Workpackage 1 : Specifications and enabling technologies Workpackage 2 : Stretchable substrate technology Workpackage 3 : Interconnection, assembly and embedding Workpackage 4 : Modelling and characterisation Workpackage 5 : Power supply Workpackage 6 : System design Workpackage 7 : Technology integration Workpackage 8 : STELLA innovation-related activities Workpackage 9 : STELLA demonstration activities Workpackage 10 : STELLA training activities Workpackage 11 : STELLA management activities

The first workpackage aims to:

• Obtain a suitable set of User Requirement Specifications (URS)
• Derive from these URS the product load profile
• Derive through a “Physics of Failure” approach a set of tests to assess the weak spots in the assembly.
• Derive from the URS and “Physics of Failure” approach the most appropriate manufacturing methodology.
• Adapt existing models for cost of manufacturing cost and yield for integration onto stretchable substrates, that allow intelligent selection among the options for specific product applications.

The accumulated requirements coming from the Workpackage leaders and the in-house partners at Freudenberg will be taken into account for establishing a plan of development of the stretchable substrate technology. Workpackage 2 will be organised in four tasks corresponding to the different sub-entities:

• Task 2.1 : Substrate materials
• Task 2.2 : Stretchable electrical conductors
• Task 2.3 : Structuring and patterning
• Task 2.4 : Surface finishing and termination

This third workpackage aims to develop a technology that allows a reliable electrical inter-connection of electronic components with stretchable or conventional conductors in a stretchable matrix. Active components can be sensors, transmitters, and controllers, or integrated passives and small SMD components. The electronics integration into the stretchable matrix by embedding of active components will be as high as possible and the need for external readout systems will be reduced to a high extent. The technologies will be developed with the perspective of large scale/ low cost production, and sufficient reliability for a reasonable lifetime of the products.

Embedding of (classic) SMD components will also be necessary, at least for passive components, and this will be investigated in Task 3.4 of this workpackage.

In contrast to conventional chip interconnection and embedding technologies the challenge is obviously to master materials interfaces with highly dissimilar mechanical properties: silicon chips as solid blocks will be integrated into a matrix with a stretchability of 5 – 50 %, therefore the electronic contacts at the interface will be subjected to very high tensile and shear deformations (not necessarily including high forces); the wiring components will be connected to either metallic or non-metallic conductive polymers.

This fourth workpackage aims to develop:

• Electrical modelling and testing the RF characteristics of the stretchable conductors.
• Simulation methodology/strategy for mechanical simulation of stretchable electronics (with strong geometric and material non-linearities) under complex loading (bending + large displacement + torsion), based on Finite Element Modelling (FEM).
• “Inventive” designs for reliable stretchable electrical conductors (probably “spring”-like solutions): electrical + mechanical study Reliable solutions for the so-called rigid areas containing embedded chips and stiffeners.
• Reliable solutions for connecting the rigid part with the stretchable conductors (= critical issue) Dedicated test equipment for complex (mixed) mechanical loading of stretchable flex structures. This equipment should test the electrical performance and mechanical integrity of the interconnection and components under cycling loading.

Workpackage 4 will also give support to the technology workpackages and the demonstration activities. This support includes:

• Specific electrical/mechanical design issues for the demonstrators Characterisation of new materials (both mechanical and electrical properties) Defining design rules based on reliability assessment studies and manufacturing exercises.
• The link between electrical and mechanical design will be strong and must lead to an optimal design which satisfies both electrical (performance) and mechanical (reliability) requirements.

The power supply of intelligent textile systems like the ones that are targeted in the STELLA project will be a high challenge that consists in developing an innovative energy storage device that can be fully integrated in the final devices. This will be achieved by treating and reaching the following two main objectives:

To realize a new thin film solid state lithium ion battery with the following characteristics:

• Voltage range: between 2.8 and 1V
• Capacity: 100 µAh/cm²
• Current density available: 2 mA/cm²
• Cycling performance: > 10.000 cycles (charge and discharge)
• Temperature stability: up to 250°C

Currently available thin film solid state batteries are not compatible with solder reflow process (required by health and fitness applications) and with the temperature required during the elaboration process in the frame of floor applications (170°C during 7 minutes). As this incompatibility is due to the presence of metallic lithium (melting point: 181 °C), a new lithium ion thin solid state Li ion battery must be realized for STELLA success.

To realize a high voltage (5V) thin film solid state lithium ion battery

Other requirements concerning for instance healthcare applications deal with a voltage as high as 5 V. The second challenge of this workpackage will then be to develop a thin film solid state lithium ion battery that can offer this voltage without loosing surface and thus capacity. This objective will be reached by stacking two micro-batteries which will permit to double the voltage. The same characteristics as for the above new thin film solid state lithium ion battery will be aimed at but with a double voltage.

The objective is to obtain a energy management system enabling to use very low currents (in the range of nA) in order to improve the life time of the battery.

In parallel to the technological development of thin film solid state battery, energy management of these energy systems devices will be studied. This task will imply an electrical modelling of the energy source behaviour. Thanks to these data, low consumption electronic blocks allowing the knowledge of the state of charge of the battery will be realized.

Technical objectives of Workpackage 6

This sixth workpackage aims to develop the sensor architecture, electrical design, including sensor interface, power strategy and implementation and the radio and antenna integration. Where possible use shall be made of existing building blocks. For instance, the radio part shall be taken according to existing low cost and available standard solutions like Bluetooth or Zigbee. Sensors themselves shall be bought from the market.

Also for the software existing solutions for individual blocks shall be used where possible. The software consist of several layers, of which the operating system is probably most widely usable. Furthermore for the different applications Application Program Interfaces (API) have to be developed.

The following specific tasks are defined within the frame of Workpackage 6:

• Task 6.1 : Wireless communication and antenna integration
• Task 6.2 : System partitioning
• Task 6.3 : Sensor node design
• Task 6.4 : Embedded control

Workpackage 7 aims to develop, create and evaluate manufacturing technologies for a reliable and cost-effective autonomous stretchable system. New technologies from other work-packages are used and we will investigate how these can be integrated in production and in what sequence. We will investigate how we can adapt or extend existing assembly infrastructures to meet functional specifications, reliability and cost.

While conventional processes call for assembling and joining components on a rigid or rigidized circuit-system, we will investigate if we need to reverse the processes and join the circuit-system to the components or modules. We will investigate under what conditions we can maximize the stretch function for the customer and the consequences for the manufacturing of that system. Certainly, we expect to answer questions relating to reliability as a function of stretch.

The STELLA Integrated Project will include also innovation-related activities relating to the protection and dissemination of knowledge, and studies on the wider socio-economic impact of that knowledge, as well as activities to promote the exploitation of the STELLA results, and the investigation of potential ‘take-up’ actions based on the outcome of the STELLA project. These activities are inter-related and will be conceived and implemented in a coherent way.

The following specific tasks are defined within the frame of Workpackage 8:

• Task 8.1 : Dissemination
• Task 8.2 : Exploitation

This ninth workpackage aims to integrate the materials, components and technologies developed in the previous research and technological development workpackages into demonstrator modules. All demonstrator modules do well represent the commercial interests of the participating partners.

Training is a general approach of strengthening the impact of the STELLA Integrated Project and is thus considered as a workpackage of its own. Each participant of the project is to his part responsible for the success of the STELLA Integrated Project and the necessary skills for a successful process should therefore be built up as soon and as broad as possible within the whole consortium. Training is also an instrument to strengthen the impact of the results outside the project. Training activities will be applied at three distinctive levels within and STELLA project:

• The exchange of STELLA information and results through staff mobility.
• Internal and external training activities on stretchable electronic technologies and applications developed within the STELLA project.
• Preparation of learning materials for the above training activities

The objective of the Workpackage 11 is to ensure the proper functioning of the STELLA Integrated Project in order to achieve the objectives and milestones of the project. This encompasses the following activities:

• The establishment of management committees and guidelines for their execution.
• The dissemination of knowledge generated in the project and the internal information gathering on related projects.
• The set-up of an effective communication infrastructure.
• The management of the processes for the capture and protection of intellectual property, including confidential information, copyrights, design rights and patents.
• The planning and execution of exploitation routes for processes, technologies and products developed within the STELLA project.
• The establishment of technical and financial reporting guidelines.