Miniature
energy storage devices simultaneously combining
high
energy output and bioavailability could greatly promote the practicability
of green, safe, and nontoxic in vivo detection, such as for noninvasive
monitoring or treatment in the gastrointestinal tract, which is still
challenging. Herein, we report ingestible and nutritive zinc-ion-based
hybrid micro-supercapacitors (ZMSCs) consisting of an edible active
carbon microcathode and zinc microanode, which can be inserted into
a standard-sized capsule and ingested in a pig stomach. With features
including flexibility, light weight, and shape adaptability, a single
microdevice displays a high energy density of 215.1 μWh cm–2, superior to that of state-of-the-art biocompatible
SCs/MSCs and even traditional ZMSCs reported previously. It also delivers
an areal capacitance of 605 mF cm–2 and a high working
voltage of 1.8 V, exceeding that of miniaturized commercial button
batteries (1.55 V, RENATA 337). Comprehensive studies in vivo and
in vitro demonstrate that the ZMSCs with high biocompatibility and
safety not only power electronic equipment in the porcine stomach
without a voltage booster but also act as a nutritional supplement
of trace element zinc within the dose range, as well as the ability
of potent antibacterial activity against bacterium Escherichia coli during the discharging process.
This work provides an example for the design and fabrication of edible
energy storage devices with high performance.
It is commonly believed that bacterial chemotaxis helps cells find food. However, not all attractants are nutrients, and not all nutrients are strong attractants. Here, by using microfluidic experiments, we studiedEscherichia colichemotaxis behavior in the presence of a strong chemoattractant (e.g., aspartate or methylaspartate) gradient and an opposing gradient of diluted tryptone broth (TB) growth medium. Our experiments showed that cells initially accumulate near the strong attractant source. However, after the peak cell density (h) reaches a critical valuehc, the cells form a “escape band” (EB) that moves toward the chemotactically weaker but metabolically richer nutrient source. By using various mutant strains and varying experimental conditions, we showed that the competition between Tap and Tar receptors is the key molecular mechanism underlying the formation of the escape band. A mathematical model combining chemotaxis signaling and cell growth was developed to explain the experiments quantitatively. The model also predicted that the width w and the peak positionxpof EB satisfy two scaling relations:w/l∼(h/hc)−1/2and1−xp/l∼(h/hc)−1/2, where l is the channel length. Both scaling relations were verified by experiments. Our study shows that the combination of nutrient consumption, population growth, and chemotaxis with multiple receptors allows cells to search for optimal growth condition in complex environments with conflicting sources.
The aging process is regarded as the progressive loss of physiological integrity, leading to impaired biological functions and the increased vulnerability to death. Among various biological functions, stress response capacity enables cells to alter gene expression patterns and survive when facing internal and external stresses. Here, we explored changes in stress response capacity during the replicative aging of Saccharomyces cerevisiae. To this end, we used a high-throughput microfluidic device to deliver intermittent pulses of osmotic stress and tracked the dynamic changes in the production of downstream stress-responsive proteins, in a large number of individual aging cells. Cells showed a gradual decline in stress response capacity of these osmotic-related downstream proteins during the aging process after the first 5 generations. Among the downstream stress-responsive genes and unrelated genes tested, the residual level of response capacity of Trehalose-6-Phosphate Synthase (TPS2) showed the best correlation with the cell remaining lifespan. By monitor dynamics of the upstream transcription factors and mRNA of Tps2, it was suggested that the decline in downstream stress response capacity was caused by the decline of translational rate of these proteins during aging.
Rapid development of portable and wearable electronic devices has triggered increased research interest in small‐scale power sources, especially in micro‐supercapacitors (MSCs) because of their high power densities, long service life, and ability to be charged and discharged quickly. Graphene, an ideal two‐dimensional energy‐storage electrode material with good conductivity, high quantum capacitance, and large specific surface area, can be used as a building block for MSCs with multi‐dimensional architectures. Considerable efforts have been devoted to constructing structures with different dimensions for advanced graphene‐based MSCs (GMSCS). In this Review, we summarize the recent progress of graphene‐based macroscopic assemblies in MSCs, including 1D fiber GMSCs, 2D planar GMSCs; and 3D in‐plane or stacked GMSCs, and discuss the relationship between the structures and applications of the devices. In addition, future prospects and challenges in the MSCs are also discussed.
As the most competitive solution for next-generation network, SDN and its dominant implementation OpenFlow are attracting more and more interests. But besides convenience and flexibility, SDN/OpenFlow also introduces new kinds of limitations and security issues. Of these limitations, the most obvious and maybe the most neglected one is the flow table capacity of SDN/OpenFlow switches. In this paper, we proposed a novel inference attack targeting at SDN/OpenFlow network, which is motivated by the limited flow table capacities of SDN/OpenFlow switches and the following measurable network performance decrease resulting from frequent interactions between data and control plane when the flow table is full. To the best of our knowledge, this is the first proposed inference attack model of this kind for SDN/OpenFlow. We implemented an inference attack framework according to our model and examined its efficiency and accuracy. The evaluation results demonstrate that our framework can infer the network parameters (flow table capacity and usage) with an accuracy of 80% or higher. We also proposed two possible defense strategies for the discovered vulnerability, including routing aggregation algorithm and multilevel flow table architecture. These findings give us a deeper understanding of SDN/OpenFlow limitations and serve as guidelines to future improvements of SDN/OpenFlow.
Current microfluidic methods for studying multicell strains (e.g., m-types) with multienvironments (e.g., n-types) require large numbers of inlets/outlets (m*n), a complicated procedure or expensive machinery. Here, we developed a novel two-layer-integrated method to combine different PDMS microchannel layers with different functions into one chip by a PDMS through-hole array, which improved the design of a PDMS-based microfluidic system. Using this method, we succeeded in converting 2 × m × n inlets/outlets into m + n inlets/outlets and reduced the time cost of loading processing (from m × n to m) of the device for studying multicell strains (e.g., m-types) in varied multitemporal environments (i.e., n-types). Using this device, the dynamic behavior of the cell-stress-response proteins was studied when the glucose concentration decreased from 2% to a series of lower concentrations. Our device could also be widely used in high-throughput studies of various stress responses, and the new concept of a multilayer-integrated fabrication method could greatly improve the design of PDMS-based microfluidic systems.
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