Maan Alkaisi | University of Canterbury/Te Whare Wānanga o Waitaha (original) (raw)

Papers by Maan Alkaisi

2021 IEEE 48th Photovoltaic Specialists Conference (PVSC)

Solvents play an important role in the preparation of the electron ETL and hole HTL transport lay... more Solvents play an important role in the preparation of the electron ETL and hole HTL transport layers and consequently in determining the optical properties, morphologies and perovskite thin-film quality. Lithium TFSI employed in HTL and FK209 cobalt TFSI used in ETL are usually dissolved by acetonitrile (ACN) solvent. However, this solvent is toxic and can accelerate the deterioration of the perovskite films. This work propose alternatives for ACN to slow down the perovskite films deterioration and improve its performance. Solar cells prepared using FK209/ethanol and lithium/isopropanol alcohol have shown excellent performance with champion device efficiency reaching 23.5%.

Cell Biochemistry and Biophysics, Oct 9, 2019

Appropriate mechanical forces on cells are vital for normal cell behaviour and this review discus... more Appropriate mechanical forces on cells are vital for normal cell behaviour and this review discusses the possibility that tumour initiation depends partly on the disruption of the normal physical architecture of the extracellular matrix (ECM) around a cell. The alterations that occur thence promote oncogene expression. Some questions, that are not answered with certainty by current consensus mechanisms of tumourigenesis, are elegantly explained by the triggering of tumours being a property of the physical characteristics of the ECM, which is operative following loading of the tumour initiation process with a relevant gene variant. Clinical observations are consistent with this alternative hypothesis which is derived from studies that have, together, accumulated an extensive variety of data incorporating biochemical, genetic and clinical findings. Thus, this review provides support for the view that the ECM may have an executive function in induction of a tumour. Overall, reported observations suggest that either restoring an ECM associated with homeostasis or targeting the related signal transduction mechanisms may possibly be utilised to modify or control the early progression of cancers. The review provides a coherent template for discussing the notion, in the context of contemporary knowledge, that tumourigenesis is an alliance of biochemistry, genetics and biophysics, in which the physical architecture of the ECM may be a fundamental component. For more definitive clarification of the concept there needs to be a phalanx of experiments conceived around direct questions that are raised by this paper.

Biodegradable casein films have significant potential for use as non-supported stand-alone sheeti... more Biodegradable casein films have significant potential for use as non-supported stand-alone sheeting in orthopaedic implants and tissue engineering substrates. Multi-scale surface patterns can be used to modulate and guide cell interaction by means of an engineered construct. The majority of work on cell-pattern interaction has so far focused on non-degradable materials. In this paper we demonstrate for the first time the fabrication of microand nano-scale geometric patterns on the surface of a crosslinked biodegradable casein film. To achieve this we introduce a two-step fabrication procedure based on polydimethylsiloxane (PDMS) softlithography. We will show the reproduction of microand nanoscale patterns in liquid-cast casein films. We also demonstrate film formation and cross-linking using glutaraldehyde and discuss the use of these films as cell-culture substrates.

We present optically resonant bipartite metal nano-cylinder arrays fabricated using electron beam... more We present optically resonant bipartite metal nano-cylinder arrays fabricated using electron beam lithography. The arrays utilise two different structure sizes with diameter differences as small as 10 nm. We show that this can be achieved and that the arrays show a resonance response that agrees with electromagnetic simulations.

EPJ Photovoltaics

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achie... more High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO2 (C-TiO2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO2 layer were characterized for various DC powers and different ratios of Ar to O2 plasma. It was found that the optimum preparation conditions for the C-TiO2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O2. A power conversion efficiency (PCE) of 15.3% in forward...

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achie... more High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO 2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO 2 (C-TiO 2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O 2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO 2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO 2 layer were characterized for various DC powers and different ratios of Ar to O 2 plasma. It was found that the optimum preparation conditions for the C-TiO 2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O 2. A power conversion efficiency (PCE) of 15.3% in forward sweep and 16.7% in reverse sweep were achieved under sunlight simulator of 100 mW/cm 2. These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO 2 layer.

Nanomaterials

Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We ... more Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We report on cesium-based hybrid perovskite solar cells with wavelength-selective properties ranging from 500 nm (UV-VIS) to 800 nm (IR). The band gap tuning was achieved through composition changes of mainly lead(II) iodide PbI2 and lead(II) bromide PbBr2. The optical spectra of the developed materials were studied, including the photoluminescence (PL), optical transparency, X-ray diffraction and external quantum efficiency for samples prepared under different compositions. It was found that a high content of iodine displayed a photoluminescence (PL) peak at 790 nm, whereas a high content of bromine showed a PL peak at 548 nm. The combined composition mixture of PbI2 and PbBr2 can be fine-tuned to prepare materials that absorbed light in the visible range (640–660 nm) or other selective wavelengths in the range from 500 to 800 nm. The illuminated current-voltage characteristics of the sola...

Nanomaterials, MDPI, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Vacuum Science & Technology B, 2021

Subradiant surface lattice resonances are of interest due to their remarkably high quality factor... more Subradiant surface lattice resonances are of interest due to their remarkably high quality factors. In this work, these high quality resonances are experimentally investigated in the visible spectrum with Au and Ag bipartite disk lattices fabricated with electron beam lithography. Subradiant resonances are also compared to unipartite surface lattice resonance with angle-resolved extinction measurements, which are supported by numerical models. Finally, the lattice parameters are optimized to show high quality factors in lattices where the elements have a diameter difference as small as 10 nm.

2020 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2020

In this paper we explore how nano-structure arrays can help improve plasmonic sensors and imaging... more In this paper we explore how nano-structure arrays can help improve plasmonic sensors and imaging devices. By using a periodic array the range of parameters that can be varied to give a specific response increases dramatically compared to devices based on individual structures. We show that plasmonic arrays can be engineered to show high quality spectral extinction peaks controlled primarily by the angle of incidence and period with minimal dependence on the structure. This gives flexibility in designing plasmonic sensing or imaging devices. The fabrication of the nanostructure arrays is presented as well as optical verification of the localised plasmon resonance response. Spectral simulation results are also obtained for the arrays using Scattering by Multiple Particles in Thin Film Systems (SMUTHI) software which proves to be a useful tool in analysing the response of plasmonic arrays.

Journal of Nanobiotechnology, 2006

A technique for permanently capturing a replica impression of biological cells has been developed... more A technique for permanently capturing a replica impression of biological cells has been developed to facilitate analysis using nanometer resolution imaging tools, namely the atomic force microscope (AFM). The method, termed Bioimprint™, creates a permanent cell 'footprint' in a non-biohazardous Poly (dimethylsiloxane) (PDMS) polymer composite. The transfer of nanometer scale biological information is presented as an alternative imaging technique at a resolution beyond that of optical microscopy. By transferring cell topology into a rigid medium more suited for AFM imaging, many of the limitations associated with scanning of biological specimens can be overcome. Potential for this technique is demonstrated by analyzing Bioimprint™ replicas created from human endometrial cancer cells. The high resolution transfer of this process is further detailed by imaging membrane morphological structures consistent with exocytosis. The integration of soft lithography to replicate biologic...

Micromachines, 2019

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovol... more Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as ...

Micromachines, 2019

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovol... more Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as ...

Micro/Nano Materials, Devices, and Systems, 2013

ABSTRACT The surface plasmon resonances induced light coupling is widely recognized as a promisin... more ABSTRACT The surface plasmon resonances induced light coupling is widely recognized as a promising way of enhancing the light absorption in photovoltic devices. This is achieved by enhanced localized electromagnetic field in the vicinity of metal surface or the strong light scattering effects from metal nanoparticles integrated on the front surface of as-fabricated solar cells. In this paper, the colloidal gold nanoparticles(Au NPs), synthesized by modified Turkevich and Frens method, were integrated onto the inverted nanopyramid silicon solar cell via a dip coating method. A 7% increase in short-circuit current density of solar cell was observed for 15 minutes dip coating. As a result, a 4.6% increase in overall efficiency was achieved. However,the dense surface coverage of Au NPs resulted in decreased fill factor.

Biofabrication, 2015

Bioimprinting, which involves capturing cell morphological details into a polymer matrix, provide... more Bioimprinting, which involves capturing cell morphological details into a polymer matrix, provides a new class of patterned surfaces which opens an opportunity to investigate how cells respond to their own signatures and may introduce possibilities for regulating their behaviour. In this study, phenotypic details of human nasal chondrocytes (HNCs) were replicated in soft polydimethylsiloxane (PDMS) mould resulting in inverse replicas of cells, which have been termed here as 'negative bioimprint'. For the first time, the information from this negative bioimprint was then transferred into another PDMS layer resulting in surfaces which resemble cell morphology and were called 'positive bioimprints'. Soft lithography was used to transfer these details from PDMS into different polymers like polystyrene, tissue culture polystyrene and clinically used block co-polymer poly (ethylene glycol) terephthalate-poly (butylene terephthalate) (PEGT-PBT). Results obtained from surfac...

Biochemical and Biophysical Research Communications

The importance of the biophysical cellular environment in cancer development has been increasingl... more The importance of the biophysical cellular environment in cancer development has been increasingly recognised but so far has been only superficially studied. Here we investigated the effect of cell-like substrate topography on ovarian cancer cell behaviour and potential underlying signalling pathways. We observed changes in cell morphology in response to substrate topography, which implies modification of structure-function associations. Differences in focal adhesion signalling and Rho/ROCK activity suggested their involvement in the biomechanically-driven cellular responses. Cell-like topography was also shown to modulate the MAPK pathway and hence potentially regulate cell proliferation. The selective regulation of the cells by the mechanotransduction pathways that we noted has wide ranging implications for understanding cancer development. We established that the physical architecture of cell culture substrate is sufficient to influence cancer cell behaviour, independent of genetic composition or biochemical milieu.

ACS applied materials & interfaces, Jan 11, 2018

Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of ... more Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of conducting polymer (CP) structures. It is precisely localized and highly controllable, thus providing great opportunities for incorporating CPs into microelectronic array devices. Herein we demonstrate 3D writing and characterization of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) pillars in an array format, by using an in-house-constructed variant of scanning ion conductance microscopy (SICM). CP pillars with different aspect ratios were successfully fabricated by optimizing the writing parameters: pulling speed, pulling time, concentration of the polymer solution, and the micropipette tip diameter. Especially, super high aspect ratio pillars of around 7 μm in diameter and 5000 μm in height were fabricated, indicating a good capability of this direct writing technique. Additions of an organic solvent and a cross-linking agent contribute to a significantly enhanced w...

2021 IEEE 48th Photovoltaic Specialists Conference (PVSC)

Solvents play an important role in the preparation of the electron ETL and hole HTL transport lay... more Solvents play an important role in the preparation of the electron ETL and hole HTL transport layers and consequently in determining the optical properties, morphologies and perovskite thin-film quality. Lithium TFSI employed in HTL and FK209 cobalt TFSI used in ETL are usually dissolved by acetonitrile (ACN) solvent. However, this solvent is toxic and can accelerate the deterioration of the perovskite films. This work propose alternatives for ACN to slow down the perovskite films deterioration and improve its performance. Solar cells prepared using FK209/ethanol and lithium/isopropanol alcohol have shown excellent performance with champion device efficiency reaching 23.5%.

Cell Biochemistry and Biophysics, Oct 9, 2019

Appropriate mechanical forces on cells are vital for normal cell behaviour and this review discus... more Appropriate mechanical forces on cells are vital for normal cell behaviour and this review discusses the possibility that tumour initiation depends partly on the disruption of the normal physical architecture of the extracellular matrix (ECM) around a cell. The alterations that occur thence promote oncogene expression. Some questions, that are not answered with certainty by current consensus mechanisms of tumourigenesis, are elegantly explained by the triggering of tumours being a property of the physical characteristics of the ECM, which is operative following loading of the tumour initiation process with a relevant gene variant. Clinical observations are consistent with this alternative hypothesis which is derived from studies that have, together, accumulated an extensive variety of data incorporating biochemical, genetic and clinical findings. Thus, this review provides support for the view that the ECM may have an executive function in induction of a tumour. Overall, reported observations suggest that either restoring an ECM associated with homeostasis or targeting the related signal transduction mechanisms may possibly be utilised to modify or control the early progression of cancers. The review provides a coherent template for discussing the notion, in the context of contemporary knowledge, that tumourigenesis is an alliance of biochemistry, genetics and biophysics, in which the physical architecture of the ECM may be a fundamental component. For more definitive clarification of the concept there needs to be a phalanx of experiments conceived around direct questions that are raised by this paper.

Biodegradable casein films have significant potential for use as non-supported stand-alone sheeti... more Biodegradable casein films have significant potential for use as non-supported stand-alone sheeting in orthopaedic implants and tissue engineering substrates. Multi-scale surface patterns can be used to modulate and guide cell interaction by means of an engineered construct. The majority of work on cell-pattern interaction has so far focused on non-degradable materials. In this paper we demonstrate for the first time the fabrication of microand nano-scale geometric patterns on the surface of a crosslinked biodegradable casein film. To achieve this we introduce a two-step fabrication procedure based on polydimethylsiloxane (PDMS) softlithography. We will show the reproduction of microand nanoscale patterns in liquid-cast casein films. We also demonstrate film formation and cross-linking using glutaraldehyde and discuss the use of these films as cell-culture substrates.

We present optically resonant bipartite metal nano-cylinder arrays fabricated using electron beam... more We present optically resonant bipartite metal nano-cylinder arrays fabricated using electron beam lithography. The arrays utilise two different structure sizes with diameter differences as small as 10 nm. We show that this can be achieved and that the arrays show a resonance response that agrees with electromagnetic simulations.

EPJ Photovoltaics

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achie... more High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO2 (C-TiO2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO2 layer were characterized for various DC powers and different ratios of Ar to O2 plasma. It was found that the optimum preparation conditions for the C-TiO2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O2. A power conversion efficiency (PCE) of 15.3% in forward...

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achie... more High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO 2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO 2 (C-TiO 2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O 2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO 2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO 2 layer were characterized for various DC powers and different ratios of Ar to O 2 plasma. It was found that the optimum preparation conditions for the C-TiO 2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O 2. A power conversion efficiency (PCE) of 15.3% in forward sweep and 16.7% in reverse sweep were achieved under sunlight simulator of 100 mW/cm 2. These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO 2 layer.

Nanomaterials

Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We ... more Perovskite materials offer high-efficiency low-cost solar cells and applications versatility. We report on cesium-based hybrid perovskite solar cells with wavelength-selective properties ranging from 500 nm (UV-VIS) to 800 nm (IR). The band gap tuning was achieved through composition changes of mainly lead(II) iodide PbI2 and lead(II) bromide PbBr2. The optical spectra of the developed materials were studied, including the photoluminescence (PL), optical transparency, X-ray diffraction and external quantum efficiency for samples prepared under different compositions. It was found that a high content of iodine displayed a photoluminescence (PL) peak at 790 nm, whereas a high content of bromine showed a PL peak at 548 nm. The combined composition mixture of PbI2 and PbBr2 can be fine-tuned to prepare materials that absorbed light in the visible range (640–660 nm) or other selective wavelengths in the range from 500 to 800 nm. The illuminated current-voltage characteristics of the sola...

Nanomaterials, MDPI, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Vacuum Science & Technology B, 2021

Subradiant surface lattice resonances are of interest due to their remarkably high quality factor... more Subradiant surface lattice resonances are of interest due to their remarkably high quality factors. In this work, these high quality resonances are experimentally investigated in the visible spectrum with Au and Ag bipartite disk lattices fabricated with electron beam lithography. Subradiant resonances are also compared to unipartite surface lattice resonance with angle-resolved extinction measurements, which are supported by numerical models. Finally, the lattice parameters are optimized to show high quality factors in lattices where the elements have a diameter difference as small as 10 nm.

2020 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2020

In this paper we explore how nano-structure arrays can help improve plasmonic sensors and imaging... more In this paper we explore how nano-structure arrays can help improve plasmonic sensors and imaging devices. By using a periodic array the range of parameters that can be varied to give a specific response increases dramatically compared to devices based on individual structures. We show that plasmonic arrays can be engineered to show high quality spectral extinction peaks controlled primarily by the angle of incidence and period with minimal dependence on the structure. This gives flexibility in designing plasmonic sensing or imaging devices. The fabrication of the nanostructure arrays is presented as well as optical verification of the localised plasmon resonance response. Spectral simulation results are also obtained for the arrays using Scattering by Multiple Particles in Thin Film Systems (SMUTHI) software which proves to be a useful tool in analysing the response of plasmonic arrays.

Journal of Nanobiotechnology, 2006

A technique for permanently capturing a replica impression of biological cells has been developed... more A technique for permanently capturing a replica impression of biological cells has been developed to facilitate analysis using nanometer resolution imaging tools, namely the atomic force microscope (AFM). The method, termed Bioimprint™, creates a permanent cell 'footprint' in a non-biohazardous Poly (dimethylsiloxane) (PDMS) polymer composite. The transfer of nanometer scale biological information is presented as an alternative imaging technique at a resolution beyond that of optical microscopy. By transferring cell topology into a rigid medium more suited for AFM imaging, many of the limitations associated with scanning of biological specimens can be overcome. Potential for this technique is demonstrated by analyzing Bioimprint™ replicas created from human endometrial cancer cells. The high resolution transfer of this process is further detailed by imaging membrane morphological structures consistent with exocytosis. The integration of soft lithography to replicate biologic...

Micromachines, 2019

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovol... more Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as ...

Micromachines, 2019

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovol... more Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as ...

Micro/Nano Materials, Devices, and Systems, 2013

ABSTRACT The surface plasmon resonances induced light coupling is widely recognized as a promisin... more ABSTRACT The surface plasmon resonances induced light coupling is widely recognized as a promising way of enhancing the light absorption in photovoltic devices. This is achieved by enhanced localized electromagnetic field in the vicinity of metal surface or the strong light scattering effects from metal nanoparticles integrated on the front surface of as-fabricated solar cells. In this paper, the colloidal gold nanoparticles(Au NPs), synthesized by modified Turkevich and Frens method, were integrated onto the inverted nanopyramid silicon solar cell via a dip coating method. A 7% increase in short-circuit current density of solar cell was observed for 15 minutes dip coating. As a result, a 4.6% increase in overall efficiency was achieved. However,the dense surface coverage of Au NPs resulted in decreased fill factor.

Biofabrication, 2015

Bioimprinting, which involves capturing cell morphological details into a polymer matrix, provide... more Bioimprinting, which involves capturing cell morphological details into a polymer matrix, provides a new class of patterned surfaces which opens an opportunity to investigate how cells respond to their own signatures and may introduce possibilities for regulating their behaviour. In this study, phenotypic details of human nasal chondrocytes (HNCs) were replicated in soft polydimethylsiloxane (PDMS) mould resulting in inverse replicas of cells, which have been termed here as 'negative bioimprint'. For the first time, the information from this negative bioimprint was then transferred into another PDMS layer resulting in surfaces which resemble cell morphology and were called 'positive bioimprints'. Soft lithography was used to transfer these details from PDMS into different polymers like polystyrene, tissue culture polystyrene and clinically used block co-polymer poly (ethylene glycol) terephthalate-poly (butylene terephthalate) (PEGT-PBT). Results obtained from surfac...

Biochemical and Biophysical Research Communications

The importance of the biophysical cellular environment in cancer development has been increasingl... more The importance of the biophysical cellular environment in cancer development has been increasingly recognised but so far has been only superficially studied. Here we investigated the effect of cell-like substrate topography on ovarian cancer cell behaviour and potential underlying signalling pathways. We observed changes in cell morphology in response to substrate topography, which implies modification of structure-function associations. Differences in focal adhesion signalling and Rho/ROCK activity suggested their involvement in the biomechanically-driven cellular responses. Cell-like topography was also shown to modulate the MAPK pathway and hence potentially regulate cell proliferation. The selective regulation of the cells by the mechanotransduction pathways that we noted has wide ranging implications for understanding cancer development. We established that the physical architecture of cell culture substrate is sufficient to influence cancer cell behaviour, independent of genetic composition or biochemical milieu.

ACS applied materials & interfaces, Jan 11, 2018

Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of ... more Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of conducting polymer (CP) structures. It is precisely localized and highly controllable, thus providing great opportunities for incorporating CPs into microelectronic array devices. Herein we demonstrate 3D writing and characterization of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) pillars in an array format, by using an in-house-constructed variant of scanning ion conductance microscopy (SICM). CP pillars with different aspect ratios were successfully fabricated by optimizing the writing parameters: pulling speed, pulling time, concentration of the polymer solution, and the micropipette tip diameter. Especially, super high aspect ratio pillars of around 7 μm in diameter and 5000 μm in height were fabricated, indicating a good capability of this direct writing technique. Additions of an organic solvent and a cross-linking agent contribute to a significantly enhanced w...