Computer-aided process planning for fabrication of three-dimensional microstructures for bioMEMS applications

In recent years, there has been increasing interest from both academies and industries in developing micro-electromechanical system (MEMS) technology for biological applications, known as bioMEMS or biochips. Targeting at high throughput biomolecule analysis, drug compound screening, and reduction of reagent and sample volume, today's bioMEMS devices come with miniaturised design and increased complexity of microstructures. Fabrication of such a complex bioMEMS structure involves a number of layer fabrication cycles. Moreover, a two-dimensional (2D) mask is required for each process. Thus, manually generating such a complex process plan has become a difficult task. With recent advances in material technology, polydimethylsiloxane (PDMS) silicone material has been widely applied in nowadays bioMEMS fabrication. This paper proposes a novel automated process planning approach for fabrication of three-dimensional (3D) microstructures in bioMEMS. This approach can handle both PDMS casting and traditional micro fabrication processes. It integrates a novel solid decomposition method and a feasibility search algorithm. Also, it can directly handle the solid model of an integrated microstructure with B-rep representation, and automatically generate the data of the fabrication process plan along with masks. A process planner prototype has been implemented. An application example is presented to demonstrate the functionality of the prototype.     

Preparation and characterization of electrospun PCL/PLGA membranes and chitosan/gelatin hydrogels for skin bioengineering applications

In this study, two distinct systems of biomaterials were fabricated and their potential use as a bilayer scaffold (BS) for skin bioengineering applications was assessed. The initial biomaterial was a polycaprolactone/poly(lacto-co-glycolic acid) (PCL/PLGA) membrane fabricated using the electrospinning method. The PCL/PLGA membrane M-12 (12% PCL/10% PLGA, 80:20) displayed strong mechanical properties (stress/strain values of 3.01 ± 0.23 MPa/225.39 ± 7.63%) and good biocompatibility as demonstrated by adhesion of keratinocyte cells on the surface and ability to support cell proliferation. The second biomaterial was a hydrogel composed of 2% chitosan and 15% gelatin (50:50) crosslinked with 5% glutaraldehyde. The CG-3.5 hydrogel (with 3.5% glutaraldehyde (v/v)) displayed a high porosity, ≥97%, good compressive strength (2.23 ± 0.25 MPa), ability to swell more than 500% of its dry weight and was able to support fibroblast cell proliferation. A BS was fabricated by underlaying the membrane and hydrogel casting method to combine these two materials. The physical properties and biocompatibility were preliminarily investigated and the properties of the two biomaterials were shown to be complementary when combined. The upper layer membrane provided mechanical support in the scaffold and reduced the degradation rate of the hydrogel layer. Cell viability was similar to that in the hydrogel layer which suggests that addition of the membrane layer did not affect the biocompatibility.     

Monomer transfer moulding and rapid prototyping methods for fibre reinforced thermoplastics for medical applications

The development of biodegradable materials for surgical applications is a growing area, especially in the area of fracture repair. A fully biodegradable composite has been developed for the manufacture of surgical implants tailored to the patient's injury. This composite consists of a poly-ϵ-caprolactone matrix and a biodegradable glass fibre reinforcement. This paper describes two approaches to the manufacture of such implants using geometries derived from patient scan data: a variant of structural reaction injection moulding or resin transfer moulding, and a rapid prototyping method based upon material deposition modelling.     

Electromechanical transducers at the nanoscale: actuation and sensing of motion in nanoelectromechanical systems (NEMS)

Electromechanical devices are rapidly being miniaturized, following the trend in commercial transistor electronics. Miniature electromechanical devices--now with dimensions in the deep sub-micrometer range--are envisioned for a variety of applications as well as for accessing interesting regimes in fundamental physics. Among the most important technological challenges in the operation of these nanoelectromechanical systems (NEMS) are the actuation and detection of their sub-nanometer displacements at high frequencies. In this Review, we shall focus on this most central concern in NEMS technology: realization of electromechanical transducers at the nanoscale. The currently available techniques to actuate and detect NEMS motion are introduced, and the accuracy, bandwidth, and robustness of these techniques are discussed.     

3D heterostructures and systems for novel MEMS/NEMS

Abstract

In this review, we consider the application of solid micro- and nanostructures of various shapes as building blocks for micro-electro-mechanical or nano-electro-mechanical systems (MEMS/NEMS). We provide examples of practical applications of structures created by MEMS/NEMS fabrication. Novel devices are briefly described, such as a high-power electrostatic nanoactuator, a fast-response tubular anemometer for measuring gas and liquid flows, a nanoprinter, a nanosyringe and optical MEMS/NEMS. The prospects are described for achieving NEMS with tunable quantum properties.     

Geometrically Structured Nanomaterials for Nanosensors,NEMS, and Nanosieves

Recently, geometrically structured nanomaterials have received great attention due to their unique physical and chemical properties, which originate from the geometric variation in such materials. Indeed, the use of various geometrically structured nanomaterials has been actively reported in enhanced-performance devices in a wide range of applications. Recent significant progress in the development of geometrically structured nanomaterials and associated devices is summarized. First, a brief introduction of advanced nanofabrication methods that enable the fabrication of various geometrically structured nanomaterials is given, and then the performance enhancements achieved in devices utilizing these nanomaterials, namely, i) physical and gas nanosensors, ii) nanoelectromechanical devices, and iii) nanosieves are described. For the device applications, a systematic summary of their structures, working mechanisms, fabrication methods, and output performance is provided. Particular focus is given to how device performance can be enhanced through the geometric structures of the nanomaterials. Finally, perspectives on the development of novel nanomaterial structures and associated devices are presented.     

细胞培养用温度敏感凝胶的合成与性能研究

用丙烯酸（ARc）对壳聚糖（CS）进行化学改性，合成反应中问体壳聚糖衍生物CS-ARc，进一步合成不同配比的CS-ARc与N-异丙基丙烯酰胺（NIPA）的共聚凝胶P（CS-AAc-NIPA），通过红外光谱和元素分析等表征了产物的结构和组成，并研究了P（CS—ARc-NIPA）凝胶在水中和细胞培养基中的溶胀性能．结果表明共聚凝胶在水中和培养基中均显示较好的温度敏感性．对P（CS-ARc-NIPA）共聚凝胶进行细胞培养研究发现，其表面可成功种植成纤维细胞（L929），细胞贴附生长情况良好，表明材料具有很好的细胞相容性．当环境温度降低后，共聚凝胶发生疏水．亲水变化，导致其表面细胞自动脱附，从而避免了使用酶解法脱附细胞造成的细胞功能损伤．’     

氧化海藻酸钠/聚丙烯酰胺水凝胶的制备与表征

通过水-乙醇和水-正丙醇两种不同的溶剂体系制备高分子量和不同氧化度的氧化海藻酸钠(OSA),然后引入聚丙烯酰胺(PAM)交联网络结构,通过二步法获得OSA/PAM复合水凝胶。探讨了不同反应体系下,HCl体积分数对OSA分子量的影响以及氧化剂(高碘酸钠NaIO_4)添加量、反应时间对OSA氧化度的影响规律。结果表明:在水-正丙醇体系下,HCl体积分数为24vol%时,氧化海藻酸钠的分子量达到170 000;调节NaIO_4的添加量和反应时间可以控制OSA的氧化度在10%~85%范围内变化。在此基础上对OSA/PAM复合水凝胶的溶胀率和力学性能进行了探讨,发现氧化度10%的复合水凝胶48h后的溶胀率达1 777%,断裂强度为0.11MPa,随着OSA氧化度的增大,OSA/PAM复合水凝胶的溶胀率增大,而拉伸强度逐渐减小。     

空心羟基磷灰石亚微球/壳聚糖可注射水凝胶的制备及表征

采用W/O/W复乳法制备空心羟基磷灰石(HAP)亚微球,将空心HAP亚微球均匀分布在壳聚糖/甘油磷酸钠(CS/GP)体系中制备可注射HAP/CS水凝胶(gel 1),同时制备可注射CS水凝胶(gel 2).用X射线衍射仪、场发射透射电镜、红外光谱、扫描电镜对空心HAP亚微球和水凝胶进行了表征,并比较分析了两种溶胶的成胶...     

纳米银/壳聚糖复合水凝胶的原位制备、表征及抗菌性能研究

在壳聚糖/1,2-丙二醇凝胶中采用抗坏血酸原位还原硝酸银生成纳米银,进而通过碱液置换得到具有不同纳米银含量的物理交联的纳米银/壳聚糖复合水凝胶.紫外-可见光谱、X射线衍射图谱和低分辨率TEM照片的结果表明,复合水凝胶内形成了分散良好的纳米银.高分辨率TEM照片结果表明纳米银的直径在20～50nm之间,但其结晶状态并不均一.抗菌性实验证明,纳米银/壳聚糖复合水凝胶对大肠杆菌和金黄色葡萄球菌均有抗菌效果.     

Processing and characterization of alumina/LAS bioceramics for dental applications

Alumina allows to recreate the functionality and aesthetics of natural teeth. However, its low fracture toughness rises concern regarding use in dental restoration. Structural reliability is addressed here by formulating a material containing alumina and a glass–ceramic from LAS system. The presence of LAS in the mixtures result in formation of glass phase during sintering, promoting densification at lower temperature and enhanced surface finishing. A composite microstructure with increased toughness can thus be produced. Powder mixtures containing 0, 20, 50, 80 and 100 wt%-LAS were prepared by planetary milling and uniaxial pressing and sintered. The compositions were investigated regarding their processability, mechanical performance and biological behaviour. Aesthetics was evaluated by comparison with a commercial dental matching guide. Variations on hardness and fracture toughness with starting LAS fraction were assessed by indentation. Interaction with biological medium was evaluated by immersion in a simulated body fluid. Resulting microstructures were characterised by FEG–SEM, EDS and XRD.     

纳米SiO2增强聚乙烯醇缩乙醛凝胶的温敏性研究

以正硅酸乙酯(TEOS)前驱体,采用溶胶-凝胶法向部分缩醛的聚乙烯醇(APVA)水溶液中引入二氧化硅(SiC2)粒子,再通过冷冻/解冻法制备了温敏性聚乙烯醇缩乙醛(APVA)/二氧化硅(SiO2)复合凝胶.用扫描电镜、红外光谱和力学性能分析仪对产物的结构、微观形貌和力学性能进行了表征,并对其温敏性的影响因素进行了研究....     

新型互穿网络超大孔水凝胶的制备、性能及表征

以丙烯酸、丙烯酰胺为基体，以乙烯基吡咯烷酮为预聚体，利用新型两步聚合法和发泡技术，制备了聚（丙烯酸．丙烯酰胺），聚乙烯基吡咯烷酮互穿网络超大孔水凝胶．采用差示扫描量热法（DSC）、红外光谱（FT-IR）和扫描电镜（SEM）等分析技术对所得水凝胶进行了表征，并研究了水凝胶的溶胀行为和凝胶强度．实验结果表明：该水凝胶具有相互连通的孔结构，溶胀行为在几分钟内即可完成；以新型两步法制备的互穿网络结构（IPN），大大提高了超大孔水凝胶的强度，新型两步法是制备IPN的有效方法之一．     

Ag/TiO2/bentonite nanocomposite for biological applications: Synthesis,characterization, antibacterial and cytotoxic investigations

Bentonite (bent) clay supported silver (Ag)/titanium dioxide (TiO₂) nanocomposite material was green synthesized by facile thermal decomposition method in the absence of reducing and precipitating agents. The samples were characterized by XRD, BET, HR-SEM with EDX mapping, TEM with SAED patterns, XPS, PSA, FT-IR, and UV–Vis DRS. XRD and EDX spectra showed peaks of Ag and TiO₂, confirming the formation of the Ag/TiO₂ nanoparticles in the composite. TEM revealed the uniform distribution of Ag/TiO₂ nanoparticles cluster on the surface of the bent with an average size of ～5 to 50 nm. The antibacterial activities of Na-bent, Ag, TiO₂, and Ag/TiO₂/bent nanocomposite samples were tested against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria by the well diffusion method. Furthermore, the cytotoxicity of Ag/TiO₂/bent nanocomposite material was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Also, the succinate-dehydrogenase release showed the nontoxic nature of the nanocomposite at low concentrations. The cytotoxicity results of samples were evaluated using human embryonic kidney cell line (HEK 293) and have given excellent biocompatibility and cell proliferation in the in vitro studies.     

Synthesis and characterization of tyramine-based hyaluronan hydrogels

Hyaluronan is particularly attractive for tissue engineering and repair because it: (1) is a normal component of the extracellular matrices of most mammalian tissues; (2) contributes to the biological and physical functions of these tissues; and (3) possesses excellent biocompatibility and physiochemical properties. In the present study, we characterize a two-step enzymatic cross-linking chemistry for production of tyramine-based hyaluronan hydrogels using fluorophore-assisted carbohydrate electrophoresis, enzymatic digestion, and spectroscopy including absorbance, fluorescence and ¹H NMR. Substitution on hyaluronan of tyramine and other adducts from unproductive side reactions depends on the molar ratio of tyramine to carbodiimide used during the substitution (step 1) reaction. Results indicate that relatively low tyramine substitution is required to form stable hydrogels, leaving the majority of hyaluronan disaccharides unmodified. Sufficient native HA structure is maintained to allow recognition and binding by b-HABP, a HA binding complex typically found in normal cartilage biology. Hydrogels were formed from tyramine-substituted hyaluronan through a peroxidase-dependent cross-linking (step 2) reaction at hyaluronan concentrations of 2.5 mg/ml and above. Uncross-linked tyramine-substituted hyaluronan was characterized after hyaluronidase SD digestion. Cross-linked hydrogels showed increased resistance to digestion by testicular hyaluronidase and hyaluronidase SD with increasing hyaluronan concentration. Cells directly encapsulated within the hydrogels during hydrogel cross-linking remained metabolically active during 7 days of culture similar to cells cultured in monolayer.     

Thermo-sensitive and photoluminescent hydrogels: Synthesis,characterization, and their drug-release property

Multifunctional hydrogels that simultaneously possess semi-interpenetrating networks structure, strong photoluminescence, and temperature sensitivity were successfully fabricated based on the crosslink of poly(acrylamide) (PAAm) in the presence of poly(N-isopropylacrylamide) (PNIPAM) and CdTe quantum dots (QDs) at a mild condition. With the increase of external temperature, the photoluminescence (PL) intensity and emission peak of the hydrogels gradually decreased and red-shifted, respectively. Decreasing the temperature, the PL intensity and emission peak of the hydrogels could back to their initial values again. Moreover, drug-release experiments on the multifunctional hydrogels demonstrated that the release rate can be tuned by the environmental temperature and the content of PNIPAM. In addition, biocompatible hyperbranched polyglycerol functionalized QDs (QD@HPGs) instead of pristine QDs can also be incorporated into the hydrogels, affording biocompatible hydrogels which could still exhibit temperature-sensitive photoluminescence and drug-release behaviors.     

Sonochemical synthesis,characterization, and electrochemical properties of MnMoO4 nanorods for supercapacitor applications

In this article, we reported the preparation of manganese molybdate (MnMoO₄) nanorods by a facile sonochemical method and investigated its electrochemical properties for supercapacitor applications. The microstructure, surface morphology and composition were characterized by using field emission scanning electron microscope (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction analysis (XRD), Raman spectroscopy and X-ray photo electron microscopy (XPS). The cyclic voltammetry (CV) curves of sonochemically synthesized α-MnMoO₄ nanorods revealed the presence of redox pairs suggesting the pseudocapacitive nature of MnMoO₄. A maximum specific capacitance of the α-MnMoO₄ nanorods was about 168.32 F g⁻¹ as observed from the galvanostatic charge–discharge (GCD) analysis at a constant current density of 0.5 mA cm⁻². Long term cyclic stability study revealed that about 96% of initial capacitance was retained after 2000 cycles.     

Preparation and characterization of curcumin thermosensitive hydrogels for intratumoral injection treatment

Objectives: This paper describes the development and optimization of curcumin thermosensitive hydrogels (CTH), a kind of gel injection for intratumoral injection treatment.

Methods: Aimed at increasing the content and stability of effective components, an optimal formulation of CTH was chosen based on the results from orthogonal tests and the optimal pH was determined by stability test. To investigate the hydrogels drug release in vitro, residence time by RP-HPLC and therapeutic effects on ascitic hepatocarcinoma cell strain with high metastasis potential in lymphatic system (HCA-F) solid tumors in mice.

Key findings: The selected optimal formulation of CTH was: 0.2% curcumin, 20% poloxamer 407, 4% poloxamer 188, 8% polyethylene glycol 400, 12% 1,2-propanediol and pH was 6.0. The drug release determined by RP-HPLC fit to the Higuchi model. The residence time of CTH was longer than the curcumin suspensions. Intratumoral injection of the CTH can effectively inhibit the growth of HCA-F solid tumors in mice.

Conclusions: The CTH prepared in this test demonstrates proper gel temperature and viscosity. It improves the solubility of curcumin with a relatively long period of drug release in vitro and residence time. Intratumoral injection of the CTH can effectively inhibit the growth of HCA-F solid tumors in mice.     

Nanostructured titanium/diamond-like carbon multilayer films: deposition, characterization, and applications

Titanium/diamond-like carbon multilayer (TDML) films were deposited using a hybrid system combining radio frequency (RF)-sputtering and RF-plasma enhanced chemical vapor deposition (PECVD) techniques under a varied number of Ti/diamond-like carbon (DLC) bilayers from 1 to 4, at high base pressure of 1 × 10(-3) Torr. The multilayer approach was used to create unique structures such as nanospheres and nanorods in TDML films, which is confirmed by scanning electron microscopy (SEM) analysis and explained by a hypothetical model. Surface composition was evaluated by X-ray photoelectron spectroscopy (XPS), whereas energy dispersive X-ray analysis (EDAX) and time-of-flight secondary ion mass spectrometer (ToF-SIMS) measurements were performed to investigate the bulk composition. X-ray diffraction (XRD) was used to evaluate the phase and crystallinity of the deposited TDML films. Residual stress in these films was found to be significantly low. These TDML films were found to have excellent nanomechanical properties with maximum hardness of 41.2 GPa. In addition, various nanomechanical parameters were calculated and correlated with each other. Owing to metallic interfacial layer of Ti in multilayer films, the optical properties, electrical properties, and photoluminescence were improved significantly. Due to versatile nanomechanical properties and biocompatibility of DLC and DLC based films, these TDML films may also find applications in biomedical science.