Veikko Surakka

Electronic skin (e‐skin) that enables machines with human‐like tactile perception requires a combination of extreme conformability, mechanical robustness, low crosstalk, and scalable, sustainable fabrication. Here, we report a fully solution‐processed, metal‐free 44 piezoelectric sensor array based on an ultrathin P(VDF‐TrFE) active layer, designed for skin‐conformal tactile sensing. By combining inkjet‐printed polymer electrodes with a 226 nm thick spin‐coated ferroelectric layer, which is the thinnest active layer reported to date for a P(VDF‐TrFE) sensor array, on an ultrathin Parylene C substrate, the resulting device achieves a total thickness of approximately 4.53 , enabling unobtrusive contact with soft and curved surfaces, including human skin. The average piezoelectric sensitivity, , is 21 pC/N, and the voltage sensitivity ranges from 65 to 221 mV/N. Notably, array‐level measurements reveal negligible mechanical crosstalk between neighboring pixels without the use of mechanical isolation structures. The observed low crosstalk is consistent with enhanced strain localization owing to the ultrathin, highly conformable device achitecture. The results highlight ultrathin, all‐polymer piezoelectric arrays as a promising design strategy for scalable, sustainable, and mechanically compliant electronic skin systems.

We present a new method for fully self-administered olfactory testing. Technical development and testing and two user studies were conducted to test the functionality of a prototype device called Automated Olfactory Threshold Test (AutomOT). Technical testing showed repeatable functioning of the developed olfactory display technology in accurately producing 11 predefined odor intensity levels over 10 different days. In User Study 1, we tested the reliability, usability, and subjective workload of the use of the device. Participants (N = 29) with a normal sense of smell performed an automated threshold test four times. The results showed that the correlations between the tests were statistically significant r = .44–.78, all p-values ≤ .018. In User Study 2, we demonstrated the functioning of the device with normosmic and hyposmic/anosmic participants (n = 23 and n = 27, respectively) who performed both the current clinical standard, Sniffin’ Sticks test, and the AutomOT test. Also, the usability and subjective workload of the use of the device were evaluated. The overall correlation of olfactory thresholds between the Sniffin’ Sticks and the AutomOT was r = .48, p < .001. In both user studies, the results indicated good usability as measured by System Usability Scale and low workload assessed by NASA Task Load Index. Overall, the results suggest that the newly developed AutomOT test is a reliable, valid, and usable tool for clinical assessment of olfactory thresholds.

The development of flexible electronics is essential for advancing technologies like wearables, environmental sensors, and electronic skin (e-skin), which are used in applications ranging from healthcare to soft robotics. E-skin, inspired by the human skin’s sensory capabilities, requires flexible and conformable materials to mimic the dynamic responses to shear, pressure, temperature, and pain. Traditional rigid electronics fabrication methods, which require high processing temperatures, are unsuitable for flexible substrates. Additionally, the requirement for low-power and energy-autonomous devices present challenges that could be addressed with piezoelectric materials. In this study, we present an all-solution processed method to fabricate an ultra-thin, piezoelectric sensor on a flexible polyimide substrate. The sensor’s electrodes are inkjet-printed using poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, while the active layer of poly(vinylidene fluoride-co-trifluoroethylene) is formed by spin coating. The fabrication process is optimized by varying annealing temperatures and using two casting solvents while spin coating, methyl ethyl ketone and dimethyl sulfoxide, to assess their impact on the active layer performance. The resulting sensor has a sandwiched structure with a final thickness of less than 1 µm, including a 289 nm thick active layer. The sensor demonstrates a remanent polarization P r of 7.9 µC cm⁻² and a piezoelectric coefficient d ₃₃ of 12.4 pC N⁻¹.