RESUMO

Thermally driven fiber actuators are emerging as promising tools for a range of robotic applications, encompassing soft and wearable robots, muscle function restoration, assistive systems, and physical augmentation. Yet, to realize their full potential in practical applications, several challenges, such as a high operational temperature, incorporation of intrinsic self-sensing capabilities for closed-loop feedback control, and reliance on bulky, intricate actuation systems, must be addressed. Here, an Ag nanoparticles-based twisted and coiled fiber actuator that achieves a high contractile actuation of ≈36% is reported at a considerably low operational temperature of ≈83 °C based on a synergistic effect of constituent fiber elements with low glass transition temperatures. The fiber actuator can monitor its contractile actuation in real-time based on the piezoresistive properties inherent to its Ag-based conductive region, demonstrating its proprioceptive sensing capability. By exploiting this capability, the proprioceptive fiber actuator adeptly maintains its intended contractile behavior, even when faced with unplanned external disturbances. To demonstrate the capabilities of the fiber actuator, this study integrates it into a closed-loop feedback-controlled bionic arm as an artificial muscle, offering fresh perspectives on the future development of intelligent wearable devices and soft robotic systems.

RESUMO

Surgical sutures are widely used for closing wounds in skin. However, the monitoring of wound integrity and promoting tissue regeneration at the same time still remains a challenge. To address this, we developed a drug-releasing electronic suture system (DRESS) to monitor the suture integrity in real-time and enhance tissue regeneration by triggered drug release. DRESS was fabricated by using a single fiber with a core-shell structure consisting of a stretchable conductive fiber core and a thermoresponsive polymer shell containing drugs. The highly conductive fiber core acts as a strain sensor that enables continuous monitoring of suture strain with high sensitivity (a gauge factor of ∼686) and mechanical durability (being able to endure more than 3000 stretching cycles). The thermoresponsive shell layer composed of flexible poly(vinyl alcohol) (PVA) grafted onto poly(N-isopropylacrylamide) (PNIPAm) facilitates on-demand drug release via Joule heating. The results of an in vitro scratch assay showed a 66% decrease in wound area upon heat-activation after 48 hours demonstrating the stimuli-responsive therapeutic efficacy of DRESS by promoting cell migration. Moreover, ex vivo testing on porcine skin demonstrated the applicability of DRESS as a electronic suture. The approach used for DRESS provides insight into multifunctional sutures and offers additional therapeutic and diagnostic options for clinical applications.

Assuntos

RESUMO

We report the electrical detection of captured gases through measurement of the quantum tunneling characteristics of gas-mediated molecular junctions formed across nanogaps. The gas-sensing nanogap device consists of a pair of vertically stacked gold electrodes separated by an insulating 6 nm spacer (~1.5 nm of sputtered α-Si and ~4.5 nm ALD SiO2), which is notched ~10 nm into the stack between the gold electrodes. The exposed gold surface is functionalized with a self-assembled monolayer (SAM) of conjugated thiol linker molecules. When the device is exposed to a target gas (1,5-diaminopentane), the SAM layer electrostatically captures the target gas molecules, forming a molecular bridge across the nanogap. The gas capture lowers the barrier potential for electron tunneling across the notched edge region, from ~5 eV to ~0.9 eV and establishes additional conducting paths for charge transport between the gold electrodes, leading to a substantial decrease in junction resistance. We demonstrated an output resistance change of >108 times upon exposure to 80 ppm diamine target gas as well as ultralow standby power consumption of <15 pW, confirming electron tunneling through molecular bridges for ultralow-power gas sensing.

RESUMO

Wearable electronic devices have attracted significant attention as important components in several applications. Among various wearable electronic devices, interest in textile electronic devices is increasing because of their high deformability and portability in daily life. To develop textile electronic devices, fiber-based electronic devices should be fundamentally studied. Here, we report a stretchable and sensitive fiber strain sensor fabricated using only harmless materials during an in situ formation process. Despite using a mild and harmless reducing agent instead of typical strong and hazardous reducing agents, the developed fiber strain sensors feature a low initial electrical resistance of 0.9 Ω/cm, a wide strain sensing range (220%), high sensitivity (∼5.8 × 104), negligible hysteresis, and high stability against repeated stretching-releasing deformation (5000 cycles). By applying the fiber sensors to various textiles, we demonstrate that the smart textile system can monitor various gestures in real-time and help users maintain accurate posture during exercise. These results will provide meaningful insights into the development of next-generation wearable applications.

Assuntos

RESUMO

This paper reports in-air monitoring of in vitro monolayer cells under air-exposure utilizing electrochemical impedance spectroscopy (EIS). In-air impedance measurement was performed by placing integrated electrodes laterally, instead of vertically, to a cell membrane, avoiding electrical disconnection, unlike conventional transepithelial-electrical-resistance (TEER). The in-air EIS sensor platform mainly consisted of two chambers, separated by a porous membrane where cells were cultured, that enabled cell exposure to both air (apical side) and liquid (basal side) for long-term measurement. On top of the membrane, EIS interdigitated electrodes were patterned and lung epithelial cells (A549 type II) were cultured with air exposure on one side. The fabricated in-air EIS sensor successfully demonstrated in situ real-time measurement of cell populations in confluency in the range of 7.8 × 104 and 9.6 × 105 cells per cm2 at a sensitivity of 3.0 × 10-2 Ω per cell in impedance and in the range of 1.0 × 104 and 9.6 × 105 cells per cm2 at a sensitivity of 0.17 × 10-15 F per cell in capacitance under AC frequencies of 100 kHz and 1 MHz, respectively. It also successfully monitored transient modulation of tight-junctions that collectively began to open in 30 minutes after the injection of 100 ng ml-1 TNF-α (a relaxation agent), reached maximum relaxation with a 12.6% increase in impedance value and a 12% decrease in capacitance in 60 minutes, and recovered back to its original junction status after 720 minutes, which confirmed the observation in animal models in the literature. Note that the opposite trends in impedance and capacitance allowed the in-air EIS sensor to distinguish cell population changes from tight junction modulation. It was concluded that the developed in-air EIS sensor in an in vitro platform can enable in situ and real-time monitoring of the population of the 'air-exposed' cells as well as the modulation of tight-junctions, which has not been demonstrated yet.

Assuntos