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a)

b)

Figure 1. (a) The DWTS manufacturing cell with a 6-axis robot. (b) The DWP (nScrypt) CAD/CAM compatible facility with a two pump system.

of 5 to 50% of the bulk Cu conductivity with post-sintering temperatures in the range of 120 to 300ยบC, and the DWTS copper had a conductivity of about 40% of the bulk copper conductivity. The DWTS spinel has good electrical insulating properties on metal surfaces thus providing the dielectric properties for different sensor structures. To demonstrate the feasibility of DWP, silver paste was used to fabricate conductive structures on polymer substrates. The other demo consisted of both 2D and 3D polymer structures. A 3D structure dispensed for the polycaprolactone (PCL) polymer is presented in Figure 2. Different sensor structures were fabricated and tested with the DWTS technique. Thermocouples (TC) sprayed on 2D samples were tested in the laboratory giving reasonable repeatability. Figure 2 shows TCs deposited on curved surfaces for temperature demonstration purposes. The strain gauges were fabricated on 2D samples and tested by MesoScribe Technologies Inc. The strain gauges performed in a similar way to those fabricated by MesoScribe. However, some needs for more tuning and material improvement were distinguished for more stable and repeatable measurement results. Strain gauges to meas-

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ure torque were also fabricated on a cylindrical shaft. Since the spray gun is manipulated by a robot, it is possible to make deposits on complicated component structures. The sensors were evaluated with a repeated pulsating load. The results showed good performance for the sensors compared with the reference sensors and proved the feasibility of using DWTS technology to fabricate stain gauges for, e.g., torque measurement [1].

Discussion and conclusions The results and demo evaluations showed good performance by DW materials and structures. Several demonstrations provided good insights into the capability of techniques and proved the huge potential the DW techniques have for future manufacturing. However, more research and development of the material used is needed in order to improve the material performance.

Exploitation potential As Direct Write (DW) technology enables new production techniques and solutions for electronics and the integration of electronics onto mechanical components it has a wide application field and huge potential in the future. The DWP technique enables miniaturization in elec-

VTT Research Highlights 3  

Production matters. VTT in global trends. Kai Häkkinen (ed.)

VTT Research Highlights 3  

Production matters. VTT in global trends. Kai Häkkinen (ed.)