric generators (TEGs) convert temperature differences into electrical power and are attractive among energy harvesting devices due to their autonomous and silent operation. While thermoelectric materials have undergone substantial improvements in material properties, a reliable and cost-effective fabrication method suitable for microgravity and space applications remains a challenge, particularly as commercial space flight and extended crewed space missions increase in frequency. This paper demonstrates the use of plasma-jet printing (PJP), a gravity-independent, electromagnetic field-assisted printing technology, to deposit colloidal thermoelectric nanoflakes with engineered nanopores onto flexible substrates at room temperature.

Ultra-compact hybrid silicon:chalcogenide waveguide temperature sensor.

We demonstrate a real-time, reusable, and reversible integrated optical sensor for temperature monitoring within harsh environments. The sensor architecture combines the phase change property of chalcogenide glasses (ChG) with the high-density integration advantages of high index silicon waveguides. To demonstrate sensor feasibility, ChG composition GeS, which is characterized by a sharp phase transition from amorphous to crystalline phase around 415 °C, is deposited over a 50 µm section of a single mode optical waveguide.

Real-time measurement of parametric influences on the refractive index and length changes in silica optical fibers.

In this paper, we present a simple cascaded Fabry-Perot interferometer (FPI) that can be used to measure in real-time the refractive index (RI) and length variation in silica optical fibers caused due to external physical parameters, such as temperature, strain, and radiation. As a proof-of-concept, we experimentally demonstrate real-time monitoring of temperature effects on the RI and length and measure the thermo-optic coefficient (TOC) and thermal expansion coefficient (TEC) by using the cascaded FPI within a temperature range of 21-486°C. The experimental results provide a TEC of 5.

Active Compensation of Radiation Effects on Optical Fibers for Sensing Applications.

Neutron and gamma irradiation is known to compact silica, resulting in macroscopic changes in refractive index (RI) and geometric structure. The change in RI and linear compaction in a radiation environment is caused by three well-known mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced compaction (RIC), and (iii) radiation-induced emission (RIE). These macroscopic changes induce errors in monitoring physical parameters such as temperature, pressure, and strain in optical fiber-based sensors, which limit their application in radiation environments.

Numerical Analysis of Radiation Effects on Fiber Optic Sensors.

Optical fiber sensors (OFS) are a potential candidate for monitoring physical parameters in nuclear environments. However, under an irradiation field the optical response of the OFS is modified via three primary mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced emission (RIE), and (iii) radiation-induced compaction (RIC). For resonance-based sensors, RIC plays a significant role in modifying their performance characteristics.

Chalcogenide Glass-Capped Fiber-Optic Sensor for Real-Time Temperature Monitoring in Extreme Environments.

We demonstrate a novel chalcogenide glass (ChG)-capped optical fiber temperature sensor capable of operating within harsh environment. The sensor architecture utilizes the heat-induced phase change (amorphous-to-crystalline) property of ChGs, which rapidly (80-100 ns) changes the optical properties of the material. The sensor response to temperature variation around the phase change of the ChG cap at the tip of the fiber provides abrupt changes in the reflected power intensity.

Fully inkjet-printed multilayered graphene-based flexible electrodes for repeatable electrochemical response.

Graphene has proven to be useful in biosensing applications. However, one of the main hurdles with printed graphene-based electrodes is achieving repeatable electrochemical performance from one printed electrode to another. We have developed a consistent fabrication process to control the sheet resistance of inkjet-printed graphene electrodes, thereby accomplishing repeatable electrochemical performance.

A Review of Inkjet Printed Graphene and Carbon Nanotubes Based Gas Sensors.

Graphene and carbon nanotube (CNT)-based gas/vapor sensors have gained much traction for numerous applications over the last decade due to their excellent sensing performance at ambient conditions. Inkjet printing various forms of graphene (reduced graphene oxide or modified graphene) and CNT (single-wall nanotubes (SWNTs) or multiwall nanotubes (MWNTs)) nanomaterials allows fabrication onto flexible substrates which enable gas sensing applications in flexible electronics. This review focuses on their recent developments and provides an overview of the state-of-the-art in inkjet printing of graphene and CNT based sensors targeting gases, such as NO, Cl, CO, NH, and organic vapors.

Inkjet-Printed Graphene-Based 1 × 2 Phased Array Antenna.

Low-cost and conformal phased array antennas (PAAs) on flexible substrates are of particular interest in many applications. The major deterrents to developing flexible PAA systems are the difficulty in integrating antenna and electronics circuits on the flexible surface, as well as the bendability and oxidation rate of radiating elements and electronics circuits. In this research, graphene ink was developed from graphene flakes and used to inkjet print the radiating element and the active channel of field effect transistors (FETs).

Observation of Third-order Nonlinearities in Graphene Oxide Film at Telecommunication Wavelengths.

All-optical switches have been considered as a promising solution to overcome the fundamental speed limit of the current electronic switches. However, the lack of a suitable third-order nonlinear material greatly hinders the development of this technology. Here we report the observation of ultrahigh third-order nonlinearity about 0.

Inkjet Printing of High Performance Transistors with Micron Order Chemically Set Gaps.

This paper reports a 100% inkjet printed transistor with a short channel of approximately 1 µm with an operating speed up to 18.21 GHz. Printed electronics are a burgeoning area in electronics development, but are often stymied by the large minimum feature size.

One-dimensional photonic crystal slot waveguide for silicon-organic hybrid electro-optic modulators.

In an on-chip silicon-organic hybrid electro-optic (EO) modulator, the mode overlap with EO materials, in-device effective r, and propagation loss are among the most critical factors that determine the performance of the modulator. Various waveguide structures have been proposed to optimize these factors, yet there is a lack of comprehensive consideration on all of them. In this Letter, a one-dimensional (1D) photonic crystal (PC) slot waveguide structure is proposed that takes all these factors into consideration.

Geometrical tuning art for entirely subwavelength grating waveguide based integrated photonics circuits.

Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to the extra degree of freedom it offers in tuning a few important waveguide properties, such as dispersion and refractive index. Devices based on SWG waveguides have demonstrated impressive performances compared to conventional waveguides. However, the high loss of SWG waveguide bends jeopardizes their applications in integrated photonic circuits.

Recent advances in silicon-based passive and active optical interconnects.

Silicon photonics has experienced phenomenal transformations over the last decade. In this paper, we present some of the notable advances in silicon-based passive and active optical interconnect components, and highlight some of our key contributions. Light is also cast on few other parallel technologies that are working in tandem with silicon-based structures, and providing unique functions not achievable with any single system acting alone.

Microfluidic channels with ultralow-loss waveguide crossings for various chip-integrated photonic sensors.

Traditional silicon waveguides are defined by waveguide trenches on either side of the high-index silicon core that leads to fluid leakage orifices for over-layed microfluidic channels. Closing the orifices needs additional fabrication steps which may include oxide deposition and planarization. We experimentally demonstrated a new type of microfluidic channel design with ultralow-loss waveguide crossings (0.

Flexible single-crystal silicon nanomembrane photonic crystal cavity.

Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development.

Highly efficient mode converter for coupling light into wide slot photonic crystal waveguide.

We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320 nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08 dB.

Grating-coupled silicon-on-sapphire integrated slot waveguides operating at mid-infrared wavelengths.

We demonstrate subwavelength bidirectional grating (SWG) coupled slot waveguide fabricated in silicon-on-sapphire for transverse electric polarized wave operation at 3.4 μm wavelength. Coupling efficiency of 29% for SWG coupler is experimentally achieved.

On-chip silicon optical phased array for two-dimensional beam steering.

A 16-element optical phased array integrated on chip is presented for achieving two-dimensional (2D) optical beam steering. The device is fabricated on the silicon-on-insulator platform with a 250 nm silicon device layer. Steering is achieved via a combination of wavelength tuning and thermo-optic phase shifting with a switching power of P(π)=20  mW per channel.