Multifunctional vertical interconnections of multilayered flexible substrates for miniaturised POCT devices

Point-of-care testing (POCT) is an emerging technology which can lead to an eruptive change of lifestyle and medication of population against the traditional medical laboratory. Since living organisms are intrinsically flexible and malleable, the flexible substrate is a necessity for successful integration of electronics in biological systems that do not cause discomfort during prolonged use. Isotropic conductive adhesives (ICAs) are attractive to wearable POCT devices because ICAs are environmentally friendly and allow a lower processing temperature than soldering which protects heat-sensitive components. Vertical interconnections and optical interconnections are considered as the technologies to realise the miniaturised high-performance devices for the future applications. This thesis focused on the multifunctional integration to enable both electrical and optical vertical interconnections through one via hole that can be fabricated in flexible substrates. The functional properties of the via and their response to the external loadings which are likely encountered in the POCT devices are the primary concerns of this PhD project. In this thesis, the research of curing effect on via performance was first conducted by studying the relationship between curing conditions and material properties. Based on differential scanning calorimetry (DSC) analysis results, two-parameter autocatalytic model (Sestak-Berggren model) was established as the most suitable curing process description of our typical ICA composed of epoxy-based binders and Ag filler particles. A link between curing conditions and the mechanical properties of ICAs was established based on the DMA experiments. A series of test vehicles containing vias filled with ICAs were cured under varying conditions. The electrical resistance of the ICA filled vias were measured before testing and in real time during thermal cycling tests, damp heat tests and bending tests. A simplified model was derived to represent rivet-shaped vias in the flexible printed circuit boards (FPCBs) based on the assumption of homogenous ICAs. An equation was thus proposed to evaluate the resistance of the model. Vias with different cap sizes were also tested, and the equation was validated. Those samples were divided into three groups for thermal cycling test, damp heat ageing test and bending test. Finite element analysis (FEA) was used to aid better understanding of the electrical conduction mechanisms. Based on theoretical equation and simulation model, the fistula-shape ICA via was fabricated in flexible PCB. Its hollow nature provides the space for integrations of optical or fluidic circuits. Resistance measurements and reliability tests proved that carefully designed and manufactured small bores in vias did not comprise the performance. Test vehicles with optoelectrical vias were made through two different approaches to prove the feasibility of multifunctional vertical interconnections in flexible substrates. A case study was carried out on reflection Photoplethysmography (rPPG) sensors manufacturing, using a specially designed optoelectronic system. ICA-based low-temperature manufacture processes were developed to enable the integration of these flexible but delicate substrates and components. In the manufacturing routes, a modified stencil printing setup, which merges two printing-curing steps (vias forming and components bonding) into one step, was developed to save both time and energy. The assembled probes showed the outstanding performance in functional and physiological tests. The results from this thesis are anticipated to facilitate the understanding of ICA via conduction mechanism and provide an applicable tool to optimise the design and manufacturing of optoelectrical vias

Supramolecular Cross-Linking and Gelation of Conjugated Polycarbazoles via Hydrogen Bond Assisted Molecular Tweezer/Guest Complexation

Supramolecular cross-linking and gelation represent a fascinating approach to improve the performance of π-conjugated polymers. Up to now, supramolecular π-conjugated polymer networks have been mainly developed by grafting noncovalent recognition motifs onto the side-chain of π-conjugated polymers. In comparison, much less attention has been paid to the construction of main-chain-type supramolecular polymer networks, in which π-conjugated polymers themselves serve as the noncovalent linkages. Herein we have developed a novel and efficient strategy to attain this objective. The design principle is primarily on the basis of noncovalent molecular recognition between bis­[alkynyl­platinum­(II)]­terpyridine molecular tweezer receptor and <i>NH</i>-type carbazole guest, which shows enhanced binding affinity due to the cooperative participation of donor–acceptor and intermolecular N–H---N hydrogen-bonding interactions. The “hydrogen-bond enhanced molecular tweezer/guest recognition” strategy can be further applied for multivalent complexation between π-conjugated polycarbazoles and homoditopic molecular tweezer cross-linker, leading to the formation of main-chain-type supramolecular polymer networks and gels with thermal and solvent responsiveness. Hence, π-conjugated polymers can be endowed with excellent processability via the supramolecular engineering approach, which provides a new avenue toward flexible optoelectronic applications

Electrically conductive adhesive enable to manufacture high performance patch probe for non-invasive physiological assessment

A reflection-mode photoplethysmographic (rPPG) patch probe has been researched to improve its performance for non-invasive physiological assessment through electrically conductive adhesives (ECAs) based manufacture processes. Special PiN photodiodes and Light Emitting Diodes (LEDs) were mounted on a flexible printed circuit to reach the objectives of both sensitivity and stability, and user comfort as well. The trial rPPG probes were successfully manufactured and evaluated in the house. The results gained from this study shown the functions of the probe could be fully realized by ECAs. The preliminary outcome demonstrates the suitability for the cardiovascular assessment

The parameter settings of our method.

<p>The parameter settings of our method.</p

The sequence segmentation results of our method for solitary pulmonary nodules.

<p>Column (a) shows the original lung CT sequence images, (b) shows the results of the local enlargement of (a), (c) shows the segmentation results of HMSLIC (first image) and the extraction of ROI images (other images), (d) shows the local enlargement of (c) (first image) and the segmentation results of the ROI images using HMSLIC (other images), (e) shows lung nodule image mask sequences obtained by the Improved DBSCAN algorithm, (f) and (g) present the final results using our method and manual segmentation by experts.</p

The sum of the distance between superpixel blocks.

<p>The sum of the distance between superpixel blocks.</p

HMSLIC algorithm.

<p>HMSLIC algorithm.</p

Light-Enhanced Hypoxia-Response of Conjugated Polymer Nanocarrier for Successive Synergistic Photodynamic and Chemo-Therapy

The tumor hypoxic environment as well as photodynamic therapy (PDT)-induced hypoxia could severely limit the therapeutic efficacy of traditional PDT. Fortunately, the smart integration of hypoxia-responsive drug delivery system with PDT might be a promising strategy to enhance the PDT efficiency that is hindered by the hypoxic environment. Herein, a novel azobenzene (AZO) containing conjugated polymers (CPs)-based nanocarriers (CPs-CPT-Ce6 NPs) was constructed for the combination of PDT with chemotherapy, as well as to enhance the hypoxia-responsive drug release by light. The conjugated polymer chains, used as a matrix to prepare the CPs-CPT-Ce6 NPs, were beneficial for loading hydrophobic photosensitizers and chemotherapy drugs, to improve their cellular uptake. Moreover, the AZO group (−NN−) in CPs, which can be reduced and cleaved by azoreductase (a typical biomarker of hypoxia) under the hypoxic environment of tumor cells, acts as the hypoxia-responsive linker component. Upon laser irradiation, the CPs-CPT-Ce6 NPs could produce ROS for PDT and then facilitate the enhancement of tumor hypoxic condition, which could further promote the dissociation of CPs via reductive cleavage of AZO bridges to subsequently release cargos (chemotherapeutic drug, CPT) and then significantly enhance the killing effects to tumor cells that were resistant to PDT. Both in vitro and in vivo studies confirmed the improvement of synergistic therapeutic effects of our CPs-CPT-Ce6 NPs. This cascade responsive approach provides an excellent complementary mode for PDT and could open new insights for constructing programmable and controllable responsive systems in biomedical applications

Diagram of the lung nodule image sequence segmentation method.

<p>Diagram of the lung nodule image sequence segmentation method.</p

The segmentation results of our method for solitary pulmonary nodules and cavitary nodules.

<p>Column (a) shows the original lung CT images, (b) shows the results of the local enlargement of (a), (c) shows the segmentation results of HMSLIC, (d) shows the results of the local enlargement of (c), (e) shows the lung nodule image masks obtained by the Improved DBSCAN algorithm, and (f) and (g) present the final results using our method and manual segmentation by experts.</p