Thin-film silicon (Si)-based transient electronics represents an emerging technology that enables spontaneous dissolution, absorption and, finally, physical disappearance in a controlled manner under physiological conditions, and has attracted increasing attention in pertinent clinical applications such as biomedical implants for on-body sensing, disease diagnostics, and therapeutics. The degradation behavior of thin-film Si materials and devices is critically dependent on the device structure as well as the environment. In this work, we experimentally investigated the dissolution of planar Si thin films and micropatterned Si pillar arrays in a cell culture medium, and systematically analyzed the evolution of their topographical, physical, and chemical properties during the hydrolysis. We discovered that the cell culture medium significantly accelerates the degradation process, and Si pillar arrays present more prominent degradation effects by creating rougher surfaces, complicating surface states, and decreasing the electrochemical impedance. Additionally, the dissolution process leads to greatly reduced mechanical strength. Finally, in vitro cell culture studies demonstrate desirable biocompatibility of corroded Si pillars. The results provide a guideline for the use of thin-film Si materials and devices as transient implants in biomedicine.
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Z. Zhu, H. Han, W. Tian, Y. Xie, L. Zhang, Y. Jia, and Z. Wei, "Broaden femtosecond Yb:YCOB laser pulse to octave-spanning spectrum by tapered fiber," in Advanced Solid State Lasers, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper AM5A.55. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article
We demonstrate a carrier-envelope phase-stabilized octave-spanning oscillator based on the monolithic scheme. A wide output spectrum extending from 480 nm to 1050 nm was generated directly from an all-chirped mirror Ti:sapphire laser. After several improvements, the carrier-envelope offset (CEO) beat frequency accessed nearly 60 dB under a resolution of 100 kHz. Using a feedback system with 50-kHz bandwidth, we compressed the residual phase noise to 55 mrad (integrated from 1 Hz to 1 MHz) for the stabilized CEO, corresponding to 23-as timing jitter at the central wavelength of 790 nm. This is, to the best of our knowledge, the smallest timing jitter achieved among the existing octave-spanning laser based frequency combs.
Conductive hydrogel-based ionic skins have attracted immense attention due to their great application prospects in wearable electronic devices. However, simultaneously achieving a combination of a single hydrogel system and excellent comprehensive performance (i.e., mechanical durability, electrical sensitivity, broad-spectrum antibacterial activity, and biocompatibility) remains a challenge. Thus, a novel poly(ionic liquid) hydrogel consisting of poly(acrylamide-co-lauryl methacrylate-co-methyl-uracil-imidazolium chloride-co-2-acryloylamino-2-methyl-1-propane sulfonic acid) (AAm-LMA-MUI-AMPS) was prepared by a micellar copolymerization method. Herein, MUI serves as a supramolecular crosslinker and conductive and bacteriostatic components. Owing to the multiple supramolecular crosslinks and hydrophobic association in the network, the hydrogel exhibits excellent mechanical properties (624 kPa of breaking stress and 1243 kPa of compression stress), skin-like modulus (46.2 kPa), stretchability (1803%), and mechanical durability (200 cycles under 500% strain can be completely recovered). Moreover, with the coordinated combination of each monomer, the hydrogel exhibits the unique advantage of high conductivity (up to 59.34 mS/cm). Hence, the hydrogel was further assembled as an ionic skin sensor, which exhibited a gauge factor (GF) of 10.74 and 7.27 with and without LiCl over a broad strain range (1-1000%), respectively. Furthermore, the hydrogel sensor could monitor human movement in different strain ranges, including body movement and vocal cord vibration. In addition, the antibacterial activity and biocompatibility of the hydrogel sensor were investigated. These findings present a new strategy for the design of new-generation wearable devices with multiple functions.
Abstract The past decades have witnessed the significant development and practical interest of in vivo biomedical imaging technologies and optical materials in the second‐near infrared (NIR‐II, 1000–1700 nm) window. Imaging with the extended emission wavelength toward the long‐wavelength end (NIR‐IIb, 1500–1700 nm) further offers micrometer imaging resolution and centimeter tissue penetration depth by taking advantage of the much‐reduced photon scattering and near‐zero tissue autofluorescence background, which have become a very hot research area. This review focuses on the recent advances in the development of lanthanide‐based NIR‐IIb probes for in vivo biomedical applications. The progress including ratiometric imaging, multiplexed imaging for wide‐field and microscopy, lifetime multiplexing and sensing, persistent luminescence, and multimodal imaging is summarized. Challenges and future directions concerning the investigation of the photophysical and photochemical properties of NIR‐IIb probes, the selection of near‐infrared cameras as well as the potential extension of the NIR‐IIb imaging sub‐window are pointed out. This review will inspire readers who have a strong interest in developing optical imaging technology and long‐wavelength fluorescence probes for high‐contrast in vivo biomedical applications.
Abstract Physical and chemical technologies have been continuously progressing advances in neuroscience research. The development of research tools for closed-loop control and monitoring neural activities in behaving animals is highly desirable. In this paper, we introduce a wirelessly operated, miniaturized microprobe system for optical interrogation and neurochemical sensing in the deep brain. Via epitaxial liftoff and transfer printing, microscale light-emitting diodes (micro-LEDs) as light sources and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-coated diamond films as electrochemical sensors are vertically assembled to form implantable optoelectrochemical probes for real-time optogenetic stimulation and dopamine detection capabilities. A customized, lightweight circuit module is employed for untethered, remote signal control, and data acquisition. After the probe is injected into the ventral tegmental area (VTA) of freely behaving mice, in vivo experiments clearly demonstrate the utilities of the multifunctional optoelectrochemical microprobe system for optogenetic interference of place preferences and detection of dopamine release. The presented options for material and device integrations provide a practical route to simultaneous optical control and electrochemical sensing of complex nervous systems.
Abstract The capability to selectively and precisely modulate neural activities represents a powerful tool for neuroscience research and clinical therapeutics. Traditional electrical stimulations associate with bulky and tethered implants, and optogenetic methods rely on genetic modification for cell targeting. Here, we report an optoelectronic, non-genetic strategy for exciting and inhibiting neural activities, accomplished by bioresorbable, thin-film silicon (Si) diodes. Under illumination, these devices establish polarity-dependent, positive or negative voltages at the semiconductor/solution interface. Such photovoltaic signals enable deterministic depolarization and hyperpolarization of cultured neurons, upregulating and downregulating intracellular calcium dynamics in vitro. Furthermore, flexible, thin-film Si based devices mounted on the nerve tissue selectively activate and silence in vivo activities, both in the peripheral nerve and the brain. Finally, these Si membranes naturally dissolve within the animal body. Such a Si-based material and device platform offers broad potential for biomedical applications.
We present a stable Yb-doped SESAM-mode-locked fiber laser operating in the similariton regime. 4.8 ps pulses were obtained at the central wavelength of 1030 nm and the de-chirped pulse duration was 83 fs.
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