This PDF file contains the front matter associated with SPIE Proceedings Volume 11757

Textile and electronic components are critical elements of most wearable technologies (wearables); both components deteriorate at different rates depending on factors of use, care, and user handling. The differences in mechanical performance characteristics (MPC) (i.e., abrasion, elongation, and bursting strength) of these components create a challenge for researchers and product designers to develop user-centric and economical wearables. For example, athletic wearables made of nylon/spandex knit blends exhibit drastically different MPC from minimal fiber content changes (1- 10%). However, the wearable's end-use remains constant. This article presents ideas and methods for testing MPC and how to evaluate results for different end-use cases. Designing for end-user activities also highlights these performance differences because specific, end-uses drive textiles design, which may or may not be the wearable design's end-use. Three American Society for Testing and Materials (ASTM) test methods were used to test MPC of athletic fabrics and soft robotic sensors (SRS) to determine the abrasion resistance, elongation, and bursting strength of these components and two-tail ttest comparisons were performed on the results. The SRS's durability is less than the textiles they are integrated into, and with no standards for MPC testing on SRS, it can be unclear how long a sensor will last. Such methods need to be developed so product developers can find efficient combinations of fibers and electronic components to ensure user-centric functionality, wearer comfort, extended product longevity, and overall consumer satisfaction.

The current landscape of clinical vital signs monitoring solutions including those designed for wound monitoring emphasizing blood oxygen saturation (SO₂) or oximetry remain limited in their scope owing to the lack of miniaturization, portability, disposability and visualization of real-time data readouts. To address such limitations, we present two wearable proof-of-concept oximeters with multi-digit, 7-segment light emitting diode (LED) displays, a ring and a patch, showcasing transmissive and reflective oximetry solutions, respectively, along with other distinctly integrated modalities such as non-coplanar electrocardiography (ECG), temperature sensing, activity and fall detection. Two miniature Bluetooth-enabled oximetry devices are showcased. The technology encompasses solutions such as blood oxygen saturation (SO₂) mapping based on reflective oximetry (4 x 4 array of LEDs and photodiodes), non-coplanar ECG using inkjet dispensed, 8 μm-thick Silver-Silver Chloride electrodes, central and peripheral temperature sensors, an accelerometer and an organic LED (OLED) display layer on a rigid flex hybrid printed circuit board (PCB) for reporting quantitative metrics from either the reflective oximeter or ECG on a wearable patch. A wearable smart ring includes transmission oximetry sensors (LEDs and photodiodes), integrated on a single flexible PCB. Here, additional sensors comprise temperature and an accelerometer. Both devices, the ring and patch comprise LED display layers for showcasing real-time quantitative parameters such as SO₂ or heart rate (HR) and HR variability.

Networks of sensors, displays, and smart devices on the body offer powerful capabilities for continuously monitoring health and delivering personalized care. Wireless technologies are essential to interconnect sensors distributed around the body, but existing approaches have inherent limitations in energy loss and data security that limit the practical use of such networks. This talk will describe recent work on wirelessly functional textiles that interact with wireless technologies such as Bluetooth, Wi-Fi, and near-field communication. Using the electronic textile toolkit, I show that clothing can be designed to transmit wireless signals between wearable devices, power battery-free sensors around the body, and sense changes in the wireless environment, all without any physical connection between clothing and electronics. I discuss applications of sensor networks based on such clothing for healthcare, athletics, and emergency personnel.

Wearable sensors have the potential to provide rapid, non-invasive, and in-home health monitoring by real-time analyzing biomarkers in human sweat and saliva. However, most current biosensors suffer from low sensing accuracy for low-level analyte detection in biofluids and are difficult to fabricate on a large scale. In this talk, I will review our latest advances in developing fully-integrated laser-engraved graphene-based biosensors which can selectively and accurately measure a wide spectrum of sweat and saliva biomarkers including metabolites, nutrients, hormones, and proteins. The clinical value of these telemedicine platforms is evaluated through multiple human studies involving both healthy and patient populations toward metabolic monitoring and stress assessment. I will also introduce our recent work on a multiplexed wireless platform for the rapid COVID-19 test which could provide information on infection status, severity, and immunity.

Recent advances in materials and fabrication concepts for the creation of soft electronics coupled with miniaturization of wireless energy harvesting schemes enable the construction of high-performance electronic and optoelectronic systems with sizes, shapes and physical properties matched to biological systems. Applications range from continuous monitors for health diagnosis to minimally invasive exploratory tools for neuroscience. This talk introduces science and engineering aspects for the creation of soft devices with wireless power transfer and data communication capabilities and discusses application in minimally invasive exploratory neuromodulation tools and imperceptible body-worn sensing devices. Specifically, we present two new classes of devices for implantable and wearable biointegrated electronic devices. Firstly, we will introduce wireless, battery free and fully implantable neuromodulation tools that provide unparalleled capabilities to modulate the central nervous system. The tools enable new experimental paradigms in a range of complex environments and contexts that cannot be explored with conventional technologies. The devices feature miniaturized form factor and technologies that are rapidly scalable to enable broad dissemination while still maintaining compatibility with noninvasive imaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI). Specifically, we will highlight 1. Current advances in highly miniaturized wireless and battery free photometric recording devices that enable the study of neural dynamics in ethnologically relevant environments in young animal models unlocking new experimental paradigms to uncover the working principles of the developing brain. 2. Wireless battery-free and subdermally implantable optogenetic stimulation tools that enable: neural activation in freely flying birds; transcranial optogenetic stimulation in mice without cranial surgery; long range neural activation in ethologically relevant environments. Secondly, we will present a new class of wearable wireless, battery free, long range, personalized and multimodal sensors system. The first of its kind device architecture is shaped by physiology and enables uninterrupted 24 hour data streams with high fidelity over long periods of time. The devices feature highly personalized device geometries that solve prevalent problems of current adhesive based wearable devices while still retaining intimate contact.

Dielectric elastomers have emerged in recent years as a smart material capable of acting as an actuator, a sensor, or a generator. When used as a sensor, this soft, flexible material exhibits a change in capacitance as it is deformed in both compression and tension. This has led to the adaptation of dielectric elastomer sensors in the wearable technology space, where careful sensor placement can enable the measurement of biomechanical movement. However, these sensors may not be measured using traditional capacitance measurement techniques due to their increased electrode resistance. Thus, a low frequency, low voltage capacitive measurement methodology needs to be derived for these sensors to thrive in wearable applications. In this work, we propose such a methodology which utilizes phase detection with the Goertzel algorithm. Traditionally used for tone detection, the Goertzel algorithm provides an efficient method for recovering individual terms of the DFT. Our sensing methodology is integrated into a low-cost microcontroller and integrated with a wireless microcontroller to enable remote measurement of the dielectric elastomers. The open sourcing of this device may jump-start the widespread adoption of dielectric elastomers as biomechanical sensors.

Fast and accurate detection and monitoring of alcohol consumption have significant importance for safety and clinical applications. The excessive consumption of alcohol causes many health issues, such as colon, rectum, mouth, and throat cancers, liver cirrhosis, stroke, cardiovascular disease, and several psychiatric comorbidities. Alcohol addiction treatments also require close monitoring of the consumption. The correlation of alcohol concentration levels in sweat with the blood alcohol content (BAC) encourages developing a wearable sensing platform for alcohol detection noninvasively, continuously, and in real-time. Moreover, sweat is considered one of the most useful body fluids for biosensing applications since it contains several biomarkers with crucial medical information and is easy to collect. ZnO has exclusive chemical and physical characteristics to enhance chemical stability in physiological environments. Moreover, it has higher catalytic activity, biocompatibility, and a higher isoelectric point (IEP) of 9.5. Such a high IEP of ZnO nanoflakes (NFs) improves any biomolecules' immobilization. Hence, there is no necessity for an additional binding layer between the enzyme and the sensing electrode. A single-step sonochemical approach was developed to synthesize a thin layer of ZnONFs virtually on any substrate. This technique is fast, catalyst-free, less expensive, and ecologically benign, which enables a well-oriented growth on polyethylene terephthalate (PET) over an extensive range. In this study, an electrochemical biosensor was fabricated by immobilization of alcohol oxidase (AOX) on ZnO nanoflakes with a thickness of 20nm, synthesized on Au-coated PET. The results demonstrated a fast response within 5s. The sensor was tested in the range of 1 mg – 400 mg, which covers the entire physiological range, and the sensitivity of the sensor was determined by 3.47 nA/mg/dL/cm².

Maintainers for DoD and commercial industry are required to inspect and perform maintenance operations in confined spaces. Due to the tight volume and small ingress points into these spaces, hazardous environmental conditions including toxic gases, low oxygen levels, and high heat indices are common. Commercial off the shelf (COTS) solutions exist for testing these environmental conditions, but not in a small, wearable form factor with real-time reporting. In this presentation NextFlex will describe how it will fill this gap via a small wearable sensor Arduino®-like platform with integrated, real-time oxygen, VOC, temperature, and humidity monitoring. NextFlex utilizes additive techniques to print conductive traces and antennas while directly attaching silicon dies and components. This flexible hybrid electronic approach produces a high-performance sensor platform with low size weight and power to ease wear by maintainers.

Inherent variation amongst human brains causes difficulty in implementing electroencephalography (EEG) into a universal brain-machine interface (BMI). Existing EEG systems suffer from an inconsistent signal quality, burdensome preparation time, and discomfort caused by rigid wires and metal electrodes in a hair cap. Additionally, leading classification methods require training on a per-subject or per-session basis. Although recent machine learning techniques offer a simpler EEG arrangement with fewer electrodes, these EEG devices still involve intrusive and bulky headgear, equipped with separate non-portable electrical hardware. Here, we introduce a fully portable, wireless, flexible scalp electronics on a soft elastomeric membrane, representing a comfortable and ergonomic wearable BMI. These imperceptible soft electronics incorporate an ultrathin nanomembrane electrode on non-hair-bearing skin, flexible conductive electrodes on the hair-bearing scalp, and low-profile, skin-conformal electronics on the neck for fully portable, wireless data acquisition. Analytical and computational studies establish the fundamental design criteria of the flexible, skin-like hybrid electronics (SKINTRONICS), enabling seamless, portable EEG recording with significantly enhanced signal quality over commercial systems. Newly designed time-domain analysis with deep convolutional neural networks allows real-time, highly accurate classification of steady-state visually evoked potentials from only two channels. This portable scalp system with six human participants achieves a high accuracy (94.54 ± 0.90%) for a corresponding information transfer rate of 122.1 ± 3.53 bits per minute. In vivo study of the fully portable BMI, enabled by the SKINTRONICS and deep-learning algorithm, shows precise, low-latency control of a wireless wheelchair, motorized vehicle, and keyboard-less presentation via two-channel EEG, which demonstrates potential implications for wide range applications of the new class of EEG-based universal BMI technologies.

The wearables market is highly saturated with activity and heart rate monitors that are prone to mimickry between various vendors. Advances such as cuffless blood pressure monitoring based on electrocardiography (ECG) and photoplethysmography (PPG) are gaining traction as novel wearable device offerings, albeit with concerns pertaining to robustness, reproducibility, motion compensation and affordability. The prohibitively higher cost of this newer device category is associated with the quantity and quality of on-board custom components along with their complex assembly and integration requirements. Here, such limitations are addressed by offering multiple sensing modalities including activity monitoring from a tri-axis accelerometer, optical PPG utilizing four light emitting diodes, two photodiodes, and single-lead ECG utilizing 10 μm-thick, screen printed Silver-Silver Chloride electrodes in a cost-effective, Bluetooth-enabled wearable wristband. Blood pressure is measured by simultaneous ECG and PPG measurements to derive the pulse transit time. The device is powered by a rechargeable 3.7V Lithium-Ion battery with 20mAh capacity. Data are transferred to either Android or iOS applications, which then based on application programming interfaces communicate with a cloud back-end for long-term data storage and retrieval of archival parameters. The added uniqueness of this wristband is that it incorporates direct over molding of the on-board electronics and assembled printed circuit boards (33 x 22.8 x 10.8 mm³) using novel low temperature (100°C) liquid silicone rubber with specialized high accuracy mixing equipment. Our approach sharply contrasts with conventional silicone which cures at temperatures reaching 150°C and higher, thereby endangering electronic components during the over molding processes.

There is scarcity of pure drinking water due to variety of pollutants present in water bodies. Out of different pollutants heavy metal ions particularly Chromium ions are highly toxic to living organism. There is a need to find out some suitable method for detection and removal of Chromium ions from water. Chromium exists in different oxidation state depending on the pH of the medium. The experiments were performed in two parts. In the first part Chromium in different oxidation states was detected spectrophotometrically by using a biogenically synthesized silver nanoparticles (Ag NPs). After detecting the presence of Cr (VI) metal ions, a batch experiment was carried out to check the removal efficiency of copper ferrite polyaniline-nanocomposite for Cr (VI) metal ions. The removal efficiency was maximum at pH 2.0. Different adsorption isotherm and kinetic models were tested.

In this work, we describe the phenomenon, Thermally-induced Optical Reflection of Sound (THORS), and how it can be used to optically steer acoustic waves around a 90 degree corner of a physical obstruction, where observed acoustic amplitudes are increased by a factor of 30. In addition, we discuss the introduction of ultrasonic waves to the THORS phenomenon, and preliminary results for THORS barriers generated in ambient air, using a 5.3-5.7 μm CO laser source.The manipulation and guiding of sound waves have typically required the use of physical barriers for the reflection of an incident pressure wave. With the manipulation of acoustic waves being critical for many applications in scientific and engineering fields, including subsurface tissue imaging, photoacoustic sensing, secure communications, acoustic stealth technology, and acoustic design engineering; the requirement for physical barriers often represents a significant limitation. The recently discovered phenomenon THermally-induced Optical Reflection of Sound (THORS), provides the ability to generate acoustically reflective barriers, in air, by exciting media in the path of an IR laser beam, causing abrupt changes in compressibility between the excited and surrounding media. In this work, we demonstrate the ability to efficiently reflect sound waves around physical obstructions using a laser. Additionally, this work demonstrates the ability to also manipulate ultrasonic waves via THORS barriers, where the reflection and suppression of ultrasonic pulses in the frequency range of 120-300 kHz are shown. Finally, preliminary results demonstrating the ability to employ THORS in ambient air using water vapor as the absorbing media and a 5.5 μm CO laser beam for excitation.

In recent years, photoacoustic imaging is a new imaging technology which combines the advantages of high resolution and rich contrast of optical imaging and high penetration depth of acoustic imaging. Therefore, photoacoustic imaging is widely used in biomedical fields, such as brain imaging, tumor detection and so on. As an important branch of photoacoustic imaging, photoacoustic microscopy imaging of optical resolution can reach the submicron level and can meet the needs of multi-scale imaging from cell to tissue. However, the strongly focused Gaussian beam is usually used in the traditional system of photoacoustic microscopy imaging of optical resolution, and so the depth of imaging is small, which makes it difficult to achieve fast imaging of large volume. In order to solve this problem, researchers have proposed many schemes, one of which is to use non-diffracted beams instead of Gaussian beams for imaging. As a nondiffracted beam, Bessel beam is applied to photoacoustic microscopy imaging of optical resolution in this study because it has the characteristic of large depth of field. However, in practice, the cost of building the system of photoacoustic microscopy imaging of optical resolution is high and its structure is complex, so there is an urgent need for the technology of virtual simulation for photothermal simulation analysis of the imaging system. In order to achieve this goal, a virtual simulation platform of photoacoustic microscopy imaging system of Bessel beam based on finite element analysis was built by using simulation software COMSOL Multiphysics. In COMSOL, the Bessel beam realized by compound axicon was constructed and then irradiated the gastric tissue and tumor. The propagation of the Bessel beam in the gastric tissue and tumor was simulated by solving the diffusion equation. And the temperature changes of the gastric tissue and tumor were obtained by solving the equation of biological heat transfer. This study is helpful to understand the propagation of Bessel beam in the gastric tissue and tumor and the interaction between them, and has a certain theoretical significance for biomedical optical imaging.

A miniaturized potentiostat integrated with a three-electrode system to monitor different analytes is presented. The potentiostat circuit has been designed to have the feature of four-channel multiplexing to operate different electrochemical cells simultaneously. It is Bluetooth-connected to a user-controlled mobile app through which the system is wirelessly controlled and data is acquired. The personalized data from the analysis are displayed and analyzed in the mobile app. The system is comprised of four units: digital to analog converter (DAC), multiplexing unit, control unit, and current to voltage converter (CVC). The circuit is run by Arduino NANO 33 BLE. The Arduino's digital pulse width modulator (PWM) signal is converted into an analog signal through the DAC unit to run the scanning in the voltage range of -1V to 2V. This output of the DAC unit is then fed into the multiplexing unit to distribute it to all four control units one at a time. Later, each control unit of the respective cells performs scanning through the three-electrode system connected to the control unit. The real-time scanning data collected from the cell, sent to the CVC unit, and converted into a voltage to be readable by the Arduino. With its small form factor, low power, and low cost the presented system can be used wearable health monitoring platforms.

We report on the numerical and experimental study of the localized surface plasmon resonance (LSPR) spectroscopy of gold nanoparticles (NPs) structures at the frustrated total internal reflection (LSPR_TIR). The investigated NPs structures were manufactured using two different microfabrication methods: the nano-sphere lithography, and the original one, involving the direct pulse laser writing. The last technology, developed by our research team, provides powerful tools for flexible patterning of the multichannel biochip with array of LSPR probes. The obtained results demonstrate a significant improvement in the LSPR wavelength sensitivity to sample refractive index and, in addition, a relatively efficient conversion of the incident light wave polarization.

Normal human pupil diameter (PD) ranges between about 2 to 8 millimeters (mm) depending on a number of factors. While the inverse relation between PD and luminance is well known, less well known and dramatic is the dependence of PD on mental workload (MWL). The PD response to MWL states are typically of small amplitude and high frequency, reflecting differential sympathetic and parasympathetic enervation. The literature shows that with contemporary objective eye tracking technology, PD behavior may prove to be a practical indication of psychophysiological status, including attention and MWL. Despite the pupil’s limited response repertoire; i.e., diameter, it is capable of potentially encoding a spectrum of information about operator state. The challenge is disambiguating PD response characteristics. A commercial, off-the-shelf eye tracker recorded PD of volunteers performing the N-back task,a standard MWL task involving auditory attention and short term memory with three levels of difficulty (easy, moderate, and difficult). The measurements were made at 3 levels of average luminance selected to assess PD when it is small, medium, and large. Each of these luminance levels fluctuated around its mean level in a sinusoidal fashion (with a ±25% modulation) at one of 4 frequencies: 1.0 hertz (Hz), 0.2 Hz, 0.1 Hz, and 0.0 Hz. The last frequency being the control condition of a 0% light modulation. Multivariate analysis revealed the effects of MWL on PD were detectable across all combinations of luminance and modulation frequency. The next step is to determine whether pupil diameter can predict MWL.

During the past several decades physical vapor transport (PVT) method has been extensively used for developing laser and electronic and optical sensor materials especially for incongruent and high vapor materials. Extensive careful studies of the NASA Marshall Space Flight Center on ZnSe growth by PVT has demonstrated that both thermal and solutal convection play very important roles on the quality of crystals and can be controlled by microgravity experiments. In case, the growth is performed by sputtering or systems such as DENTON, it is very difficult to control fluid flow and both thermal and solutal convective flows. We have demonstrated that by controlling the transport path, temperature of substrate and source and using purified source micron size thick ness can be achieved. We will present the experimental results of pure and doped lead selenide (PbSe) which demonstrated various morphologies and bandgap based on size of particles based on growth condition.

Transcranial magnetic stimulation (TMS) is one of the most effective non-invasive neuromodulation techniques used to treat neurological and psychiatric disorders. It is also highly popular to be used for studying and understanding brain functions and mechanisms. Multisite simultaneous or sequential stimulation of different brain regions provides a new methodology to study and comprehend the functional dependence and causal relationships among different regions and networks. However, due to the large coil size, which doesn't allow more than two coils being simultaneously utilized, and the non-ideal field focality and penetration depth of existing commercial coils, multisite simulation methods have not been well exploited. In this study, an angle-wrapped and multi-stacked circular coil is proposed to form an array of coils and used for this purpose. The induced electric field hot spot of the single coil and the coil array designs for fixed multisite stimulation were studied with the finite element method. The FEM simulations were then verified with experiments performed on fabricated coils. The performed simulations and experiments indicated the proposed coils' enhanced performance regarding the hot spot size and electric field decay rate compared to conventional circular coils. The successfully demonstrated close proximity and small spot size of stimulation show great potential for future fixed and adjustable multisite brain stimulation.

ZnSe has been a great choice for the rare-earth and transition metal doping to develop lasers. It is an excellent material for variety of optical applications due to wide transparency range, good fabricability and very low optical absorption similar to other selenides. NASA Marshall Space Flight Center has developed large crystals using physical vapor deposition (PVD) doped with transition metals for lasing. GaAs based quasi-phase matched structures have a lot of limitations including difficulty of frequency conversion from available high-power lasers. We are developing Si- and GaAs- based templates and using microfabrication process to deposit ZnSe using physical vapor transport (PVT) method. Experimental results of the fabrication of templates and growth of ZnSe on templates will be presented.

In this manuscript, We have reported the synthesis and characterization of Mg-doped and un-doped BCTO ceramic (Bi_2/3Cu_3-xMg_xTi₄O₁₂, x=0, 0.05, 0.1 and 0.2) sintered at 1173 K for 8 h, which have been prepared by the semi-wet route. The Single-phase formation of ceramic was approved by the XRD pattern. The Microstructural properties were studied by TEM. The samples were characterized by dielectric and impedance spectroscopic properties. The dielectric constant (ε_r) was calculated to be 3024 for BCTO ceramics at 423 K and 100Hz. The tangent loss (tan δ) value was calculated to be 0.45 for BCTO ceramic at 423 K and 10 kHz. The internal Barrier Layer Capacitance (IBLC) mechanism was responsible for the high value of the dielectric constant.. It was observed from Impedance studies that there was the existence of the Maxwell-Wagner form of relaxation in the ceramics. In the temperature range 300-500 K, the Bi_2/3Cu_3-xMg_xTi₄O₁₂ (where x=0, 0.05, 0.1, 0.2) ceramic follows Arrhenius behavior with an almost single slope. Pervoskite material plays a significant role in the biosensing field like DNA hybridization. This research provided a newtype and promising perovskite for the development of efficient biosensors.

The performance of optical and electronic detectors and sensors are affected by surface and bulk impurities. In some cases, nanoscale thin films are used as detectors and their life cycle is significantly decreased. In the case of conformal shapes, surfaces with different polishing, decoration and geometries exhibit unusual wetting and nucleation characteristics for impurities and this requires continuous attention for cleaning. The situation for space borne components and vehicles surfaces exposed to wetting liquids requires remote cleaning. In the present paper, we report the effect of surface topographies of substrates with nanoengineered titanium oxide and copper oxide nanoparticles embodied in polystyrene and study the effect of the composites to create different hydrophobic characteristics with great potential for detectors and sensors operating in ultra-violet and infrared regions.