The paper describes a stretchable, microfabricated power generator that will be attached on the skin and will produce energy based on the movements of the human body. The device was fabricated on a polymeric, elastomeric, poly(dimethylsiloxane) (PDMS) sheet. It consists of a piezoelectric thin film of ZnO sandwiched between two stretchable gold electrodes. An innovative technique was used for the deposition of ZnO thin film on the gold electrode-coated polymeric substrate at low temperatures below 150 °C. This is the first attempt to use a uniform film of ZnO, for energy harvesting. The ZnO film had the thickness at the submicron scale and the surface at the centimeter scale. We demonstrated that under a strain of 8% the voltage output from this power generator was equal to 2 V, the power output was equal to 160 μW and the corresponding power density was 1.27 mW/cm². This device has great potential for application in power sensors attached on the human body, such as temperature sensors or wearable electrocardiography systems.

Blood viscosity is the defining health indicator for hyperviscosity syndrome patients. This paper introduces an alternative approach for the real-time monitoring of blood viscosity by employing a surface-horizontal surface acoustic wave (SH-SAW) device at room temperature. A novel bi-layer waveguide is constructed on top of the SAW device. This device enables the SAW sensing of liquid droplets utilizing a bi-layer waveguide, consisting of a zinc oxide (ZnO) enhancement layer and Parlyene C, that facilitates the promotion of the surface horizontal mode. The ZnO piezoelectric thin-film layer enhanced the local particle displacement and dielectric coupling while the Parylene C layer constrained the wave mode at the interface of the piezoelectric material and polymer material. The device was tested with a liquid drop on the SAW delay-line path. Both experimental and finite element analysis results demonstrated the benefits of the bi-layer waveguide. The simulation results confirmed that the displacement field of local particles increased 9 times from 1.261 nm to 11.353 nm with the Parylene C/ZnO bi-layer waveguide structure. The device demonstrated a sensitivity of 3.57 ± 0.3125 kHz shift per centipoise enabling the potential for high precision blood viscosity monitoring.

As a strain rate-dependent material, bone has a different mechanical response to various loads. Our aim was to evaluate the effect of water and different loading/unloading rates on the nanomechanical properties of canine femur cortical bone. Six cross-sections were cut from the diaphysis of six dog femurs and were nanoindented in their cortical area. Both dry and wet conditions were taken into account for three quasistatic trapezoid profiles with a maximum force of 2000 μN (holding time = 30 s) at loading/unloading rates of 10, 100, and 1000 μN/s, respectively. For each specimen,254±9(mean ± SD) indentations were performed under different loading conditions. Significant differences were found for the elastic modulus and hardness between wet and dry conditions (P<0.001). No influence of the loading/unloading rates was observed between groups except for the elastic modulus measured at 1000 μN/s rate under dry conditions (P<0.001) and for the hardness measured at a rate of 10 μN/s under wet conditions (P<0.001). Therefore, for a quasistatic test with peak load of 2000 μN held for 30 s, it is recommended to nanoindent under wet conditions at a loading/unloading rate of 100–1000 μN/s, so the reduced creep effect allows for a more accurate computation of mechanical properties.

In this paper, we report the study of Surface Acoustic Wave (SAW) sensors for cryogenic temperature and strain measurements, which has great potentials for aerospace applications. Our SAW devices used an interdigitated transducer (IDT) emitter and multiple reflectors that were fabricated on 128 ^° YX LiNbO ₃ substrates. Measurement results demonstrated no degradation in the signals quality of LiNbO3-based SAW devices when they were cooling down from 300K to 78K. The temperature dependence of the phase shift decreases with the temperature decreasing from 300K down to 78K. The temperature coefficients of the delay (TCD) at the temperature of 300K and at the temperature of 80K are around -78.9ppm/K and -31.1ppm/K respectively. The strain coefficient of the delay (SCD) of the device is in the order of -0.57 ppm/με at room temperature. The results indicate that LiNbO ₃ SAW devices are a potential solution for cryogenic temperature and strain sensing applications.

This paper presents the fabrication and testing of a novel Electric Cell-substrate Impedance Spectroscopy (ECIS) biosensor. This is the first time when ECIS electrodes were fabricated on a stretchable polydimethylsiloxane (PDMS) substrate and ECIS measurements on mammalian cells exposed to cyclic strain of 4% and 8% were performed. The stretchable ECIS biosensors simulate in vitro the dynamic environment of organism, such as pulsation, bending and stretching, which enable the investigation on cell behavior that undergoes mechanical stimuli in biological tissue. This novel stretchable ECIS sensor was demonstrated to measure the cell impedance in static and stretching states.