3D Printing Technology: Role in Safeguarding Food Security.

The rising threats to food security include several factors, such as population growth, low agricultural investment, and poor distribution systems. Consequently, food insecurity results from a confluence of issues, including diseases, processing limitations, and distribution deficiencies. Food insecurity usually occurs in vulnerable areas where certain technologies and traditional food safety testing are not a viable solution for foodborne disease detection. In this regard, 3D printing technologies and 3D printed sensors open the platform to produce portable, accurate, and low-cost sensors that address the gaps and challenges in food security. In this paper, we discuss the perspective role of 3D printed sensors in food security in terms of food safety and food quality monitoring to provide reliable access to nutritious, affordable food. In each section, we highlight the advantages of 3D printing technology in terms of cost-effectiveness, accuracy, accessibility, and reproducibility compared to traditional manufacturing methodologies. Recent developments in robotic technologies for mechanization, such as food handling with soft grippers, are also discussed. Lastly, we delve into the applications of advanced 3D printing technologies in agricultural monitoring, particularly the future of plant wearables, environmental sensing, and overall plant health monitoring.

3D designed battery-free wireless origami pressure sensor.

A pressure monitoring structure is a very useful element for a wearable device for health monitoring and sports biomechanics. While pressure sensors have been studied extensively, battery-free functions working in wireless detection have not been studied much. Here, we report a 3D-structured origami-based architecture sensor for wireless pressure monitoring. We developed an architectured platform for wireless pressure sensing through inductor-capacitor (LC) sensors and a monopole antenna. A personalized smart insole with Miura-ori origami designs has been 3D printed together with conductive 3D printed sensors seamlessly. Wireless monitoring of resonant frequency and intensity changes of LC sensors have been demonstrated to monitor foot pressure for different postures. The sensitivity of the wireless pressure sensor is tunable from 15.7 to 2.1 MHz/kPa in the pressure ranges from 0 to 9 kPa and from 10 to 40 kPa, respectively. The proposed wireless pressure-sensing platform can be utilized for various applications such as orthotics, prosthetics, and sports gear.

A 3D-printed neuromorphic humanoid hand for grasping unknown objects.

Compared with conventional von Neumann's architecture-based processors, neuromorphic systems provide energy-saving in-memory computing. We present here a 3D neuromorphic humanoid hand designed for providing an artificial unconscious response based on training. The neuromorphic humanoid hand system mimics the reflex arc for a quick response by managing complex spatiotemporal information. A 3D structural humanoid hand is first integrated with 3D-printed pressure sensors and a portable neuromorphic device that was fabricated by the multi-axis robot 3D printing technology. The 3D neuromorphic robot hand provides bioinspired signal perception, including detection, signal transmission, and signal processing, together with the biomimetic reflex arc function, allowing it to hold an unknown object with an automatically increased gripping force without a conventional controlling processor. The proposed system offers a new approach for realizing an unconscious response with an artificially intelligent robot.

Involvement of frontline clinicians in healthcare technology development: Lessons learned from a ventilator project.

Co-development of healthcare technology with users helps produce user-friendly products, ensuring safe device usage and meeting patients' needs. For developers considering healthcare innovations, engaging user experience can reduce production time and cost while maximizing device application. The purpose of this paper is to report lessons learned from the development of a 3D printed origami ventilator prototype in response to the rise of ventilator demand due to the Coronavirus disease (COVID-19) pandemic. We conducted focus groups with frontline clinicians working in an Intensive Care Unit of a large urban hospital in Vancouver, British Columbia, Canada. In the interdisciplinary focus groups, we identified challenges, practical tips about product development, the human needs of technology, and cross-discipline peer learning. The focus group discussions provide useful insight into the technology development for complex clinical contexts. Based on our experiences, we articulate five practical tips for co-development of healthcare technology - AGILE: Analyse users' needs first, Gain insights into complex context, Involve users early and frequently, Lead with a prototype, and Educate and support. Through sharing the tips and lessons learned, we wish to emphasize the necessity of meaningful multi-disciplinary collaboration during healthcare technology development and promote the inclusion of frontline clinicians during these initiatives. Supplementary Information: The online version contains supplementary material available at 10.1007/s12553-022-00655-w.

New Frontiers in 3D Structural Sensing Robots.

Advanced robotics is the result of various contributions from complex fields of science and engineering and has tremendous value in human society. Sensing robots are highly desirable in practical settings such as healthcare and manufacturing sectors through sensing activities from human-robot interaction. However, there are still ongoing research and technical challenges in the development of ideal sensing robot systems. The sensing robot should synergically merge sensors and robotics. Geometrical difficulty in the sensor positioning caused by the structural complexity of sensing robots and their corresponding processing have been the main challenges in the production of sensing robots. 3D electronics integrated into 3D objects prepared by the 3D printing process can be the potential solution for designing realistic sensing robot systems. 3D printing provides the advantage to manufacture complex 3D structures in electronics in a single setup, allowing the ease of design flexibility, and customized functions. Therefore, the platform of 3D sensing systems is investigated and their expansion into sensing robots is studied further. The progress toward sensing robots from 3D electronics integrated into 3D objects and the advanced material strategies, used to overcome the challenges, are discussed.

Artificial Xylem Chip: A Three-Dimensionally Printed Vertical Digital Microfluidic Platform.

Digital microfluidics (DMF) is a promising lab-on-a-chip technology which has been applied in a wide variety of fields, including chemical sensing, biological detection, and even mechanical transportation. However, the appearance and functions of current DMF have been limited within two-dimensional planar space because of the conventional fabrication methods, such as photolithography or screen printing. In this paper, we report a DMF system which utilizes the advantage of three-dimensional (3D) printing to develop the novel form factor of electrodes and conversion of channels from planar to 3D forms. Vertical channels have been fabricated through combined 3D printing methods to facilitate stable and controlled movement of water droplets. The interfaces among liquid, gas, and solid were analyzed through Young-Lippmann law. We calculated the actuation force in a series of different configurations to enable us to optimize the system. Inspired by xylem structures in plants, the vertical movement and pumping of droplets are demonstrated by a programmable control system with a built-in boost converter for a real-time operating and portable DMF system. This work validates the promise of 3D printing to make 3D vertical DMF devices and the potential of the artificial xylem chip for micropumping applications.

Additively Manufactured Digital Microfluidic Platforms for Ion-Selective Sensing.

Digital microfluidic (DMF) sensors integrated with circuit systems have been applied to a broad range of applications including biology, medicine, and chemistry. Compared with the conventional microfluidic devices that require extra liquid as a carrier and a complex pumping system to operate, DMF is an ideal platform for ion-selective sensing as it enables the droplet operation in a discrete, accurate, and automatic way. However, it is quite rare that DMF platform is utilized for the ion-selective detection. In this paper, we report an integrated DMF system which combines DMF and ion-selective sensing for facile blending of multiple ions, and detection of targeted primary ion. The platform is fabricated through an additive manufacturing method, together with the real-time droplet's motion monitoring feedback system. Thus, the fabricated system demonstrates controlled droplet manipulation ability including droplet actuation, mixing, and speed control. Targeted primary ion is selectively detected under concentration range from 10-6 to 1 M. The interference study with blended ions has been investigated through on-chip ion selective membranes.

Hierarchically Designed Electron Paths in 3D Printed Energy Storage Devices.

Three-dimensional (3D) microsupercapacitors (MSC) have been spotlighted, because they overcome limited areal capacitance of two-dimensional planar MSCs. Specially, 3D printing technology offers numerous advantages to generate 3D electrodes for MSCs, which includes time-saving, cost-effective manufacturing, and realization of tailorable complex electrode designs. In this paper, we report novel hierarchical 3D designs of conductive 3D electrodes for MSC by digital light processing (DLP)-based 3D printing. Photocurable composite resin with silver nanowires was optimized for DLP printing for the hierarchical design of high aspect ratio in 3D electrodes. The hierarchical 3D electrodes showed unique patterns on the structure corresponding to stacking of layers in the direction of 3D printing. The fabricated 3D MSCs demonstrated low electrical resistance to be used as feasible MSC electrodes. Energy storage from silver redox reactions was demonstrated in hierarchical 3D electrodes designed with mechanically durable 3D octet trusses.

Nozzle Shape Guided Filler Orientation in 3D Printed Photo-curable Nanocomposites.

Here, we report guided orientation of silver nanowires (AgNWs) in extruded patterns with photo-curable 3D printing technology. A printable conductive composite material composed of polymer matrix and silver nanowires shows significantly varied electrical properties depending on the cross-sectional shape of printing nozzles: flat or circular. The composite is designed to have highly conductive AgNWs and a dielectric polymer matrix like photo-curable methacrylate resin. The dielectric permittivity of photo-curable composite resin with 1.6 vol. % of AgNWs printed through a circular nozzle showed 27. However, the same resin showed much lower permittivity with 20 when it is printed with a flat nozzle. The cross-sectional sample morphology shows that AgNWs printed with a circular nozzle are aligned, and AgNWs printed with a flat nozzle are randomly distributed. A computational simulation of paste extrusion with two different nozzle shapes showed clearly different fluidic velocities at the nozzle exit, which contributes to different fiber orientation in printed samples. A radio frequency identification sensor is fabricated with 3D printed composite using a flat nozzle for the demonstration of AgNW based 3D printed conductor.

Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics.

We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 102 S/cm has been achieved from the demonstrated 3D printable composite with 1.9 vol. % loading of silver nanowires. Utilizing the high conductivity of the printable composites, 3D printing of designed battery electrode pastes is demonstrated. Rheology study shows superior printability of the electrode pastes aided by the cellulose's strong thixotropic rheology. The designed anode, electrolyte, and cathode pastes are sequentially printed to form a three-layered lithium battery for the demonstration of a charging profile. This study opens opportunities of 3D printable conductive materials to create printed electronics with the next generation additive manufacturing process.

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles.

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration.

Reversibly stretchable transparent conductive coatings of spray-deposited silver nanowires.

Here, we report the creation of highly adhesive transparent and stretchable coatings via spray-deposition of solution-based silver nanowires (AgNWs). The AgNW dispersion was spray-deposited on a polydopamine-modified stretchable elastomeric substrate to prepare thin, stretchable, transparent, highly conductive films. The polydopamine layer on the elastomeric substrate created a highly hydrophilic surface, which facilitated the subsequent spraying of the AgNW solution. Additionally, the spray-deposited AgNWs demonstrated excellent adhesion to the substrate, which allowed the fabrication of stretchable electrodes with high conductivity. The AgNW-coated elastomeric substrate exhibited ~80% transmittance with an average sheet resistance of ~35 Ω/□, making it suitable for transparent electrode applications. The conductivity of the transparent electrode was maintained up to ~20% mechanical elongation, which demonstrated the stretchable characteristics of the AgNW-coated elastomeric substrate.

Facile fabrication of super-hydrophobic nano-needle arrays via breath figures method.

Super-hydrophobic surfaces which have been fabricated by various methods such as photolithography, chemical treatment, self-assembly, and imprinting have gained enormous attention in recent years. Especially 2D arrays of nano-needles have been shown to have super-hydrophobicity due to their sharp surface roughness. These arrays can be easily generated by removing the top portion of the honeycomb films prepared by the breath figures method. The hydrophilic block of an amphiphilic polymer helps in the fabrication of the nano-needle arrays through the production of well-ordered honeycomb films and good adhesion of the film to a substrate. Anisotropic patterns with water wettability difference can be useful for patterning cells and other materials using their selective growth on the hydrophilic part of the pattern. However, there has not been a simple way to generate patterns with highly different wettability. Mechanical stamping of the nano-needle array with a polyurethane stamp might be the simplest way to fabricate patterns with wettability difference. In this study, super-hydrophobic nano-needle arrays were simply fabricated by removing the top portion of the honeycomb films. The maximum water contact angle obtained with the nano-needle array was 150°. By controlling the pore size and the density of the honeycomb films, the height, width, and density of nano-needle arrays were determined. Anisotropic patterns with different wettability were fabricated by simply pressing the nano-needle array at ambient temperature with polyurethane stamps which were flexible but tough. Mechanical stamping of nano-needle arrays with micron patterns produced hierarchical super-hydrophobic structures.PACS: 05.70.Np, 68.55.am, 68.55.jm.

Protein micropatterning on bifunctional organic-inorganic sol-gel hybrid materials.

Active protein micropatterns and microarrays made by selective localization are popular candidates for medical diagnostics, such as biosensors, bioMEMS, and basic protein studies. In this paper, we present a simple fabrication process of thick (approximately 20 microm) protein micropatterning using capillary force lithography with bifunctional sol-gel hybrid materials. Because bifunctional sol-gel hybrid material can have both an amine function for linking with protein and a methacryl function for photocuring, proteins such as streptavidin can be immobilized directly on thick bifunctional sol-gel hybrid micropatterns. Another advantage of the bifunctional sol-gel hybrid materials is the high selective stability of the amine group on bifunctional sol-gel hybrid patterns. Because amine function is regularly contained in each siloxane oligomers, immobilizing sites for streptavidin are widely distributed on the surface of thick hybrid micropatterns. The micropatterning processes of active proteins using efficient bifunctional sol-gel hybrid materials will be useful for the development of future bioengineered systems because they can save several processing steps and reduce costs.

Double component long period waveguide grating filter in sol-gel material.

An efficient, tunable Long Period Waveguide Grating (LPWG) filter based on a new hybrid sol-gel material is demonstrated. The LPWG exhibits an attenuation of -22 dB and a high temperature sensitivity of ~3.3 nm/ degrees C. At room temperature the device shows an almost polarization independent wavelength. We took the advantage of the UV-curable sol-gel materials and used soft lithography to demonstrate a simple approach of integrating two LPWG filters on the same structure. The gratings were fabricated on the top and on the bottom of the same ridge waveguide and operate at communication wavelengths of 1550 and 1310 nm, respectively.

Fluorinated organic-inorganic hybrid mold as a new stamp for nanoimprint and soft lithography.

In this paper, we fabricated a fluorinated organic-inorganic hybrid mold using a nonhydrolytic sol-gel process which can produce a crack-free mold without leaving any trace of solvent. No special chemical treatment of a release layer is needed because the fluorinated hybrid mold has fluorine molecules in the backbone. The other advantages of the hybrid mold are thermal stability over 300 degrees C. The hybrid mold produced from UV nanoimprint lithography (UV-NIL) was used as a mold for the next UV-NIL and soft lithography without requiring use of an antisticking layer. Various nanometer scale patterns including sub-100 nm patterns could be obtained from the hybrid mold. Nanopatterning processes using this low-cost mold are useful because they preserve the expensive original master.