This proposal is concerned with the research and development of new manufacturing and assembly methods that add electronics functionality to textiles. Textiles are ubiquitous and are used, for example, in clothing, home furnishings as well as medical, automotive and aerospace applications. Textiles are one of the most common materials with which humans come into contact, but, at present, their functionality is limited to their appearance and physical properties. There is considerable and growing interest in SMart and Interactive Textiles (SMIT) that add electronic functionality to textiles. SMIT offer a far greater range of functionality that can include sensing, data processing and interaction with the user and, as a result, can be applied in a vast range of applications potentially wherever textiles are present. The overall objective of the research is to develop new manufacturing assembly methods that enable the reliable packaging of advanced electronic components (e.g. microcontrollers) in ultra-thin die form within a textile yarn. The programme of research will investigate approaches for mounting the ultra-thin die onto thin flexible polymer films strips that contain patterned conductive interconnects and bond pads. Individual die will be located on the strip and conductive tracks on the plastic substrate will them together forming a long, very thin, flexible circuit or filament. The filaments will then be surrounded by classical textile fibres (e.g. polyester, cotton, wool, silk) and connected to conductive wires to form an electronic yarn (EY) that will, essentially, appear to be a standard textile yarn but which has embedded within it, circuitry and components. The ultimate goal is to incorporate these EYs into the textile in such a way as to protect the electronic components and interconnects from the rigours of use whilst maintaining the feel, drape and breathability of the textile. A key aspect of the technology is the use of ultra-thin die which are highly flexible and, together with a rectangular footprint, will minimise the profile of the die within the filament. This will then serve to reduce the impact on the yarn making the electronics virtually invisible and minimising yarn diameter.