SAND: a modular application development platform for miniature wireless sensors Martin Ouwerkerk, Frank Pasveer, Nur Engin Philips Research, Eindhoven, The Netherlands martin.ouwerkerk@philips.com Abstract A modular application development platform for miniature wireless sensor/actuator devices called Small Autonomous Network Devices (SANDs) is described. As an application example a system power breakdown of a real-time ECG analysis is presented. The application development SANDs have a volume of about one cubic centimeter. Based upon testing and optimization the schematics and specifications are obtained for the mass-production SANDs. Utilizing System in Package (SiP) technology the volume can be reduced up to five times. These devices can be used in a truly unnoticeable and unobtrusive way to serve as the smallest components of a personal health care monitoring system or an ambient intelligence system. Introduction Current state-of-the-art technology in wireless sensor networks has opened the way to miniaturized health monitoring systems, the so-called body sensor networks. They provide the opportunity for continuous monitoring and analysis of physiological parameters. In case of calamities a warning can be wirelessly send to the user and/or doctor. Field testing application opportunities of miniature wireless sensors is usually done with custom made off the shelf electronics. This often results in relatively large and poorly packaged devices. The Mote-series of sensor platforms (see, for example [1]) developed by University of California at Berkeley and sold commercially by Crossbow Inc. and MoteIV [2] have become one of the best-known research tools in sensor networking. Typical design of a mote comprises a small PCB on which a simple micro-controller, various interfaces, and a wireless communication subsystem (predominantly IEEE 802.15.4 in recent designs) is installed. Although these sensors “work well”, they are unpackaged which is a major disadvantage for field testing. The solution to the packaging problem boils down to solving the problem of stacking and connecting multiple chips in a single sealed package. The best-known manufacturing examples are the Philips, IMEC and VDMA systems. One of the smallest packaged 3D stacked sensor systems is the device developed at IMEC in the HUMAN++ Project [3]. The working group Match-X [4] in the German Engineering Association VDMA developed another small but modular device. It consists of different building blocks, measuring 12.5x12.5 mm, each having a different functionality. Recently, a re-configurable sensor system has been developed at Philips Research called SAND (Small Autonomous Network Devices). The SAND solution has the advantage of providing a packaged system being fully reconfigurable while preserving its hermetic properties, allowing even use for implantable devices. The package target size is to be about 1 cm 3 and have an average energy consumption that is low enough to allow field testing of applications. The present article aims at an overview of the technology behind the sensor platform, and will discuss the feasibility of a specific application taking into account all the requirements concerning power- management. Hardware description A reconfigurable modular approach was chosen for SAND, although from a miniaturization point of view it does not yield optimal results. Each module has a specific functionality, such as transceiver, micro- controller, power supply or sensor. With this approach a large number of different configurations becomes possible with a limited number of different modules. A variety of applications both for body sensor networks and for other areas can therefore make use of the same technology. In Figure 1 an exploded view of a typical device is shown. The outer diameter of the modules is 14 mm resulting in a device volume of 1-2 cubic centimeter. Proceedings of the International Workshop on Wearable and Implantable Body Sensor Networks (BSN’06) 0-7695-2547-4/06 $20.00 © 2006 IEEE