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A User’s Guide

The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features “on-the-fly.” To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates.

https://www.pnas.org/content/pnas/113/22/6137.full.pdf

Laser-assisted direct ink writing of planar and 3D metal architectures

Advances in the field of extrusion based 3-D printing have recently allowed the incorporation of embedded electronics and interconnects, in order to increase the functionality of these structures. This paper builds on previous work in the area of fine-pitch copper mesh and embedded copper wire capacitive sensors encapsulated within a 3-D printed structure. Three varieties of sensors were fabricated and tested, including a small area wire sensor (320-μm width), a large area mesh sensor (2 cm
 2
), and a fully embedded demonstration model. In order to test and characterize these sensors, three distinct tests were explored. Specifically, the capacitive sensors were able to distinguish between three metallic materials and distinguish salt water from distilled water. These capacitive sensors have many potential sensing applications, such as biomedical sensing, human interface devices, material sensing, electronics characterization, and environmental sensing. As such, this paper also characterizes the capacitive sensors for an active microfluidic mixer.

Encapsulated Copper Wire and Copper Mesh Capacitive Sensing for 3-D Printing Applications

A singlemode-multimode-singlemode (SMS) fiber structure consists of a short section of multimode fiber fusion- spliced between two SMS fibers. The mechanism underpinning the operation of an SMS fiber structure is multimode interference and associated self-imaging. SMS structures can be used in a variety of optical fiber systems but are most commonly used as sensors for a variety of parameters, ranging from macro-world measurands such as temperature, strain, vibration, flow rate, RI and humidity to the micro-world with measurands such as proteins, pathogens, DNA and specific molecules. While traditional SMS structures employ a short section of standard multimode fiber, a large number of structures have been investigated and demonstrated over the last decade involving the replacement of the multimode fiber section with alternatives such as a hollow core fiber or a tapered fiber. The objective of replacing the multimode fiber has most often been to allow sensing of different measurands or to improve sensitivity. In this paper, several different categories of SMS fiber structures, including traditional SMS, modified SMS and tapered SMS fiber structures are discussed with some theoretical underpinning and reviews of a wide variety of sensing examples and recent advances. The paper then summarizes and compares the performances of a variety of sensors which have been published under a number of headings. The paper concludes by considering the challenges faced by SMS based sensing schemes in terms of their deployment in real world applications and discusses possible future developments of SMS fiber sensors.

/pdf/singlemode-multimode-singlemode-fiber-structures-for-sensing-414kj1fml3.pdf

Singlemode-Multimode-Singlemode Fiber Structures for Sensing Applications—A Review

Recent advances in the field of 3D printing have utilized embedded electronic interconnects in order to construct advanced electronic devices. This work builds on these advances in order to construct and characterize arbitrarily formed capacitive sensors using fine-pitch copper mesh and embedded copper wires. Three varieties of sensors were fabricated and tested, including a small area wire sensor (320μm width), a large area mesh sensor (2cm2), and a fully embedded demonstration model. In order to test and characterize these sensors in FDM materials, three distinct tests were explored. Specifically, the sensors were able to distinguish between three metallic materials and distinguish salt water from distilled water. These capacitive sensors have many potential sensing applications, such as biomedical sensing, human interface devices, material sensing, electronics characterization, and environmental sensing. As such, this work specifically examines optimum mesh/wire capacitive parameters as well as potential applications such as 3D printed integrated material sensing.

3D printed capacitive sensors

A horizontal printed Write-Once-Read-Many (WORM) resistive memory has been developed for use in wireless sensor tags targeting single-event detection in smart packaging applications. The WORM memory can be programmed using a 1.5-V printed battery. An alternative programming method is to use chemical sintering which allows the development of exposure-time triggered single event tags that can be accessed wirelessly. The new WORM memory has very low losses in the ON-state which allows direct integration into antenna structures. A sensor tag that utilizes the WORM memory functionality and the well established Electronic Article Surveillance (EAS) communication standard has been outlined. Both active and fully passive sensor tag solutions have been proposed. The role of printed electronics in smart packaging applications has been reviewed and discussed. Important enabling factors for the future development have been highlighted, such as the need for hierarchical design and test tools, better printed interconnect technologies as well as better components that allow communication with existing information and communication technology (ICT) standards. This is illustrated and underlined by the presented smart packaging concept demonstrators.

Printed Write Once and Read Many Sensor Memories in Smart Packaging Applications

There is an increasing demand for compact, reliable and versatile sensor concepts for pH-level monitoring within several industrial, chemical as well as bio-medical applications. Many pH sensors concepts have been proposed, however, there is still a need for improved sensor solutions with respect to reliability, durability and miniaturization but also for multiparameter sensing. Here we present a conceptual verification, which includes theoretical simulations as well as experimental evaluation of a fiber optic pH-sensor based on a bio-compatible pH sensitive material not previously used in this context. The fiber optic sensor is based on a Mach-Zehnder interferometric technique, where the pH sensitive material is coated on a short, typically 20-25 mm thin core fiber spliced between two standard single mode fibers. The working principle of the sensor is simulated by using COMSOL Multiphysics. The simulations are used as a guideline for the construction of the sensors that have been experimentally evaluated in different liquids with pH ranging from 1.95 to 11.89. The results are promising, showing the potential for the development of bio-compatible fiber optic pH sensor with short response time, high sensitivity and broad measurement range. The developed sensor concept can find future use in many medical- or bio-chemical applications as well as in environmental monitoring of large areas. Challenges encountered during the sensor development due to variation in the design parameters are discussed.

A Bio-Compatible Fiber Optic pH Sensor Based on a Thin Core Interferometric Technique

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns Monitoring the type of pollution and concentration levels is vit 

https://www.mdpi.com/2227-9040/6/3/30/pdf

Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate

Excited state absorption (ESA) measurements performed on Yb-doped silica bers show the onset of a strong absorption band in the visible range. In this work, we perform experiments to investigate the possibility for ESA to be part of the induced optical losses (photodarkening) observed in Yb-doped ber lasers. Our results indicate that an ESA process, from the 2F5/2 excited state manifold in the Yb3+ ion to the charge-transfer state with absorption bands in the UV range, may constitute a transfer route for pump- and laser photons in the near-infrared range. © 2013 Copyright SPIE.

Strong excited state absorption (ESA) in Yb-doped fiber lasers

Sensing pH in blood with an silica multimode optical fiber. This sensor is based on evanescent wave absorption and measures the change of the refractive index and absorption in a cladding made of a ...

Krister Hammarling

Papers

Printed Write Once and Read Many Sensor Memories in Smart Packaging Applications

A Bio-Compatible Fiber Optic pH Sensor Based on a Thin Core Interferometric Technique

Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate

Strong excited state absorption (ESA) in Yb-doped fiber lasers

Blood pH optrode based on evanescent waves and refractive index change