The "e-Grain" Concept Building Blocks for Self-Sufficient Distributed Microsystems

In information and communication technology, the future has already begun. The transfer of vast amounts of data is routinely done via the Internet, and mobile or portable multiple-use devices or workstations ensure that the information we require is at ready hand, anywhere and at any time. System integration technologies and the Internet as a user platform will soon succeed to be even more integral parts of our daily lives, at work as well as in the home. The trend in PC or smaller device development tends towards ever tinier, ever more complex and autonomous systems, which communicate via interfaces. This means that their miniaturization is quickly advancing and eventually leading to integrated 3D-microsystems of very few cubic millimeters only. The project "Self-sufficient distributed microsystems AVM* aims to investigate certain aspects of and technologies for these systems as well as to develop solutions which will make a significant contribution to meeting the challenges presented by them. Übersicht In der Informationsund Kommunikationstechnik hat die Zukunft schon begonnen. Das Internet erlaubt den grenzenlosen Datentransfer; mobile universell einsetzbare Endgeräte machen Informationen immer und überall verfügbar. In absehbarer Zeit werden die Systemintegrationstechnologien und das Internet als Anwendungsplattform immer schneller und umfassender alle Bereiche unseres beruflichen und privaten Lebens verändern. Bei der Geräteentwicklung geht der Trend hin zu immer kleineren, komplexeren und autarken Systemen, welche über Schnittstellen miteinander verbunden sind. Dabei schreitet die Miniaturisierung der Geräte immer weiter voran und wird in vemetzten, wenigen Kubikmillimeter großen 3-dimensionalen Mikrosystemen münden. Für die Dokumentation e-Grain / Autarke Mikrosysteme / Systemintegration Frequenz 58(2004) 3-4 1. A new approach to system integration and the realization of self-sufficient distributed microsystems With microelectronics as the technology and the Internet as its applications platform, the changes to all areas of our professional and private lives will be ever-more rapid and far-reaching. Today, visions of the future are all founded on a common theme: Seamless communication based on the Internet and mobile multifunctional terminal devices. As is apparent with mobile phones, the trend is moving towards smaller, more complex, autonomous systems, in which phoning itself is of diminishing, almost insignificant importance. The mobile phone is emerging as a universal information and communication terminal, characterized by extreme miniaturization and the integration of a wide range of Services. This trend will inevitability be carried forward into the future. In the process, present-day systems integration requires production of ever-more complex systems, comprising an increasing number of active and passive components while reducing production costs. In order to reduce the physical space requirements of a system, researchers are firstly looking to develop new integration technologies which also use the third dimension for systems integration; secondly, they need an alternative to replace the conventional method of systems integration. This represents the framework for a new concept of systems integration, based on so-called "electronic grains" "e-Grains" [1]. -Grains are tiny, autonomous, functional units, and are distinctive, not only through their ability to communicate with each other, but also because they are freely programmable and to a certain degree modular. At the same time, these units are universal and partly specialized, for example, through the integration of selective sensors. (Fig. 1) * Fraunhofer Institute for Reliability and Microintegration Rg. 1: " -Grain' application scenario: In the near future a hundred gram of 'system dust', " -Grain", will fulfill a specific demand in the information and communication technology. The independent, functional units could be integrated in every one's environment, connected into a global and home network 2. From self-sufficient distributed microsystems to electronic grains (e-Grains) In terms of hardware, technology and software design, system integration based on the innovative "e-Grain" concept represents an entirely new challenge and requires a synergy of individual technologies at an exceptionally early stage. And naturally, through the differing nature of the approaches used to find a system solution, it also holds a particular techno-scientific appeal, at the same time yielding extremely high innovative potential. This technology poses particular challenges with regard to the desirable sizes (a few cubic millimeters), the need to achieve continuous operation through an integrated or external wireless power supply, and the necessity of allowing multiple e-Grains to 51 Frequenz communicate. The system is characterized by a large number 58 (2004) of individual interconnected "e-Grains". The "e-Grain" vision 3-4 therefore represents a new approach to system integration that will help to develop complex, flexible and cost-efficient integrated systems with black-start capability, based on ultra-small subcomponents. Due to the high density required for integration, the realization of "e-Grains" necessarily involves stacking thin functional films which are then bonded together. To do this, a new three-dimensional bonding technique based on conductive polymer films is under consideration. The development of highly integrated three-dimensional wiring calls for a vertical-integration technology that allows interconnections to be fabricated and precisely aligned on ultra-thin substrates. The production of ultrathin functional films as well as their integration to form a complete wafer-level system is therefore a key technology. In addition to reducing the size of active chip surfaces, the miniaturization of passive components is also fundamentally important for the complete system. The "e-Grain" system requires that the tiny electronic units are capable of meeting their own energy requirements autonomously, over a certain period of time or during their entire operating life. This necessitates energy storage devices with high power density compatible with the system in terms of dimensions and production technology. Another important task of the "e-Grain" system is wireless linking of individual "eGrain" cells. Microwave front end technology will therefore assume a key position as a connecting link between data-processing electronics and the transmission channel. Communication between the large number of tiny, highly integrated "e-Grains" presents a particular challenge in the design and implementation of this communications system. One of the important parameters for communication between a number of "e-Grains" is the available energy capacity which is greatly limited by the low volume. Special attention is also given to the way in which two individual "e-Grains" communicate, address assignment within a self-organized network, a flexible semantics-based grouping of messages within an "e-Grain" network as well as interfaces to applications and management The creation of a self-organized ad-hoc network that can comprise a large arbitrary number of "e-Grains" requires a suitable operating-system environment that provides the necessary administration service. In its entirety, this form of ad-hoc network can be seen as the configurable system, whereby the networked components represent the configurable resources. The actual operating system provides the necessary administration services to monitor and control this type of system. This also includes the programming of individual "e-Grains". In addition, the operating system offers a μ-network interface though which the applications themselves can access the network components. For linking the "e-Grain" μ-network to other networks (LAN, Internet), the operating system provides gateways with the corresponding address and protocol conversion functions. Consequently, the "e-Grain" concept endeavors to link all types of system integration techniques. The objective supports the future creation of complex, hyper-miniaturized systems. Moreover, they will be autonomous, small, efficient, mobile, interactive and will feature wireless and bi-directional data communication. The "e-Grain" concept makes it possible to produce cost-effective microsystems based on standardized miniature modules which are wireless connected in a μ-network and linked to other existing local and global networks. The basic idea for "e-Grains" has already found world-wide acceptance as a strategic goal, and similar approaches such as the so-called 'ubiquitous systems' are under investigation. Scientists at Berkeley University are working on programs called "Smart Dust" and "Pico Radio for autonomous sensor networks" [2, 3], and at the MIT-Media Lab they are working on networking of wireless distributed sensor systems [4]. In Europe there are activ52 ities on Pervasive Computing at the ΕΤΗ Z rich [5] (Fig. 2). • Self-sufficient > Wireless, bidirectional communication