三维微小凹图式的加工及其与人神经母细胞瘤细胞的复合

采用紫外光光刻、硅蚀刻及软光刻技术分别制备了阴性光刻胶SU-8和聚乳酸及聚羟基乙酸共聚物(PLGA)微小凹图式.以人神经母细胞瘤细胞SH-SY5Y与三维微结构进行复合,采用扫描电子显微镜、光学显微镜及caicein荧光染色评价所加工图式的结构形态及细胞的生长行为.实验制备出名义直径约100/μm、高纵横比(接近或大于1)并可叠加微通道连接的SU-8及PLGA三维微小凹图式.所加工的图式透明,符合三维细胞生物传感器的光学检测的需要.细胞培养结果表明,该结构尺寸的图式能引导在三维环境神经细胞的排布、神经突起延伸及形态分化.     

Flexible SU-8 microstructures for neural implant design

This work investigates the use of SU-8 microstructures for applications within flexible neural implants. Six different microstructures are fabricated and tested in both tension and bending to determine their Young’s modulus and their failure stress when deformed about a small radius of curvature. A numerical model is presented that accurately predicts the performance of the structures under bending, and physical testing shows that stresses of up to 300 MPa are achievable.     

Process research of high aspect ratio microstructure using SU-8 resist

SU-8 is a negative, epoxy type, near-UV photoresist. This resist has been specifically developed for ultrathick, high-aspect-ratio MEMS-type applications using standard lithography equipment. However, in practice, SU-8 has shown to be very sensitive to process parameter variation. The orthogonal array was used in our experiments in order to improve the lithography quality and analyze the interaction among the parameters. The analyses show that the interaction between the exposure dose and post exposure bake has played an important role in adhesion between SU-8 resist and the substrate. The proposed process conditions are given. The output structure has straight sidewall profile, fine line and good space resolution. The aspect ratio is larger than 20. Moreover, several metallic films are used as substrates. The Ti film with oxidation treatment was found to have the strongest adhesion to the resist. The result will help to open possibilities for low-cost LIGA-type process for MEMS applications.     

聚乳酸三维微结构条件下人神经母细胞瘤细胞电压依从式钙通道的功能响应性

以紫外光光刻、硅蚀刻及软光刻技术制备了聚乳酸( poly-L-lactide,PLLA)三维微小凹图式,考察入神经母细胞瘤细胞( SH-SY5Y)在微小凹结构上的生长与分布行为.以共聚焦显微技术结合钙离子荧光染料Calcium Green-1,AM评价SH-SY5Y细胞在PLLA三维微小凹图式和平面基底上电压依从式钙离子通道(VGCCs)的功能响应性.实验发现,分布在微小凹顶部的细胞为二维生长方式,凹内侧壁的为三维生长方式,凹内底部的为边界二维生长方式;以50 mmol/L高钾溶液去极化刺激发现,三维及边界二维细胞VGCCs阳性响应比率为75%和81%,较平面培养的91.2%明显降低.上述结果     

Adhesive bonding with SU-8 in a vacuum for capacitive pressure sensors

This paper describes a method for fabricating capacitive pressure sensors through the use of adhesive bonding with SU-8 in a vacuum. The influence of different parameters on the bonding of structured wafers was investigated. It was found that pre-bake time, pumping time, and the thickness of the crosslink layer are the most important factors for successful bonding. Bonding quality was evaluated by inspection through the transparent glass of the sensor and through the use of an SEM photograph, with 90% of the area successfully bonded and an ultimate yield of 70% of the sensors. The measured bonding strength was 17.15 MPa and 19.6 MPa for wafers bonded in 80 °C and 100 °C, respectively. The pressure–capacitance characteristic test results show that this bonding process is a viable micro electro mechanical systems (MEMS) fabrication technology for cavity sealing in a vacuum.     

Reduction of diffraction effect for fabrication of very high aspect ratio microchannels in SU-8 over large area by soft cushion technology

Edge bead due to spin coating has been found to cause an air gap as large as 53 m for a 99-m thick (measured at the wafer center) SU-8 coating over a 4-in. wafer. This caused poor mask width replication and non-uniformity of SU-8 pattern width. We have devised a process using a soft cushion technology to improve mask dimension replication and large-area pattern uniformity. A soft cushion was placed beneath the substrate to produce convex bending of the wafer in order to improve the contact between the mask and photoresist top surface during UV exposure. Dramatic improvements in pattern uniformity, from over 30% variation in SU-8 width across the wafer to less than 10%, and mask width replication, from 54% deviation from mask width to 20%, have been demonstrated. Numerically calculated increases in SU-8 width from the wafer center to the edge bead using the Fresnel diffraction equation match well with observed values. Further, employment of this technique with a narrow (10 m) dark-field mask enabled the fabrication over the entire surface of 4-in. diameter wafers of dense SU-8 gratings separated by microchannels with aspect ratio over 18.