Zheng Li

Biomaterials bridging the biotic–abiotic interface in plants offer the opportunity to precisely deliver agrochemicals and continuously monitor plant health, with the goals of increasing resilience to climate change, enhancing crop production and mitigating environmental impact. In this study we report the manipulation of silk fibroin assembly with inorganics nucleation at their phase front to nanomanufacture porous and hollow microneedles that can be interfaced with plants. Plant growth analysis and quantification of wounding gene expression show a non-significant systemic wounding response to the injection of silk microneedles in tomato plants. Microneedles with a hollow structure enable the systemic delivery of plant micronutrients to treat chlorosis in tomato plants and crop biofortification through transport of human micronutrients injected in the petiole and loaded into tomato fruits. Hollow microneedles also provide access to plant vasculature for sap sampling, enabling continuous monitoring and early detection of phytoaccumulation of environmental contaminants such as cadmium.

Classical transport of electrons and holes in nanoscale devices leads to heating that severely limits performance, reliability, and efficiency. In contrast, recent theory suggests that interband quantum tunneling and subsequent thermalization of carriers with the lattice results in local cooling of devices. However, internal cooling in nanoscale devices is largely unexplored. Here, using a novel scanning thermal microscopy technique with millikelvin temperature resolution and nanometer spatial resolution, we directly record the cross-sectional temperature in functional InGaAs tunnel diodes. Our measurements reveal large, localized cooling of 2-3 W/cm^{2} at the tunnel junction, which is in quantitative agreement with the bipolar Peltier process associated with interband tunneling. These advances hold significant potential for integration into electronic and energy conversion devices and improving their performance.

Decarbonizing food production and mitigating agriculture's environmental impact require new technologies for precise delivery of fertilizers and pesticides to plants. The cuticle, a waxy barrier that protects the surface of leaves, causes 60%–90% runoff of fertilizers and pesticides, leading to the wastage of intensive resources, soil depletion, and water bodies pollution. Solutions to mitigate runoff include adding chemicals (e.g., surfactants) to decrease surface tension and enhance cuticles' permeability but have low efficacy. In this study, vapor‐induced synergistic differentiation (VISDi) is used to nanomanufacture echinate pollen‐like, high payload content (≈50 wt%) microcapsules decorated with robust spines that mechanically disrupt the cuticle and adhere to the leaf. VISDi induces a core–shell structure in the spines, enabling the release of agrochemicals from the microparticles' body into the leaf. As proof of concept, precise and highthroughput delivery of iron fertilizer in Fe‐deficient spinach plants is demonstrated. Spray of spiny microparticles improves leaf adhesion by mechanical interlocking, reduces wash‐off by an ≈12.5 fold, and enhances chlorophyll content by ≈7.3 times compared to the application of spherical counterparts. Together, these results show that spiny microparticles can mitigate agricultural runoff and provide a high‐throughput tool for precise plant drug delivery.

Hydrogen sulfide (H₂S), a critical gas signaling molecule, and N-acetyltransferase 2 (NAT2), a key enzyme in drug metabolism, are both known active biomarkers for liver function. However, the interactions and effects of H₂S and NAT2 in living cells or lesion sites remain unknown due to the lack of imaging tools to achieve simultaneous detection of these two substances, making it challenging to implement real-time imaging and precise tracking. Herein, we report an activity-based two-photon fluorescent probe, TPSP-1, for the cascade detection of H₂S and NAT2 in living liver cells. Continuous conversion from TPSP-1 to TPSP-3 was achieved in liver cells and tissues. Significantly, leveraging the outstanding optical properties of this two-photon fluorescent probe, TPSP-1, has been effectively used to identify pathological tissue samples directly from clinical liver cancer patients. This work provides us with this novel sensing and two-photon imaging probe, which can be used as a powerful tool to study the physiological functions of H₂S and NAT2 and will help facilitate rapid and accurate diagnosis and therapeutic evaluation of hepatocellular carcinoma.

High-resolution, three-dimensional fluorescence microscopy is widely used in biology and neuroscience. The challenges of conventional three-dimensional fluorescence microscopy which relies on scanning the focal spot across the object include limited imaging cycles due to photobleaching of the fluorophores, ambiguous spatiotemporal information in dynamic samples due to long scanning times, and mechanical perturbation during the scanning process. In this paper, we report a snapshot three-dimensional fluorescence microscopy method (CausWEI) where three-dimensional sample information is encoded in a single wide-field image by engineering a high-contrast, laterally invariant point-spread function composed of caustics generated via the interaction of a uniform, thick glass sample holder and a high-numerical aperture objective. The three-dimensional information is computationally reconstructed from the caustic pattern recorded at the camera plane. The method can be implemented with a wide-field fluorescence microscope, without any internal modification in the microscope optics. We qualitatively and quantitatively evaluate CausWEI’s capabilities and limitations with reference fluorescent beads, neural cells on three-dimensional scaffolds, and spinal cord tissue sections. CausWEI microscopy is of importance when fluorescently labelled features are located in a depth range significantly larger than the depth-of-field of the objective lens.

We realize single-mode, waveguide-coupled, electrically driven silicon light emitting diodes in commercial, unmodified silicon photonics foundry processes and develop a model of both the electrical and optical behavior to understand the performance limitations. We measure a center wavelength of 1130 nm, a 90 nm 3 dB optical bandwidth, and 200 pW of optical power propagating in each direction. We show on-chip modulation and detection of the generated light using native resonant photodetectors integrated in the same chip. Our work unveils a new native light source available in silicon photonics processes, which can find applications ranging from device screening and fabrication quality assessment to imaging, refractive index sensing, or intra-chip communication.

Light detection and ranging (LIDAR) is a widely used technique for measuring distance. With recent advancements in integrated photonics, there is a growing interest in miniaturizing LIDAR systems through on-chip photonic devices, but a LIDAR light source compatible with current integrated circuit technology remains elusive. In this letter, we report a pulsed CMOS LED based on native Si, which spectrally overlaps with Si detectors’ responsivity and can produce optical pulses as short as 1.6 ns. A LIDAR prototype is built by incorporating this LED and a Si single-photon avalanche diode (SPAD). By utilizing time-correlated single-photon counting (TCSPC) to measure the time-of-flight (ToF) of reflected optical pulses, our LIDAR successfully estimated the distance of targets located approximately 30 cm away with sub-centimeter resolution, approaching the Cramér-Rao lower bound set by the pulse width and instrument jitter. Additionally, our LIDAR is capable of generating depth images of natural targets. This all-Si LIDAR demonstrates the feasibility of integrated distance sensors on a single photonic chip.

Despite remarkable progress in the development of halide perovskite materials and devices, their integration into nanoscale optoelectronics has been hindered by a lack of control over nanoscale patterning. Owing to their tendency to degrade rapidly, perovskites suffer from chemical incompatibility with conventional lithographic processes. Here, we present an alternative, bottom-up approach for precise and scalable formation of perovskite nanocrystal arrays with deterministic control over size, number, and position. In our approach, localized growth and positioning is guided using topographical templates of controlled surface wettability through which nanoscale forces are engineered to achieve sub-lithographic resolutions. With this technique, we demonstrate deterministic arrays of CsPbBr₃nanocrystals with tunable dimensions down to <50 nm and positional accuracy <50 nm. Versatile, scalable, and compatible with device integration processes, we then use our technique to demonstrate arrays of nanoscale light-emitting diodes, highlighting the new opportunities that this platform offers for perovskites’ integration into on-chip nanodevices.

Nanoscale, sub-wavelength size light-emitting diodes (LEDs) have attractive features including high spatial coherence, fast modulation, and high array density. Here we present digital holography and time-of-flight ranging using nanoscale CMOS LEDs.