Fabrication and mechanical characterisation of inkjet printed strain gauges

The present study focuses on printing strain sensors directly on tensile test specimens using inkjet printing technology. This type of strain gauges has the advantage over conventional strain gauges that no glue or carrying platelet is present between the sensor and the surface that should be measured. Therefore, strains in thin foils can possibly be measured with printed strain gauges. First, proof of principle is given in this paper by successfully printing strain gauges on FR4. The printed strain gauges prove to behave linearly up to strains of 0.2% and can measure the strains within 3.5% accuracy

Performance of inkjet-printed structures on different substrate materials under high humidity and elevated temperature conditions

Inkjet printing is widely being researched as enabling technology for printed electronics; however, there are scarce publications concerning the reliability of inkjet-printed structures on different substrates. The reliability of such structures under high humidity and high temperature conditions is treated in this work. To do so, the adhesion and resistivity of printed structures on PET, Rogers, PI and FR-4 materials are studied before and after a moisture resistance test. The samples present average resistivity values in the range of 12-106 μΩ·cm and only one specimen of the Rogers sample fails the reliability test. The Rogers sample presents perfect adhesion characteristics, the adhesion can be improved for the rest of the samples, especially for the PI sample. The general performance of inkjet-printed structures on different substrate materials is good

Reliable inkjet-printed interconnections on foil-type li-ion batteries

Shapeable rechargeable Li-ion batteries are a good option for the power source of system-in-package devices; nevertheless, their size and temperature limitations are a constraint during the fabrication process. Inkjet-printed interconnections on top of the battery are proposed in order to reduce the size and costs of wireless sensor network devices that require the use of Li-ion batteries. The reliability of such interconnections under high-humidity and elevated-temperature conditions is characterized in terms of electrical and adhesion properties; the micro- and macrostructures of the ink are observed in detail. Two silver inks are used to print the interconnections. The resistivity values of printed structures are in the range of 8.6-47.6 μΩ·cm, and all of them pass the reliability tests. The adhesion characteristics are good for Ink A; however, Ink B presents failures under high-humidity conditions. For a good adhesion, a plasma treatment should be performed prior to printing. The electrical performance of the interconnections is not affected by high-humidity and high-temperature conditions. Furthermore, there is no indication of silver migration. It is recommended that the curing temperature of the ink is kept low (<; 155°C) in order to avoid cracks in the ink structure and damages to the battery's packaging foil. The interconnections should be printed before filling the battery to avoid the decomposition of the electrolyte which happens at 80 °C