Benjamin R. Whiteside

Investigation of Plasma Treatment on Micro-Injection Moulded Microneedle for Drug Delivery.

Plasma technology has been widely used to increase the surface energy of the polymer surfaces for many industrial applications; in particular to increase in wettability. The present work was carried out to investigate how surface modification using plasma treatment modifies the surface energy of micro-injection moulded microneedles and its influence on drug delivery. Microneedles of polyether ether ketone and polycarbonate and have been manufactured using micro-injection moulding and samples from each production batch have been subsequently subjected to a range of plasma treatment. These samples were coated with bovine serum albumin to study the protein adsorption on these treated polymer surfaces. Sample surfaces structures, before and after treatment, were studied using atomic force microscope and surface energies have been obtained using contact angle measurement and calculated using the Owens-Wendt theory. Adsorption performance of bovine serum albumin and release kinetics for each sample set was assessed using a Franz diffusion cell. Results indicate that plasma treatment significantly increases the surface energy and roughness of the microneedles resulting in better adsorption and release of BSA.

Micromoulding – precision processing for controlled products

Micromoulding is an emerging field which has seen the evolution of conventional polymer injection moulding techniques for the manufacture of 3-dimensional components of sub-milligramme masses and/or microscale surface features. Micromoulding incurs extremely high strain rates and temperature gradients, particularly at the gate of the cavity. A range of issues associated with this, including high strain rate rheology of polymers (including experimental observation of in-cavity flows) and effects on orientation, residual stress and property developments, including surface replications have been explored in our laboratories and with collaborators. A major aim is to achieve controlled, repeatable dimensions and properties in micromoulded products, and to model this process – including molecular-feature models. The key factors determining control of precision products are discussed.

Microneedle-assisted transdermal delivery of Zolmitriptan: effect of microneedle geometry, in vitro permeation experiments, scaling analyses and numerical simulations

Abstract Objective: The present study was aimed to investigate the effect of salient microneedle (MN) geometry parameters like length, density, shape and type on transdermal permeation enhancement of Zolmitriptan (ZMT). Methods: Two types of MN devices viz. AdminPatch® arrays (ADM) (0.6, 0.9, 1.2 and 1.5 mm lengths) and laboratory fabricated polymeric MNs (PM) of 0.6 mm length were employed. In the case of PMs, arrays were applied thrice at different places within a 1.77 cm2 skin area (PM-3) to maintain the MN density closer to 0.6 mm ADM. Scaling analyses was done using dimensionless parameters like concentration of ZMT (Ct/Cs), thickness (h/L) and surface area of the skin (Sa/L2). Results: Micro-injection molding technique was employed to fabricate PM. Histological studies revealed that the PM, owing to their geometry/design, formed wider and deeper microconduits when compared to ADM of similar length. Approximately 3.17- and 3.65-fold increase in ZMT flux values were observed with 1.5 mm ADM and PM-3 applications when compared to the passive studies. Good correlations were observed between different dimensionless parameters with scaling analyses. Numerical simulations, using MATLAB and COMSOL software, based on experimental data and histological images provided information regarding the ZMT skin distribution after MN application. Discussion: Both from experimental studies and simulations, it was inferred that PM were more effective in enhancing the transdermal delivery of ZMT when compared to ADM. Conclusions: The study suggests that MN application enhances the ZMT transdermal permeation and the geometrical parameters of MNs play an important role in the degree of such enhancement.

In-process 3D assessment of micromoulding features

Micro injection moulding (micromoulding) technology has recently emerged as a viable manufacturing route for polymer, metal and ceramic components with micro-scale features and surface textures. With a cycle time for production of a single component of just a few seconds, the proces offers the capability for mass production of microscale devices at a low marginal cost. However, the extreme stresses, strain rates and temperature gradients characteristic of the process have the consequence that a slight fluctuation in material properties or moulding conditions can have a significant impact on the dimensional or structural properties of the resulting component and in-line process monitoring is highly desirable. This paper describes the development of an in-process, high speed 3-dimensional measurement system for evaluation of every component manufactured during the process. A high speed camera and microscope lens coupled with a linear stage are used to create a stack of images which are subsequently processed using extended depth of field techniques to form a virtual 3-dimensional contour of the component. This data can then be used to visually verify the quality of the moulding on-screen or standard machine vision algorithms can be employed to allow fully automated quality inspection and filtering of sub-standard products. Good results have been obtained for a range of materials and geometries and measurement accuracy has been verified through comparison with data obtained using a Wyko NT1100 white light interferometer.