High-resolution 3D direct-write prototyping for healthcare applications

The healthcare sector has much to benefit from the vast array of novelties erupting from the manufacturing world. 3D printing (additive manufacturing) is amongst the most promising recent inventions with much research concentrated around the various approaches of 3D printing and applying this effectively in the health sector. Amongst these methods, the direct-write assembly approach is a promising candidate for rapid prototyping and manufacturing of miniaturised medical devices/sensors and in particular, miniaturised flexible capacitive pressure sensors. Microstructuring the dielectric medium of capacitive pressure sensors enhances the sensitivity of the capacitive pressure sensor. The structuring has been predominantly achieved with photolithography and similar subtractive approaches. In this project high-resolution 3D direct write printing was used to fabricate structured dielectric mediums for capacitive pressure sensors. This involved the development and rheological characterisation of printability-tuned water soluble polyvinyl pyrrolidone (PVP) based inks (10%-30% polymer content) for stable high-resolution 3D printing. These inks were used to print water soluble micromoulds that were filled and cured with otherwise difficult to structure low G’ materials like PDMS. Our approach essentially decouples ink synthesis from printability at the micrometre scale. The developed micro moulding approach was employed for printing pyramidal micro moulds, that were used as templates for fabricating pyramid structured dielectric mediums for capacitive pressure sensing. The power of the approach was used to alter the microstructures and reap enhanced pressure sensing characteristics for effective miniaturised capacitive pressure sensors. A pressure sensing ring – that could be worn by doctors and surgeons – was prototyped with our approach and employed successfully to monitor in real-time the radial pulse signal of a 29 year old male volunteer. The print resolution of the inks was enhanced by formulating and rheologically characterising a PVP/PVDF polymer blend ink that would wet the printing nozzle less due to the hydrophobicity of the PVDF

Automatic Microassembly System for tissue engineering- Assisted with top-view and force control

Master'sMASTER OF ENGINEERIN

Shaping surface acoustic waves for cardiac tissue engineering

The heart is a non-regenerating organ that gradually suffers a loss of cardiac cells and functionality. Given the scarcity of organ donors and complications in existing medical implantation solutions, it is desired to engineer a three-dimensional architecture to successfully control the cardiac cells in vitro and yield true myocardial structures similar to native heart. This thesis investigates the synthesis of a biocompatible gelatin methacrylate hydrogel to promote growth of cardiac cells using biotechnology methodology: surface acoustic waves, to create cell sheets. Firstly, the synthesis of a photo-crosslinkable gelatin methacrylate (GelMA) hydrogel was investigated with different degree of methacrylation concentration. The porous matrix of the hydrogel should be biocompatible, allow cell-cell interaction and promote cell adhesion for growth through the porous network of matrix. The rheological properties, such as polymer concentration, ultraviolet exposure time, viscosity, elasticity and swelling characteristics of the hydrogel were investigated. In tissue engineering hydrogels have been used for embedding cells to mimic native microenvironments while controlling the mechanical properties. Gelatin methacrylate hydrogels have the advantage of allowing such control of mechanical properties in addition to easy compatibility with Lab-on-a-chip methodologies. Secondly in this thesis, standing surface acoustic waves were used to control the degree of movement of cells in the hydrogel and produce three-dimensional engineered scaffolds to investigate in-vitro studies of cardiac muscle electrophysiology and cardiac tissue engineering therapies for myocardial infarction. The acoustic waves were characterized on a piezoelectric substrate, lithium niobate that was micro-fabricated with slanted-finger interdigitated transducers for to generate waves at multiple wavelengths. This characterization successfully created three-dimensional micro-patterning of cells in the constructs through means of one- and two-dimensional non-invasive forces. The micro-patterning was controlled by tuning different input frequencies that allowed manipulation of the cells spatially without any pre- treatment of cells, hydrogel or substrate. This resulted in a synchronous heartbeat being produced in the hydrogel construct. To complement these mechanical forces, work in dielectrophoresis was conducted centred on a method to pattern micro-particles. Although manipulation of particles were shown, difficulties were encountered concerning the close proximity of particles and hydrogel to the microfabricated electrode arrays, dependence on conductivity of hydrogel and difficult manoeuvrability of scaffold from the surface of electrodes precluded measurements on cardiac cells. In addition, COMSOL Multiphysics software was used to investigate the mechanical and electrical forces theoretically acting on the cells. Thirdly, in this thesis the cardiac electrophysiology was investigated using immunostaining techniques to visualize the growth of sarcomeres and gap junctions that promote cell-cell interaction and excitation-contraction of heart muscles. The physiological response of beating of co-cultured cardiomyocytes and cardiac fibroblasts was observed in a synchronous and simultaneous manner closely mimicking the native cardiac impulses. Further investigations were carried out by mechanically stimulating the cells in the three-dimensional hydrogel using standing surface acoustic waves and comparing with traditional two-dimensional flat surface coated with fibronectin. The electrophysiological responses of the cells under the effect of the mechanical stimulations yielded a higher magnitude of contractility, action potential and calcium transient

Developing Instrumentation for Multi-parametric Investigation of Mechanisms of Mechanosensitivity in Ion Channels

Mechanosensitive (MS) channels are implicated in pathologies of the renal and pulmonary systems. Abnormal activity in MS channel reduces cell viability causing a variety of pathologies. MS channels are also responsible for sensation of pain and hearing. Despite the vital importance of MS channels, very little is known about the gating mechanisms of these channels. Attempts to study the mechanisms are severely limited by the lack of suitable instrumentation. A better understanding of the structure-function interaction of MS channels is necessary to find pharmacological leads for the pathologies. Activation data based on indirect activation of MS channels using hypo- or hyper-osmotic solutions or viscous drag is confounded by factors like membrane stretch and cytoskeletal stress. Traditional patch clamp does not allow direct access to the cell by other probes. While a planar patch clamp chip may allow for such access, most of the existing planar patch clamp chips are focused on high throughput screening for pharmaceutical targets and have designs that limit multi-parametric studies. We present here instrumentation that combines atomic force microscopy with cellular electrophysiology based on planar patch clamp approach. The instrumentation allows multi-parametric studies on single cells and provides unique insights into mechanisms of activation of not just MS channels, but ion channels in general by combining cellular electrophysiology, optical microscopy and atomic force microscopy. Using HaCaT cells as our model system we have obtained functional maps of distribution MS channels across cell surface. The maps reveal that the distribution of MS channels on HaCaT cells is highly non-uniform and that the channels are present in small clusters instead of dispersed as single entities. Our results using direct mechanical stimulation of single cells reveal that threshold stress level is required in order to activate MS channels and that the stress has a limited spatial range. Investigation of kinetics of the electrical response to direct mechanical stimulation reveals that the MS channels respond to the mechanical signal after a small time lag, which we attribute to the conformational changes necessary while the channel is being gated. We hope that the insights gained from studying the mechanosensitive channels of HaCaT cells will also advance the understanding of MS channels in general. Apart from opening new avenues in MS channel research, the instrumentation can also be useful in studying the dynamics and gating of ligand gated channels by appropriately tagging the AFM cantilever. With further improvements in the speed of AFM imaging, it will also be possible to observe the gating of channels in real time at molecular scale by imaging the channel on the cell while the channel is being gated

International Workshop on MicroFactories (IWMF 2012): 17th-20th June 2012 Tampere Hall Tampere, Finland

This Workshop provides a forum for researchers and practitioners in industry working on the diverse issues of micro and desktop factories, as well as technologies and processes applicable for micro and desktop factories. Micro and desktop factories decrease the need of factory floor space, and reduce energy consumption and improve material and resource utilization thus strongly supporting the new sustainable manufacturing paradigm. They can be seen also as a proper solution to point-of-need manufacturing of customized and personalized products near the point of need

Microfluidics for Biosensing

There are 12 papers published with 8 research articles, 3 review articles and 1 perspective. The topics cover: Biomedical microfluidics Lab-on-a-chip Miniaturized systems for chemistry and life science (MicroTAS) Biosensor development and characteristics Imaging and other detection technologies Imaging and signal processing Point-of-care testing microdevices Food and water quality testing and control We hope this collection could promote the development of microfluidics and point-of-care testing (POCT) devices for biosensing

Microdevices and Microsystems for Cell Manipulation

Microfabricated devices and systems capable of micromanipulation are well-suited for the manipulation of cells. These technologies are capable of a variety of functions, including cell trapping, cell sorting, cell culturing, and cell surgery, often at single-cell or sub-cellular resolution. These functionalities are achieved through a variety of mechanisms, including mechanical, electrical, magnetic, optical, and thermal forces. The operations that these microdevices and microsystems enable are relevant to many areas of biomedical research, including tissue engineering, cellular therapeutics, drug discovery, and diagnostics. This Special Issue will highlight recent advances in the field of cellular manipulation. Technologies capable of parallel single-cell manipulation are of special interest