N. S. Dinesh

A hollow stainless steel microneedle array to deliver insulin to a diabetic rat

A novel fabrication process has been described for the development of a hollow stainless steel microneedle array using femto second laser micromachining. Using this method, a complicated microstructure can be fabricated in a single process step without using masks. The mechanical stability of the fabricated microneedle array was measured for axial and transverse loading. Skin histology was carried out to study the microneedle penetration into the rat skin. Fluid flow through the microneedle array was studied for different inlet pressures. The packaging of the microneedle array, to protect the microneedle bore blockage from dust and other atmospheric contaminations, was also considered. Finally, the microneedle array was tested and studied in vivo for insulin delivery to a diabetic rat. The results obtained were compared with the standard subcutaneous delivery with the same dose rate and were found to be in good agreement.

Position control of DC motors with Experience Mapping based Prediction Controller

The paper presents a new controller inspired by the human experience based, voluntary body action control (dubbed motor control) learning mechanism. The controller is called Experience Mapping based Prediction Controller (EMPC). EMPC is designed with auto-learning features without the need for the plant model. The core of the controller is formed around the motor action prediction-control mechanism of humans based on past experiential learning with the ability to adapt to environmental changes intelligently. EMPC is utilized for high precision position control of DC motors. The simulation results are presented to show that accurate position control is achieved using EMPC for step and dynamic demands. The performance of EMPC is compared with conventional PD controller and MRAC based position controller under different system conditions. Position Control using EMPC is practically implemented and the results are presented.

Development of cup shaped microneedle array for transdermal drug delivery

Microneedle technology is one of the attractive methods in transdermal drug delivery. However, the clinical applications of this method are limited owing to: complexity in the preparation of multiple coating solutions, drug leakage while inserting the microneedles into the skin and the outer walls of the solid microneedle can hold limited quantity of drug. Here, the authors present the fabrication of an array of rectangular cup shaped silicon microneedles, which provide for reduced drug leakage resulting in improvement of efficiency of drug delivery and possibility of introducing multiple drugs. The fabricated solid microneedles with rectangular cup shaped tip have a total height of 200 μm. These cup shaped tips have dimensions: 60 × 60 μm (length × breadth) with a depth of 60 μm. The cups are filled with drug using a novel in-house built drop coating system. Successful drug dissolution was observed when the coated microneedle was used on mice. Also, using the above method, it is possible to fill the cups selectively with different drugs, which enables simultaneous multiple drug delivery.

Micro stepping of Shape Memory Alloy based Poly Phase motor

In literature we find broadly two types of shape memory alloy based motors namely limited rotation motor and unlimited rotation motor. The unlimited rotation type SMA based motor reported in literature uses SMA springs for actuation. An attempt has been made in this paper to develop an unlimited rotation type balanced poly phase motor based on SMA wire in series with a spring in each phase. By isolating SMA actuation and spring action we are able achieve a constant force by the SMA wire through out its range of operation. The Poly phase motor can be used in stepping mode for generating incremental motion and servo mode for generating continuous motion. A method of achieving servo motion by micro stepping is presented. Micro stepping consists of controlling single-phase temperature with a position feedback. The motor has been modeled with a new approach to the SMA wire Hysterysis model. Motor is simulated for different responses and the results are compared with the experimental data.

Photo-Defined Electrically Assisted Etching Method for Metal Stencil Fabrication

Metal stencils are well known in electronics printing application such as for dispensing solder paste for surface mounting, printing embedded passive elements in multilayer structures, etc. For microprinting applications using stencils, the print quality depends on the smoothness of the stencil aperture and its dimensional accuracy, which in turn are invariably related to the method used to manufacture the stencils. In this paper, fabrication of metal stencils using a photo-defined electrically assisted etching method is described. Apertures in the stencil were made in neutral electrolyte using three different types of impressed current, namely, dc, pulsed dc, and periodic pulse reverse (PPR). Dimensional accuracy and wall smoothness of the etched apertures in each of the current waveforms were compared. Finally, paste transfer efficiency of the stencil obtained using PPR was calculated and compared with those of a laser-cut electropolished stencil. It is observed that the stencil fabricated using current in PPR waveform has better dimensional accuracy and aperture wall smoothness than those obtained with dc and pulsed dc. From the paste transfer efficiency experiment, it is concluded that photo-defined electrically assisted etching method can provide an alternate route for fabrication of metal stencils for future microelectronics printing applications.

Application of EMPC for under-damped Type-1 systems

This paper presents design of a new controller based on the concept of Experience Mapping based Predictive Controller (EMPC) for an under-damped Type 1 system. The earlier design of EMPC uses rectangular pulse input as control action for well damped Type 1 systems. However, this control action is not suitable for under-damped systems as it produces undesirable oscillations. The proposed design modifies the basic control action to suit under-damped systems by reducing overshoots and oscillations. The proposed controller is used to control a DC motor based positioning system with a load coupled through a flexible shaft, which constitutes an under damped position system. The simulation results show that the proposed controller performs better than traditional controllers like the Proportional-Derivative (PD), and State Space based controllers like the Linear Quadratic Regulator (LQR) and the Linear Quadratic Gaussian (LQG) controller.

Optimal position control of a DC motor using LQG with EKF

This paper deals with the implementation of the Linear Quadratic Gaussian (LQG) with an Extended Kalman Filter (EKF) for the position control of a PMDC motor. LQG is a popularly used linear optimal control technique in literature. However, the direct implementation of LQG with the use of the Kalman Filter as the optimal estimator is incapable of adapting to changes in the system parameters which results in a deviation from the expected optimal performance. EKF allows for the estimation of the system parameter values along with the unknown states of the system. The estimated values are used to constantly update the plant model and calculate the gains for optimal performance. The effectiveness of this technique on the DC motor position control system for various changes in system parameter values is studied in this paper and compared with the performance of a simple Kalman Filter to show the improvement in performance. The results show improvements in both step responses and tracking performances with the use of the EKF estimator along with the LQG controller.

DC Motor speed control using Experience Mapping based Prediction Controller (EMPC)

Experience Mapping based Prediction Controller (EMPC) is a recently proposed controller for DC motor based position control, whose design is inspired from human motor control. As it is developed for a Type-1 system, the algorithms developed there, cannot be directly used for Type-0 systems. This paper presents the modified EMPC for Type-0 systems and the principle is applied to a DC motor speed control system. EMPC uses past experience for generating the control action in each scenario and it works in quasi-open-loop unlike conventional control systems which work in tight close loop. The paper presents the details of development of EMPC algorithm and simulations to show its performance on a DC motor based speed controller. The performance of EMPC is compared with that of a conventional PID controller for different scenarios. The speed control of DC motor using EMPC is practically implemented and the experimental results are presented.

Packaged peristaltic micropump for controlled drug delivery application

Micropump technology has evolved significantly in the last two decades and is finding a variety of applications ranging from μTAS (micro Total Analysis System) to drug delivery. However, the application area of the micropump is limited owing to: simple pumping mechanism, ease of handling, controlled (microliter to milliliter) delivery, continuous delivery, and accuracy in flow rate. Here, the author presents the design, development, characterization, and precision flow controlling of a DC-motor driven peristaltic pump for controlled drug delivery application. All the micropump components were fabricated using the conventional fabrication technique. The volume flow variation of the pump has been characterized for different viscous fluids. The change in volume flow due to change in back pressure has been presented in detail. The fail-safe mode operation of the pump has been tested and leak rate was measured (∼0.14% leak for an inlet pressure of 140 kPa) for different inlet pressures. The precision volume flow of the pump has been achieved by measuring the pinch cam position and load current. The accuracy in the volume flow has been measured after 300 rotations. Finally, the complete system has been integrated with the necessary electronics and an android application has been developed for the self-administration of bolus and basal delivery of insulin.

Out-of-plane cup shaped stainless steel microneedle array for drug delivery

To improve the transdermal delivery of drug, there are many techniques have been reported (Chemical, Iontophoresis, Sonophoresis and Microneedle). Among these techniques, the microneedle technology gained the more attention in recent years. Mainly, there are two types (Solid and Hollow) of microneedles have been reported for the successful drug delivery application. In this paper, we report on the fabrication of out-of-plane solid Stainless Steel (SS) microneedles and formation of microcup structure within them suitable for drug delivery application. Array of out-of-plane solid SS microneedles were fabricated using Electric Discharge Machining (EDM) method. Subsequently, the microcup structures on the solid SS microneedles were formed using Focused Ion Beam (FIB) technique. The microcup structure on the microneedles acts as a dedicated region to fill the drug, so that the possible drug leakage while inserting the microneedles into the skin can be avoided. The drug filling into the microcup structures was performed using drop coating method. This coating method in combination with cup shaped microneedle array enables to deliver multiple drugs simultaneously in desired proportion.