Query: fpcb，wearable

title: Wireless battery free wearable sweat sensor powered by human motion
abstract: Wireless battery free wearable sensor powered by human motion is able to analyze sweat biomarkers for personalized health care. Wireless wearable sweat biosensors have gained huge traction due to their potential for noninvasive health monitoring. As high energy consumption is a crucial challenge in this field, efficient energy harvesting from human motion represents an attractive approach to sustainably power future wearables. Despite intensive research activities, most wearable energy harvesters suffer from complex fabrication procedures, poor robustness, and low power density, making them unsuitable for continuous biosensing. Here, we propose a highly robust, mass producible, and battery free wearable platform that efficiently extracts power from body motion through a flexible printed circuit board (FPCB) based freestanding triboelectric nanogenerator (FTENG) The judiciously engineered FTENG displays a high power output of ~416 mW m 2. Through seamless system integration and efficient power management, we demonstrate a battery free triboelectrically driven system that is able to power multiplexed sweat biosensors and wirelessly transmit data to the user interfaces through Bluetooth during on body human trials.

title: Wearable Circuits Sintered at Room Temperature Directly on The Skin Surface for Health Monitoring.
abstract: A soft body area sensor network presents a promising direction in wearable devices to integrate on body sensors for physiological signal monitoring and flexible printed circuit boards (FPCBs) for signal conditioning/readout and wireless transmission. However, its realization currently relies on various sophisticated fabrication approaches such as lithography or direct printing on a carrier substrate before attaching to the body. Here we report a universal fabrication scheme to enable printing and room temperature sintering of metal nanoparticle on paper/fabric for FPCBs and directly on the human skin for on body sensors with a novel coating layer. Consisting of polyvinyl alcohol (PVA) paste and nanoparticle additives in the water, the novel coating layer reduces the sintering temperature. Together with the significantly decreased surface roughness, it allows for the integration of a submicron thick conductive pattern with enhanced electromechanical performance. Various on body sensors integrated with an FPCB to detect health conditions illustrate a system level example.

title: Water Splitting Assisted Electrocatalytic Oxidation of Glucose with Metal Organic Framework for Wearable Nonenzymatic Perspiration Sensing.
abstract: In this work, a nonenzymatic electrochemical sensor based on electrochemical water splitting assisted electrocatalysis is developed for wearable perspiration glucose analysis. Pd nanoparticles (Pd NPs) encapsulated in Co based zeolitic imidazolate framework (ZIF 67) is prepared and used as the electrocatalyst. In comparison to previously reported nonenzymatic glucose sensors which detect glucose in alkaline buffers, the proposed sensor analyses glucose under physiological pH with no additional reagents, which enables wearable, maintenance free perspiration glucose monitoring for a long time. The non enzymatic sensor and a flexible printed circuit board (FPCB) is integrated into a sweatband for real time analysis of perspiration glucose. The test results of perspiration glucose using our sensor are correlated to those of blood glucose tests by a commercial glucose meter. The sensitivity of the sensor remains stable within 2 months when it is stored unpacked at ambient conditions. Therefore, we believe it is promising for wearable nonenzymatic glucose monitoring for noninvasive clinical analysis and sport applications.

title: Wearable thermoelectric generator to harvest body heat for powering a miniaturized accelerometer
abstract: Wearable thermoelectric generators (TEGs) enable the conversion of human body heat into microwatts to milliwatt electricity, which can be utilized to power miniaturized electronic devices for motion detection and healthcare monitoring. This paper presents a novel wearable TEG with 52 pairs of cubic shaped thermoelectric legs to harvest human body heat. The thermoelectric legs are made of P type and N type Bi2Te3 based powder materials, and are connected electrically in series through soldering. The flexible printed circuit board (FPCB) with special holes is designed and used as substrate to enhance the flexibility of the TEG for wearable applications. The performances of the TEG, including the bulk thermoelectric legs, are characterized. The results show that the TEG can generate an open circuit voltage of 37.2 mV at DT 50 K, and the internal resistance of the TEG is quite low at a value of 1.8 O. Then the TEG was worn on a human wrist to harvest body heat and power a 3 axis miniaturized accelerometer for detection of body motion at DT 18 K. The results demonstrate that the developed wearable TEG features high output performance and could be utilized for powering electronics and/or sensors by harvesting human body heat.

title: Position: Smart KT Tape A Bendable Wearable System for Muscle Fatigue Sensing
abstract: We see a major hurdle, as well as a window of opportunity, in wearable system design making the system soft and bendable for skin surface sensing. In this position statement, we present our design of an FPCB (flexible printed circuit board) based wearable system for muscle fatigue sensing, referred to as the Smart KT Tape.

title: Flexible heartbeat sensor for wearable device.
abstract: We demonstrate a flexible strain gauge sensor and its use in a wearable application for heart rate detection. This polymer based strain gauge sensor was fabricated using a double sided fabrication method with polymer and metal, i.e. polyimide and nickel chrome. The fabrication process for this strain gauge sensor is compatible with the conventional flexible printed circuit board (FPCB) processes facilitating its commercialization. The fabricated sensor showed a linear relation for an applied normal force of more than 930 kPa, with a minimum detectable force of 6.25Pa. This sensor can also linearly detect a bending radius from 5mm to 100mm. It is a thin, flexible, compact, and inexpensive (for mass production) heart rate detection sensor that is highly sensitive compared to the established optical photoplethysmography (PPG) sensors. It can detect not only the timing of heart pulsation, but also the amplitude or shape of the pulse signal. The proposed strain gauge sensor can be applicable to various applications for smart devices requiring heartbeat detection.

title: Flexible Hybrid Electronics: Direct Interfacing of Soft and Hard Electronics for Wearable Health Monitoring
abstract: The interfacing of soft and hard electronics is a key challenge for flexible hybrid electronics. Currently, a multisubstrate approach is employed, where soft and hard devices are fabricated or assembled on separate substrates, and bonded or interfaced using connectors; this hinders the flexibility of the device and is prone to interconnect issues. Here, a single substrate interfacing approach is reported, where soft devices, i.e. sensors, are directly printed on Kapton polyimide substrates that are widely used for fabricating flexible printed circuit boards (FPCBs) Utilizing a process flow compatible with the FPCB assembly process, a wearable sensor patch is fabricated composed of inkjet printed gold electrocardiography (ECG) electrodes and a stencil printed nickel oxide thermistor. The ECG electrodes provide 1 mVp p ECG signal at 4.7 cm electrode spacing and the thermistor is highly sensitive at normal body temperatures, and demonstrates temperature coefficient, a 5.84% K 1 and material constant, b 4330 K. This sensor platform can be extended to a more sophisticated multisensor platform where sensors fabricated using solution processable functional inks can be interfaced to hard electronics for health and performance monitoring, as well as internet of things applications.

title: Systematic study and experiment of a flexible pressure and tactile sensing array for wearable devices applications
abstract: In this paper, we present the development of a 10 x 10 sensing element capacitive flexible pressure and tactile sensing array for normal stress measurement for wearable device applications. The sensor array combines micro fabricated polydimethylsiloxane (PDMS) structures and a flexible printed circuit board (FPCB) with 100 um thick polyimide as substrate. Each sensing element has one Cr/Au floating electrode embedded in the PDMS, two Cu/Au sensing electrodes on the FPCB and two Cu electrodes embedded underneath in the FPCB for electromagnetic shielding to isolate the environmental influence from the surface where the sensor patch is placed. The PDMS based pressure sensing membrane inbetween the floating electrode and sensing electrodes was specifically designed and fabricated. The thickness of the sensing membrane ranged from 0.6 1.3 mm. To increase the device sensitivity a membrane with micro pillar was also selected. Membrane with various structures, different micro pillar height and without pillar were fabricated and characterized. Two sensing elements with different sizes but the same pitch on the sensors were compared, regarding the device sensitivity, sensing range and the cross talk influence of the sensing elements. Results from 16 devices with different structures were obtained. Lastly, the hysteresis effect of the sensor and temperature influence was tested and analyzed. The corresponding 10 x 10 scanning circuits were implemented and the 100 sensing measurement results were displayed in 0.8 s periods in real time. The developed pressure/tactile sensors with different sensing range and sensitivity provide a guide for the design and selection of pressure/tactile sensing devices with a variety of applications.

title: Design of a Wearable Thermoelectric Generator for Harvesting Human Body Energy
abstract: This paper presents the design and fabrication of a wearable thermoelectric generator (TEG) with high power density for harvesting the human body heat energy. The proposed TEG was fabricated using a flexible printed circuit board (FPCB) as the substrate. The P type and N type thermoelectric blocks were made of Bi2Te3 based thermoelectric material and welded on the FPCB, and they were surrounded by the soft PDMS material. The prototyped TEG consisted of 18 thermocouples, which was connected by FPCB and silver paste over an area of 42 x 30 mm2. The fabricated TEG could generate a voltage of 48 mV for a temperature difference of 12 K. Then, the TEG was mounted onto the human wrist skin to harvest the human body heat energy. Results showed that the measured output power was 130.6 nW at ambient temperature of 25 degC. Thus, the developed TEG has the potential for human body heat energy harvesting and utilized for the development of wearable self powered mobile devices.

title: Evaluation of body worn FPCBs with bluetooth low energy, capacitive touch, and resistive flex sensing
abstract: Commercially available flexible printed circuit boards (FPCBs) have the potential to embed electronics, connectivity, and interactivity into the same surface. This makes them an ideal platform for untethered and interactive wearable devices. However, we lack an understanding how well FPCB based antennas and sensors perform when worn directly on the body. This work contributes an understanding by studying body worn FPCBs in three technical evaluations: First, we study the integration of Bluetooth Low Energy and compare the signal strength of our body worn FPCB with a rigid BLE developer board. Second, we study the accuracy of capacitive touch sensing with two electrode sizes. Finally, we develop a resistive flex sensor based on commercially available FPCB materials and compare its accuracy with a state of the art flex sensor. Taken together, our results demonstrate a high usability of FPCB based wearable devices.