In biomedical sciences, there is demand for electronic skins with highly sensitive tactile sensors, having applications in patient monitoring, human–machine interfaces, and on‐body sensors. In clinical applications, it would be especially beneficial if the sensors would be disposable. Here, an all plant‐material‐based biodegradable capacitive tactile pressure sensor for disposable electronic skins is reported. Silver‐nanowire‐coated leaf skeletons are used as breathable and flexible electrodes while freeze‐dried rose petals are used as the dielectric layer. The leaf skeleton electrodes have a rough fractal‐like architecture, which provides good adhesion to the silver nanowires and maintains interconnections between the silver nanowires when the electrodes are bent. The electrodes display low constant resistance up to curvature of 800 m−1. The rose petal dielectric layer has a multiscale 3D cell wall microstructure, which compresses elastically when subjected to pressure. The fabricated sensor can respond to pressures ranging from 0.007 to at least 60 kPa, with a maximum sensitivity of ≈0.08 kPa−1. The signal is stable for at least 5000 pressure cycles, after an initial break‐in period. Owing to the all biomaterial constituents, the sensor is biodegradable under aqueous conditions. The sensor is successfully applied as an e‐skin in touch sensing and gesture monitoring.
We present a facile method to prepare flexible, transparent, biodegradable, and fast resistive heaters by applying silver (Ag) nanowires onto fractal-like leaf skeletons. The fractal-like structure of the leaf skeleton maximizes its surface area, improving the transfer of heat to its surroundings and thus making the heater fast, without compromising transparency. Ag ion layer on the leaf skeleton helps to conformally cover the surface with Ag nanowires. The sheet resistance of the heater can be controlled by the loading of Ag nanowires, without sacrificing the optical transmittance (~80% at 8 Ω sq−1). The heating is uniform and the surface temperature of a 60 mm × 60 mm heater (8 Ω sq−1) can quickly (5–10 s) raise to 125 °C with a low voltage (6 V). The heater displays excellent mechanical flexibility, showing no significant change in resistance and heating temperature when bent up to curvature of 800 m−1. Finally, we demonstrate the potential of the bioinspired heater as a thermotherapy patch by encapsulating it in a biodegradable tape and mounting it on the human wrist and elbow. This study shows that fractal-like structures from nature can be repurposed as fractal designs for flexible electronics.
Manipulation of cells,
droplets, and particles via ultrasound within
microfluidic chips is a rapidly growing field, with applications in
cell and particle sorting, blood fractionation, droplet transport,
and enrichment of rare or cancerous cells, among others. However,
current methods with a single ultrasonic transducer offer limited
control of the position of single particles. In this paper, we demonstrate
closed-loop two-dimensional manipulation of particles inside closed-channel
microfluidic chips, by controlling the frequency of a single ultrasound
transducer, based on machine-vision-measured positions of the particles.
For the control task, we propose using algorithms derived from the
family of multi-armed bandit algorithms. We show that these algorithms
can achieve controlled manipulation with no prior information on the
acoustic field shapes. The method learns as it goes: there is no need
to restart the experiment at any point. Starting with no knowledge
of the field shapes, the algorithms can (eventually) move a particle
from one position inside the chamber to another. This makes the method
very robust to changes in chip and particle properties. We demonstrate
that the method can be used to manipulate a single particle, three
particles simultaneously, and also a single particle in the presence
of a bubble in the chip. Finally, we demonstrate the practical applications
of this method in active sorting of particles, by guiding each particle
to exit the chip through one of three different outlets at will. Because
the method requires no model or calibration, the work paves the way
toward the acoustic manipulation of microparticles inside unstructured
environments.
As the Earth's atmosphere contains an abundant amount of water as vapors, a device which can capture a fraction of this water could be a cost-effective and practical way of solving the water crisis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.