Seed Imbibition Monitoring Using Millimeter-Scale Wireless Sensing Systems

Imbibition can be thought of as the resultant of soil moisture, soil structure, and pericarp permeability. Accurate imbibition monitoring enables to characterize one of three by holding the other two constant. It helps scientists and farmers find better soil or genotypes by assessing biologically-available soil moisture. However, we now know that a previous imaging-based approach is not effective since it cannot take images through the soil. Accordingly, there is an urgent need to develop a tool to measure imbibition in soil in situ. Also, it is important that the new method should not disturb original imbibition behavior significantly. In this project, the PI will develop a millimeter-scale wireless sensing system with a seed holding structure that measures the growth rate ofa swelling maize seed in soil in situ and collects data wirelessly by a remote gateway. A maize seed is just an example. The developed technology can be applied to other types of seed with proper modification of a seed holding structure. The central hypothesis is that imbibition can be monitored by recording force generated by a single seed. The proposed approach digitizes resistance sensitive to force. Also, it minimizes an artificial impact on seed imbibition by minimizing form factor of the system based on die-stacked structure without discrete components. Once the system becomes available, we move one step forward for agriculture people to accurately evaluate their different types of soil or species based on measured imbibition

High‐efficiency photovoltaic modules on a chip for millimeter‐scale energy harvesting

Photovoltaic modules at the millimeter scale are demonstrated in this work to power wirelessly interconnected millimeter‐scale sensor systems operating under low‐flux conditions, enabling applications in the Internet of things and biological sensors. Module efficiency is found to be limited by perimeter recombination for individual cells and shunt leakage for the series‐connected module configuration. We utilize GaAs and AlGaAs junction barrier isolation between interconnected cells to dramatically reduce shunt leakage current. A photovoltaic module with eight series‐connected cells and total area of 1.27 mm2 demonstrates a power conversion efficiency of greater than 26% under low‐flux near‐infrared illumination (850 nm at 1 μW/mm2). The output voltage of the module is greater than 5 V, providing a voltage up‐conversion efficiency of more than 90%. We demonstrate direct photovoltaic charging of a 16‐μAh pair of thin‐film lithium‐ion batteries under dim light conditions, enabling the perpetual operation of practical millimeter‐scale wirelessly interconnected systems.We demonstrate monolithic GaAs photovoltaic modules at the millimeter scale to efficiently power wirelessly interconnected millimeter‐scale sensor systems operating under low‐flux conditions. Eight series‐connected cells are used to provide an operating voltage of 5 V for direct battery charging. Module power conversion efficiency greater than 26% is achieved under weak 850‐nm near‐infrared illumination and 90% voltage up‐conversion efficiency utilizing AIGaAs junction barrier isolation as a critical technique in reducing shunt leakage current.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149283/1/pip3132_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149283/2/pip3132.pd

Association Between Knowledge and Attitude About Aging and Life Satisfaction Among Older Koreans

SummaryPurposeThe purpose of this study was to measure knowledge and attitude about aging and life satisfaction among older Korean adults and to examine the influence of attitude and knowledge about aging on these adults' life satisfaction.MethodsA cross-sectional and correlational design was used. A total of 405 older adults were surveyed using a written questionnaire at six elderly welfare centers in a metropolitan city in South Korea in mid April 2011. The data were analyzed using descriptive statistics, Pearson's correlation analysis, and multiple regression.ResultsThe score of knowledge on aging was below the medium level. Attitude about aging was neutral, and life satisfaction was at the medium level. Variables such as female sex, age, economic status, monthly allowance, living with a spouse, self-rated overall health, knowledge and attitude about aging accounted for 33.8% of the total variance in predicting life satisfaction of the older adults. Older age and lower economic status reduced life satisfaction. Being female, having a monthly income of 300,000 Korea Republic Won or more, living with a spouse, and better knowledge and attitude about aging were associated with enhanced life satisfaction.ConclusionThe effect of knowledge and attitude about aging on life satisfaction is significant. Economic status, living with a spouse and self-rated overall health status are also predictive factors in life satisfaction. Consequently, nursing interventions for education and psychological support to increase knowledge about aging and induce a positive attitude towards it should be developed to improve older adults' life satisfaction

Dynamic analysis of the extended space charge layer using chronopotentiometric measurements

In this paper, we experimentally verified the length (LESC) and the concentration (cESC) of the extended space charge (ESC) layer in front of the electrical double layer (EDL) using the chronopotentiometric measurement and the equivalent circuit model analysis. From the experimentation, the coupled-response of the EDL and the ESC layer was discriminated from the contribution of electro-osmotic flow (EOF). In addition, we derived the potential differences across the ESC (VESC) layer using the circuit model of the ICP layer under rigorous consideration of ESC and EDL. As a result, we obtained that VESC was linearly proportional to the square of the applied current (iapplied). Hence, LESC and cESC were quantitatively provided, where LESC is linear to the iapplied and cESC is constant regardless of iapplied. Thus, this experimentation could not only clarify an essential ICP theory but also guide in ESC-based applications.This work is supported by the Basic Research Laboratory Project (NRF2018R1A4A1022513) and Mid-Career Project (NRF-2020R1A2C3006162) by the Ministry of Science and ICT. I. Cho was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (NRF-2020R1F1A1072960)

Intracellular Nanomaterial Delivery via Spiral Hydroporation

In recent nanobiotechnology developments, a wide variety of functional nanomaterials and engineered biomolecules have been created, and these have numerous applications in cell biology. For these nanomaterials to fulfill their promises completely, they must be able to reach their biological targets at the subcellular level and with a high level of specificity. Traditionally, either nanocarrier- or membrane disruption-based method has been used to deliver nanomaterials inside cells; however, these methods are suboptimal due to their toxicity, inconsistent delivery, and low throughput, and they are also labor intensive and time-consuming, highlighting the need for development of a next-generation, intracellular delivery system. This study reports on the development of an intracellular nanomaterial delivery platform, based on unexpected cell-deformation phenomena via spiral vortex and vortex breakdown exerted in the cross- and T-junctions at moderate Reynolds numbers. These vortex-induced cell deformation and sequential restoration processes open cell membranes transiently, allowing effective and robust intracellular delivery of nanomaterials in a single step without the aid of carriers or external apparatus. By using the platform described here (termed spiral hydroporator), we demonstrate the delivery of different nanomaterials, including gold nanoparticles (200 nm diameter), functional mesoporous silica nanoparticles (150 nm diameter), dextran (hydrodynamic diameters between 2–55 nm), and mRNA, into different cell types. We demonstrate here that the system is highly efficient (up to 96.5%) with high throughput (up to 1 × 106 cells/min) and rapid delivery (∼1 min) while maintaining high levels of cell viability (up to 94%)

Fundamental Spin Interactions Underlying the Magnetic Anisotropy in the Kitaev Ferromagnet CrI3_3

We lay the foundation for determining the microscopic spin interactions in the two-dimensional (2D) ferromagnets by combining our angle-dependent ferromagnetic resonance (FMR) experiments on high quality CrI$_3$ single crystals with theoretical modeling based on symmetries. In the 2D limit, ferromagnetism is stabilized by magnetic anisotropy. We find the largest anisotropy arises from Kitaev interactions of strength $K~\sim-5.2$ meV, larger than the Heisenberg exchange $J~\sim-0.2$ meV. We further discover that the symmetric off-diagonal anisotropy $\Gamma\sim-67.5$ $\mu$eV, though small, plays the crucial role of opening a gap in the magnon spectrum and stabilizing ferromagnetism in the 2D limit. The resolution of the FMR data is sufficient to reveal a $\mu$eV-scale quadrupolar contribution in the $S=3/2$ magnet. Our identification of the interactions underlying ferromagnetism and exchange anisotropies opens paths towards 2D ferromagnets with higher T_\rm{C} and magnetically frustrated quantum spin liquids based on Kitaev physics.Comment: 5 pages, 4 figure

Simultaneous Transitions in Cuprate Momentum-Space Topology and Electronic Symmetry Breaking

The existence of electronic symmetry breaking in the underdoped cuprates, and its disappearance with increased hole-density $p$, are now widely reported. However, the relationship between this transition and the momentum space ($\vec{k}$-space) electronic structure underpinning the superconductivity has not been established. Here we visualize the $\vec{Q}$=0 (intra-unit-cell) and $\vec{Q}\neq$0 (density wave) broken-symmetry states simultaneously with the coherent $\vec{k}$-space topology, for Bi$_2$Sr$_2$CaCu$_2$O$_{8+d}$ samples spanning the phase diagram 0.06$\leq p \leq$0.23. We show that the electronic symmetry breaking tendencies weaken with increasing $p$ and disappear close to $p_c$=0.19. Concomitantly, the coherent $\vec{k}$-space topology undergoes an abrupt transition, from arcs to closed contours, at the same $p_c$. These data reveal that the $\vec{k}$-space topology transformation in cuprates is linked intimately with the disappearance of the electronic symmetry breaking at a concealed critical point.Comment: Journal reference added. Main materials: 13 pages, 4 figures. Supplementary materials: 18 pages, 9 figure