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Wearable pressure sensors have attracted significant attention owing to their potential applications in health monitoring and connectivity to internet‐based apps. Polymers such as poly(vinylidene fluoride) have been used in sensors. However, being petroleum‐derived materials, they do not decompose and remain in the soil when disposed. Poly(l‐lactic acid) (PLLA) is a promising material because of its biodegradable nature and its derivation from plant‐based materials. In addition, the electrospun PLLA fiber mat contains real charges and exhibits electromechanical properties. However, the detailed charging properties of the PLLA fiber mats remain unclear. Herein, the charge distribution of these fiber mat is presented, and a charging model of the fiber mat and a numerical model of the output charges from the fiber mats with electrodes are proposed. Additionally, the retention properties of the stored charges are determined using surface potential measurements at different temperatures. In addition, a self‐power‐generating touch sensor and mask‐type sensor are developed using biodegradable materials produced from biomass. These studies contribute to the improvement in the charge properties of PLLA fiber mats and the resulting wearable biodegradable sensors.

Disposable masks are widely used, particularly in medicine to prevent the spread of infections, as they afford hygiene and convenience. Recently, sensor‐integrated masks are explored for monitoring human voice and respiration. However, masks equipped with acoustic/respiration sensors containing nano/microfiber mats cannot be used as readily as conventional disposable masks because of their high material and manufacturing costs. To address these issues, in this article, a self‐power‐generating mask‐type acoustic/respiration sensor (MTAS) incorporated with electrospun atactic poly(styrene) (aPS) microfiber‐nonwoven mats is proposed. aPS is integral to the MTAS fabrication strategy as it is inexpensive and amenable to the one‐step production of charged electrospun microfiber mats. When subjected to acoustic waves, the MTAS generates a voltage corresponding to the sound pressure and frequency owing to its ferroelectric properties. Furthermore, when a tablet is connected to the mask worn by a subject who is vocalizing, the uttered words are converted into text on the tablet. Additionally, the MTAS worn by a person can output a voltage in response to breathing. Overall, the devised mask can pioneer the development of systems that can link voice and breathing in virtual spaces, enable real‐time translation of speech, and monitor respiratory diseases.

Electromechanically active nano/microfibers are promising components of sensors and actuators; however, piezoelectric polymers are normally expensive. To address this issue, this study examined the geometrical and electrostatic densities of an inexpensive highly sparse as-electrospun atactic polystyrene microfiber mat. The densities of porous individual fibers and the highly sparse fiber mat were experimentally determined to be 0.88 and 0.051 g cm−3, respectively, with corresponding material filling ratios of 80 % and 4.7 %, respectively. A high theoretical surface charge density of approximately 1.4 × 10−3 C m−2 was determined for the fiber mat after excluding air spaces in both individual fibers and the mat. These findings provide a pathway to outstanding electrets that are ultra-lightweight and have high charge densities.

As-electrospun microfiber mats comprising atactic polystyrene (aPS), a low-cost commodity polymer, have demonstrated beneficial electromechanical properties. However, the variability of the electromechanical properties of fiber mats produced using different electrospinning conditions has not been investigated. Therefore, herein, the direct electromechanical properties of aPS fiber mats produced using different deposition times (tdep) and electrospinning voltages (VES) are investigated. The resulting apparent piezoelectric d constant (dapp) of the fiber mats demonstrates a specific peak value for tdep as high as ~1600 pC N−1 under 1-kPa pressure application after ~0.2-kPa pre-pressure application, although the dapp of the fiber mats produced with some conditions is nearly zero pC·N−1. Furthermore, the peak position of dapp with tdep is fundamentally determined with σEff0/YD(h-hpre) [σEff0: effective surface charge density, YD(h-hpre): secant modulus of elasticity]. Charge distribution models for fiber mats with different tdep are established. The models explain the characteristics of the significant changes in YD(h-hpre) and σEff0 with tdep. These findings provide significant directions for the production of fiber mats with improved direct electromechanical properties.