A novel microdevice for the treatment of hydrocephalus: design and fabrication of an array of microvalves and microneedles

We present an implantable, microfabricated device for the treatment of hydrocephalus. Hydrocephalus is a medical condition, in which an abnormal accumulation of cerebrospinal fluid (CSF, a water-like fluid that circulates around and protects the brain and spinal cord.) occurs in the brain. The novel microdevice presented here mimics the function of natural one-way valves, arachnoid villi, found in the human brain. Hence, we name it microfabricated arachnoid villi (MAV). The MAV consists of an array of one-way microvalves and hollow microneedles. The one-way microvalves control flow based on pressure differential. A Parylene microvalve array with a dome petal geometry was designed and fabricated. Initial flow tests demonstrated the desired low cracking pressure of the valve and a sufficient mechanical stability. The hollow microneedle array was designed to pierce the dura mater membrane (A tough fibrous membrane covering the brain and the spinal cord and lining the inner surface of the skull.) and provide a conduit for CSF. An SU-8 microneedle array was designed and successfully microfabricated. The innovative MAV may open a new era in the treatment of hydrocephalus.     

A novel polymer microneedle fabrication process for active fluidic delivery

In this article, we explore a new fabrication process for a flexible, all polymer, active fluidic delivery system, incorporating a fusion of laser micromachining and microfabrication techniques as well as rapid prototyping technology. Here, we show selective fluidic delivery from isolated microchannels through an electrochemically driven pumping reaction, demonstrate the dispensing of dose volumes up to 5.5 μl, and evaluate the device’s performance in terms of its delivery speed and ejection efficiency. Finally, we move this work toward an implantable microfluidic drug delivery device by investigating the device’s biocompatibility through a statistical approach that overviews the viability of bovine aortic endothelial cells on polyimide and silicon substrates.     

Silicon microneedle array with biodegradable tips for transdermal drug delivery

This paper presents the fabrication process, characterization results and basic functionality of silicon microneedle array with biodegradable tips for transdermal drug delivery. In order to avoid the main problems related to silicon microneedles; the breaking of the top part of the needles inside the skin, a simple solution can be the fabrication of microneedle array with biodegradable tips. A silicon microneedle array was fabricated by deep reactive ion etching (RIE), using the photoresist reflow effect and RIE notching effect. The biodegradable tips were successfully realized using the electrochemical anodization process that selectively generated porous silicon only on the top part of the skin. The porous tips can be degraded within a few weeks if some of them are broken inside the skin during the insertion and release process. The paper presents also the results of in vitro release of calcein with animal skins using a microneedle array with biodegradable tips. Compared to the transdermal drug delivery without microneedle enhancer, the microneedle array had presented significant enhancement of drug release.     

A PZT insulin pump integrated with a silicon microneedle array for transdermal drug delivery

Many of the compounds in drugs cannot be effectively delivered using current drug delivery techniques (e.g., pills and injections). Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of the skin. As the primary barrier to transport is located in the upper tissue, Micro-Electro-Mechanical-System (MEMS) technology provides novel means, such as microneedle array and PZT pump, in order to increase permeability of human skin with efficiency, safety and painless delivery, and to decrease the size of the pump. Microneedle array has many advantages, including minimal trauma at penetration site because of the small size of the needle, free from condition limitations, painless drug delivery, and precise control of penetration depth. These will promote the development of biomedical sciences and technology and make medical devices more humanized. So far, most of the insulin pumps being used are mechanical pumps. We present the first development of this novel technology, which can assemble the PZT pump and the microneedle array together for diabetes mellitus. The microneedle array based on a flexible substrate can be mounted on non-planar surface or even on flexible objects such as a human fingers and arms. The PZT pump can pump the much more precision drug accurately than mechanical pump and the overall size is much smaller than those mechanical pumps. The hollow wall straight microneedle array is fabricated on a flexible silicon substrate by inductively coupled plasma (ICP) and anisotropic wet etching techniques. The fabricated hollow microneedles are 200 μm in length and 30 μm in diameter. The microneedle array, which is built with on-board fluid pumps, has potential applications in the chemical and biomedical fields for localized chemical analysis, programmable drug-delivery systems, and very small, precise fluids sampling. The microneedle array has been installed in an insulin pump for demonstration and a leak free packaging is introduced.The support from Ministry of Science and Technology of the People’s Republic of China with contract number of 2005AA40420.     

Fabrication of microneedle array using LIGA and hot embossing process

We demonstrate a novel fabrication technology of the microneedle array applied to painless drug delivery and minimal invasive blood extraction. The fabrication technology consists of a vertical deep X-ray exposure and a successive inclined deep X-ray exposure with a deep X-ray mask whose pattern has a hollow triangular array. The vertical exposure makes triangular column array with a needle conduit. With the successive inclined exposure, the column array shapes into the microneedle array without deep X-ray mask alignment. Changing the inclined angle and the gap between the mask and PMMA (PolyMethylMetaAcrylic) substrate, different types of microneedle array are fabricated in 750–1000 m shafts length, 15^o–20^o tapered tips angle, and 190–300 m bases area. The masks are designed to 400–600 m triangles length, 70–100 m conduits diameter, 25–60EA/5 mm² arrays density, and various tip shapes such as triangular, rounded, or arrow-like features. In the medical application, the fabricated PMMA microneedle array fulfills the structural requirements such as three-dimensional sharp tapered tip, HAR (High-Aspect-Ratio) shafts, small invasive surface area, and out-of-plane structure. In the skin test, the microneedle array penetrates back of the hand skin with minimum pain and without tip break and blood is drawn after puncturing the skin. Hot embossing process and mold fabrication process are also investigated with silicon and PDMS mold. The processed tetrahedral PMMA structures are fabricated into the microneedle array by the additional deep X-ray exposure. With these processes, the microneedle array can be utilized as the mold base for electroplating process.The author thanks the staff in 9 C LIGA beamline, Pohang Light Source (PLS), Korea for their assistance on the fabrication process.     

Geometrical strengthening and tip-sharpening of a microneedle array fabricated by X-ray lithography

A novel fabrication method for LIGA (from the German “Lithographie”, “Galvanik”, and “Abformung”) microneedles with through holes is presented. Such microneedles are in demand by most bio-medical MEMS applications and in some fluidic MEMS applications. We propose a technique that combines conventional deep X-ray lithography, plane-pattern to cross-section transfer (PCT) process, and alignment X-ray lithography. The technique provides precise hole alignment with ± 3 μm tolerance. Finite-element simulations on various hole locations were performed to determine the optimum position. We previously fabricated a microneedle with a 100-μm base and a 300-μm height by a right-triangular mask. The resultant microneedle had a very sharp tip but was excessively steep, and thus resulted in a very low strength. Improved strength and tip sharpness was consequently achieved by changing the mask-pattern from a triangular pattern to a polygonal mask and changing the dimensions of the microneedle to have a 300-μm base with various heights between 350 and 800 μm. Using the proposed technique, we could produce a total of 100 hollow microneedles on a 5 × 5 mm² chip. Moreover, we successfully fabricated sharpened microneedles that were stronger than that we have fabricated so far. The molding process or electroplating and the cost list of the LIGA microneedle will also be included.     

The fabrication and property of a novel coated out-of-plane microneedle arrays

The efficiency of transdermal drug delivery (TDD) is often undermined by stratum corneum of skin. In this paper, a novel design and fabricating process was developed to coat microneedles (MNs). Testing results of facture strength of the MNs demonstrated that the Ni coated microneedle can meet the mechanical requirement for practical TDD applications. Dip-coating experiment demonstrated that it was practical to load baicalin onto the surfaces of the MNs. The amount of loaded drug was increased simply by increasing times of dip-coating operation. It was also demonstrated that upon coated by HPMC or PVP, drug can be released from the MNs in a more sustainable manner. Coating solution had great impact on drug releasing rate, indicating that the required drug concentration can be achieved by proper coating solution.     

A novel Hough transform method for line detection by enhancing accumulator array

In this paper, an improved Hough transform (HT) method is proposed to robustly detect line segments in images with complicated backgrounds. The work focuses on detecting line segments of distinct lengths, totally independent of prior knowledge of the original image. Based on the characteristics of accumulation distribution obtained by conventional HT, a local operator is implemented to enhance the difference between the accumulation peaks caused by line segments and noise. Through analysis of the effect of the operator, a global threshold is obtained in the histogram of the enhanced accumulator to detect peaks. Experimental results are provided to demonstrate the efficiency and robustness of the proposed method.     

A novel hybrid invasive weed optimization algorithm for pattern synthesis of array antennas

By introducing novel strategies in Invasive Weed Optimization (IWO), a hybrid algorithm called IWO‐simplified quadratic approximation (SQA) is proposed, in which an adaptive standard deviation is designed to improve the convergence performances of the original IWO, and SQA is embedded into IWO as a local search operator to enhance the overall search capability of the algorithm. Simulated results for six benchmark functions show that the proposed algorithm performs better than the original IWO algorithm. In addition, the proposed algorithm is used to the pattern synthesis of array antennas. Compared to the genetic algorithm (GA) and particle swarm optimization (PSO), the advantages of IWO‐SQA algorithm are shown. As another application, the phase‐only pattern reconfigurable arrays are synthesized by IWO‐SQA algorithm, and the numerical results show that IWO‐SQA algorithm is superior to GA. All the testing results show that it is an effective improvement to embed SQA into IWO algorithm. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:154–163, 2015.     

A novel active vibration isolator applied for micro-gyro by array of deposited electrodes

Micro-gyroscopes are usually driven into resonance so that the sensitivity and resolution can be enhanced. However, if any substantial vibration of the gyroscope base, over which the seismic proof mass is seated, was present, then the preset resonant frequency would be altered and the performances of the gyroscopes could be much degraded. In this paper, an innovative three degree-of-freedom (DOF) isolation system is proposed to attenuate the undesirable vibrations caused by the ambient environments. The mathematic model of the proposed 3-DOF micro-machined isolation system is established and analyzed such that the transfer function of transmissibility is obtained. The pull-in instability and associated pull-in voltage for the actuators of the isolation system are numerically unveiled so that the interval of the applied voltage to generate the electrostatic control force can be set to ensure the stability of the suspension system. In addition, a fuzzy logic proportion and derivative (PD) controller is synthesized for disturbance rejection. Five sensing electrodes, in cooperation with the isolator, are used to provide the feedback signals of the relative displacements of the proof mass with respect to the base, i.e., pitch, yaw and lateral linear displacement. Ten tuning electrodes are utilized to generate the required electrostatic forces to preserve the seismic proof mass from external disturbance. In comparison with the traditional PD action, the proposed fuzzy logic PD control strategy is verified by intensive simulations to illustrate its superior vibration isolation capability.     

A novel pattern‐reconfigurable grid array antenna

This article presents the design of a grid array antenna with pattern reconfigurable ability. Discussion of various factors that affect the radiation pattern is presented. Interdigital structure, which serves as short radiation line of grid array antenna is then introduced to reconfigure radiation pattern. Change of main beam direction is realized via state change of PIN diodes loaded in interdigital structure and variation of feed point. The scanning angle varies from ?33° to +38° and the average gain is about 10 dBi. The proposed antenna was fabricated and measured. Measured results show the proposed antenna possesses good beam‐scanning characteristics and has potential value in long‐distance power supply for various passive nodes.     

基于聚吡咯纳米阵列的葡萄糖传感器研究

该文以聚碳酸酯为模板,运用电化学聚合法制备了聚吡咯纳米阵列电极,以戊二醛作为交联剂实现了葡萄糖氧化酶在聚吡咯纳米阵列上的稳定固载.通过循环伏安(CV)以及i-t曲线实验研究了基于聚吡咯纳米阵列修饰葡萄糖传感器的电化学性能.实验结果表明,该修饰电极对葡萄糖具有良好的电化学响应,其线性范围为5.0×10-6 mol/L～6.0×10-3 mol/L,检测限为1.0×10-7 mol/L.该传感器具有检测限低、响应速度快、稳定性好等特点,应用于人体血液样品的检测取得了满意的结果.     

A novel combined structure for decoupling E/H‐plane microstrip antenna array

A novel structure combined of an I‐shaped microstrip line and eight slots etched from the ground plane is proposed to decouple both E‐plane and H‐plane antenna arrays. Five types of antenna arrays at 5.25 GHz with different linear placements are discussed for the first time and the decoupling structure is valid to them all. The edge‐to‐edge distances of the H‐plane arrays and the E‐plane arrays are 0.09 and 0.17 _, respectively. Simulated and measured results indicate that the combined structure can effectively reduce the mutual coupling, with the maximum values reaching to 22.62, 28.41, 21.04, 22.33, and 26.04 dB for five types, respectively. The proposed structure is potential in the application of multielement arrays and communication MIMO system.     

A novel high degree of freedom sparse array with displaced multistage cascade subarrays

The coprime array is a recently developed sparse array that is widely used in direction-of-arrival (DOA) estimation. The degree of freedom (DOF) for existing coprime arrays relies on the virtual array model, which is limited to the array structure. Furthermore, the continuous virtual array aperture is restricted. This paper aims to propose a novel high DOF sparse array with displaced multistage cascade subarrays to further increase the length of the continuous virtual array and improve the DOF. Through cascading and separating the same sparse arrays, the continuous virtual array aperture is improved and the accuracy of the direction-of-arrival estimation is increased. It is proved that the range of the displaced distance for the maximized continuous virtual array can be obtained. The comparison between the array configuration presented in this paper and the existing common arrays are analyzed. The simulation experiments show that, compared with the uniform array, the coprime array, the nested array, and the coprime array with displaced subarrays (CADiS), the sparse array configuration proposed in this paper can significantly increase the aperture of the continuous virtual array, greatly improve the array DOF and the DOA estimation accuracy, and effectively estimate the DOA of multiple sources in underdetermined conditions.     

Design and fabrication of MEMS-based microneedle arrays for medical applications

Fabrication results for MEMS-based microneedle arrays are presented in this paper. The microneedle array was fabricated by employing a bi-mask technique to facilitate sharp tips, a cylindrical body and side openings. The presented array has advantages over previously published microneedle arrays in terms of ease of fabrication and bonding; high needle density and robustness; and side openings, which are expected to minimize the potential for clogging from skin debris during insertion. In addition, control over the process via etch-stop markers employed as stop layers, which assure the depth of long blind holes and the structure of the needle top, allows for different needle lengths and needle top structures to be easily implemented. The preliminary fluid flow and insertion experiments were performed to demonstrate the efficiency of the microneedle arrays.     

A systolic array for the longest common subsequence problem

We introduce a linear systolic array for the Longest Common Subsequence (LCS, for short) problem. We first present an array of m identical cells which computes the length of an LCS of two strings of length m and n, respectively, in linear time (i.e., in time proportional to m + n). Then we show that, by extending any cell with the systolic stack introduced by Guibas and Liang (1982), a new array can be designed to recover an LCS in linear time.     

基于阵列信号处理的一体化模块设计

当今通信设备飞速发展,但由于频谱资源的限制,通信设备之间的互扰问题越来越严重。为了解决这一日益突出的问题,对阵列信号处理技术进行了研究。阵列信号处理技术是利用多个天线采用空时滤波的手段消除干扰信号。本文研究了针对阵列信号处理技术的一体化模块的设计,根据阵列信号处理的需求完成了天线和射频部分的制作,并进行了测试。天线单元实现轴比3 d B的仰角范围是±60°,轴比6 d B的仰角范围为±77°;3 d B轴比带宽为20 MHz,6 d B轴比带宽在40 MHz以上。射频单元采用多通道一体化设计,经测试该模块幅度误差<1 d B,相位误差<2°。并对此模块进行了半实物仿真,其滤波效果优于60 d Bc。     

A two-layered mesh array for matrix multiplication

A two-layered mesh array for matrix multiplication is presented. It computers the matrix product faster than the standard array.     

A systolic array for cyclic-by-rows Jacobi algorithms

The major concern of this paper is the systolic realization of Jacobi algorithms with a cyclic-by-rows iteration scheme. This aim can be achieved by construction of an algorithm which is well suited for parallel processing and is essentially equivalent to the above-mentioned type of algorithm. Moreover, a large variety of applications for Jacobi algorithms is presented as well as a comparison to other parallel schemes for the same problem. Finally, a systolic array is derived which requires (n + 1)²/4 processing cells and has a time complexity of O(n) for each sweep.     

A processor-time-minimal systolic array for transitive closure

Using a directed acyclic graph (DAG) model of algorithms, the authors focus on processor-time-minimal multiprocessor schedules: time-minimal multiprocessor schedules that use as few processors as possible. The Kung, Lo, and Lewis (KLL) algorithm for computing the transitive closure of a relation over a set of n elements requires at least 5n-4 parallel steps. As originally reported. their systolic array comprises n² processing elements. It is shown that any time-minimal multiprocessor schedule of the KLL algorithm's dag needs at least n²/3 processing elements. Then a processor-time-minimal systolic array realizing the KLL dag is constructed. Its processing elements are organized as a cylindrically connected 2-D mesh, when n=0 mod 3. When n≠0 mod 3, the 2-D mesh is connected as a torus