Monolithic mtesla-level magnetic induction by self-rolled-up membrane technology.

Monolithic strong magnetic induction at the mtesla to tesla level provides essential functionalities to physical, chemical, and medical systems. Current design options are constrained by existing capabilities in three-dimensional (3D) structure construction, current handling, and magnetic material integration. We report here geometric transformation of large-area and relatively thick (~100 to 250 nm) 2D nanomembranes into multiturn 3D air-core microtubes by a vapor-phase self-rolled-up membrane (S-RuM) nanotechnology, combined with postrolling integration of ferrofluid magnetic materials by capillary force. Hundreds of S-RuM power inductors on sapphire are designed and tested, with maximum operating frequency exceeding 500 MHz. An inductance of 1.24 µH at 10 kHz has been achieved for a single microtube inductor, with corresponding areal and volumetric inductance densities of 3 µH/mm2 and 23 µH/mm3, respectively. The simulated intensity of the magnetic induction reaches tens of mtesla in fabricated devices at 10 MHz.

Monolithic radio frequency SiN x self-rolled-up nanomembrane interdigital capacitor modeling and fabrication.

Monolithic capacitors operating at radio frequencies (RF) serve as critical components in integrated circuits for wireless communication. Design and fabrication innovations for high capacitance density RF capacitors are highly desired for the miniaturization of RFIC chips. However, practical and simple solutions are limited by existing capabilities in three-dimensional (3D) structure construction and the effective configuration of electrodes. We report a unique route to achieve unprecedentedly high capacitance density at a high operating frequency through a capacitor configuration of 3D coil interdigital electrodes using planar semiconductor processing compatible materials and fabrication methods. A systematic mechanical-electrical design principle is demonstrated, and fabricated devices show a maximum 21.5 pF capacitance, which is 17.2× larger after rolling up. The corresponding capacitance density is as large as 371 pF mm-2, with resonant frequency of 1.5 GHz. The performance could be improved significantly by simply rolling up more turns with minimal change to the area footprint.

Aligning Synthetic Hippocampal Neural Circuits via Self-Rolled-Up Silicon Nitride Microtube Arrays.

Directing neurons to form predetermined circuits with the intention of treating neurological disorders and neurodegenerative diseases is a fundamental goal and current challenge in neuroengineering. Until recently, only neuronal aggregates were studied and characterized in culture, which can limit information gathered to populations of cells. In this study, we use a substrate constructed of arrays of strain-induced self-rolled-up membrane 3D architectures. This results in changes in the neuronal architecture and altered growth dynamics of neurites. Hippocampal neurons from postnatal rats were cultured at low confluency (∼250 cells mm-2) on an array of transparent rolled-up microtubes (µ-tubes; 4-5 µm diameter) of varying topographical arrangements. Neurite growth on the µ-tubes was characterized and compared to controls in order to establish a baseline for alignment imposed by the topography. Compared to control substrates, neurites are significantly more aligned toward the 0° reference on the µ-tube array. Pitch (20-60 and 100 µm) and µ-tube length (30-80 µm) of array elements were also varied to investigate their impact on neurite alignment. We found that alignment was improved by the gradient pitch arrangement and with longer µ-tubes. Application of this technology will enhance the ability to construct intentional neural circuits through array design and manipulation of individual neurons and can be adapted to address challenges in neural repair, reinnervation, and neuroregeneration.

Is Nicotine Replacement a Safe Alternative to Smoking in Plastic Surgery Patients?

BACKGROUND: E-cigarettes, nicotine transdermal patches, and nicotine chewing gum are occasionally used as cigarette replacements by patients, but it is unknown if their use is a safe alternative to smoking in the perioperative period. METHODS: All patients undergoing major surgery at a single outpatient ambulatory surgery center for a 5-year period were tested for urine cotinine, a nicotine metabolite, the day of surgery. Patients were divided into 4 groups: never smoked (group A), quit smoking with negative urine test (group B), continued to smoke (group C), and quit smoking with positive urine test (group D). Statistical significance of complications among groups was tested using right tailed chi-square test and point biserial correlation coefficient calculations. To control for confounding factors, age and BMI of each group were compared using unequal sample size and variance t tests. RESULTS: Four hundred seventy patients were included in the study. Patient count in each group was group A n = 380, group B n = 48, group C n = 32, and group D n = 10. Complication frequency was as follows D > C > A > B. Statistically significant differences were observed between D + C (cotinine positive) and A + B (cotinine negative) P = 0.0001 and between D (nicotine replacement) and B (nicotine abstinence) P = 0.00026. There was neither statistical difference between groups A and B, nor C and D. CONCLUSIONS: Nicotine replacement carries similar risks as continued smoking and is not as safe as abstinence in the perioperative period in plastic surgery patients. Importantly, patients who stopped smoking for the surgery had equivalent risk for postoperative complications as patients who had never smoked.