This PDF file contains the front matter associated with SPIE Proceedings Volume 12485, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

Flexible and stretchable stress and strain sensing materials have gained a lot of research interest recently as the development of wearable sensors for health monitoring, motion capturing and soft robotics. In these applications where dynamic stress and strain are common, piezoelectricity becomes a suitable sensing mechanism due to its fast response and high sensitivity. Existing research on flexible piezoelectric materials includes nanocomposites and sandwich composites made of piezoelectric fillers and elastomers. However, the giant modulus mismatch between the two distinct phases makes nanocomposites or sandwich materials prone to inaccurate sensing under large strains due to the weak stress transfer efficiency. In this research, polyvinylidene fluoride (PVDF) and unvulcanized nitrile rubber (NBR) are both dissolved in N,N-dimethylformamide (DMF) and then precipitation printed into a water bath to produce PVDF/NBR polymer blends. The blends are further vulcanized via hot pressing. The resulting blends exhibit polar phases of PVDF, highly uniform blend morphology, as well as excellent stretchability. As a stretchable sensor, the PVDF/NBR (2:8) shows consistent open circuit voltage-strain and open circuit voltage-stress relationships, as well as a high operating strain range up to 70%. Therefore, the PVDF/NBR blend can be used as a promising dynamic stress/strain sensing material for wearable sensors or soft robotic sensors.

Monitoring electrolytes is critical for newborns and babies in the intensive care unit. However, the gold standard methods use a blood draw, which is painful and only offers discrete measures. Here, we introduce a smart, wireless, bioelectronic pacifier for salivary electrolyte monitoring of neonates, which can detect real-time continuous sodium and potassium levels without a blood draw. The miniature system facilitates the seamless integration of the ultralight and low-profile device with a commercial pacifier without additional fixtures or structural modifications. The portable device includes ion-selective sensors, flexible circuits, and microfluidic channels, allowing non-invasive electrolyte monitoring. The flexible microfluidic channel enables continuous and efficient saliva collection from the mouth. In vivo study with neonates in the intensive care unit captures the device's feasibility and performance in the natural saliva-based detection of the critical electrolytes.

The prevalence of blindness and low vision is skyrocketing as the population ages. Independent, efficient, and safe navigation for persons with blindess and low vision requires hard work, practice, and development of strong orientation and mobility skills. In this vein, orientation and mobility training provides tools to familiarize oneself with new environments and maintain an independent lifestyle. In recent years, orientation and mobility training has adopted electronic travel aids, smart devices developed to assist those with blindness and low vision during navigation. However, learning how to use an electronic travel aid in orientation and mobility training sessions may prove dangerous for, as an end user. Early in use, the end user may misinterpret the information provided by the electronic travel aid. In fact, there may be a shallow learning curve during initial implementation. To this end, we built a multiplayer virtual reality platform to simulate an orientation and mobility training, involving trainer and trainee, for practicing with an electronic travel aid in a controlled, safe but realistic environment. We interfaced the virtual reality platform with a custom electronic travel aid created by our team. The electronic travel aid consists of a specially designed camera on a backpack and a haptic belt, along with software that can relays information about the location of near obstacles in the virtual environment through spatiotopic vibrotactile stimulation of the abdomen. In the virtual environment, the trainer can instruct the trainee in the use of the electronic travel aid while navigating complex urban environments. The efficacy of the communication between trainer and trainee towards teaching the correct use of the electronic travel aid and its performance in assisting navigation will be evaluated through series of systematic experiments.

This study presents the initial study for a new approach to visualize an acoustic sound aimed at mimicking the traveling wave propagation of the basilar membrane within the human cochlea. Typically, a fast Fourier transform (FFT) is required to extract the frequency information from acoustic sound (i.e., voice) for speech recognition. Although this algorithm ensures real-time frequency extraction due to the inherent fast recursive structure, it is necessary to develop a new frequency selectivity technique for advanced speech recognition. We explore the potential of the cochlea-inspired sound visualization to deliver new frequency selectivity by using an image sensor. The experimental prototyping model is fabricated, and we capture images of frequency dependent wave propagation motion using a camera and reproduce 2D images through motion magnification. This approach offers a promising application for speech recognition systems because no FFT is required to extract the frequency information, although there are outstanding technical problems that need to be further examined.

Electrical Impedance Tomography (EIT) is a medical imaging technique that reconstructs impedance distribution inside a target object by injecting electrical currents into pairs of electrodes and measuring induced voltages on the remaining electrodes. Since neural signals result from the activity of ion channels causing impedance changes in the cell membrane, EIT can image these neural activities for understanding brain function and medical purposes. In our research, our self-developed electronic prototype board was used to generate high-quality electrical current and collect the data on electrodes with a high sampling rate and bit-resolution. In image reconstruction, a preprocessing data analysis algorithm was newly developed and applied to improve the accuracy of our EIT imaging. The human head has complex anatomical geometry and non-uniform resistivity distribution along with the highly resistive skull, which makes brain-EIT remains challenging inaccurate image reconstruction. To mimic the human head, a multi-layered human head phantom was designed and tested to investigate the effect of the skull structure on imaging. In this presentation, comparison studies for measurements and simulation results will be introduced to discuss the source of errors and improve the accuracy and efficiency of our brain-EIT system.

Tattoo-like sensors represent a class of emerging wearable devices that can be directly applied to flexible and stretchable surfaces, like the human skin, without causing any peeling and dusting. Currently, available tattoo sensors are typically applied through a thin metal coating or conducting particle infiltrated nanofibrous network, which would interfere with the users’ sense of touch. Herein, we report flexible tattoo-like sensor based on laser-induced reduced graphene oxide (rGO) that can be easily transferred printed onto flexible surfaces with minimal sensory interference. Via direct writing, the rGO can be designed with arbitrary shape and geometry on a liquid surface. The rGO can then be transferred conformally onto a flexible surface. This rGO-based wearable sensor is capable of sensing external stimuli, such as applied tactile pressure. The ease of application, the thin form factor, and flexible nature of the rGO-based tattoo sensor ensured device can perform reliably, while providing user comfort and minimal sensory interference.

The aramid nanofibers (ANFs) are isolated from commercial para-aramid fiber, a class of strong and heat-resistant synthetic fibers. They comprise dense inter-molecular hydrogen bonds among highly aligned molecular chains, resulting in outstanding modulus and strength-to-weight properties comparable to carbon fiber and cellulose nanofiber. The aramid nanofibers show a high aspect ratio with a nano-sized diameter and micro-scaled length. These have been spotlighted as promising nano-building blocks with their excellent mechanical properties and thermal stability. In addition, it is an eco-friendly and cost-effective system as one way to recycle waste aramid fibers generated from the rapidly growing aramid textile market. Herein, ANFs-based multidimensional structures with high specific modulus, strength and toughness, such as 1D ANFs assembled filament, 2D ANF nanocomposite film, and 3D ANF reinforced polymer structures, are introduced with various designed fabrication technologies.

Disposable plastic straws negatively impact the environment and human health while their alternatives such as paper straws are not satisfactory owing to limited mechanical performance and poor user experience. In this report, all-natural and biocompatible straws are fabricated from starch and polyvinyl alcohol slurries respectively. The functionality of the slurries is enhanced by integrating economical resources such as kraft lignin and citric acid. By doctor blading of the slurries followed by subsequent heat treatment, self-bonding straws are fabricated without the use of binders or adhesives. Through heat treatment, our straws achieve excellent strength than paper-based straws. Owing to the strong ester bond network, the straws display superior performance that surpasses commercial plastic counterparts thus meeting the requirements for practical applications. Specifically, the straws are hydro-stable for over 24 hrs. and display a desirable closed-loop degradability aspect making our straws eco-friendly substitutes for synthetic plastic straws.

In this paper, an object classification system by thermal conductivity is introduced. This system comprises a module of a flexible thermoelectric device (TED) and a resistance temperature detector sensor (RTD). The module is integrated with a silicone finger cot and is equipped onto a robot hand. Before grasping an object, the TED on the robot hand is heated to a specific temperature in degrees Celsius higher than room temperature. While the robot hand grasps an object, heat generated by the TED is transferred to the object. Sequentially, the RTD sensor detects heat variation of the object. And then, data from the sensor is computer-processed to classify the object. This object classification system successfully manipulates a real-time object identification by utilizing an intrinsic material property: thermal conductivity.

From smart skins to human-machine interfaces, soft conductive materials have immense potential in wearable applications because of their conformity to the human skin. These materials may be adapted for healthcare devices and sensing functionalities, as well as for rehabilitation purposes like surface functional electrical stimulation (sFES), the process of inducing contractions in paralyzed muscles with electric currents. However, variabilities in muscle distribution among individuals pose new challenges against the development of wearable and personalized sFES platforms. To account for the intricate differences between muscles on different sites of the body, we developed a novel material to actualize stimulation electrodes that are adaptable to be of any shape and size, with self-adhesive properties to ensure conformity to body morphology and guarantee stimulation signal stability. The bio-based polymer of carboxymethyl cellulose is used for the hydrogel matrix due to its water solubility, along with poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the conductive additive and tannic acid as the adhesive additive. A mild and biocompatible gelation method involving hydrogen bonds is implemented via the addition of phytic acid, forming the printed hydrogel for the bioelectronic interface within minutes. Compared with conventional stimulation electrodes, the printable hydrogel electrodes can induce muscle movement during sFES with better precision and accuracy.

Stimuli-responsive soft actuators can actuate from an external stimulus. Compared to traditional actuators, these soft actuators offer advantages such as flexibility, conformability, better biomimicking ability, lower cost, and higher power to-weight ratio. These advantages are ideal for the vibration damping of transportation vehicles where there is a need for strong and lightweight designs whilst maintaining user comfort to encourage widespread public adoption. Piezoelectric materials are extensively used as sensors and actuators due to its piezoelectric property, and magnetic actuation is known for its accurate control. The current study investigates the development of a nanocomposite that can exhibit both piezoelectric and magnetic effects in terms of sensing and actuation, respectively. To achieve this, iron (III) oxide (Fe₃O₄) nanoparticles were attached to the surfaces of functionalized single walled carbon nanotubes (f-CNT), and the resulting nanofiller was embedded into a PVDF matrix. The Fe₃O₄ will provide magnetic actuation while the SWCNT will enhance the sensing performance of PVDF through its piezoelectric property. The proposed Fe3O4/f-CNT/PVDF showed effective vibration sensing and damping of excessive vibration on next generation of transportation vehicles for enhanced human safety and comfort. This research will assist in advancing multi stimuli-responsive materials and improve functionality and commerciality of soft smart material devices.

Many of the electroactive polymers are dielectric and often demand high operating voltages for actuation (<<10 MV/m). These EAP-based actuators require metallic electrode layers on the surface to apply the voltage. Due to high operating voltage, heat is produced at the surface of electrodes due to resistive heating and dielectric losses in polymer material. In the case of actuators based on active and passive layer configurations with metallic electrodes, this heat could affect the performance, as the generated heat is transferred between the layers. In the present work, a PVDF terpolymer and Kapton tape-based bilayer actuator is developed, and simulation and experimental study are carried out to check the effect of DC high voltages on heat production within layers. The contribution of this heat to the bending of the actuator is also analyzed. It is found that significant heat is generated that can affect deflection process of the EAP actuator. The total electromechanical bending deflection produced at the E-field of 20 MV/m is ~80 degrees whereas deflection due heat generated at this voltage is ~15 degrees. Hence, the total deflection produced can be claimed as a combination of thermal and electro-mechanical effects.

Light beam deflectors and scanners have great potential in displays and microscopy for industrial and medical applications. A liquid crystal (LC) material that responds to external stimuli is a promising candidate for such applications. The goal of the proposed work is to create a miniature light scanning device without any moving parts using integrated electro-optic(EO) LC material. The design is based on changing the propagation direction of a light beam when it is incident to an electro-optic medium with a voltage-controlled index of refraction. The current design consists of two horizontal LC cell cascaded prisms (active Prism I and II) for horizontal beam deflection and a vertical prism (passive) at the end of the horizontal stage for vertical beam deflection. In the present work, a mathematical model and simulation study is conducted on the proposed design to achieve 2D deflection of the beam (λ=632 nm). The optimized prism or apex angle of active prisms I and II are 63 and 56.7 respectively, whereas the prism angle of the passive prism is 37.5. With an incident beam angle (θ1) of 9 at the entry of prism I, maximum horizontal deflection of >36 and maximum vertical deflection of >13 is achieved through theoretical and simulation study.

The petroleum-based derived materials are used in industrial applications due to their specific properties. However, they are increasing environmental concerns because they produce toxic gases when disposed of and burned [1, 2]. Thus, biomass-derived epoxy resins have gained significant attention due to their low-cost, easy synthetic route, and environmentally friendly. CNF can be a promising approach for the future generation to design all-green materials with bio-mass-derived resins for various applications [3, 4]. This research aims to explore the strategies for hydrophilic CNF film to make it useable for high-performance applications. In this regard, the bio-based vanillin-derived epoxy resin was proposed to improve hydrophobicity of CNF film, making them ideal for TENG applications.

Smart packaging of food products is a new promising technology aiming to the preservation of consumer’s health and safety while prolonging the products’ self-life in transport and mass storage. Smart packaging can be applied by using chemical and/or biological sensors for monitoring indicators associated with bacterial growth and spoilage, as well as pathogen contamination. Poultry meat is a nutrient-rich matrix which supports the growth of various micro-organisms and the extended storage time can allow the proliferation of different microbial species on meat surfaces. The nature of the packaging approaches and storage factors can dictate the nature of the spoilage that transpires, with respect to the dominant microflora of the end-product. In the present study an innovative approach is explored for the development of cost-effective 3D-printed biosensors for monitoring known indicators associated with bacterial growth and spoilage in poultry meat. Spoilage was also independently measured using MSI and FT-IR spectroscopic methods. The development of a protocol for pathogen screening was also investigated with real-time polymerase chain reactions (qPCR).