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A monopole antenna inspired from Rotman Lens is presented in this paper. It is designed to operate in the unlicensed 60 GHz millimeter-wave band from 54.318-64.477 GHz. It also has a high gain of 5.25 dBi, suitable for millimeter-wave communication. It has more than 90% of radiation efficiency due to the use of Rogers 5880 low loss substrate. It has dual beam radiation pattern in azimuth plan and back radiations are less than −10 dB. The antennas overall dimensions are $5\times 4.5\ \text{mm}^{4}$ , ensuring small form factor. It has a planar structure and along with its other attractive features such as high gain, large bandwidth and dual beam, is deemed quite suitable for future 5G, millimeter-wave communication in the unlicensed 60 GHz band as well as indoor communications.

This paper demonstrates the hardware design and thermal solution of video accelerator cards in the M.2 and mini PCI express (mPCIe) form factor. The video accelerator cards have video processing units (VPU) which act as extra graphics engine in addition to the processor in a system. It is the first in industry that video accelerator card can be designed in such small form factor without compromising performance. As the accelerator cards are small, the board design can be of high challenge to ensure essential components and layout routing are done correctly to comply with design rules. In addition, high power density on the accelerator cards requires good thermal design and power management to ensure the temperature on the VPU does not exceed specification during intended operation. The performance improvement on a host system equipped with the accelerator cards will also be shown to prove the business acumen.

When power consumption in smartphones becomes much higher, several significant impacts occur due to its small form factor, such as performance degradation and worse user experience. Thus, power estimation/mapping is essential and useful for dynamic power management and power model validation for smartphones. In this work, first, we build the power-to-temperature (P-to-T) equations for thermal sensors from the existing system-level thermal model and calibrate them using the least squares fitting. Furthermore, we develop an efficient method for the temperature-to-power (T-to-P) mapping, which obtains the power consumption of components by utilizing temperatures of thermal sensors. Experiments show that this work can estimate power profile efficiently for both steady-state and transient results.

Fan-Out Wafer-Level Interposer Package-on-Package (PoP) design has many advantages for mobile applications such as low power consumption, short signal path, small form factor and heterogeneous integration for multi-functions. In addition, it can be applied in various package platforms, including PoP, System-in-Package (SiP) and Chip Scale Package (CSP). These advantages come from advanced interconnection technology called a redistribution layer (RDL).However, a PoP-type RDL-base platform requires dual-side RDLs on both top and bottom sides to stack another package on top. In a monolithic process flow, that means the second RDL only can be fabricated after finishing all the first RDL and the assembly processes such as flip-chip bonding, molding and grinding. Therefore, this process flow is not quite as advantageous as a non-PoP type platform because chips can be lost during the second RDL process.In this paper, to address this RDL-base Interposer PoP challenge, a real chip-last process flow with a chip-to-wafer (C2W) bonding technology is introduced. And the results are presented of building and testing an RDL-base wafer-level Interposer PoP with a size of 12.5 x 12.5 mm2 and thickness of 0.357 mm including solder ball. The bottom side has a 3-layer RDL structure and the top RDL for the package stacking has a 1-layer structure. These RDLs are implemented with copper (Cu) lines with 5 μm/10 μm of line & space (L/S) and copper (Cu) cored solder balls (CCSBs) are used as the vertical interconnect components. The silicon die and CCSBs’ joint quality is confirmed by reliability testing. The test vehicle package passed all the reliability tests of moisture resistance test (MRT) L3, Temperature Cycle, Condition B (TCB) 1,000 cycles and high temperature storage (HTS) 1,000 hrs.

We demonstrate a fully integrated wireless surface electromyography (sEMG) system using Fan-Out Wafer-Level Packaging on a flexible biocompatible package with two corrugated high conductivity electroplated Cu wiring levels for efficient routing. The assembly has reliable performance under repeated flexing of >3000 times. The advanced Au capped Cu-based sensing electrode array architecture provides a high spatial resolution sEMG measurement with SNR comparable to standard Ag/AgCl electrodes, allowing for muscle activation signals to be recorded and transmitted wirelessly for off-line post processing. The system, which is compatible with our wireless charging system has a small form factor of 65 mm x 40 mm x 1 mm and light weight of < 5 gm, making sEMG widely available outside the hospital setting.

The Internet of Things (IoT) is a promising vision to cover a wide range of applications. However, battery-operated devices at the edge of the Internet, have a limited lifetime or involve significant maintenance effort. Energy Harvesting (EH) is one of the most investigated technologies to extend the battery lifetime. Nevertheless, the further miniaturization of devices poses challenges, mainly due to the small form factor needed. In particular, harvesting energy from miniaturized transducers (i.e., millimeter-sized solar panels) is significantly more challenging. Among other EH technologies, transmitting power wirelessly is growing in popularity as it can be controlled, and it is less unpredictable than environmental sources. This work investigates different technologies to supply small size and low power smart devices for IoT applications with wireless power transmission. The paper illustrates with experimental measurements, the power acquired with a commercial radiofrequency power transmission system from Powercaset. According to this evaluation, the RF power transfer to the battery ranged from mW to μW using millimeter-sized antennas up to meters of distance. Thus the system is an effective solution for the supply of small size IoT devices.

In this paper, PI (Power Integrity) performance of interposer package-on-package (POP) is analyzed with respect to types of package decoupling capacitors and relative location of package decoupling capacitors to CPU (Central Processing Unit) PDN (Power Distribution Network) of package. Packages with the decoupling capacitor within SOC package substrate, and that on bottom ball land side are being analyzed and compared in terms of system-level core PDN impedance. Moreover, decoupling capacitor’s placement with respect to that of CPU cores are being analyzed. In addition to the PI performance improvement of the package using decoupling capacitor, the system-level PI performance were analyzed and improved through co-optimization of on-chip PDN.

Mobile application or appliance demands multi-functions, high speed, light or small form factor and low cost. One of the common approaches to meet all these requirement is put one package over another package. This approach is commonly known as Package on Package. Package on Package can be realized by assembled the package either through the use of organic substrate, or fan-out wafer level package. The top package is stacked on top of the bottom package using solder balls or copper pillars.In this paper, we used fan-out wafer level package’s approach to demonstrate the vertically integrated package on package. The top and bottom package are merged together using fan-out wafer level approach during the assembly process to form Vertically Integrated Package on Package.

Compliance sensation is a unique feature of the human skin that electronic devices could not mimic via compact and thin form-factor devices. Due to the complex nature of the sensing mechanism, up to now, only high-precision or bulky handheld devices have been used to measure compliance of materials. This also prevents the development of electronic skin that is fully capable of mimicking human skin. Here, we developed a thin sensor that consists of a strain sensor coupled to a pressure sensor and is capable of identifying compliance of touched materials. The sensor can be easily integrated into robotic systems due to its small form factor. Results showed that the sensor is capable of classifying compliance of materials with high sensitivity allowing materials with various compliance to be identified. We integrated the sensor to a robotic finger to demonstrate the capability of the sensor for robotics. Further, the arrayed sensor configuration allows a compliance mapping which can enable humanlike sensations to robotic systems when grasping objects composed of multiple materials of varying compliance. These highly tunable sensors enable robotic systems to handle more advanced and complicated tasks such as classifying touched materials.

The development and validation of prognostic algorithms and digital twins for Electromechanical Actuators (EMAs) requires datasets of operating parameters that are not commonly available. In this context, we are assembling a test bench able to simulate different operating scenarios and environmental conditions for an EMA in order to collect the operating parameters of the actuator both in nominal conditions and under the effect of incipient progressive faults. This paper presents the design and manufacturing of a planetary gearbox for the EMA test bench. Mechanical components were conceived making extensive use of Fused Deposition Modelling (FDM) additive manufacturing and off-the-shelf hardware in order to limit the costs and time involved in prototyping. Given the poor mechanical properties of the materials commonly employed for FDM, the gears were not sized for the maximum torque of the electric motor, and a secondary torque path was placed in parallel of the planetary gearbox to load the motor through a disc brake. The architecture of the gearbox allowed a high gear ratio within a small form factor, and a bearingless construction with a very low number of moving parts.

Applications for stand-alone systems with small form factor, long lifetime and high energy density have arisen. Nuclear batteries have the potential to achieve specific powers of 1-50mW/g and devices that utilize the beta emitter titanium tritide (TiT2) have the most potential. We present our progress in making textured TiT2 based devices and their performance as compared to planar devices. In planar devices a 200nm 4H-SiC P+N junction is used for charge collection. Dark current measured less than 6.1 pA/cm2. Samples measured with tritium foil produced an open circuit voltage of 2.09V, short circuit current of 75.47nA/cm2, fill factor of 0.86 and power efficiency of 18.6%. This device is near the practical limit efficiency. In order to increase the power output the effective area of the beta source is increased by patterning the topmost absorption layer into channels 10 micron in height. Textured devices achieved open circuit voltage of 1.91V and short circuit current of 11.3nA.

This paper presents progress on the development of a high-performance single-chip timing and inertial measurement unit (TIMU) based on environmentally-robust high-frequency micromechanical devices and the hermetically-sealed HARPSS+ silicon MEMS process. The fabrication platform provides the unique capability of producing deep-sub-micron capacitive gaps (i.e. nano-gaps) in various orientations, including 54°-slanted electrodes, enabling low-voltage mode-matching and alignment of triaxial high-frequency resonator gyroscopes with high sensitivity. The resonator (i.e. mode-matched) gyroscopes and quasi-static accelerometers are sealed in separate cavities with different pressure levels through a single bonding step, which allows for the co-fabrication and co-packaging of high-dynamic-range high-Q bulk acoustic wave (BAW) resonator 3-axis gyroscopes and critically-damped high-bandwidth (above 10kHz) micro-gravity 3-axis accelerometers. High-frequency and high-Q nano-gap timing resonators with low motional impedance are fabricated on the same substrate with the IMU, which favors low-jitter high-frequency oscillator implementations and enables OCXO demonstrations with sub-ppm stability. Fabricated devices were tested against wafer thinning process, high shocks, aging effects and extensive temperature variations, verifying the robustness of the designs and fabrication process. The high performance, high robustness, and small form factor make the HARPSS+ precision TIMUs an attractive solution for demanding inertial navigation and guidance applications.

This paper presents several novel designs of small form factor underwater radio antennas operating in the 2 MHz, 50 MHz and 2.4 GHz bands. These antennas efficiently excite surface electromagnetic waves (SEW) which propagate along the surface of seawater. The antenna operation is made possible due to implementation of an impedance matching enclosure, which is filled with de-ionized water. Enhanced coupling to surface electromagnetic waves is enabled by the enhancement of the electromagnetic field at the antenna apex. These features allow us to make antenna dimensions considerably smaller compared to typical free space designs. They also considerably improve coupling of electromagnetic energy to the surrounding seawater. Since SEW propagation length is considerably larger than the skin depth in seawater, this technique is useful for underwater broadband wireless communication. We conclude that the developed broadband underwater radio communication technique will be useful in networking of unmanned underwater vehicles.

Autonomous drones have become increasingly popular in applications such as trusted delivery and law enforcement. This makes them vulnerable to midair attacks for profit and vandalism. While modern aircrafts can detect and defend against projectile attacks using radar and antenna arrays, small drones cannot leverage such techniques. The primary challenges are their (a) small form factor and weight carrying capacity, (b) limited computational power, and (c) limited power source. We envision to develop an ecosystem of lightweight and low-power defense modules for small drones. This project explores the viability of this vision. As proof of concept, we develop a single microphone-based acoustic sensing mechanism capable of identifying if an approaching projectile is about to hit the drone. Our system, called DopplerDodge, transmits acoustic signals and leverages doppler frequency shifts in the reflected signal to predict the projectile's intention.

Free-space optical communication (FSO) enables high-bandwidth data links that are difficult to detect, intercept, and jam. In this paper we provide an overview of a small form factor FSO prototype intended for UAVs called OCELOT (Optical Communication Efficient Low-profile Terminal). NRL designed, developed, and tested an OCELOT prototype, and demonstrated a 1 Gbps duplex link 16 km across the Chesapeake Bay. We will discuss the design decisions and tradeoffs, highlighting the low-SWaP FSO technologies used in the prototype.

We present an integrated hardware and sensor fusion development platform consisting of a variety of sensors for attitude, heading, height, position and velocity estimation. Small form factor and low power consumption enable multiple use-cases, including not only land-based but also sea- and air-based applications. The platform allows high-speed data acquisition and algorithm evaluation to gain insights into the particular application’s demands. A required feature for many of those applications is rapid initial heading estimation using redundant data sources. Among those are dual global navigation satellite system (GNSS) receivers and dissimilar MEMS inertial sensors.

A three-band LTE Cat-M1 PCB antenna is simulated and measured and these results are compared in this paper. Antenna resonance frequency at 700 MHz is matching well with simulations. Above 1.5 GHz resonances have a difference of about 70 MHz. With tuned antenna measured efficiencies are 1 dB worse on average than simulated efficiencies when difference at reflection coefficient is taken into account. Active TRP measurements finally show maximum efficiency difference between simulation and measurement of 2.2 dB. As results show there are some differences between the measurements and simulations. However, these differences are small enough that new design round for the device is not needed and the device can be finished with tuning component changes only.

This paper introduces a novel method to simultaneously super-resolve and colour-predict images acquired by snapshot mosaic sensors. These sensors allow for spectral images to be acquired using low-power, small form factor, solid-state CMOS sensors that can operate at video frame rates without the need for complex optical setups. Despite their desirable traits, their main drawback stems from the fact that the spatial resolution of the imagery acquired by these sensors is low. Moreover, chromatic mapping in snapshot mosaic sensors is not straightforward since the bands delivered by the sensor tend to be narrow and unevenly distributed across the range in which they operate. We tackle this drawback as applied to chromatic mapping by using a residual channel attention network equipped with a texture sensitive block. Our method significantly outperforms the traditional approach of interpolating the image and, afterwards, applying a colour matching function. This work establishes state-of-the-art in this domain while also making available to the research community a dataset containing 296 registered stereo multi-spectral/RGB images pairs.

We are developing a 1x8 single mode (SM) optical interface to facilitate the adoption of dense wavelength division multiplexing (DWDM) silicon photonic (SiPh) optical interconnects in exascale computing systems. A common method for fiber attachment to SiPh transceivers is ‘pigtailing’- the permanent adhesive bonding of fiber/v-groove arrays to onchip grating couplers (GC). This approach precludes standard high throughput surface mounting and solder reflow assembly of the transceiver onto system printed circuit boards. Our approach replaces the fixed pigtail with a low profile, small form factor, detachable expanded beam optical connector which consists of four essential parts: a GC array, a surface mount glass microlens array chip, an injection molded solder reflowable optical socket, and an injection molded SM light turn ferrule. The optical socket and ferrule are supplied by US Conec Ltd. To design the GC, we developed an optical simulator that considers CMOS foundry constraints in the optimization process. On-wafer measurements of the GC coupling loss to SMF28 fiber at 1310nm is ~1.4dB with a 1dB bandwidth of ~22nm. This ensures a wide low loss spectral window for at least 16 DWDM channels. The geometry of the optical system is arranged so that only a simple spherical lens is required for efficient mode matching in the expanded beam space. The fiber to fiber insertion loss through the light turn ferrule, two microlenses and GCs, and a looped back SOI waveguide ranged from 4.1-6.3dB, with insertion loss repeatability of 0.2dB after multiple mating cycles.

Wireless sensor nodes with low power and small form factor are desirable for emerging IoT applications. These nodes usually consist of a processor, memory, radio, sensors, battery, and two quartz crystals: one at 32kHz to synchronize data transmission and the other in the MHz range to synthesize RF signals. SoC integration of the memory, processor, and radio is common; however the MHz crystal remains external, which makes up a significant portion of the entire wireless node size.

The previous chapter reviewed the various optical building blocks used in typical AR and MR headsets. This chapter addresses the main challenges that must be overcome with those building blocks in order to meet the following specs simultaneously: - a large FOV and wide stereo overlap, - a large IPD coverage (large eyebox), - a large eye relief allowing prescription lens wear, - a high angular resolution close to 20/20 vision, and - a small form factor, low weight, and a CG close to the head.

This work presents a fully integrated neural interface system in a small form factor (1.9 g), consisting of a μLED silicon optoelectrode (12 μLEDs and 32 recording sites in a 4-shank configuration), an Intan 32-channel recording chip, and a custom optical stimulation chip for controlling 12 μLEDs. High-resolution optical stimulation with approximately 68.5 nW radiant flux resolution is achieved by a custom LED driver ASIC, which enables individual control of up to 48 channels with a current precision of 1 μA, a maximum current of 1.024 mA, and an update rate of >10 kHz. Recording is performed by an off-the-shelf 32-channel digitizing front-end ASIC from Intan. Two compact custom interface printed circuit boards were designed to link the headstage with a PC. The prototype system demonstrates precise current generation, sufficient optical radiant flux generation $({\Phi _e} > \text{0.16}\, \mu \text{W})$ , and fast turn- on of μLEDs $(t_{{\rm{rise}}} . Single animal in vivo experiments validated the headstage's capability to precisely modulate single neuronal activity and independently modulate activities of separate neuronal populations near neighboring optoelectrode shanks.

This paper details an architecture that includes a recess in motherboard (RiMB) to enable increased packaging density of functional components for next generation mobile personal computing products. The recess depth, manufacturing methods, and SMT assembly data are included to provide the reader with a full overview of the manufacturing and assembly challenges.

The purpose of this paper is to investigate methods for improving power delivery from low-voltage, low-power energy harvesting sources, such as small form-factor dye-sensitised solar cells (DSSCs) as used in autonomous wireless sensing applications in buildings and homes. Energy harvesting powered wireless sensors enable existing and new structures to comply with Industry 4.0 and become smart buildings. Due to the size constraints of wireless sensor systems and the inherently low-power levels generated by energy harvesting sources, available power is limited and therefore the efficiency of power conversion and energy management circuitry connected between the source and output load has a significant impact on output power delivery. Most research to date focuses on improving the efficiency of individual components of such systems, without considering the impact of one stage on the others. In this paper, the potential of varying energy harvesting source configuration in combination with power converter operation to improve overall power delivery is investigated, where it is shown that by connecting sections of a DSSC in series rather than as a single cell, higher power conversion efficiency and therefore power delivery is achieved. Limitations to varying cell configurations and low-power DC-DC topologies are illustrated in order to demonstrate the scope of solutions available for small-sized, low-power, energy harvesting sources. It is shown that 8% improvement in overall power delivery is achieved for series vs. single cell connections within a fixed module area. This will translate into increased wireless sensor functionality and range, thereby furthering the development of the Industrial Internet of Things in buildings and homes.

The photogrammetric acquisition of 3D object models can be achieved by Structure from Motion (SfM) computation of photographs taken from multiple viewpoints. All-around 3D models of small artefacts with complex geometry can be difficult to acquire photogrammetrically and the precision of the acquired models can be diminished by the generic application of automated photogrammetric workflows. In this paper, we present two versions of a complete rotary photogrammetric system and an automated workflow for all-around, precise, reliable and low-cost acquisitions of large numbers of small artefacts, together with consideration of the visual quality of the model textures. The acquisition systems comprise a turntable and (i) a computer and digital camera or (ii) a smartphone designed to be ultra-low cost (less than $150). Experimental results are presented which demonstrate an acquisition precision of less than 40 μ m using a 12.2 Megapixel digital camera and less than 80 μ m using an 8 Megapixel smartphone. The novel contribution of this work centres on the design of an automated solution that achieves high-precision, photographically textured 3D acquisitions at a fraction of the cost of currently available systems. This could significantly benefit the digitisation efforts of collectors, curators and archaeologists as well as the wider population.

In this work we present a wireless, energy harvesting powered solution for vibration analysis. In order to ensure minimal power consumption the system is equipped with our own radiofrequency protocol, which is tailored for the needs of energy harvesting.Our system has a small form factor, all the while containing everything needed for a wireless energy harvesting sensor unit. It has two switchable MEMS accelerometers to ensure minimal power consumption and to maintain wide frequency range if needed. The on-board processing unit with floating point hardware accelerator makes Fourier transformation, thus vibration spectrum analysation efficient. The energy management unit is designed with dual topology, making it able to accept both low and high impedance energy harvesters at the same time (hybrid harvesting). The radiofrequency module may work with our own radio frequency protocol or with the Bluetooth standard (Bluetooth 5, BLE with long range PHY).

A novel planar ultra-wideband (UWB) biconical antenna is presented in this paper. The antenna design has been optimized for best performance in the range 3.1 to 10.6 GHz. The antenna has an omni-directional radiation pattern. The antenna has been manufactured and tested. It has a low profile and a small form factor. This antenna is suitable for use in wireless applications such as: UWB systems, sub-6 GHz 5G systems, and wearable wireless devices.

Along with the rapid spread of portable electronic products on the mobile computing market, the increase in the use of video streaming, photo sharing and also other data-intensive applications keep growing up continuously for now. More and more IoT/Wearable and 5G connectivity devices are required with Radio Frequency (RF) and Front-End Module (FEM) which has driven the development of IC packaging towards on small form factor, thin profile, better electrical and thermal performance, as well as 3D stacking for multi-function integration [1]. To approach these requirements, the System in Package (SiP) can be a combination of one or more chips plus optionally passive components by using Surface Mount Technology (SMT) and 3D structure of double side into a single package to offer a small form factor, high performance and systemization implemented. The high speed SMT process accomplishes the high-density with more than 50 discrete passive as well as active components and heterogeneous integration on package level approach. The development of double side technology offers the advantage of package size shrinkage by the same integrating discrete passive and active components layout. In this paper, the innovative packaging solutions of 3D double side SiP including the platform for both strip form of substrate base and wafer form of Fan-Out Redistribution Layer (RDL) base will be well introduced. Fan-Out RDL is an extension approach of Wafer Level Chip Scale Package (WLCSP), this technology is different from conventional wire bond or flip chip packages because the redistribution dielectrics and fine-line plated conductors are used for interconnection to replace the packaging substrates. As a case study, the calculation of 3D SiP package size can be shrunk around 50% area and the total package thickness can achieve around 15% z-height reduction with thin form coreless substrate and Fan-Out RDL technology utilization. The characterization analysis will apply simulation methodology for electrical comparison on DC resistance and parasitic inductance, thermal comparison on Theta JA (°C/W) and warpage comparison on the package structure of 3D double side SiP. Also, the typical reliability testing (Temperature Cycle Test, High Temperature Storage Life Test, Unbiased High Accelerated Stress Test) are built to verify 3D double side SiP structure for future IoT/Wearable and 5G devices application. Currently the market trends clearly drive towards 3D double side SiP, so this article illustrates the innovative packaging solutions with both substrate base and Fan-Out RDL base to provide a unique opportunity for enabling 3D integration and system in package.

A microarray biosensor that measures the electrical impedance of cell suspensions is presented. Single-cell–resolution measurement was facilitated by physically positioning individual cells on sensing electrodes by dielectrophoresis, obviating chemical or biological surface modification. The high-density (104 × 104) electrode array was incorporated with a complementary metal-oxide-semiconductor (CMOS) integrated chip (IC) to support impedance spectroscopy at frequencies ranging from 100 kHz to 1 MHz, achieving a rapid and cost-effective platform with a small form factor. Experiments with microbeads (10, 15, and 20 μm in diameter) and a live breast cancer cell line (MCF-7) have demonstrated that the developed prototype quantifies loaded microbeads or cells rapidly (

In order to simplify the receiver configuration in a wavelength division multiplexed optical fiber network, compact wavelength tunable filters have long been expected to be used as channel selectors. Bragg reflector inherently has the most suitable reflection spectrum for filtering a single wavelength from the densely multiplexed wavelength signal. Polymer has high thermo-optic coefficient and good thermal insulation property compared to the other optical waveguide materials such as silicon and silica materials. This can be used to broadly tune the reflection spectrum of Bragg reflector using a simple micro-heater. In this work, a micro-optic circulator component and a polymeric Bragg reflector device are assembled to produce a small form factor tunable receiver. Compared to the integrated-optical versions, the micro-optics are based on well-developed manufacturing processes and can achieve competitive production yields. The device exhibits high reflectivity with a flat top passband, and a polarization dependence of 0.06 nm achieved by virtue of the low birefringence of LFR polymer, which make a significant contribution to the implementation of polarization independent tunable receiver. The wavelength tuning range of 40 nm is demonstrated by using a bottom located heater with a groove for heat isolation.

Due to the advantages of small form factor, high performance, low power consumption, and high density integration, three-dimensional integrated circuits (3D ICs) have been generally acknowledged as the next generation semiconductor technology. Low temperature bonding is the key technology to ensure the chip (or wafer) stacking in 3D ICs. In this paper, different low temperature bonding methods for chip (or wafer) stacking were reviewed and described systematically. Materials, processing and reliability will be extremely important, their effects on the 3D IC structure were addressed in detail, the challenging reliability issues may be considered as the major concern in the future work. The latest development of low temperature bonding in 3D ICs is also given here, which helpful may provide a reference for the further study of low temperature bonding.

Recent wearable devices offer portable monitoring of biopotentials, heart rate, or physical activity, allowing for active management of human health and wellness. Such systems can be inserted in the oral cavity for measuring food intake in regard to controlling eating behavior, directly related to diseases such as hypertension, diabetes, and obesity. However, existing devices using plastic circuit boards and rigid sensors are not ideal for oral insertion. A user-comfortable system for the oral cavity requires an ultrathin, low-profile, and soft electronic platform along with miniaturized sensors. Here, we introduce a stretchable hybrid electronic system that has an exceptionally small form factor, enabling a long-range wireless monitoring of sodium intake. Computational study of flexible mechanics and soft materials provides fundamental aspects of key design factors for a tissue-friendly configuration, incorporating a stretchable circuit and sensor. Analytical calculation and experimental study enables reliable wireless circuitry that accommodates dynamic mechanical stress. Systematic in vitro modeling characterizes the functionality of a sodium sensor in the electronics. In vivo demonstration with human subjects captures the device feasibility for real-time quantification of sodium intake, which can be used to manage hypertension.

Integrating surface plasmon resonance (SPR) devices upon single-mode fiber (SMF) end facets renders label-free sensing systems that have a simple dip-and-read configuration, a small form factor, high compatibility with fiber-optic techniques, and invasive testing capability. Such devices are not only low cost replacement of current equipments in centralized laboratories, but also highly desirable for opening paths to new applications of label-free optical sensing technologies, such as point-of-care immunological tests and intravascular ultrasound imaging. In this paper, we explain the requirements and challenges for such devices from the perspectives of biomolecule and ultrasound detection applications. In such a context, we review our recent work on SMF end-facet SPR cavities. This include a glue-and-strip fabrication method to transfer a nano-patterned thin gold film to the SMF end-facet with high yield, high quality and high alignment precision, the designs of distributed Bragg reflector (DBR) and distributed feedback (DFB) SPR cavities that couple efficiently with the SMF guided mode and reach quality factors of over 100, and the preliminary results for biomolecule interaction sensing and ultrasound detection. The particular advantages and potential values of these devices have been discussed, in terms of sensitivity, data reliability, reproducibility, bandwidth, etc.

Pyroelectric infrared sensors (PIR) are excellent devices to detect humananimal presence with a small form factor and rugged design, for cost-effective surveillance. They are widely used to trigger an intruder alarm and activate household appliances upon the presence of a human. However, the analog output from the sensor is proportional to several spatial and temporal relationships between an object in the field of view of the sensor, the sensitivity of the sensor, PIR lens features, and the environmental heat conditions. This article shows the use of only one PIR sensor in conjunction with signal processing and machine learning algorithms to clearly estimate the presence, direction, and distance of the human movements in a hallway. Simulation results show that more than 99 and 93 accuracy, respectively, in classifying direction and distance of the movements in the field of view of the PIR sensor module. Moreover, hardware and software resources are used to address the limited computational capabilities of commercially available general purpose microcontroller and sensory components to reduce the cost of the entire PIR system module. This article uses only one PIR sensor module with many well-known machine learning and computer vision methods for analog pattern recognition and movement classification. Primarily, this information is used to monitor occupational analysis of a particular floor in a building. However, the application domain can be extended to any one of the earlier mentioned areas in this abstract.

This paper presents the design of a small printed ultra wideband antenna with Band Notched characteristics. Both the free space and on-body performances of this antenna were investigated through simulation. The newly designed UWB antenna is more revised small form factor sized, with the ability to avoid interference caused by WLAN (5.15 - 5.825 GHz) and WiMAX (5.25 - 5.85 GHz) systems with a band notch. The return loss response, gain, radiation pattern on free space of the antenna were investigated. After that, the on-body performances were tested on 3-layer human body model with radiation pattern, gain, return loss, and efficiency at 3.5, 5.7, 8, 10 GHz and all the results were compared with free space results. As the on-body performance was very good, the proposed antenna will be suitable to be used for multi-purpose medical applications and sports performance monitoring.

In this paper, we employed a one-step localized substrate removal (LSR) process to fabricate a backside-illuminated CMOS photovoltaic (PV) mini-module suitable for high-voltage and low-power applications. LSR can be considered an upgrade of multichip module technology, by providing a 50- $\mu \text{m}$ physical gap between on-chip PV cells for electrical isolation, while avoiding the need for time-consuming pick-and-place steps. A proof-of-concept PV module achieved open-circuit voltage of 12.5-V and $\mu \text{A}$ -scale short-circuit current within a small form factor (3.13 V/mm2). The fabrication of this PV mini-module is based on standard microelectronics manufacturing/packaging processes, thereby ensuring easy integration with other microelectronics for self-powered systems.

Generating optical combs in a small form factor is of utmost importance for a wide range of applications such as datacom, LIDAR, and spectroscopy. Electrically powered mode-locked diode lasers provide combs with a high conversion efficiency, while simultaneously allowing for a dense spectrum of lines. In recent years, a number of integrated chip scale mode-locked lasers have been demonstrated. However, thus far these devices suffer from significant linear and nonlinear losses in the passive cavity, limiting the attainable cavity size and noise performance, eventually inhibiting their application scope. Here, we leverage the ultra-low losses of silicon-nitride waveguides to demonstrate a heterogeneously integrated III-V-on-silicon-nitride passively mode-locked laser with a narrow 755 MHz line spacing, a radio frequency linewidth of 1 Hz and an optical linewidth below 200 kHz. Moreover, these comb sources are fabricated with wafer scale technology, hence enabling low-cost and high volume manufacturable devices.

Bio-impedance is a method to assess the body composition safely, non-invasively and inexpensively. This method finds application for assessing body fluid and body composition for multiple disease scenarios in clinical environments and for at-home monitoring of chronic ailments. Bio-impedance sensors require higher power than most other bio-signal acquisition systems due to need of high frequency current and voltage management. Currently used bio-impedance devices are bulky due to incorporation of large batteries and cannot be used for long term monitoring, especially for wearable applications. This limits the widespread implementation of bio-impedance measurement devices. We present the design and implementation of a wireless wearable bio-impedance sensor node, ImpediSense, which has a low power system design that achieves long duration operability without compromising on sensor measurement accuracy and precision. Experimental evaluation show a battery life of several months for measuring bio-impedance with power duty cycling every 1 min over ten frequencies in the range of 10 kHz–100 kHz, using a small form factor 250 mA h Li-ion battery. The lifetime is achieved due to several power optimization implemented in system design of hardware and firmware resulting in active power of 53 mW and idle power of 15.7 μW. Additionally, the presented sensor node shows high performance in terms of accuracy of impedance measurement with an error less than 1.5 % and precision of 0.6 Ω when measuring tetrapolar bio-impedance of the human body. With the inclusion of a small sized battery, ImpediSense has a compact form factor with dimensions 3 cm × 1.8 cm × 0.6 cm, making it more conducive for incorporation in wearable systems.

Head impact sensors are increasingly used to quantify the frequency and magnitude of head impacts in sports. A dearth of information exists regarding head impact in un-helmeted sport, despite the substantial number of concussions experienced in these sports. This study evaluated the performance of one small form factor head impact sensor in both laboratory and field environments. In laboratory tests, sensor performance was assessed using a Hybrid III headform and neck. The headform assembly was mounted on a low-friction sled and impacted with three sports balls over a range of velocities (10–31 m/s) at two locations and from three directions. Measures of linear and angular acceleration obtained from the small form factor wireless sensor were compared to measures of linear and angular acceleration obtained by wired sensors mounted at the headform center of mass. Accuracy of the sensor varied inversely with impact magnitude, with relative differences across test conditions ranging from 0.1% to 266.0% for peak linear acceleration and 4.7% to 94.6% for peak angular acceleration when compared to a wired reference system. In the field evaluation, eight male high school soccer players were instrumented with the head impact sensor in seven games. Video of the games was synchronized with sensor data and reviewed to determine the number of false positive and false negative head acceleration event classifications. Of the 98 events classified as valid by the sensor, 20.5% (20 impacts) did not result from contact with the ball, another player, the ground or player motion and were therefore considered false positives. Video review of events classified as invalid or spurious by the sensor found 77.8% (14 of 18 impacts) to be due to contact with the ball, another player or player motion and were considered false negatives.

As the demand for advanced microelectronic devices of small form factor and high power density has increased, the capability of the miniaturized mechanical solutions for effective cooling has become critical. Electrohydrodynamic (EHD) air blowers have great potential as alternative cooling solutions over the traditional mechanical systems to meet the thermal management requirements with flexible design and considerable flow production for effective heat removal. In this paper, a numerical analysis and optimization of wire-to-plane EHD air blowers are performed based on 2-D developed models validated against previous data. For a range of blower heights from 2 to 10 mm, the location and length of the collecting plane located at the blower walls apart from the emitter wire electrode are investigated and optimized based on pumping efficiency using the ranges of fixed operating powers and voltages. Simple relations for each optimization method are presented to determine the optimal blower configuration. Results of flow rate and static pressure obtained by each optimized blower show good agreement with those predicted by EHD scaling laws previously presented.

As electronic products become smaller and thinner with increasing number of functions, the demand for high density and high integration becomes stronger. Glass has many properties that make it an ideal substrate for high integration substrate such as; ultra high resistivity, adjustable thermal expansion (CTE) high modulus, low dielectric constant, low dielectric loss and manufacturability with large panel sizes. Multi-bands with carrier aggregation, Wi-Fi/GPS coexistence, and LTE-U make RF front end more and more complicated. 3D IPD (integrated passive devices) on Glass substrate technology could be advantage solution include reducing power consumption and small form factor. This paper presents a demonstration of 3D RF front end filters using 3D solenoid inductors with through glass vias (TGV) and Cu-SiN-Cu MIM structure on Gen1 glass substrate (300mm × 400mm) panel format using color filter manufacturing line for flat panel display. For inductors, drastic performance (size and low resistance therefore high-quality factor) improvement have been demonstrated by technology evolutions from 3D solenoid using TGV with conformal Cu plating method, achieving low resistance of 3.1mohm per 70um diameter TGV on a 400um thick glass panel. This low-resistance TGV with 2.7mOhm/sq TGV connections on both sides of the glass substrate, record high inductor quality factor of 39 was obtained at 2.5GHz using five and half turn inductor of 7.9nH inductance, For capacitors, we have successfully integrated a Cu MIM (metal-insulator-metal) structure by using 15um thick Cu plates and dielectric, resulting in high capacitance density of 0.26nF/mm2 for RF application. By integrating TGV inductor-first and MIM capacitor-next, high-performance and high-density LC components are synthesized to perform as RF front end filters such as low-pass filters, diplexers, triplexers, and multiplexers. The 3D inductors, Cu MIM, LC resonators and filters were successfully integrated using glass panel manufacturing infrastructure for the first time. Process characterization and process control monitors were evaluated at the panel level to address high-volume and high-yield manufacturability of RF filters with the unprecedented filter performance in terms of insertion loss and out of band rejections in smaller form factor than any other technologies have achieved so far. Furthermore, the TGV filters were mounted on electrical evaluation boards as well as JEDEC standard testing boards to check any device-level, chip-level, and board-level reliabilities associated with glass or TGV materials as well as their interaction with Cu, SiN, polymer inter layer dielectric materials, and solder joints, showing no performance degradations during thermal cycling, drop shock, bending, or high-power testing situations.

The increasing demand for radar sensors and the wide distribution of handheld communication devices push the development of low-cost components with a small form factor. One approach to achieve smaller, low-cost devices is the integration of the required components on a monolithic microwaveintegrated circuit (MMIC). At frequencies above 100 GHz, passive components are small enough to be integrated onto a chip, and the advances in semiconductor technology make it possible to build active components that can operate at millimeter (mm)-wave frequencies [1], [2]. The available bandwidths of several gigahertz at mm-wave frequencies offer high data rates for communication devices or high resolution for remote-sensing applications. By integrating the radio-frequency (RF) components and the antennas, lossy off-chip transitions can be avoided, thus limiting the required connections to the power supply and baseband signals.

Although wireless sensor networks (WSNs) have been an active field of research for many years, the modules incorporated by WSN nodes have been mainly manufactured utilizing conventional fabrication techniques that are mostly subtractive, requiring significant amounts of materials and increased chemical waste. The new era of the Internet of Things (IoT) will see the fabrication of numerous small form factor devices for wireless sensing for a plurality of applications, including security, health, and environmental monitoring. The large volume of these devices will require new directions in terms of manufacturing cost and energy efficiency, which will be achieved with redesigned, energy-aware modules. This paper presents the state of the art of printed passives, sensors, energy harvesting modules, actives, and communication front ends, and summarizes the challenges of implementing modules that feature low power consumptions without compromising the low fabrication cost. The plethora of the modules presented herein will facilitate the implementation of low cost, additively manufactured, energy-aware IoT nodes that can be fabricated in large volumes with green processes.

We have developed a rechargeable fetal micropacemaker in order to treat severe fetal bradycardia with comorbid hydrops fetalis. The necessarily small form factor of the device, small patient population, and fetal anatomy put unique constraints on the design of the recharging system. To overcome these constraints, a custom high power field generator was built and the recharging process was controlled by utilizing pacing rate as a measure of battery state, a feature of the relaxation oscillator used to generate stimuli. The design and in vitro and in vivo verification of the recharging system is presented here, showing successful generation of recharging current in a fetal lamb model.

Specific detection of protein biomarkers has a wide range of applications in areas such as medical science, diagnostics, and pharmacology. Quantitative detection of protein biomarkers in biological media, such as serum, is critically important in detecting disease or physiological malfunction, or tracking disease progression. Among various detection methods, electrical detection is particularly well suited for point-of-care (POC) specific protein detection, being of low cost, light weight and small form factor. A portable system for sensitive and quantitative detection of protein biomarkers will be highly valuable in controlling and preventing diseases outbreaks. Recently, an alternating current electrokinetic (ACEK) capacitive sensing method has been reported to demonstrate very promising performance on rapid and sensitive detection of specific protein from serum. In this work, a low cost and portable analyzer with good accuracy is developed to use with ACEK capacitive sensing to produce a true POC technology. The development of a board-level capacitance readout system is presented, as well as the adaption of the protocol for use with ACEK capacitive sensing. Results showed that the developed system could achieve a limit of detection of 10 ng/mL, comparable to a sophisticated benchtop instrument. With its small size and light-weight similar to a smart phone, the developed system is ready to be applicable to POC diagnostics. Further, the readout system can be readily expanded for multichannel monitoring and telecommunication capabilities.