Atomistic investigation of FIB-induced damage in diamond cutting tools under various ion irradiation conditions

Focused Ion Beam (FIB) has been demonstrated as a promising tool to the fabrication of micro- and nanoscale diamond cutting tools. In-depth understanding of the ion-solid interaction in diamond leading to residual damage under different processing parameters are in high demand for the fabrication of nanoscale diamond tools. Molecular dynamics (MD) simulation method has long been regarded as a powerful and effective tool for analysing atomistic interactions with regard to its capacity of tracking each atom dynamically. Developing on the previous research work on single ion collision process in diamond, a novel Gauss random distribution multi-particle collision MD model was developed in this paper to study FIB-induced damage in diamond under various ion irradiation conditions. A multi-timestep algorithm was developed to control the whole collision process. The results show that the proposed model can effectively track the impulse of each single ion leads to atomic displacements in diamond and finally to a U-shape residual damaged layer at the core irradiation area. The multi-timestep algorithm can increase the computing efficiency by 12 times while still holding high simulation accuracy in terms of the thickness of residual damaged layer and the range of incident gallium distribution. The simulation model was further used to study the ion-induced damage layer in diamond under various beam voltages (5 kV, 8 kV, and 16 kV) and incident angles (0˚, 15˚, 30˚, and 45˚). Less damage range were found under the beam energy of 5 kV with the ion incident angle of 45˚, which indicated that a post ion beam polishing process (low beam energy with large incident angle) would be an effective way in practice to remove/minimise the residual damage layer when shaping the diamond cutting tools

Atomistic investigation of the wear of nanoscale diamond cutting tools shaped by focused ion beam

In recent years, micro/nanoscale diamond cutting tools shaped by focused ion beam (FIB) has been developed to the deterministic fabrication of micro/nano-structures owing to its unprecedented merits of high throughput, one-step, and highly flexible precision capabilities. However, the exposure of a diamond tool to FIB will result in the implantation of ion source material and the irradiation damage in cutting edges, and thus affect the tool life. In this work, molecular dynamics (MD) simulation has been carried out to study the effects of FIB induced damage on the wear resistance of nanoscale multi-tip diamond tool under different cutting conditions. A novel nanoscale multi-tip diamond tool model was built with the implanted Ga+ and amorphous damaged layer around tool tips. A damage free tool model with the same tool geometry was built as a reference. The wear resistance of the cutting tool was characterized by the total number of defect atoms formed during nanometric cutting of single crystal copper. The results show that the FIB irradiation induced doping and defects significantly degrade the wear resistance of the diamond tool. For the damage free tool cutting, the sp2 bonded carbon atoms were formed and accumulated on the surface layers. However, the sp2 bonded carbon atoms were found both on the surface and the deep inside of tool when using the tool of predefined defects. The implanted gallium atoms were found to move to the tool surface and left vacuums inside diamond tool tip, which would further degrade the wear resistance of the tool. Moreover, the variation of the sp2-bonded carbon atoms against the depth of cut and the cutting speed has been further analysed. The research findings from this study inform the in-depth understanding of tool wear of FIB shaped multi-tip diamond tool observed in previous nanometric cutting experiment

Role of the porous structure of the bioceramic scaffolds in bone tissue engineering

The porous structure of biomaterials plays a critical role in improving the efficiency of biomaterials in tissue engineering. Here we fabricate successfully porous bioceramics with accurately controlled pore parameters, and investigate the effect of pore parameters on the mechanical property, the cell seeding proliferation and the vascularization of the scaffolds. This study shows that the porosity play an important role on the mechanical property of the scaffolds, which is affected not only by the macropores size, but also by the interconnections of the scaffolds. Larger pores are beneficial for cell growth in scaffolds. In contrast, the interconnections do not affect cell growth much. The interconnections appear to limit the number of blood vessels penatrating through adjacent pores, and both the pores size and interconnections can determine the size of blood vessels. The results may be referenced on the selective design of porous structure of biomaterials to meet the specificity of biological application

Review on FIB-induced damage in diamond materials

Background: Although various advanced FIB processing methods for the fabrication of 3D nanostructures have been successfully developed by many researchers, the FIB milling has an unavoidable result in terms of the implantation of ion source materials and the formation of damaged layer at the near surface. Understanding the ion-solid interactions physics provides a unique way to control the FIB produced defects in terms of their shape and location. Methods: We have carefully selected peer-reviewed papers which mainly focusing on the review questions of this paper. A deductive content analysis method was used to analyse the methods, findings and conclusions of these papers. Based on their research methods, we classify their works in different groups. The theory of ion-matter interaction and the previous investigation on ion-induced damage in diamond were reviewed and discussed. Results: The previous research work has provided a systematic analysis of ion-induced damage in diamond. Both experimental and simulation methods have been developed to understand the damage process. The damaged layers created in FIB processing process can significantly degrade/alter the device performance and limit the applications of FIB nanofabrication technique. There are still challenges involved in fabricating large, flat, and uniform TEM samples in undoped non-conductive diamond. Conclusions: The post-facto-observation leaves a gap in understanding the formation process of ioninduced damage, forcing the use of assumptions. In contrast, MD simulations of ion bombardment have shed much light on ion beam mixing for decades. These activities make it an interesting and important task to understand what the fundamental effects of energetic particles on matter are

The significance of Notch ligand expression in the peripheral blood of children with hand, foot and mouth disease (HFMD)

BACKGROUND: Hand, foot and mouth disease (HFMD), a virus-induced infectious disease that usually affects infants and children, has an increased incidence in China in recent years. This study attempted to investigate the role of the Notch signaling pathway in the pathogenesis of HFMD. METHODS: Eighty-two children diagnosed with HFMD were enrolled into this study. The HFMD group was further divided into the uncomplicated HFMD and HFMD with encephalitis groups. The control group included 40 children who underwent elective surgery for treatment of inguinal hernias. RESULTS: Children with HFMD displayed significantly reduced CD3+, CD3+CD4+ and CD3+CD8+ cell subsets, but substantially enhanced CD3−CD19+ cell subset (p < 0.05 versus control subjects). The expression levels of Notch ligands Dll1 and Dll4 in the peripheral blood of the HFMD group were significantly higher than those in the control group (p < 0.05). There were statistically significant differences in CD3+, CD3+CD4+ and CD3−CD19+ cell subsets, but not in Notch ligand expression, between the uncomplicated HFMD and HFMD with encephalitis groups. Dll4 expression in HFMD subjects correlated negatively with the CD3+ and CD3+CD8+ cell subsets (p < 0.05), but positively with the CD3−CD19+ cell subset (p < 0.05). Furthermore, Dll4 expression in HFMD with encephalitis subjects correlated positively with total white blood cell (WBC) counts and total protein contents in cerebrospinal fluid (CSF) (p < 0.05). CONCLUSIONS: The Notch ligand Dll4 exhibits a strong correlation with the CD3+, CD3+CD8+ and CD3−CD19+ cell subsets in children with HFMD, indicating that the Notch signaling may be involved in the development of HFMD by affecting the number and status of peripheral lymphocytes

Multi-tests for pore structure characterization-A case study using lamprophyre

The pore structure plays an important role to understand methane adsorption, storage and flow behavior of geological materials. In this paper, the multi-tests including N2 adsorption, mercury intrusion porosimetry (MIP) and CT reconstruction have been proposed on Tashan lamprophyre samples. The main findings are listed: (1) The pore size distribution has a broad range ranging from 2-100000nm, among which the adsorption pores (\u3c100nm) occupies the mainly specific surface areas and pore volume while the seepage pores (\u3e100nm) only account for 34% of total pore volume. (2) The lamprophyre open pores are mainly slit-like/plate-like and ink-bottle-shaped pores on a two-dimensional level. The lamprophyre 3D pore structure shows more stochastic and anisotropic extension on the z axis to form a complex pore system on a three-dimensional level. (3) The closed pores (\u3e647nm) occupy averaged 74.86% and 72.75% of total pores (\u3e647nm) volume and specific surface area indicating a poor connectivity pore system. The revealed results provide basic information for understanding the abnormal methane emission reasons in similar geological conditions with lamprophyre invasions

Anti-proliferation effects of Sirolimus sustained delivery film in rabbit glaucoma filtration surgery

Purpose: To investigate the efficacy, safety, and mechanisms of Sirolimus sustained delivery film on prevention of scar formation in a rabbit model of glaucoma filtration surgery. Methods: Sixty-four New Zealand white rabbits who underwent trabeculectomy in the right eye were randomly allocated to one of the four treatment regimens: Sirolimus sustained delivery film treatment group (Group A), or drug-free film treatment group (Group B), or 30 ng/ml Sirolimus-soaked sponge treatment group (Group C), or no adjunctive treatment group (Group D), and each group consists of 16 rabbits. Intraocular pressure (IOP), morphologic changes of bleb, anterior chamber flare, and corneal endothelial cell count and complications were evaluated over a 28-day period follow-up time. Aqueous humor samples were gathered from Group A, and the concentration of Sirolimus was measured regularly post-operation. Rabbits were sacrificed on the 7th, 14th, and 28th day post-operation separately, and the fibroblast hypertrophy, infiltration of inflammatory, and proliferation of new collagen fiber formation in each group were evaluated with HE and Masson staining. Proliferative cell nuclear antigen (PCNA) and fibroblast apoptosis were evaluated by immunohistochemistry and terminal deoxynucleotidyl transferasemediated dUTP nick end labeling (TUNEL) assay at the 28th day post-operation. Results: Both Sirolimus sustained delivery film (Group A) and Sirolimus alone (Group C) were well tolerated in this model, and significantly prolonged bleb survival compared with no drug treatment group (Group B and D; p&lt;0.001). Group A had the longest bleb survival time in comparison with other groups (p&lt;0.001). There were significant differences in IOP readings between Group A and other groups at the last follow-up (p&lt;0.05). The concentration of Group A maintained stable for over 2 weeks, drops from (10.56 +/- 0.05) ng/ml at day 3 to (7.74 +/- 0.05) ng/ml at day 14. The number of corneal endothelial cells of Group A was not statistically significant between pre and post-operation. Histologic examination demonstrated that eyes treated with Sirolimus, especially the Sirolimus sustained delivery film, showed an obvious reduction in subconjunctival fibroblast scar tissue formation compared with no drug treatment groups, and had minimal evidence of inflammatory cell infiltration and new collagen deposition in the subconjunctiva. Immunohistochemistry assay showed that PCNA-expression was lower in the Group A (16.25 +/- 3.24%) compared to other groups (p&lt;0.01). TUNEL assay showed a significant increase in the number of apoptotic fibroblasts around the surgical area in Group A and Group C (9.75 +/- 1.71% and 8.50 +/- 1.92%) compared to the Group B and D (p&lt;0.01). Conclusions: Sirolimus drug sustained delivery film can inhibit inflammatory cell activity, impede fibroblast proliferation activity, and induce fibroblast apoptosis in the filtration surgery sites in rabbit. The results indicate a safe and effective treatment strategy in anti-scaring treatment in glaucoma surgery.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000295289900001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biochemistry &amp; Molecular BiologyOphthalmologySCI(E)9ARTICLE270-712495-25061