Biocompatibility Of Silicon Research Articles

Colloidal Silicon Quantum Dot‐Based Cavity Light‐Emitting Diodes with Narrowed and Tunable Electroluminescence

AbstractLuminescent colloidal silicon quantum dots (SiQDs) are explored as alternatives to metal‐based quantum dots for light‐emitting diodes (LEDs) because of the abundance and biocompatibility of silicon. To date, the broad electroluminescence (EL) bandwidth (>100 nm) and blueshifting of EL at high applied voltages of SiQD‐LEDs are outstanding challenges that limit a competitive spectral purity and device stability. Herein, the fabrication and testing of SiQD‐LEDs that incorporate a Fabry–Pérot cavity are reported which exhibit a narrow spectral linewidth as low as ≈23 nm. The presented devices also provide wavelength and visual stability from +4 to +8 V, as well as spectral tunability.

Silicon Quantum Dot-Polymer Fabry-Pérot Resonators with Narrowed and Tunable Emissions.

Luminescent silicon nanoparticles have been widely recognized as an alternative for metal-based quantum dots (QDs) for optoelectronics partly because of the high abundance and biocompatibility of silicon. To date, the broad photoluminescence line width (often >100 nm) of silicon QDs has been a hurdle to achieving competitive spectral purity and incorporating them into light-emitting devices. Herein we report fabrication and testing of straightforward configuration of Fabry-Pérot resonators that incorporates a thin layer of SiQD-polymer hybrid/blend between two reflective silver mirrors; remarkably these devices exhibit up-to-14-fold narrowing of SiQD emission and achieve a spectral bandwidth as narrow as ca. 9 nm. Our polymer-based, SiQD-containing Fabry-Pérot resonators also provide convenient spectral tunability, can be prepared using a variety of polymer hosts and substrates, and enable rigid as well as flexible devices.

(Invited) Printed Poly-Si TFTs on Paper for Beyond Plastic Electronics

Solution process has received many attentions in recent years because of low-cost manufacturability of flexible electronic devices owing to the additive process. Organic and metal-oxide semiconductors can be printed at low-temperature however carrier mobility and reliability of TFTs using those materials are still much inferior than those for silicon. Silicon as the base material, on the other hand, has advantages in terms of high-mobilities for the both of electron and holes, chemical and electrical stability, and low-power consumption by CMOS circuit configuration. Silicon can be printed using liquid silicon ink, which is a mixture of polymerized cyclopentasilane (CPS) and a solvent [1]. However, low-temperature formation and fabrication of polycrystalline-Si (poly-Si) and transistors on top of low-cost flexible substrates, such as paper, were outstanding challenges. In this paper, we review a novel method that forms poly-Si patterns directly on paper using the same liquid silicon with doctor-blade coating and local irradiation of excimer-laser with room temperature process [2]. We review also the process and electrical properties of poly-Si TFTs fabricated on the paper [3]. Both p- and n-channel poly-Si TFTs were fabricated directly on top of paper with field-effect mobilities of 6.2 cm2/Vs and 2.0 cm2/Vs, respectively. Owing to the low-cost, biodegradable nature of paper, and superior electrical performance and reliability and biocompatibility of silicon, this technique will break-though the printed electronics by enabling applications such as fast printed electronics that are inexpensive, fully-recyclable, biodegradable and even edible. [1] T. Shimoda, et al., “Solution-processed silicon films and transistors” Nature 440, 783-786 (2006). [2] M. Trifunovic, T. Shimoda and R. Ishihara, “Solution-processed polycrystalline silicon on paper”, Appl. Phys. Lett. 106, 163502 (2015) [3] M Trifunovic, PM Sberna, T Shimoda, R Ishihara, “Solution-based polycrystalline silicon transistors produced on a paper substrate”, npj Flexible Electronics 1 (1), 12 (2017)

Dissolution chemistry and biocompatibility of silicon- and germanium-based semiconductors for transient electronics.

Semiconducting materials are central to the development of high-performance electronics that are capable of dissolving completely when immersed in aqueous solutions, groundwater, or biofluids, for applications in temporary biomedical implants, environmentally degradable sensors, and other systems. The results reported here include comprehensive studies of the dissolution by hydrolysis of polycrystalline silicon, amorphous silicon, silicon-germanium, and germanium in aqueous solutions of various pH values and temperatures. In vitro cellular toxicity evaluations demonstrate the biocompatibility of the materials and end products of dissolution, thereby supporting their potential for use in biodegradable electronics. A fully dissolvable thin-film solar cell illustrates the ability to integrate these semiconductors into functional systems.

Emulsions of β-cyclodextrins grafted to silicone for the transport of antifungal drugs

The transport of pharmaceutical or cosmetic active substances that are not soluble in water requires their solubilisation or encapsulation in a suitable dosage form. A material combining the solubilising properties of β-cyclodextrins and the biocompatibility of silicone has been prepared as an aqueous emulsion and used for the encapsulation of an antifungal molecule. β-cyclodextrins have been chemically grafted to the poly(methylhydrosiloxane) polymer or poly(methylhydrosiloxane-co-dimethylsiloxane) copolymer through hydrosilylation reaction. The multi-step synthesis includes the regioselective attachment of tosyl group to one of the primary hydroxyls, its conversion into allylic derivative and subsequent acetylation of the remaining hydroxyl groups. The final step consists in grafting the cyclodextrin derivative to silicone polymer by means of hydrosilylation reaction. Such polymers that bear peracetylated β-cyclodextrins have been emulsified by the “spontaneous emulsification” method, giving stable emulsions with sizes ranging between 200 and 500 nm. The emulsions could encapsulate the antifungal substance griseofulvin inside the β-cyclodextrin cavity by formation of inclusion complex. The encapsulation rate was limited to the 1:1 stoichiometry of the complex. Supplementary amount of griseofulvin could not be encapsulated and slowly precipitated as crystalline particles. Emulsions of silicone oil investigated as reference formulations did not incorporate even a small amount of griseofulvin.

Silicon grid devices for attachment of cultured fibroblast collagen lattices

In this paper we demonstrate a new method to attach cultures of collagen lattices on a silicon microdevice. First, we demonstrate the silicon biocompatibility feasibility and study, and then we describe a solution based on a specific grid directly etched on a 200 μm thick silicon plate. The collagen lattice can grow around this grid and attach the silicon plate during its development.

The Biocompatibility of Silicone, Fluorosilicone and Perfluorocarbon Liquids as Vitreous Tamponades

Purpose: To investigate the interactions occurring at the interface between some currently used vitreous tamponading substances and the ocular tissues, in an early follow-up after surgery. Methods: Adult albino rabbit eyes underwent vitrectomy and were injected intravitreally with silicone oils at 1,000 or 3,000 cSt, fluorosilicone oil and perfluorodecalin. Different morphological techniques (light microscopy, scanning and electron microscopy, immunohistochemistry) were applied. Results: All the tested materials, although non-toxic, penetrate the ocular tissues also at the anterior segment level, and in the long-term follow-up this can yield functional impairment. No massive inflammation has been detected in the zones in contact with the materials, but immunoglobulins and complement fractions are anyway present in the stroma of various tissues and around the droplets of emulsified materials, suggesting a local immune reaction. Conclusions: Data from this study confirmed that a permanent vitreous substitute, showing a perfect biocompatibility, still does not exist. The indication to remove the tamponading substance within 2 months after the surgery emerges from this investigation, confirming previous studies. Despite some negative features, silicone oil still appears the most biocompatible material for vitreous replacement.

Assessment of the Lymphocyte Response to Silicone

The biocompatibility of silicone is once again the focus of increased interest. Long considered inert, silicone has now been reported to be responsible for macrophage inhibition in rats and to possibly cause adjuvant disease in humans, and the related compound silica has elicited an antibody response in mice. The present study evaluates lymphocytic response to silicone as expressed by the demonstration of immunologic memory, or changes in specific lymphocyte subpopulations. Thirty-six female Lewis rats (250 gm body weight) were used as test animals. Group 1 (n = 12) was injected subcutaneously with 2.5 ml Freund's Complete Adjuvant (FCA) alone. Group 2 (n = 12) was injected with 2.5 ml FCA sonicated with silicone gel. Group 3 (n = 6) was injected with 2.5 ml FCA, and at 4 weeks, gel-filled silicone implants were placed subcutaneously. Group 4 (n = 6) was injected with 2.5 ml FCA sonicated with silicone gel, and gel-filled silicone implants were placed at 4 weeks. An additional group of six rats (group 5) served as control for the experimental animals, and a group of four rats (group 6) served as naive control. Groups 1 and 2 were sacrificed at 4 weeks, and splenic lymphocytes were obtained for lymphocyte transformation assays performed against silicone. Assays also were run with the addition of the known mitogens Con A, PHA, LPS, and pokeweed. Cytofluorographic analysis of pan-T, T-helper, T-suppressor, and B-cell populations was performed. Groups 3, 4, 5, and 6 were harvested at 8 months, and splenic lymphocytes were subjected to lymphocyte transformation assay.(ABSTRACT TRUNCATED AT 250 WORDS)