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Wafer-Level Chip Scale Packages (WLCSPs) are becoming commonplace in the industry due to their small form factor. Applications include industrial and automotive which demand high reliability performance. Additionally, WLCSPs may be superior in some implementations to other package options for RF performance in the mmWave spectrum, which is desired for automotive radar application. But board level reliability can be a challenge for some WLCSP package due to CTE mismatch between Si and PCB. Variety of factors including PCB materials, sphere alloys, and board level underfills can influence the board level reliability of WLCSP packages. In this study the industry’s first auto grade 1 capable large WLCSP package. (~ 72 mm2 body size, 18x15 BGA array, 0.5 mm pitch) is presented. Board level underfill application was utilized to achieve automotive grade board level reliability. Underfills are typically selected based on thermomechanical properties of unaged materials. An understanding of the evolution of underfill material properties under thermal aging is important for selecting a stable material capable of meeting the reliability requirements. This study evaluates board level underfills and edge bond materials in the form of stand-alone samples and applied to a large daisy-chain WLCSP. The underfilled daisy-chain WLCSPs and the stand-alone samples are placed in a ‑40/125C air cycling chamber (1 cycle/hour). Glass transition temperature (Tg), elastic modulus (E), and coefficient of thermal expansion (CTE) are measured using Dynamic Mechanical Analysis (DMA) and Thermomechanical Analysis (TMA) on the stand-alone samples at various intervals to monitor the evolution of material properties. Simultaneously, the underfilled daisy chain WLCSPs are monitored electrically using an event detector. The combination of material property measurements and cycles to electrical failure can be used to correlate underfill material properties and WLCSP board-level reliability. The results of this study can provide material property guidance for underfill selection.

In this article, a power converter based on an asymmetrical half-bridge flyback topology is analyzed and optimized for small form factor and fast-charging power adaptors. Two resonant control methods, taking advantage of the forward and flyback characteristics of the converter, as well as the benefits of each of them depending of the operation point are discussed. The analysis is nourished with the equivalent circuits in each phase of operation and the equations that define them. Particularly innovative is the proposed zero voltage resonant valley switching control method for the mentioned converter; in this case, it is operated similarly to a flyback converter, allowing safe output voltage ramp up, which is one of the challenges that has limited the usage of this topology up to now. The manuscript also describes how to achieve high efficiency and power density using zero-voltage switching and zero-current switching techniques over the full range of the input voltage and the output load. Finally, the advantages of the proposed control methods are demonstrated in a 65-W adaptor prototype achieving a peak efficiency over 94.6% and an efficiency of 93.8% @ V ac ≥ 100 V at full load over the range of the input voltage, as well as a world-class power density of 35 W/in3 uncased.

This paper proposes a hybrid control strategy of a novel linear piezoelectric walking stage based on two sorts of piezoelectric actuators, which takes the load variation into account. The proposed stage consists of two parallel 4-bar lever amplification mechanisms with flexure hinges actuated by piezoelectric stacks to heighten the vertical distance (that is more tolerable to the assembly discrepancy), two compression springs (that is able to maintain a fixed linear position without powering), and two shear piezoelectric actuators (that can achieve longer and equivalent to walking motion) in a small form factor. The proposed stage has two operating modes, namely a coarse positioning mode with a more extensive travel range and a fine positioning mode with a nanometer-level resolution, to possess excellent performance for the linear piezoelectric walking stage of load variations. One multimodal switching controller and one feedforward-feedback controller conduct the coarse mode and fine mode, respectively. The optimal frequency for a specific load is obtained through a backpropagation neural network in the multimodal switching control. In the feedforward-feedback control, the inverse mathematical model based on the Bouc-Wen hysteresis model is used to mitigate the hysteresis effect in the feedforward part while the proportional–integral–derivative controller in the feedback part handles the external system disturbances. Experimental results show the proposed hybrid coarse/fine mode control strategy's effectiveness to satisfy an efficient and accurate positioning task.

For ultra-compact near-eye display, waveguides provide a small form factor because they are thin shape plate, but projectors are too large due to the imaging sources, which results in bulky near-eye displays. Recent advances in fiber-scanning technology can overcome this limitation. Fiber-scasnning projectors produce an image by vibrating an optical fiber, and they can be small because only thin fibers and actuators are required. However, uneven brightness occurs when augmented reality images from the fiber-scanning projector are displayed using a conventional waveguide. In this paper, we propose a novel waveguide that duplicates a narrow beam by multiple reflections of a pre duplicator, which is a flat-plate-shaped optics with mirror and half-mirror surfaces. The proposed waveguide enables uniform luminance distribution with a fiber-scanning projector by providing narrow duplication intervals. We experimentally confirmed that the contrast of luminance unevenness decreased from 0.60 to 0.15 with our waveguide. Our fiber scanning projector size is less than 0.03 cc and can be placed on the temples of eyeglasses, which is impossible with general projectors of about 5 cc. Therefore, the proposed waveguide and fiber scanning projector enable the realization of eyeglasses shape near-eye displays.

This letter presents a vertically-stacked photovoltaic (PV)/bypass diode (BPD) module fabricated via localized substrate removal and flip-chip assembly with the aim of improving shadow performance under Gaussian laser illumination. The proposed scheme also prevents the direct illumination of BPDs to eliminate reverse current leakage. The proposed PV/BPD module achieved output voltage (electrical power) of 4.24V (1.6 mW) in a small form factor (4.84 mm2), as well as a linear shadow response with −0.118 mW electrical power loss per shaded PV cell. Under laser misalignment conditions ( $>0.4$ mm shift), the electrical power generated by the PV/BPD module was 2~4 times higher than that of a PV module without BPD. The fact that the PV and BPD chips can both be fabricated using foundry bulk CMOS processes facilitates the integration of the proposed module with sensor circuits and/or (super)capacitors to form a compact self-powered system.

Gallium nitride (GaN)-on-diamond technology offers key parameters of high thermal conductivity, high power density, high electrical resistivity and small form factor at both the device and system levels, making GaN-on-diamond power amplifier devices very attractive for high-power radio-frequency (RF) applications, such as commercial base stations, satellite communications and defence applications. Current GaN-on-diamond integration technology involves either a diamond growth process or a diamond bonding process, both of which require precise interface engineering with appropriate interfacial layers. While such interfacial layers are of vital importance to make high-quality GaN-on-diamond integration possible, they also contribute to a large portion of the effective thermal boundary resistance (TBReff) at the interface, which has to be minimized to justify the benefit of GaN-on-diamond technology compared with the mainstream GaN on silicon carbide (SiC) technology. In this paper, we review the ongoing effort to develop interface engineering processes that position GaN-on-diamond as a promising technology for enabling the next generation of power devices.

Organic light-emitting diode (OLED) microdisplays have attracted much attention as displays for small form factor augmented reality (AR) devices. To realize glass-like thin and wide field of view (FoV) AR devices, we designed a display module with a high aspect ratio microdisplay and a thin optical component. For the high aspect ratio microdisplay, we developed the color OLED microdisplay with a 32:9 aspect ratio and a 0.8-inch diagonal ∼2,490-ppi CMOS backplane. To express color and reduce optical crosstalk, we fabricated the color filter (C/F) patterning directly on the white OLED. We also developed a pin mirror lens with 11 pin mirrors to improve the optical efficiency and quality with a thin lens. By combining the microdisplay with LetinAR’s pin mirror lens, we successfully demonstrated an AR device with a wide horizontal FoV of 46° but with a small form factor 4 mm lens.

As a key approach to augment Moore’s Law scaling, 3D integration technologies have enabled small form factor, low cost, diverse, modular and flexible assembly of integrated circuits in the semiconductor industry. It is therefore essential to adopt these technologies to the quantum computing devices which are at the nascent stage and generally require large scale integration to be practical. In this review, we focus on four popular quantum bit (qubit) candidates (trapped ion, superconducting circuit, silicon spin and photon) which are encoded by distinct physical systems but all intrinsically compatible with advanced CMOS fabrication process. We introduce the specific scalability bottlenecks of each qubit type and present the current solutions using 3D integration technologies. We evaluate and classify these technologies into three main categories based on the hierarchy. A brief discussion regarding to the thermal management is also provided. We believe this review serves to provide some useful insights on the contributions of interconnect, integration and packaging to the field of quantum computing where rapid development is ongoing. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Published version This work was supported by ANR-NRF Joint Grant Call (NF2020- NRF-ANR073 HIT) and A*STAR Quantum Technology for Engineering (A1685b0005).

This paper presents a fabrication method and results from optical and acoustic characterization of a miniature fiber Fabry-Perot ultrasound detector. A high Q-factor was achieved by creating a self-aligned polymer waveguide within the resonator cavity to restrict diffraction losses. As a result of the improved optical Q-factor upon introduction of the waveguide, a high acoustic sensitivity was achieved. The device presented in this paper demonstrates an optical resonator Q-factor of >2000, and a Noise Equivalent Pressure of 350 Pa over a 25MHz bandwidth on a $125~\mu \text{m}$ fiber with a $9~\mu \text{m}$ waveguide. Sensitivity can be further improved significantly with the use of dielectric mirrors. The high sensitivity of these waveguided fiber Fabry-Perot ultrasound detectors makes them suitable for detection of both ultrasound and photoacoustic signals, while their small size makes this technology suitable for adoption in applications requiring small form factor, such as in interventional cardiology.

Conventional electronic devices powered by lithium-ion batteries or supercapacitors face the challenge of offering long-term and self-sustaining operations. Self-powered devices based on emerging energy harvesting technologies can help of the development of long-lasting transducers with a small form factor. Organolead halide perovskites due to their excellent electro-optical properties are promising photosensitive materials for the development of such self-powered devices. The following review aims at summarizing recent developments made in the field of organolead halide perovskite based self-powered applications. The underlying mechanism driving the self-powered operation in electronic devices such as photodetectors, tactile sensors, and gas sensors is discussed in detail. Finally, the current challenges and prospects of these perovskite based optoelectronic applications are highlighted.

Concentric Tube Continuum Robots are among the smallest and most flexible instruments in development for minimally invasive surgery, thereby enabling operations in areas within the human body that are difficult to reach. Unfortunately, integrating state-of-the-art force sensors is challenging for these robots due to their small form factor, although contact forces are essential information in surgical procedures. In this work, we propose a novel data-driven approach based on Deep Direct Cascade Learning (DDCL) to create a virtual sensor for computing the tip contact force of Concentric Tube Continuum Robots. By exploiting the robot’s backbone’s inherent elasticity, deflection is used to estimate the respective external tip contact force. We evaluate our approach on different data representations for a single tube and apply it subsequently on a three-segment Concentric Tube Continuum Robot. Furthermore, we devise a novel transfer learning approach through DDCL to improve the estimation accuracy by pre-training a cascaded network with simulated data. Subsequently, we fine-tune the network based on a small real-world data set recorded from the physical robot.

Additive manufacturing (AM) is an emerging method for cost-efficient fabrication of nuclear reactor parts. AM of metallic structures for nuclear energy applications is currently based on the laser powder bed fusion process, which can introduce internal material flaws, such as pores and anisotropy. Integrity of AM structures needs to be evaluated nondestructively because material flaws could lead to premature failures due to exposure to high temperature, radiation and corrosive environments in a nuclear reactor. Thermal tomography (TT) provides a capability for non-destructive evaluation of sub-surface defects in arbitrary size structures. We investigate TT of AM stainless steel 316L specimens with imprinted internal porosity defects using a relatively low-cost, small form factor infrared camera based on an uncooled micro-bolometer detector. Sparse coding-related K-means singular value decomposition machine learning, image processing algorithms are developed to improve the quality of TT images through removal of additive white Gaussian noise without blurring the images.

Distribution of wireless power charging field uniformly on a large area pad is critical for power receivers, particularly for wearable devices, wherein small form factor coils are involved. Since the receiver coil size is quite limited in these types of applications, the device is very sensitive to the amount of field it could retain and hence, it needs special placement or snapping mechanism to fix it at an optimum location for reliable wireless charging. In order to overcome this limitation for the end-user, a dual-mode multi-coil power transceiver system is proposed; utilizing resonance filtering to increase the amount of total power delivered with the rather uniform spatial distribution. Two concentric coils; center one driven by 6.78-MHz high-frequency driver (A4WP) and the outer larger one with a 200-KHz low-frequency driver (Qi) with resonant blocker could transfer up to 50 mW standards compliant flat power to a 13-mm radius 30-turns wearable receiver coil everywhere across an 8-cm radius charging pad area without any alignment requirement or snapping. Two different feedback topologies corresponding to each of the H-Bridge power drivers were also presented as an automatic series resonance coil drive frequency lock mechanism, extracting peak powers for each system individually from a standard 5 V-1A USB wall charger.

A microwave pulse compressor (MPC) consisting of an iris, a straight waveguide section, and a T-junction can be used in order to convert a long pulse with lower power to a shorter pulse with a higher power. A significant compression gain can be achieved, provided that the system is designed precisely. The duration of the compressed pulse is proportional to the cavity length, thus imposing a constraint on the development of mobile systems. In this work, we present the circuit/transmission-line-based design methodology that we follow in order to fold the cavity (while retaining the same electrical length) by using T-junction turns. For example, we design a 1.3-GHz folded compressor and compare its performance to the corresponding one of a straight-cavity compressor. The 3-D full-wave simulations with CST Studio Suite and experimental measurements with the developed compressor confirm the accuracy of the proposed design methodology.

This paper proposes a method that reconstructs the original video data signal from leaking electromagnetic emanations of multiple video signal sources using a software-defined radio (SDR). The results of the method give valuable insights into the potential risk of this threat of obtaining sensitive information in an everyday situation. The leaking emanations of co-located identical high definition liquid crystal displays are analyzed for possible data reconstruction using a SDR of a small form factor. It is proven that the leaked emanations of multiple identical active video display units (VDUs) can be separated from each other and that their separate video images can be reconstructed individually from one data acquisition. Moreover, this is done by recovering the synchronization frequencies and the image resolution by exploiting multiple leakage channels without having any foreknowledge of the VDU's properties. A multitude of leakage channels is investigated and analyzed for their radiation pattern and their signal-to-noise ratio, and is exploited to increase the quality of the reconstructed images employing multiple-input multiple-output based techniques. As far as we can see, our results and new insights in the nature and mechanisms of multiple compromising emanations are crucial for improving video data security.

This article presents the design, fabrication, and evaluation of miniature magnetic resonance (MR) compatible wireless markers, which can provide three-dimensional (3-D) positional tracking under magnetic resonance imaging (MRI). To achieve the small size of such markers, rectangular spiral planar coils were stacked in multiple layers, which can be fabricated on a flexible printed circuit board. Finite-element-based simulations and analytical modeling were applied to ensure the proper adjustment of the MRI scanner resonant frequency while maintaining a high circuit quality factor. A four-layer planar tracking coil was prototyped with a size of 6.7 × 1.5 × 0.3 mm3, and a quality factor of 28.5. This design and fabrication approach is reportedly the first design to initiate wireless markers in such a small size, enabling straightforward integration with interventional tools. When validated under MRI, the tracking marker appeared as a very high contrast spot on the MR images. For a 48 mm distance from the isocenter, the estimated maximum errors in 3-D position was 0.48 mm. And the inherent standard deviation of marker localization was 0.12 mm. With the high MR contrast signal generated, the presented markers enable automatic and real-time tracking in 3-D but without MR image construction. In combination with the small form factor, this marker would facilitate the MRI-guided navigation of interventional tools, in particular for those assisted by teleoperated robots.

Metal-oxide gas sensors have great potential for emerging applications, including breath analysis due to their small form factor, low cost, and low power, which enables integration in consumer electronics, such as smartphone accessories, wearables, and, in the future, smartwatches and phones. Acetone concentration in breath is an important biomarker for well-being and biomedical applications, such as weight loss and ketoacidosis monitoring. In this article, we present a monolithically integrated array of gas sensors combined with a flow sensor in order to provide better quantification of acetone. In particular, this work demonstrates improvement in the acetone selectivity thanks to the combination of three different metal oxides and the ability to compensate with the flow variation.

Health and safety considerations of room occupants in enclosed spaces is crucial for building management which entails control and stringent monitoring of CO2 levels to maintain acceptable air quality standards and improve energy efficiency. Smart building management systems equipped with portable, low-power, non-invasive CO2 sensing techniques can predict room occupancy detection based on CO2 levels exhaled by humans. In this work, we have demonstrated the development and proof-of-feasibility working of an electrochemical RTIL- based sensor prototype for CO2 detection in exhaled human breath. The portability, small form factor, embedded RTIL sensing element, integrability with low-power microelectronic and IOT interfaces makes this CO2 sensor prototype a potential application for passive room occupancy monitoring. This prototype exhibits a wide dynamic range of 400–8000 ppm, a short response time of ~10 secs, and a reset time of ~6 secs in comparison to commercial standards. The calibration response of the prototype exhibits an R2 of 0.956. With RTIL as the sensing element, we have achieved a sensitivity of 29 pF/ppm towards CO2 at ambient environmental conditions and a three times greater selectivity towards CO2 in the presence of N2 and O2. CO2 detection is accomplished by quantifying the capacitance modulations arising within the electrical double layer from the RTIL- CO2 interactions through AC- based electrochemical impedance spectroscopy and DC- based chronoamperometry.

This paper presents several component prototypes towards a low-latency, small-form-factor optical link designed for the ATLAS Liquid Argon Calorimeter Phase-I trigger upgrade. A prototype of the custom-made dual-channel optical transmitter module, the Miniature optical Transmitter (MTx), with separate transmitter optical sub-assemblies (TOSAs) has been demonstrated at data rates up to 8 Gbps per channel. A Vertical-Cavity Surface-Emitting Laser (VCSEL) driver ASIC has been developed and is used in the current MTx prototypes. A serializer ASIC prototype, operating at up to 8 Gbps per channel, has been designed and tested. A low-latency, low-overhead encoder ASIC prototype has been designed and tested. The latency of the whole link, including the transmitter latency and the receiver latency but not the latency of the fiber, is estimated to be less than 57.9 ns. The size of the MTx is 45 mm x 15 mm x 6 mm., 12 pages, 13 figures

Microwave Photonics is promising for generation and synthesis of radio frequency, microwave as well as millimeter wave signals of outstanding spectral purity and arbitrary wave form. High optical quality factors lead to the low noise of the signals. Small size of the optical components results in small form factor of the photonic devices. As such, the photonic oscillators outperform the majority of high frequency microwave ones of purely electronic nature. In this letter we review the major recent advances and trends as well as discuss future steps in the development of the field.

The Industrial Internet of Things (IIoT) is an evolution of real-time monitoring and inspection in construction through sensors and wireless devices. One of the important elements of the equipment is the antenna which decides the quality and accuracy of supervising information over various communication standards. In this paper, we proposed a triple band Vivaldi antenna in which all detailed dimensions are optimized by CST software. Based on FR4 substrate with a height of 1.6mm, the total size of the Vivaldi antenna is 58.5 x 40 x 1.6 mm3 that can be fitted on a small form factor. Operating at 2.44GHz, 4GHz, and 5.6GHz with a large bandwidth of 8.09%, 12.5%, and 19.29% respectively, the proposed antenna bandwidth covers almost all popular IIoT bands such as Wi-Fi, Bluetooth, and 5G below 6GHz ones.

In this paper, wide-band, multiple-input-multiple-output (MIMO) antenna system is proposed for mobile applications. The MIMO is an emerging field which aims to improve the signal-to-noise ratio in communication channels. The MIMO antenna system consists of two compact monopole antenna elements for 5G standard covering bands (n48, n77, n78) between 3.3 and 4.2 GHz. The dimensions of the board are equal to 100 × 60 × 1.6 mm, which is identical to typical smartphone’s back panel. The size of antenna is only 10 × 7.8 mm. The length of the antenna trace is for about λg/4 which has been L-shaped folded to make it resonate at desired frequency. Both antennas give better than −10 dB return loss and 80% efficiency. The antennas are placed at the PCB corner and the center edge of the board, with both positions supporting optimum MIMO performance. This compact size of antenna allows the designer the freedom to allocate the other electronic components. The proposed antennas are well suitable for small form factor wireless devices.

Aerial manipulation with a multi-rotor drone and manipulator systems or omni -directional drones has critical barriers such as limited flight time, insufficient payload, and inaccurate onboard sensing and control. To overcome these limitations, the Large-size Aerial Skeleton with Distributed Rotor Actuation (LASDRA) was proposed in previous research [1]. In this paper, we develop a downsized LASDRA with a novel joint locking device. The developed downsized LASDRA with joint locking device can work in narrower spaces with more DoF and generates a bigger operational force by joint locking. The joint locking device employs a capstan brake and latch mechanism to generate large locking torques with a small form factor. As an experimental result, the payload of a 3-link downsized LASDRA increased from 0.4 kg to 1.2 kg with joint locking, while the length of each link decreased from 1 m to 0.76 m.

Cardiovascular diseases (CVDs) have been listed among the most deadly diseases worldwide. Many CVDs are likely to manifest their symptoms some time prior to the onset of any adverse or catastrophic events, and early detection of cardiac abnormalities is incredibly important. However, traditional electrocardiography (ECG) monitoring systems face challenges with respect to their scalability and affordability as they require direct body contact and cumbersome equipment. As a step forward from the large-scale direct-contact ECG monitoring devices, which are inconvenient for the user in terms of wearability and portability, in this research, we present a small-sized, non-contact, real-time recording system for mobile long-term monitoring of ECG signals. The device mainly comprises three non-contact electrodes to sense the bio-potential signal, an AD8233 AFE IC to extract the ECG signal, and a CC2650 MCU to read, filter, and transmit them. The device is powered by a 2000 mAh lithium-ion battery with isolation between digital and analog powers on the board using two low-dropout regulators (LDOs). The board’s dimension is 8.56 cm × 5.4 cm, the size of a credit card, making it optimal to be worn in a shirt chest pocket. In spite of its small form factor, the device still manages to achieve a continuous measurement battery life of over 16 h, total harmonic distortion below −30 dB across the interested frequency range, an input-referred noise as low as 1.46 µV for contacted cases and 5.15 µV for non-contact cases through cotton, and clear ECG recording for both contact and non-contact sensing, all at a cost around USD 50.

For the past decade, optics and display hardware developments for mixed reality and smart glasses were merely a shot in the dark, providing enough display immersion and visual comfort for developers to build up apps, especially for the enterprise field. Today, as universal use cases for consumer emerge such as co-presence, digital twin and remote conferencing, new optical functionalities are required to enable such experiences. It is not only a race to smaller form factor and light weight devices for large field of view (FOV) and lower power, but the requirements are also on additional display and sensing features specifically tuned to implement such new universal use cases. Broad acceptance of wearable displays especially in the consumer field is contingent on enabling these new display and sensing requirements in small form factors and low power. This talk will focus on waveguide combiner technologies and how these architectures have evolved over the past years to address such new requirements

With the advent of the 5G era, power devices and telecom equipment require small form factor and excellent thermal performance. Flip-chip Land Grid Array (FC-LGA) is rapidly becoming the package choice for those devices, because of its low RDS (ON) and high frequency operation. However, it also brings great challenges to reliability design. Large number of flip chip solder joints between die and substrate lead to a more rigid package body, which will accumulate strong thermomechanical stress under alternating temperature and so inevitably trigger package reliability issues. Excessive warpage and body crack will occur if without appropriate package design consideration. In this study, the thermo-mechanical behaviors of FC-LGA were investigated by finite element simulation under different TCC conditions. Due to the complexity of the LGA substrate, the simulation with detail substrate model in use will incur expensive computation. This work proposed a simplification method considering a substrate of complicated structure as an equivalent anisotropic volume. With simulation models simplified, DoE study was performed to investigate the influence of packaging materials and geometry on the thermo-mechanical reliability of FC-LGA packages in high efficiency. A higher die-to-EMC thickness ratio will result in a more severe package convex warpage, while using a thinner die and a thicker EMC layer can prevent package body from cracking during heating or cooling processes. Besides packaging geometry, the influence of substrate layouts and EMC mechanical properties were also studied to find the optimal packaging design to mitigate the risks of excessive package warpage and body crack.

Headphones continue to become more intelligent as new functions (e.g., touch-based gesture control) appear. These functions usually rely on auxiliary sensors (e.g., accelerometer and gyroscope) that are available in smart headphones. However, for those headphones that do not have such sensors, supporting these functions becomes a daunting task. This paper presents HeadFi, a new design paradigm for bringing intelligence to headphones. Instead of adding auxiliary sensors into headphones, HeadFi turns the pair of drivers that are readily available inside all headphones into a versatile sensor to enable new applications spanning across mobile health, user-interface, and context-awareness. HeadFi works as a plug-in peripheral connecting the headphones and the pairing device (e.g., a smartphone). The simplicity (can be as simple as only two resistors) and small form factor of this design lend itself to be embedded into the pairing device as an integrated circuit. We envision HeadFi can serve as a vital supplementary solution to existing smart headphone design by directly transforming large amounts of existing "dumb" headphones into intelligent ones. We prototype HeadFi on PCB and conduct extensive experiments with 53 volunteers using 54 pairs of non-smart headphones under the institutional review board (IRB) protocols. The results show that HeadFi can achieve 97.2%--99.5% accuracy on user identification, 96.8%--99.2% accuracy on heart rate monitoring, and 97.7%--99.3% accuracy on gesture recognition.

Near-ground sensing data, such as geospatial measurements of soil apparent electrical conductivity (ECa), are used in precision agriculture to improve farming practices and increase crop yield. Near-ground sensors provide valuable information, yet, the process of collecting, assessing, and interpreting measurements requires significant human labor. Automating parts of this process via the use of mobile robots can help decrease labor burden, and increase the accuracy and frequency of data collections, and overall increase the adoption and use of ECa measurement technology. This paper introduces a roboticized means to autonomously perform geospatial ECa measurements and map soil moisture content in micro-irrigated orchard systems. We retrofit a small wheeled mobile robot with a small electromagnetic induction sensor by studying and taking into consideration the effect of the robot body to the sensor's readings, and develop a software stack to enable autonomous logging of geo-referenced measurements. The proposed roboticized ECa measurement method is evaluated by mapping a $50\mathrm{m}\times 30\mathrm{m}$ field against the baseline of human-conducted measurements obtained by walking the sensor in the same field and following the same path. Experimental testing reveals that our approach yields roboticized measurements comparable to human-conducted ones, despite the robot's small form factor.

The Dual Band Pass Filters (DBPF) with high stop band rejection at center frequencies of 122 and 330 MHz are designed. The DBPF filters are fabricated in low temperature co-fired ceramic (LTCC) technology using a lumped element approach. Measured results show close agreement with simulations with very small form factor. The overall size of the dual band-pass filter is 32 mm×18 mm×2.2 mm.

This work-in-progress project describes the evolution of a design for a small form factor, affordable tactile display using simple, easily obtainable motors and mechanical linkages. Performance characteristics of each display are given, as are plans for experimental validation of their potential to support visually impaired smartphone users.