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Diastolic blood pressure is typically considered to indicate arterial stiffness. Atherosclerosis develops as the functioning of vascular endothelial cells diminishes. When blood flows rapidly through those endothelial cells, they release a vasodilator called nitric oxide （NO）．NO relaxes smooth muscle in the tunica media and it dilates blood vessels. In other words, blood vessels stiffen and lose their elasticity depending on the level of NO. Research over the past few years has suggested that performing an exercise with a grip strength of about 30% may decrease blood pressure. However, no studies thus far have examined the decrease in blood pressure as a result twisting an object. Moreover, the relationship between twisting motion and grip strength has yet to be determined. The current authors hypothesized that gripping and twisting action might have similar effects. Accordingly, the aims of the current study were to observe muscle activity and hemodynamics during repeated twisting action and to ascertain the relationship between grip strength and twisting action. Thus, left and right grip strength was measured in a standing position, and maximum twisting strength was measured in a seated position while twisting a twist bar in the opposite direction with the right and left hands. In addition, grip strength of the right hand was measured in a seated position, and maximum twisting strength was measured with a twist bar. Muscle activity of the brachioradialis and flexor carpi ulnaris was measured during that action, and the relationship between muscle activity and twisting action was examined. Results indicated that twisting action was correlated with grip strength. Grip strength was correlated with the level of muscle activity of the flexor carpi ulnaris and the brachioradialis during twisting action. The appropriate pace for twisting motion was not evident, so the pace of twisting was examined. Subjects performed 40, 50, or 60 twists for 1 min continuously, rested for 1 min, and then performed the twisting action for another min. Before and afterwards, blood flow volume around the flexor carpi ulnaris and the brachioradialis was measured, and blood pressure was also measured. Results indicated that blood flow volume tended to increase after twisting action at all 3 paces. Blood flow volume around the brachioradialis in particular was significantly greater at a pace of 60 twists per min. Moreover, blood flow volume in the vicinity of the flexor carpi ulnaris increased significantly at all 3 paces. Systolic blood pressure increased after twisting action at all 3 paces. In contrast, diastolic blood pressure tended to decrease at all 3 paces, and it was significantly lower particularly at a pace of 40 twists per min. Based on these findings, repeatedly performing continuous twisting action alternately activates the brachioradialis and the flexor carpi ulnaris. As a result, blood flow volume increases and the stretchability of the vascular wall increases, presumably causing diastolic blood pressure to decrease.

Poly(lactic acid) (PLA) has a high piezoelectric constant due to molecular orientation by uniaxial elongation and crystallization by heat treatment. The piezoelectric constant of PLA yarn is approximately 10 pCN−1. In our previous study, we reported the strong antibacterial effect of piezoelectric PLA fabrics that we had developed with fabric extension and contraction [Ando et al., Jpn. J. Appl. Phys. 56, 10PG01 (2017)]. In this study, we simulated the generating voltage of the yarn under tensile stress, considering filament slippage among adjacent filaments. Measurements were conducted to confirm the generating voltage and resulting electric field strength. Further, we confirmed that the growth of bacteria was suppressed, based on the electric field that formed in the fabric. Testing of the fabrics across multiple production lots repeatedly revealed a strong antibacterial effect, and scanning electron microscope image of dead bacteria in the fabric was different from those under the heat, drying and acid test.

Poly(lactic acid) (PLA) is a well-known, environmentally-friendly polymer. Piezoelectric poly(L-lactic acid) (PLLA), a type of chiral polymer, exhibits a high shear piezoelectric constant, is highly transparent, and is not pyroelectric. New human machine interface devices with intuitive control can be fabricated using piezoelectric PLLA as a deformation sensor. Specifically, for projected capacitive touch panels widely used in smartphone technology, the PLLA film as a pressure sensor with multiple electrodes allows pressure-sensitive functions to be added to the touch panel display.

Poly(lactic acid) (PLA) is a widely used biomass-derived polymer. It is chiral because the lactic acid monomer has an asymmetric carbon. If the L-lactide is polymerized, then the PLA polymer is an L-type PLA or poly(L-lactic acid) (PLLA); if the D-lactide in PLA is polymerized, then the polymer is a D-type PLA (PDLA). When these polymers undergo drawing or elongation, they exhibit shear piezoelectricity. PLA films are highly transparent and do not exhibit pyroelectricity because of the lack of intrinsic polarization. Therefore, if a PLLA film is used for a touch panel, which is operated by pressure, there is no spurious signal due to heating from the fingers. This suggests that PLLA films may be suitable for touch panels using pressure detection. We used PLLA as the base film of a projected capacitive touch panel with multiple electrodes, and demonstrated a multitouch gesture screen that was sensitive to pressure applied on the screen. This touch panel technology has potential applications for smart phones and tablet personal computers.

Synthetic piezoelectric polymer films produced from petroleum feedstock have long been used as thin-film sensors and actuators. However, the fossil fuel requirements for synthetic polymer production and carbon dioxide emission from its combustion have raised concern about the environmental impact of its continued use. Eco-friendly biomass polymers, such as poly(L-lactic acid) (PLLA), are made from plant-based (vegetable starch) plastics and, thus, have a much smaller carbon footprint. Additionally, PLLA does not exhibit pyroelectricity or unnecessary poling. This suggests the usefulness of PLLA films for the human–machine interface (HMI). As an example of a new HMI, we have produced a TV remote control using a PLLA film. The intuitive operation provided by this PLLA device suggests that it is useful for the elderly or handicapped.