We present a capacitive force sensor based on a polydimethylsiloxane (PDMS) film integrated into a printed circuit board (PCB) on a flexible substrate whose layout is defined by inkjet printing. The influence of the dielectric thickness on the sensor behavior is presented. The thinner PDMS film of about 45 μm shows a sensitivity of up to 3 pF/N but poorer dynamic response. The dielectrics with thicknesses above 200 μm show a significantly reduced sensitivity. The best compromise between sensitivity and dynamic response is found for PDMS film of about 100 μm, showing about 1.1 pF/N and less than 15 s of recovery time. This film is integrated into a flexible PCBS including a microcontroller capable of evaluating the sensor. Interconnects of the circuit are defined by silver nanoparticles deposited by inkjet printing. The working principle of the circuit is demonstrated, proving that this simple approach can be used for artificial skin applications.

Carbon nanotubes (CNTs) are an interesting material for mechanically flexible electronic devices. The possibility to fabricate CNT thin films from solution by scalable coating and printing techniques has paved the way for large-area and low-cost sensor applications. In this paper, we demonstrate mechanically flexible capacitive tactile sensors utilizing spray deposited CNT thin-films and microstructured PDMS spacers. The capacitance is monitored during sensor operation and forces smaller than 10 mN could be detected and changes of up to 20% are achieved for 1 N of applied force. Sensor response can be tailored through an appropriate design of the dielectric spacer. The long-term operational stability of the proposed sensors is demonstrated. Further, a theoretical model is proposed and fitted to experimental data, providing a powerful tool to facilitate the design process.

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Al 2 O 3 and AlN nanotubes were fabricated by depositing conformal thin films via atomic layer deposition (ALD) on electrospun nylon 66 (PA66) nanofiber templates. Depositions were carried out at 200°C, using trimethylaluminum (TMAl), water (H 2 O), and ammonia (NH 3 ) as the aluminum, oxygen, and nitrogen precursors, respectively. Deposition rates of Al 2 O 3 and AlN at this temperature were ~1.05 and 0.86 Å/cycle. After the depositions, Al 2 O 3 -and AlN-coated nanofibers were calcinated at 500°C for 2 h in order to remove organic components. Nanotubes were characterized by using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). AlN nanotubes were polycrystalline as determined by high resolution TEM (HR-TEM) and selected area electron diffraction (SAED). TEM images of all the samples reported in this study indicated uniform wall thicknesses.