Gerard Cummins

Inkjet printing of conductive materials: a review

Purpose – The purpose of this paper is to present an exhaustive review of research studies and activities in the inkjet printing of conductive materials.Design/methodology/approach – This paper gives a detailed literature survey of research carried out in inkjet printing of conductive materials.Findings – This article explains the inkjet printing process and the various types of conductive inks. It then examines the various factors that affect the quality of inkjet printed interconnects such as printing parameters, materials and substrate treatments. Methods of characterising both the inkjet printing process and the electrical properties of printed conductive materials are also presented. Finally relevant applications of this technology are described.Originality/value – Inkjet printing is currently one of the cheapest direct write techniques for manufacturing. The use of this technique in electronic manufacturing, where interconnects and other conductive features are required is an area of increasing rele...

Optimization and characterization of Drop-on-Demand inkjet printing process for platinum organometallic inks

Inkjet printing has been extensively used over the past 30 years in the graphic arts and packaging industries. This technology involves dispensing accurately positioned droplets of ink onto a substrate, which then solidifies through the evaporation of the constituent solvent, the cross-linking of a polymer or through crystallization. The mask-less, flexible, rapid and low cost nature of inkjet printing, combined with the development of a range of functional inks, has led to the adoption of this technology in system manufacturing. The SMART Microsystems research project underway at the Institute for Integrated Systems is investigating the use of this technique in the rapid customization of CMOS foundry wafers for More-than-Moore applications. This paper presents results obtained during the development and optimization of a drop-on-demand inkjet printing process for initial batches of platinum organometallic inks. Drop-on-Demand (DOD) inkjet printing works by inducing a transient pressure pulse in the ink reservoir through electrical excitation of either a thermal or piezoelectric element. The correct implementation of this excitation signal is necessary to produce a pressure pulse capable of reproducibly and reliably generating a series of droplets. The effects of system parameters on the formation of these droplets are investigated. Methods used to characterize droplet ejection are also described.

Carbon screen-printed electrodes on ceramic substrates for label-free molecular detection of antibiotic resistance

The growing threat posed by antimicrobial resistance on the healthcare and economic well‐being of mankind is pushing the need to develop novel and improved diagnostic platforms for its rapid detection at point of care, facilitating better patient management strategies during antibiotic therapy. In this paper, we present the manufacturing and characterisation of a low‐cost carbon screen‐printed electrochemical sensor on a ceramic substrate. Using label‐free electrochemical impedance spectroscopy, the sensor is demonstrated for the detection of blaNDM, which is one of the main antimicrobial resistance factors in carbapenem‐resistant Enterobacteriaceae. The electrochemical performance of the newly fabricated sensor was initially investigated in relation to the function of its underlying composite materials, evaluating the choice of carbon and dielectric pastes by characterising properties like surface roughness, wetting and susceptibility of unspecific DNA binding. Subsequently, the sensor was used in an electrochemical impedance spectroscopy assay for the sensitive and specific detection of synthetic blaNDM targets achieving a detection limit of 200 nM. The sensor properties and performance demonstrated in this study proved the suitability of the new electrode materials and manufacturing for further point‐of‐care test development as an inexpensive and effective alternative to gold electrodes sensor.

Progress towards a multi-modal capsule endoscopy device featuring microultrasound imaging

Current clinical standards for endoscopy in the gastrointestinal (GI) tract combine high definition optics and ultrasound imaging to view the lumen superficially and through its thickness. However, these instruments are limited to the length of an endoscope and the only clinically available, autonomous devices able to travel the full length of the GI tract easily offer only video capsule endoscopy (VCE). Our work seeks to overcome this limitation with a device (“Sonopill”) for multimodal capsule endoscopy, providing optical and microultrasound (μUS) imaging and supporting sensors1.μUS transducers have been developed with multiple piezoelectric materials operating across a range of centre frequencies to study viability in the GI tract. Because of the combined constraints of μUS imaging and the low power / heat tolerance of autonomous devices, a hybrid approach has been taken to the transducer design, with separate transmit and receive arrays allowing multiple manufacturing approaches to maximise system efficiency. To explore these approaches fully, prototype devices have been developed with PVDF, high-frequency PZT and PMN-PT composites, and piezoelectric micromachined ultrasonic transducer arrays. Test capsules have been developed using 3D printing to investigate issues including power consumption, heat generation / dissipation, acoustic coupling, signal strength and capsule integrity. Because of the high functional density of the electronics in our proposed system, application specific integrated circuits (ASICs) have been developed to realise the ultrasound transmit and receive circuitry along with white-light and autofluorescence imaging with singlephoton avalanche detectors (SPADs). The ultrasound ASIC has been developed and the SPAD electronics and optical subsystem have been validated experimentally. The functionality of various transducer materials.

Nanocomposite-Based Microstructured Piezoresistive Pressure Sensors for Low-Pressure Measurement Range

Piezoresistive pressure sensors capable of detecting ranges of low compressive stresses have been successfully fabricated and characterised. The 5.5 × 5 × 1.6 mm3 sensors consist of a planar aluminium top electrode and a microstructured bottom electrode containing a two-by-two array of truncated pyramids with a piezoresistive composite layer sandwiched in-between. The responses of two different piezocomposite materials, a Multiwalled Carbon Nanotube (MWCNT)-elastomer composite and a Quantum Tunneling Composite (QTC), have been characterised as a function of applied pressure and effective contact area. The MWCNT piezoresistive composite-based sensor was able to detect pressures as low as 200 kPa. The QTC-based sensor was capable of detecting pressures as low as 50 kPa depending on the contact area of the bottom electrode. Such sensors could find useful applications requiring the detection of small compressive loads such as those encountered in haptic sensing or robotics.

Progress towards filling through silicon vias with conductive ink

Inkjet printing is a promising additive manufacturing technology that is being increasingly used in applications such as displays, electronics and electronic packaging. Through Silicon Vias (TSVs) is an important enabling technology for advanced electronic packaging. The direct write nature of inkjet printing would also allow flexible packaging solutions through the cheap and sustainable filling of vias. This paper describes the progress to date with using this printing technology to fill TSVs and some of the challenges encountered to date.

Luminally expressed gastrointestinal biomarkers

ABSTRACT Introduction: A biomarker is a measurable indicator of normal biologic processes, pathogenic processes or pharmacological responses. The identification of a useful biomarker is challenging, with several hurdles to overcome before clinical adoption. This review gives a general overview of a range of biomarkers associated with inflammatory bowel disease or colorectal cancer along the gastrointestinal tract. Areas covered: These markers include those that are already clinically accepted, such as inflammatory markers such as faecal calprotectin, S100A12 (Calgranulin C), Fatty Acid Binding Proteins (FABP), malignancy markers such as Faecal Occult Blood, Mucins, Stool DNA, Faecal microRNA (miRNA), other markers such as Faecal Elastase, Faecal alpha-1-antitrypsin, Alpha2-macroglobulin and possible future markers such as microbiota, volatile organic compounds and pH. Expert commentary: There are currently a few biomarkers that have been sufficiently validated for routine clinical use at present such as FC. However, many of these biomarkers continue to be limited in sensitivity and specificity for various GI diseases. Emerging biomarkers have the potential to improve diagnosis and monitoring but further study is required to determine efficacy and validate clinical utility.

Ultrasound capsule endoscopy: sounding out the future

Video capsule endoscopy (VCE) has been of immense benefit in the diagnosis and management of gastrointestinal (GI) disorders since its introduction in 2001. However, it suffers from a number of well recognized deficiencies. Amongst these is the limited capability of white light imaging, which is restricted to analysis of the mucosal surface. Current capsule endoscopes are dependent on visual manifestation of disease and limited in regards to transmural imaging and detection of deeper pathology. Ultrasound capsule endoscopy (USCE) has the potential to overcome surface only imaging and provide transmural scans of the GI tract. The integration of high frequency microultrasound (µUS) into capsule endoscopy would allow high resolution transmural images and provide a means of both qualitative and quantitative assessment of the bowel wall. Quantitative ultrasound (QUS) can provide data in an objective and measurable manner, potentially reducing lengthy interpretation times by incorporation into an automated diagnostic process. The research described here is focused on the development of USCE and other complementary diagnostic and therapeutic modalities. Presently investigations have entered a preclinical phase with laboratory investigations running concurrently.

Characterization and development of materials for an integrated high-temperature sensor using resistive test structures

This paper reports the application of test structures to the evaluation of tantalum nitride (Ta-N) as a material for integration with high temperature electronics. The test structure fabrication involves the reactive sputtering of Ta-N and its consequent annealing in a vacuum to reach the target specifications of low temperature coefficient of resistance (TCR). A test wafer has been designed to both evaluate the temperature performance of thin films and to study the possibility of integrating different metal films into a single sensing device. The Ta-N resistors resulting from this work have a TCR of -150 ppm/°C which remains stable after 6 hours of annealing at 600°C.

Novel dual layer electroformed stencils for high resolution LTCC circuit manufacture

This article reports the silver paste printing onto LTCC substrates at sub-100µm linewidths using a microengineered electroformed dual layer stencil. It is demonstrated that such a stencil can serve as a screen replacement and print tracks of line widths down to 40µms with a gap of 25µm. Two commercially available Ag pastes designed for either screen printing tracks or stencil printing vias were analyzed to gain insight into what material properties are best suited for fine line printing using a dual layer stencil. It is shown that the same stencil and paste material can be used to fill in vias down to 200µm diameter for ceramic green tapes of 50µm thickness indicating that these line printing and via filling processes could be combined, allowing thereby increased throughput, resolution and registration benefit in LTCC manufacture.