Increase in population and limited resources have created a growing demand for a futuristic living environment where technology enables the efficient utilization and management of resources in order to increase quality of life. One characteristic of such a society, which is often referred to as a ‘Smart City’, is that the people are well informed about their physiological being as well as the environment around them, which makes them better equipped to handle crisis situations. There is a need, therefore, to develop wireless sensors which can provide early warnings and feedback during calamities such as floods, fires, and industrial leaks, and provide remote health care facilities. For these situations, low-cost sensor nodes with small form factors are required. For this purpose, the use of a low-cost, mass manufacturing technique such as inkjet printing can be beneficial due to its digitally controlled additive nature of depositing material on a variety of substrates. Inkjet printing can permit economical use of material on cheap flexible substrates that allows for the development of miniaturized freeform electronics. This thesis describes how low-cost, inkjet-printed, wireless sensors have been developed for real-time monitoring applications. A 3D buoyant mobile wireless sensor node has been demonstrated that can provide early warnings as well as real-time data for flood monitoring. This disposable paper-based module can communicate while floating in water up to a distance of 50 m, regardless of its orientation in the water. Moreover, fully inkjet-printed sensors have been developed to monitor temperature, humidity and gas levels for wireless environmental monitoring. The sensors are integrated and packaged using 3D inkjet printing technology. Finally, in order to demonstrate the benefits of such wireless sensor systems for health care applications, a low-cost, wearable, wireless sensing system has been developed for chronic wound monitoring. The system called ‘Smart Bandage’ can provide early warnings and long term data for medical diagnoses. These demonstrations show that inkjet printing can enable the development of low-cost wireless sensors that can be dispersed in the environment or worn on the human body to enable an internet of things (IoT), which can facilitate better and safer living.

This diploma thesis deals with the study of inkjet print degradation on handmade paper modified by polymer layer containing light stabilizers and inorganic filler. The polymer layer coated on the medium consisted of polyvinylalcohol, titanium dioxide and light stabilizer. The influence of light promoted degradation and light stabilizers was observed. The experiments were carried out on Q-SUN Xenon Test Chamber device, Model Xe-1-B/S. Colorimetric values of test chart were measured and the influence of different light stabilizers on the color difference between original and faded sample was evaluated.

This thesis is focused on the effect of ozone on ink-jet prints. The knowledge about print technologies, materials for ink-jet printing, influence of environmental factors on the prints degradation and the methods of print lifetime estimation are discussed in the theoretical part of the thesis. Test-charts of 108 samples of C, M, Y primary colours and their overprints were prepared. I used two types of papers designed for ink-jet printing. These samples were exposed the effect of ozone in various concentrations to perform an accelerated aging experiment. Optical density values, La*b* coordinates, colour difference values were calculated from the measured spectral data. Changes of colours of the ink due to ozone exposure were determined and discussed. The validity of the reciprocal law due to ozone exposure was studied, too. The reciprocal behaviour was not confirmed for both types of the studied papers.

<p>Additive manufacturing (AM) of hydrogels has gained increasing interest across various fields. Drop-on-demand (DOD) printing (also known as inkjet printing) shows the great potential to construct 3D hydrogels with spatially controlled properties and compositions. However, a limited mechanistic understanding of the behavior of printed polymer drops makes it challenging to design and optimize DOD printing protocols for a wide variety of hydrogels. Here, we have demonstrated an extensive and in-depth study from the theoretical and experimental research of drop-wise structure to the development of functional materials by DOD printing of polymer inks. First, computational and experimental studies are performed to establish a mechanism of the water-matrix interaction within printed polymer drops. The results ultimately enabled a dimensionless parameter that characterizes water transport during the dehydration process of printed polymer drops. Next, as particles are suspended in polymer inks to add functionality, this dimensionless parameter was further extended to characterize particle movement and distribution patterns in the printed particle-laden hydrogels. By correlating the intra-drop particle distribution to the similarity parameter, a scaling law is confirmed to guide ink formulation and printing protocol that enables advanced materials with spatially digitized functionality (i.e., digital hydrogels). Finally, cells that serve as active particles are embedded in the hydrogels to mimic the native tissues. A "digital cell printing" method based on DOD printing of "two colors" cell-laden (i.e., cancer cells and CAFs) polymer inks is developed to rapidly (< 1 day) create 3D tumor models with tumor-stroma interface (i.e., tumoroids) and high cell density (~108 cells/cm3) that closely recapitulate the tumor microenvironment in vivo. Overall, DOD printing of particulate-laden polymer inks showed the great potential to construct 3D functional hydrogels with spatially controlled properties and compositions.</p>

Chemical and topographic surface patterning for the preparation of functional surfaces and particle arrays has been intensively investigated and widely applied in sensor technology, engineering of adhesion and wetting, catalysis, as well as nanobioanalytics. However, the parallel high-throughput functionalization of surfaces with microparticle arrays under ambient conditions by state-of-the-art surface patterning methods has remained challenging. The aim of this thesis is the parallel generation of microparticle arrays on surfaces to tailor the surface properties. Two strategies are studied for this purpose. The first strategy, inspired by the functional principles of adhesive secretion of insect feet’s hairy contact elements yielding tiny droplets as footprints onto contact substrates, involves the formation of microdot arrays by capillary submicron stamping using spongy continuous nanoporous block copolymer stamps with regular hexagonal arrays of contact elements. After infiltration of AgNO3 solution from the stamps’ backside, arrays of discrete two-dimensional AgNO3 microdots with an average diameter ~ 730 nm on silicon wafers extending several square millimetres were generated, while under higher pressure holey AgNO3 films were obtained. Subsequently, the patterns were transferred into Si wafers by surface-limited metal-assisted chemical etching (MACE). Topographically patterned silicon (tpSi) characterized by hexagonal arrays of wells resulted from MACE of Si wafers patterned with AgNO3 microdots, while MACE of Si wafers patterned with holey AgNO3 films yielded ordered Si pillar arrays. H2PtCl6, PdCl2 and HAuCl4 aqueous solutions were also employed as inks for preparation of tpSi by insect-inspired capillary sub-microstamping and MACE. Exploratory experiments suggest that inkjet printing of polymeric inks onto tpSi could yield persistent and scratch-resistant polymer blot patterns without coffee ring-like features for potential utilization as permanent identity labels or quick response codes. Hexagonal arrays of Au microparticles were rationally positioned by solid-state dewetting of thin gold films on tpSi at an elevated temperature under Ar atmosphere. The rationally positioned Au microparticles subsequently acted as seeds for the growth of dense, homogeneous layers of overlapping three-dimensional (3D) gold nanodendrites by templated galvanic displacement reactions. The obtained 3D gold nanodendrite layers on tpSi featuring high specific surfaces as well as abundance of sharp edges and vertices showed promising performances in SERS-based sensing and the heterocatalytic reduction of 4-nitrophenol to 4-aminophenol. The second example involves the functionalization of polymer surfaces with arrays of inorganic lubricant microparticles for friction management and the tailoring of tribological properties based on an imprint lithographic approach. For example, the tailoring of the interfacial shear behavior of a movable polymer part might be customized in this way by functionalizing the polymeric parts’ surfaces with MoS2 microparticle arrays. Monodomain monolayers of MoS2 microparticles were prepared on SiO2-coated Si wafers via thermal sulfurization arrays of ammonium tetrathiomolybdate microparticles obtained by imprint lithography. After transfer of the MoS2 microparticle arrays to poly(methyl methacrylate) (PMMA) monoliths (PMMA_MoS2) under conservation of the array order in such a way that the MoS2 microparticles were partially embedded into the PMMA and partially exposed, the obtained PMMA_MoS2 exhibited modified mechanical properties characterized by low friction coefficients half as that of non-modified PMMA monoliths. Therefore, the functionalization of surfaces with microparticle arrays is a viable and promising strategy to generate unprecedented surface functionalities.

Although small spacecraft are small in size and light in weight compared to the conventional satellites, they can offer lots of possibilities for space exploration, scientific observation, data collection and telecommunication. Also, they cost a lot less money than the conventional satellites, and the scientific missions can be planned in a relatively short period of time by using the COTS (Commercial Off-The-Shelf) materials. However, there is a big challenge for the small spacecraft that is the limited surface area of the small spacecraft and the outnumbered components to be mounted on the surface of the small spacecraft. The most obvious one is that the competition for the limited real estate between the antenna and solar cells. UAVs, also known as drones, have become so popular that it is not only used for military and scientific applications, but also they are available for recreational use for ordinary people. Although they are getting smaller in size so that one can put them in his pocket or on his palm, they are becoming multifunctional, which requires more sensors to be mounted on the surface of the drone to achieve its multifunctionality. For example, a recreational drone can not only take pictures and videos, but also it can transmit the picture or video in real time to the operator, which needs a camera to take the picture or videos and needs an antenna to transmit the recorded data to the operator. This requires that the limited surface area needs to be efficiently used in order to accommodate the multiple needed components. This thesis presented a faster, better and cheaper way of inkjet printing conformal antennas on the cover glass of the solar cells of the small spacecraft or on the wing or other parts of the UAV body to integrate the antenna with the solar panels of the CubeSats or with or directly printing the antenna on the UAV body to efficiently use the limited real estate. Several meshed and solid patch antennas printed on a space certified AF32 glass substrate using the printing procedure outlined in this thesis and measured to verify the effectiveness of the inkjet printing procedures. A high gain reflectarray with optical transparency of 95% was inkjet printed on space certified AF32 glass and BOROFLOAT glass and measured to verify the antenna performance and solar panel efficiency. Measurement results showed that the inkjet printed reflectarray integrated on top of the solar panel has a gain of 21.5 dB. The solar panel efficiency was dropped by around 6% due to the inkjet printed reflectarray on glass. A simple conformal dual-band antenna for UAV application was designed with ANSYS HFSS and fabricated in the lab using a foam substrate. The measured antenna performances agreed well with the simulation results. This dual-band antenna also can be inkjet printed directly on the wing or other parts of the UAVs using the printing techniques discussed in this thesis.

Inkjet printing is an attractive patterning technology that has received tremendous interest as a mass fabrication method for a variety of electronic devices due to its manufacturing exibility and low-cost feature. However, the printing facilities that are being used, especially the inkjet printer, are very expensive. This thesis introduces an extremely cost-friendly inkjet printing method using a printer that costs less than $100. In order to verify its reliability, linearly and circularly polarized (CPd) planar and conformal microstrip antennas were fabricated using this printing method, and their measurement results were compared with copper microstrip antennas. The result shows that the printed microstrip antennas have similar performances to those of the copper antennas except for lower efficiency. The effects of the conductivity and thickness of the ink layer on the antenna properties were studied, and it is found that the conductivity is the main factor affecting the radiation efficiency, though thicker ink yields more effective antennas. This thesis also presents the detailed antenna design for a sub-payload. The sub-payload is a cylindrical structure with a diameter of six inches and a height of four inches. It has four booms coming out from the surface, which are used to measure the variations of the energy flow into the upper atmosphere in and around the aurora. The sub-payload has two types of antennas: linearly polarized (LPd) S-band antennas and right-hand circularly polarized (RHCPd) GPS antennas. Each type of antenna has various requirements to be fully functional for specific research tasks. The thesis includes the design methods of each type of antenna, challenges that were confronted, and the possible solutions that were proposed. As a practical application, the inkjet printing method was conveniently applied in validating some of the antenna designs.

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Additive manufacturing technologies, including inkjet printing, have significantly transformed both research and industry, offering cost-effective and accessible solutions with innovative equipment capabilities. This study focuses on advancing p-type depletion and enhancement-mode poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) through molecular de-doping and rheological measurements, achieving a printing resolution of 30 μm. The versatility of these inks is demonstrated from three distinct perspectives. Firstly, the electrochemical stability of the enhancement-mode behavior opens new possibilities for low-power consumption, stable and sensitive platforms useful for detection of DopamineC and Ascorbic Acid at various concentrations. Secondly, we exemplify the democratization of in-house fabrication through fully printed, all-PEDOT:PSS, transparent, flexible, and bendable paper-based Organic Electrochemical Transistors (OECTs). This showcases the feasibility of employing inkjet printing to create functional electronic devices with ease. Lastly, we explore optimizations that enable deeper personalization by employing multiple material localizations and adjusting the electrical conductivity of OECTs. This engineering approach has resulted in the design of Organic Electrochemical Complementary Amplifiers (OECAs), we incorporated a second formulated enhancement-mode conducting polymer poly(benzimidazobenzophenanthroline) (BBL) as the n-type material to complement the PEDOT:PSS de-doped ink. These developments aim to foster global innovation, representing a significant leap forward in the field of organic electronics and in-house fabrication by complementing this engineering improvement from both fabrication and electrochemistry approaches.