Investigation of fabrication and encapsulation processes for a flexible tag microlab

The aim of this paper is to present an integrated process flow for a smart tag with integrated sensors and RFID communication, a flexible tag microlab (FTM). The heart of the designed container tracing system is an RFID system (Reader + Tag) with gas sensing capabilities on board. In the former prototypes, the chemical sensors were integrated on the reader, whereas the tags where addressed like conventional RFID-tags containing also physical (temperature, humidity and light) sensors. However, this paper will show how the gas sensing reader functionalities are being transferred to the tag, reaching a FTM, which represents a real innovation in the field of flexible labels. Key issues for the realisation of the FTM, such us flexible substrates and gas sensor integration technologies will be presented. The process flow employed for the two metal levels interconnect fabrication will be described in detail. The material used is the DuPont? Pyralux^® AP 8525R double-sided copper-clad laminate, formed by a Kapton foil with a copper layer on each side. The vias and windows openings are performed by femtosecond laser ablation. The copper interconnections are realized by photolithography and wet chemical etching. The MOX sensors hotplates specially developed to fulfil the FTM constrains in terms of low power consumption has been used to prove two integration technologies into the flexible substrates: chip on flex (COF) wire bonding and anisotropic conductive adhesive (ACA) flip chip bonding. Both technologies will be compared and benchmarked for future product developments.     

Optimization of a wafer-level process for the fabrication of highly reproducible thin-film MOX sensors

Thin-film metal oxide semiconductor (MOX) gas sensors are characterized by high sensitivity and fast response. Those characteristics make them very promising among the several existing technologies for the production of solid state gas sensors. Furthermore, by means of silicon micro-machining technology, MOX sensors can be made on micro hotplates, allowing to reach very low-power consumption, and the batch production guaranties a high yield. However, reproducibility and reliability are still major issues preventing the use of thin-film MOX sensors in mass-market applications.

In this work, a wafer-level fabrication process for micro-machined low-power consumption thin-film MOX sensor arrays is reported. Different solutions for the optimization of the fabrication process are investigated, aiming to increase the reproducibility. The critical technological steps related to signal generation and acquisition, like the thin-film definition and positioning and the definition of the sensing layer electrodes, have been optimized. The devices considered are 4-sensor arrays based on thin films of SnO₂ deposited by a modified rheotaxial growth and thermal oxidation (M-RGTO) technique on micro-machined low-power hotplates.

The different fabrication techniques are described in detail. 45 sensors from 3 wafers, made using the different fabrication techniques, are comparatively characterized. The spread of the main sensor functional parameters values shows an evident decrease when the optimized fabrication process is used.     

Zeroing for HW-efficient compressed sensing architectures targeting data compression in wireless sensor networks

The design of ultra-low cost wireless body sensor networks for wearable biomedical monitors has been made possible by today technology scaling. In these systems, a typically multi-channel biosignal sensor takes care of the operations of acquisition, data compression and final output transmission or storage. Furthermore, since these sensors are usually battery powered, the achievement of minimal energy operation is a fundamental issue. To this aim, several aspects must be considered, ranging from signal processing to architectural optimization. In this paper we consider the recently proposed rakeness-based compressed sensing (CS) paradigm along with its zeroing companion. With respect to a standard CS base sensor, the first approach allows us to further increase compression rate without sensible signal quality degradation by exploiting localization of input signal energy. The latter paradigm is here formalized and applied to further reduce the energy consumption of the sensing node. The application of both rakeness and zeroing allows for trading off energy from the compression stage to the transmission or storage one. Different cases are taken into account, by considering a realistic model of an ultra-low-power multicore DSP system.     

一种用于食品链信息管理的RFID读写器的设计

介绍了一种符合ISO/IEC 15693协议的电子标签读写器系统,提出了一种适合于食品链信息管理的便携式RFID读卡器设计方案.该读卡器系统包括控制模块、射频识别通信模块、无线传感网数传模块、信息存储模块、电源管理模块、网络接口模块以及服务器数据备份等.本文主要介绍系统备模块的框架设计,并给出了信息的处理方法.     

Flexible and large area pressure sensors for human-neuroprostheses and human-neurorobotic interface assessment

Promising results on flexible and large area pressure sensors for human-neuroprostheses and human-neurobotic interface assessment are presented. Sensor arrays of 4?×?4 and 8?×?8 based on a plastic electronics concept, with a resolution of 1 and 0.25?cm², respectively, have been fabricated and characterized. The working pressure range is between 0 and 1?kg/cm² and the offset measured is around 0.03?kg/cm². The response time is around 1?ms. Using these sensor arrays, a sedestation–bipedestation field test by a pressure sensor integrated in a gait orthosis has been carried out in order to corroborate the medical application scenarios cerebrovascular accidents, spinal cord injuries and cerebral palsy.     

利用探测器网状网络解决RFID通信中的阴影区域问题

在当今社会的各个领域,无线探测器网络被认为是一种十分有效的环境探测和信息收集工具,因此如何使用和如何提高探测网络的性能成为了研究热点。在装载和使用RFID电子探测器(Tag)集装箱的物流港口和物流仓库里,对读取器(Reader)和电子探测器(Tag)的通信范围以外存在阴影区域的问题进行观察和研究后,提出通过网状网络的特性来解决这一问题。不仅对解决读取器(Reader)和电子探测器(Tag)之间不能通信的阴影区域有很大的帮助,同时与通常增加读取器(Reader)的方式相比较,这一方案还可以减少安装基础设备的费用。更重要的一点是,对于不适合安装读取器这样的网络基础设施的地方,只能安装电子探测器(Tag),利用这一方案快速地构建覆盖整个区域的无线网络。实验结果及其分析表明,该方案能够在解决RFID通信中产生的阴影区域问题上获得理想的效果。     

Autonomous planar conductivity array sensor for fast liquid distribution imaging in a fluid coupling

In this article, we introduce a new autonomous planar array sensor based on the measurements of electrical conductivity which has been applied to the visualization of fluid distributions inside a fluid coupling during normal operation. The sensor is composed of approximately 1000 interdigital sensing structures which are used to measure the two-dimensional electrical conductivity distribution at the sensor's surface with a fast multiplexed probing–sensing scheme at up to 10 kHz frame rate. Two such sensors were used to measure dynamic two-phase flow patterns in a fluid coupling at full operation at 790 rpm speed. Therefore, the sensors were mounted on the pressure-side and the suction-side walls of a blade channel inside a test coupling. The whole measurement system is run on a battery and controlled via wireless link, thus being fully autonomous, which enables sensor and electronics to rotate together with the coupling.     

Structural environmental informatization using sensor network with heterogeneous sensors

In the present paper, a configuration of a sensor network system for monitoring the usage patterns of a house is proposed. The sensor network system has many active type radio-frequency identifications (RFIDs) as a network node. The RFID has advantages of low cost and low power consumption. Also the RFID can connect various sensors for measuring environment information, since having I/O port as external interface. Environment information is stored on a database through the RFID’s wireless radio communication function. The sensor types in this system are variety from slow changing information like temperature and humidity data to event notification like a human detection data. The paper will be described a acquisition procedure for various characteristic sensor data on the same sensor network. Also, the installation locations of the sensors are critical for highly accurate detection of the environmental conditions. Finally, based on the sensor data, capability of analysis of the usage pattern for a house will be discussed.     

RFID Authentication Efficient Proactive Information Security within Computational Security

We consider repeated communication sessions between a RFID Tag (e.g., Radio Frequency Identification, RFID Tag) and a RFID Verifier. A proactive information theoretic security scheme is proposed. The scheme is based on the assumption that the information exchanged during at least one of every n successive communication sessions is not exposed to an adversary. The Tag and the Verifier maintain a vector of n entries that is repeatedly refreshed by pairwise xoring entries, with a new vector of n entries that is randomly chosen by the Tag and sent to the Verifier as a part of each communication session. The general case in which the adversary does not listen in k≥1 sessions among any n successive communication sessions is also considered. A lower bound of n⋅(k+1) for the number of random numbers used during any n successive communication sessions is proven. In other words, we prove that an algorithm must use at least n⋅(k+1) new random numbers during any n successive communication sessions. Then a randomized scheme that uses only O(nlog n) new random numbers is presented. A computational secure scheme which is based on the information theoretic secure scheme is used to ensure that even in the case that the adversary listens in all the information exchanges, the communication between the Tag and the Verifier is secure.     

超高频RFID标签芯片基带处理器的低功耗设计

设计了一种符合ISO18000-6B协议的超高频无源电子标签的数字基带处理器,芯片采用TSMC 0.18μm 1P5M嵌入式EEPROM的混合CMOS工艺实现,己成功通过流片,并对其进行了验证和测试.从测试结果看,本芯片完成了符合ISO18000-6B协议的所有强制命令以及部分建议命令,达到完成标签盘存操作、读写操作以...     

Data aggregation in sensor networks: Balancing communication and delay costs

In a sensor network the sensors, or nodes, obtain data and have to communicate these data to a central node. Because sensors are battery powered they are highly energy constrained. Data aggregation can be used to combine data of several sensors into a single message, thus reducing sensor communication costs at the expense of message delays. Thus, the main problem of data aggregation is to balance the communication and delay costs.     

金属氧化物气体传感器阵列参数的讨论

本文对金属氧化物气体传感器特性进行分析，提出传感器阵列的灵敏度矩阵与被测气体浓度矢量和传感器阵列中各传感器响应矢量间的夹角有关。从而得出气体传感器阵列的灵敏度为各气体浓度矢量与传感器输出矢量夹角余弦的关系。     

Capacitive flexible pressure sensor: microfabrication process and experimental characterization

Kapton-based flexible pressure sensor arrays are fabricated using a new technology of film transfer. The sensors are dedicated to the non-invasive measurement of pressure/force in robotic, sport and medical applications. The sensors are of a capacitive type, and composed of two millimetric copper electrodes, separated by a polydimethylsiloxane (PDMS) deformable dielectric layer. On the flexible arrays, a very small curvature radius is possible without any damage to the sensors. The realized sensors are characterized in terms of fabrication quality. The inhomogeneity of the load free capacitances obtained in the same array is ±7 %. The fabrication process, which requires 14 fabrication steps, is accurate and reproducible: a 100 % transfer yield was obtained for the fabrication of 5 wafers gathering 4 sensor arrays each (215 elementary sensors). In the preliminary electro-mechanical characterization, a sensor (with a PDMS dielectric layer of 660 μm thickness and a free load capacitance of 480 fF) undergoes a capacitance change of 17 % under a 300 kPa normal stress.     

Locating sensor nodes on construction projects

Localization of randomly distributed wireless sensor nodes is a significant and fundamental problem in a broad range of emerging civil engineering applications. Densely deployed in physical environments, they are envisioned to form ad hoc communication networks and provide sensed data without relying on a fixed communications infrastructure. To establish ad hoc communication networks among wireless sensor nodes, it is useful and sometimes necessary to determine sensors’ positions in static and dynamic sensor arrays. As well, the location of sensor nodes becomes of immediate use if construction resources, such as materials and components, are to be tracked. Tracking the location of construction resources enables effortless progress monitoring and supports real-time construction state sensing. This paper compares several models for localizing RFID nodes on construction job sites. They range from those based on triangulation with reference to transmission space maps, to roving RFID reader and tag systems using multiple proximity constraints, to approaches for processing uncertainty and imprecision in proximity measurements. They are compared qualitatively on the basis of cost, flexibility, scalability, computational complexity, ability to manage uncertainty and imprecision, and ability to handle dynamic sensor arrays. Results of field experiments and simulations are also presented where applicable.     

无线传感器网络的安全机制

近年来，随着微电子技术和无线通信技术的进步，推动了低功耗、低价格、多功能传感器的快速发展，进而也促进了无线传感器网络的发展．无线传感器网络在军事、医疗、商业等多个领域均有广阔的应用市场．针对无线传感器网络的特点，本文主要阐述它在通信过程中存在的安全威胁、分析它的安全需求和采取的安全机制，确保无线通信的安全．     

Proposal for preprogrammed control applied to a current-sensorless PFC boost converter

The development of front-end converters for power factor correction and DC link voltage control of power electronics converters such as, UPS, Inverters, and Switched Power Supplies, has been attracting great interest from the scientific community that works toward the achievements of cost reduction, high efficiency, and reliability. In this context, this paper proposes a microprocessed control technique for sinusoidal input line current imposition in front-end ac–dc converters. This gave rise to an innovative sensorless boost converter, named in this work as PFC-Boost-CSL. The proposed method is based on experimental acquisition of gate-drive signal sequences for different load conditions. These signals correspond to a complete cycle of the AC input voltage and are recorded in the microcontroller memory in order to be reproduced when used in a boost converter without current sensor. In the operation of PFC-Boost-CSL, a suitable switching sequence is sent to drive the power switch in order to minimize output voltage error and maintain a sinusoidal input current. Aiming to prove the proposed control concept, a 600 W PFC-Boost-CSL prototype was built and analyzed in laboratory and the main experimental results are presented herein.     

High precision intelligent flexible grasping front-end with CMOS interface for robots application用于智能机器人精细抓握的高灵敏度柔性抓握前端

This paper presents a high-precision intelligent flexible robot grasping front-end with an integrated capacitive tactile sensor array and a conditioning chip. The capacitive tactile sensor is the primary part of the front-end, it determines the overall performance. The micro-needle array sandwich structure in the tactile sensor increases the repeatability and stability, and ensures the sensitivity. The assembled sensor exhibits a saturation at 10.53 N (421 kPa) with a sensitivity of 1.9%/kPa. Furthermore, a conditioning chip is utilized in a custom readout interface to achieve better performance by reducing signal attenuation, and to increase the compatibility of the front-end. The chip is optimized for the parasitic shunt capacitance in the capacitor array. A dual bidirectional charge-discharge conversion method and a two-port detection method are matched to achieve the goal of reducing the shunting influence, and attenuating the offset voltage or the noise input effects. A prototype of the interface has been fabricated using 180-nm CMOS technology. Sensor with the value of 0.5 pF shunted by capacitors of 47 pF has been detected with an error of 1% within 100 μs.     

Fabrication of wireless sensors on flexible film using screen printing and via filling

Wireless sensors are fabricated on flexible plastic films by means of screen printing and via-hole filling. The wireless sensors are battery free with data and power transmission functions. The sensors, fabricated on polyethylene terephtalate films, are designed based on RFID technology. Using an additive patterning process known as screen printing, metallization on polymer films is created. Both sides of a polymer film are printed with metallic patterns and connected with micro vias filled with conductive paste. One side of the film consists of printed electrical traces for discrete components like resistors and transistors that would be mounted onto it; the other side consists of a printed inductive coil used for wireless data and power transmission. The micro vias, which have a diameter of 120 μm, are formed by mechanical punching and filled with conductive silver paste. The size of one sensor unit is approximately 2 cm × 1.5 cm; an array of 4 × 7 sensor units are printed over an area of 15 cm × 15 cm on a PET film. Details of manufacturing processes, component assembly and functionality test are presented in this paper.     

CMOS图像传感技术及其在影像产品中的应用

随着超大规模集成技术的发展，CMOS图像传感器显示出强劲的发展趋势。CMOS图像传感器具有在单芯片内集成时序和控制电路、A／D转换、信号处理等功能。本文介绍了CMOS图像传感器的结构和工作原理，并与CCD图像传感器进行比较，综述了CMOS图像传感器的最新进展及其在影像产品中的应用。     

Flexible hot-film anemometer arrays on curved structures for active flow control on airplane wings

A set of flexible MEMS sensor arrays for flow measurements in boundary layers is presented. The sensor principle of these anemometers is based on convective heat transfer from a hot-film into the fluid. Each sensor consists of a nickel sensing element between copper supply tracks. The functional layers are attached either on a ready-made polyimide foil or on a spin-on polyimide layer. These variants are designed to meet the requirements of measurements in different environments. Spin-on technology enables the use of very thin polyimide layers, ideally suited for measurements in transient flows. It is a unique characteristic of the presented arrays that their total thickness can be scaled from 7 to 52 μm. This is essential, because the sensor thickness has to be adapted to the varying thickness of the boundary layers in different aerodynamic tests. With these sensors we meet the special requirements of a wide range of fluid mechanic experiments but in particular those of future active flow control on airplane wings. For less critical flow conditions with much thicker boundary layers, thicker sensors might be sufficient and cheaper, so that sensors fabricated on ready-made foils are perfect for these applications. Since the presented sensors are flexible, they can be attached on curved aerodynamic structures without any geometric mismatches. The entire development, starting from theoretical investigations, is described. Further, the micro-fabrication is discussed, including photolithography, sputtering and wet-etching. In particular the wet-etching of the sensing element is found to be critical for the functional characteristics.