The development of microneedles that penetrate the skin barrier, but are small enough not to stimulate nerves, has the potential to deliver drugs across skin in a painless way. Controlled injection by convective flow into skin using hollow microneedles, however, has remained a challenge. To address this challenge, the goals of this study were (i) to provide experimental measurements coupled with numerical simulations to quantitatively describe fluid mechanics of flow within microneedles over a range of experimental conditions and needle geometries, (ii) to demonstrate and study the effects of diffusion-based delivery of insulin to diabetic rats in vivo using solid and hollow microneedles and (iii) to determine the effect of experimental parameters on microinfusion through hollow microneedles into skin to optimize drug delivery protocols and identify rate-limiting barriers to flow. Experimentally, we quantified the relationship between pressure drop and flow rate through microneedles as a function of fluid viscosity and microneedle length, diameter, and cone half-angle. Microneedle tip diameter and taper angle were the primary controlling parameters for flow through conically tapered microneedles as shown by numerical simulations. Flow rates over a range of 1.4 56 l/s were achieved through microneedles (in the absence of skin) with pressure drops in the range of 4.6 196.5 kPa. This work also studied the use of solid and hollow microneedle arrays to insert into the skin of diabetic animals for transdermal delivery of insulin. Blood glucose levels dropped by as much as 80% in diabetic rats in vivo. Larger drops in blood glucose level and larger plasma insulin concentrations were shown due to higher donor solution insulin concentration, shorter microneedles insertion time and fewer repeated insertions. The final scope of this work was to determine the effect of microneedle geometry and infusion protocols on microinfusion flow rate into skin in vitro. Infusion flow rates ranged from 21 to 1130 l/h was demonstrated using glass microneedles. The presence of a bevel at the microneedle tip, larger retraction distance and insertion depth, larger infusion pressure and the presence of hyaluronidase led to larger infusion flow rates.

Diss. (sammanfattning) Stockholm : Karol. inst., 2000. / Härtill 7 uppsatser.

No description available.

No description available.

Accurate needle placement is critical to the success of needle-based interventions. Needle deflection due to tissue non-homogeneity and dynamic forces results in targeting error, potentially requiring repeated insertions. Real-time imaging enables closed-loop control of the needle during insertion, improving insertion accuracy. The needle localization algorithm proposed in this thesis models the needle as a parametric polynomial equation optimized to minimize beam bending energy relative to a set of observed needle coordinates. Simulated insertions using an MRI dataset show that the minimum bending energy model allows planning of subsequent imaging planes to capture the moving needle while estimating the shape of the needle with low error.

Surgical operations and processing of natural product require accurate presentation of the target area in order to achieve precise incisions. An excellent example is the deboning automation for chicken breast meat, for which the pose of the wing can greatly affect the cutting efficiency, ability to fix the structure, and product yield. In contrast to engineering objects, biological products present difficulties such as variation in size, shape, and material properties. Unlike past research, which generally found ways to emulate the manual cutting motion, this thesis investigates the effects of wing manipulation on incision tasks. The objective of this thesis is to develop an analytical model for characterizing the manipulation for pose presentation of a musculoskeletal structure for a specified incision. The manipulation model consists of joint kinematics, the mechanics of bio-materials, and a grasping mechanism to determine the joint pose and forces for a given manipulation trajectory. The model provides a basis for monitoring the cutting of bio-material via non-visual information, as well as for design of a compliant mechanism that can be used in an industrial automation application. To gain a better understanding, a wing manipulation test-bed consisting of a force/torque sensor at the point of wing manipulation has been developed. Two specific examples are investigated. The first is needle insertion into bio-materials, and the other is the shoulder cutting operation associated with chicken breast meat deboning. The effects of manipulation on needle insertion forces are used to quantify improvements in insertion point accuracy and required insertion force. Force signatures are also developed for insertion into the biomaterials located within the shoulder joint. The information gathered from both the manipulation model and needle insertion experiments provide a basis for successful implementation of the automation of the shoulder cut. While the experimentation presented in this thesis is developed in the context of poultry processing, which has immediate contributions as a tool that would facilitate the design of the automated cutting mechanisms in poultry industry, we expect that the development of the models will find a broad range of applications ranging from general meat processing, to surgical simulation, and physical therapy.

In this study, an electrolytic micro-machining tester is employed to investigate the effects of supply voltage and initial machining position on the geometry of the tungsten needle using the single-point and the reciprocating methods. The tungsten needle to be electrolyzed is dipped in an aqueous electrolyte of 2wt % sodium hydroxide as the anode, and the stainless steel needle with a diameter of 100 £gm as the cathode, and the electrode gap is set to be 10 £gm. Experimental results show that it is difficult to control the diameter of the tungsten needle because the reduction rate of its diameter is quite fast and the bubbles are generated violently to cause the breakage of the tungsten needle at the higher supply voltage. At the lower supply voltage, the tungsten needle can be machined to a finer scale, but it takes a long machining time. Under the single-point machining condition, it can be used to manufacture a short, uniform, and smooth tungsten needle with the diameter of 9 £gm at the supply voltage of 12V and the initial machining position of 75 £gm. Under the reciprocating machining condition, a long uniform micro-cylinder tungsten needle can be manufactured, but its surface becomes rough slightly at the supply voltage of 4V and the initial machining position in the range between -50 and 0 £gm. A tungsten needle with the aspect ratio of 30 and the diameter of 9 £gm can be manufactured using the following process: the machining time of 24 min at the supply voltage of 4V, and then the machining time of 28 min at the supply voltage of 2V. Key words¡Gtungsten needle, sodium hydroxide

Thesis (M. Med. Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 71-78).

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

A pose estimation method is proposed for measuring the position and orientation of a biopsy needle. The technique is to be used as a touchless needle guide system for guidance of percutaneous procedures with 4D ultrasound. A pair of uncalibrated, light-weight USB cameras are used as inputs. A database is prepared offline, using both the needle line estimated from camera-captured images and the true needle line recorded from an independent tracking device. A nonparametric learning algorithm determines the best fit model from the database. This model can then be used in real-time to estimate the true position of the needle with inputs from only the camera images. Simulation results confirm the feasibility of the method and show how a small, accurately made database can provide satisfactory results. In a series of tests with cameras, we achieved an average error of 2.4mm in position and 2.61° in orientation. The system is also extended to real ultrasound imaging, as the two miniature cameras capture images of the needle in air and the ultrasound system captures a volume as the needle moves through the workspace. A new database is created with the estimated 3D position of the needle from the ultrasound volume and the 2D position and orientation of the needle calculated from the camera images. This study achieved an average error of 0.94 mm in position and 3.93° in orientation.