Electrochemical metal 3D printing

Additive manufacturing (AM) is the process of creating 3D objects from digital models through the layer-by-layer deposition of materials. Electrochemical additive manufacturing (ECAM) is a relatively new technique which can create metallic components-based on depositing layers of metal onto the surface of the conductive substrate through the reduction of metal ions. It is advantageous compared to other metal AM processes due to the absence of high temperature processes enabling a lower-cost and safer fabrication process, however, to date, all of the presented ECAM methods (Localized Electrochemical Deposition (LED) and Meniscus Confined Electrochemical Deposition (MCED) have been designed to achieve micro or nanoscale structures with limited deposition rates, and only focused on single material fabrication. Furthermore, all the printed structures are limited in the complexity of geometries, with the majority being wire-based architectures of porous and rough morphologies, with limited characterisation of the properties of the printed structures. Additionally, there is no available system able to create temperature-reactive multi-metallic functional 4D structures and no research has been presented on the potential application of ECAM in the field of electrochemical energy storage devices. To bridge the gaps, this thesis investigates the development of a low-cost ECAM system capable of producing single and multi-metal structures by using multi-meniscus confined extrusion heads with volumetric deposition rates 3 times higher than what has previously been reported (~ 2×104 μm3.s-1), enabling large-scale fabrication of complex structures in multiple metallic materials. Scanning electron microscopy, X-ray computed tomography and energy dispersive X-ray spectroscopy measurements confirm that multi-metallic structures can be successfully created, with a tightly bound interface. Analysis of the thermo-mechanical properties of the printed strips shows that mechanical deformations can be generated in Cu-Ni strips at temperatures up to 300 °C, which is due to the thermal expansion coefficient mismatch generating internal stresses in the printed structures. Electrical conductivity measurements show that the bimetallic structures have a conductivity between those of nanocrystalline copper and nickel. Vicker’s hardness tests, show that there is a clear correlation between the applied potential and the hardness of the printed product, with higher potentials resulting in a harder deposition. This increased hardness was found to be due to the smaller grain sizes produced during higher potential deposition which restricted dislocation movement through the material. Finally, this thesis presents the first reported combination of electrochemical 3D printing and electrospinning for building a high mass loading and high performance copper-fibre based supercapacitor which enables the potential to create more integrated electrodes and eventually to enhance the performance of supercapacitors. The results highlight the influence of the substrate conditioning and the resulting effects on the wetting characteristics of the meniscus and the subsequent distribution of the deposition which impacts the electronic conductivity of the overall electrode. In this the fibre-based supercapacitor was constructed, the carbon was doped with manganese oxides to enhance the capacitance through introducing pseudo-capacitance at the cost of electronic conductivity. With the printing of current collectors, a highly bound electrode-current collector interface was formed, reducing the interfacial resistance and enhancing the accessible capacitance at high scan rates. In summary, this thesis presents work towards creating lower cost metal additive manufacturing through the development of an electrochemical metal 3D printer. A meniscus confined approach was taken to localise the deposition, with subsequent microstructural, mechanical and spectroscopic analysis of the printed product. Novel contributions to the field were further presented through developing understanding around multi-metal ECAM, with investigations around their coupled thermo-mechanical properties. Finally, the applicability of this approach was investigated in the field of electrochemical devices, where the influence of a porous substrate was investigated, whereby tightly bound and highly conductive current collectors were printed onto fibre based supercapacitors, enhancing their accessible capacitance. This work, therefore, demonstrates the potential for the ECAM approach in a diversity of applications.Open Acces

Combinatorial ink-jet printing for ceramic discovery

PhDAn aspirating and dispensing printer established inside a robot gantry equipped with furnace and measurement table is used to prepare thick-film combinatorial libraries. Implementation of series of screening tests for ceramic inks that address stability against sedimentation, evaporation and particle segregation during drying, has provided a series of calibration inks can be used for calibration of this printer. The instrument can assemble ceramic mixtures with compositional accuracy of 1-3 wt %. By changing the amount of dispersant used in the inks or by printing onto a porous substrate, the geometry of residues from dried ceramic ink droplets can be modified to facilitate property measurements and uniform composition, as planned, can be achieved. The same material prepared in three ways, in the form of dried ink, ink-jet printed as for a combinatorial sample and by conventional compaction gave similar dielectric measurements. A combinatorial system has been developed so that combinatorial libraries can be printed, fired and screened automatically. A ternary A1203-TiO2-ZrO2 system was first studied using the developed combinatorial method. The particle segregation during drying of multi-component ceramic ink drops is not due to preferential sedimentation unless dispersant addition is restricted. The segregation is due to the partitioning of particles between the growing peripheral 'foot' that develops during drying and the diminishing liquid pool which contains vigorous recirculation flows. Better dispersed particles remain in the pool and hence are found in excess on the upper surface of residues. Less well dispersed particles join the 'foot' earlier in the drying process. The contact angle and height of droplets containing large amounts of dispersant, steadily reduced during drying until a minimum value was reached; the contact diameter being almost unchanged during drying. These droplet residues retained a dome shape. Droplets of suspensions containing small additions of dispersant terminated in a 'doughnut' shaped residue

Additive manufacturing: unlocking the evolution of energy materials

The global energy infrastructure is undergoing a drastic transformation towards renewable energy, posing huge challenges on the energy materials research, development and manufacturing. Additive manufacturing has shown its promise to change the way how future energy system can be designed and delivered. It offers capability in manufacturing complex 3D structures, with near-complete design freedom and high sustainability due to minimal use of materials and toxic chemicals. Recent literatures have reported that additive manufacturing could unlock the evolution of energy materials and chemistries with unprecedented performance in the way that could never be achieved by conventional manufacturing techniques. This comprehensive review will fill the gap in communicating on recent breakthroughs in additive manufacturing for energy material and device applications. It will underpin the discoveries on what 3D functional energy structures can be created without design constraints, which bespoke energy materials could be additively manufactured with customised solutions, and how the additively manufactured devices could be integrated into energy systems. This review will also highlight emerging and important applications in energy additive manufacturing, including fuel cells, batteries, hydrogen, solar cell as well as carbon capture and storage

DC and radio-frequency transmission characteristics of double-walled carbon nanotubes-based ink

In this paper, double-walled carbon nanotubes (DWNTs) network layers were patterned using inkjet transfer printing. The remarkable conductive characteristics of carbon nanotubes (CNTs) are considered as promising candidates for transmission line as well as microelectronic interconnects of an arbitrary pattern. In this work, the DWNTs were prepared by the catalytic chemical vapor deposition process, oxidized and dispersed in ethylene glycol solution. The DWNTs networks were deposited between electrodes contact and then characterized at DC through current-voltage measurements, low frequency, and high frequency by scattering parameters measurements from 40 MHz up to 40 GHz through a vector network analyzer. By varying the number of inkjet overwrites, the results confirm that the DC resistance of DWNTs networks can be varied according to their number and that furthermore the networks preserve ohmic characteristics up to 100 MHz. The microwave transmission parameters were obtained from the measured S-parameter data. An algorithm is developed to calculate the propagation constant "γ", attenuation constant "α" in order to show the frequency dependence of the equivalent resistance of DWNTs networks, which decreases with increasing frequency

Wireless ion selective electrode autonomous sensing system

A paradigm shift in sensing methods and principles is required to meet the legislative demands for detecting hazardous substances in the molecular world. This will encompass the development of new sensing technologies capable of performing very selective and sensitive measurements at an acceptable cost, developed by multidisciplinary teams of chemists, engineers and computer scientists to harvest information from a multitude of molecular targets in health, food and the environment. In this study we present the successful implementation of a low-cost, wireless chemical sensing system that employs a minimum set of components for effective operation. Specifically, our efforts resulted in a wireless, tri-electrode, ISE pH sensor for use in environmental monitoring. Sensor calibration and validated insitu field trials have been carried out and are presented in this paper

3D printed neuromorphic sensing systems

Thanks to the high energy efficiency, neuromorphic devices are spotlighted recently by mimicking the calculation principle of the human brain through the parallel computation and the memory function. Various bio-inspired \u27in-memory computing\u27 (IMC) devices were developed during the past decades, such as synaptic transistors for artificial synapses. By integrating with specific sensors, neuromorphic sensing systems are achievable with the bio-inspired signal perception function. A signal perception process is possible by a combination of stimuli sensing, signal conversion/transmission, and signal processing. However, most neuromorphic sensing systems were demonstrated without signal conversion/transmission functions. Therefore, those cannot fully mimic the function provides by the sensory neuron in the biological system. This thesis aims to design a neuromorphic sensing system with a complete function as biological sensory neurons. To reach such a target, 3D printed sensors, electrical oscillators, and synaptic transistors were developed as functions of artificial receptors, artificial neurons, and artificial synapses, respectively. Moreover, since the 3D printing technology has demonstrated a facile process due to fast prototyping, the proposed 3D neuromorphic sensing system was designed as a 3D integrated structure and fabricated by 3D printing technologies. A novel multi-axis robot 3D printing system was also utilized to increase the fabrication efficiency with the capability of printing on vertical and tilted surfaces seamlessly. Furthermore, the developed 3D neuromorphic system was easily adapted to the application of tactile sensing. A portable neuromorphic system was integrated with a tactile sensing system for the intelligent tactile sensing application of the humanoid robot. Finally, the bio-inspired reflex arc for the unconscious response was also demonstrated by training the neuromorphic tactile sensing system

Design and fabrication by inkjet printing of electrodes for electromyography

Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013A utilização de impressoras de jacto de tinta (inkjet printers) tem dado um enorme contributo na indústria eletrónica reduzindo as dimensões dos componentes e introduzindo processos de fabricação mais rápidos e menos dispendiosos. Uma das grandes vantagens deste método de fabricação é a facilidade de design dos circuitos, a deposição de materiais directamente no substrato sem haver contacto, a sobreposição de desenhos impressos e a versatilidade de materiais utilizados, tirando o maior partido das suas características. Duas formas de tirar partido das funcionalidades de uma impressora inkjet, em engenharia biomédica, é, por um lado, desenvolver circuitos elétricos desenhados especialmente para aquisição de sinais fisiológicos. Esses circuitos, aliados às capacidades da impressão por jacto de tinta, poderão resultar em eletrónica flexível com materiais com elevada biocompatibilidade, promovendo desta forma uma próxima interacção com o corpo humano. Por outro lado, as aplicações da impressora inkjet podem levar ao desenvolvimento de eletródios impressos enquadrando-os no conceito de pele eletrónica, isto é, integrar dispositivos eletrónicos utilizando características da pele humana (flexibilidade, extensibilidade e compatibilidade). Assim, o principal objectivo deste trabalho é fabricar, utilizando esta técnica, elétrodos com a capacidade de medir sinais electromiográficos dos músculos responsáveis pelo movimento da mão e dedos. A fim de utilizar as potencialidades da tecnologia inkjet, os eléctrodos devem obter medições congruentes do ponto de visto fisiológico e devem se mostrar vantajosos face aos, já convencionais, eléctrodos descartáveis. A finalidade da construção destes eléctrodos deverá preencher a carência que os eléctrodos convencionais possuem, de não serem flexíveis e de não serem utilizados durante largos períodos de tempo. As vantagens extraídas de eléctrodos impressos poderão ainda ser mais vastas não só a nível económico, pela construção de eléctrodos low-cost, mas também a nível de desempenho, biocompatibilidade e design, com o desenvolvimento de eléctrodos finos, paper-like e passiveis de acoplarem circuitos eletrónicos também impressos. O desenvolvimento do trabalho apresentou uma variedade de tarefas, com inicio na aprendizagem dos conceitos e métodos de funcionamento da impressora FujiFilm Dimatrix 2831 Materials Printer. Esta impressora, utilizada para obtenção de todos os eléctrodos e circuitos aqui referidos, possui uma tecnologia drop-on-deman coordenada por material piezoeléctrico, conseguindo uma resolução até -5 um. As voltagens induzidas a este material tem um enorme impacto na formação das gotas de tinta, e por isso a uma boa qualidade de impressão. No entanto, outros factores como a viscosidade da tinta e a tensão de superfície também desempenham importantes papeis para aumento da qualidade de impressão. As tarefas seguintes incluíram a otimização dos procedimentos para tratamento dos substratos de forma a que a deposição da tinta de prata fosse óptima. Os substratos utilizados neste trabalho foram: papel fotográfico, biocelulose e polidimetilsiloxano (PDMS). Também os métodos de impressão tiveram que ser optimizados controlando a velocidade e a direcção da deposição das gotas de tinta. Uma vez que foi apenas utilizado um tipo de tinta prata, uma dispersão de nanopartículas de prata, foi utilizada a mesma velocidade de deposição das gotas, 10 m/s com temperatura do tinteiro constante, de 30ºC. Por fim, houve necessidade de melhorar o processo de sinterização que visa a remoção do solvente e outras substâncias presentes na tinta de prata, e que tem enorme impacto na resistividade final do padrão impresso. Um bom processo de sinterização faz com que as nanopartículas de prata tenham um forte contacto entre elas, aumentando consideravelmente a conductividade do material. Para este fim, foi testada a sinterização térmica padrão e introduzida um novo método, a sinterização elétrica cuja aplicação de uma diferença de potencial permite a passagem de corrente elétrica gerando calor localmente. Para impressão de eléctrodos, os seus designs foram adaptados às características dos materiais, sendo que, por exemplo, para materiais mais flexíveis foram implementadas conexões serpenteadas entre pequenos eléctrodos. Para outros substratos, como o papel fotográfico, foi optado um design semelhante ao dos eléctrodos convencionais para obter melhor termo de comparação. Já para aplicação de sinterização elétrica, optou-se por um design que consiste num único filamento para que seja possível a aplicação de uma diferença de potencial em ambas as extremidades. Durante o aperfeiçoamento dos eléctrodos, foi elaborado uma série de estudos acerca das características dos mesmos (resistividade e impedância) e as suas medições foram comparadas com os resultados obtidos, em condições semelhantes, aos eléctrodos tipicamente utilizados em ambiente clínico. Como resultados de medições de sinais electrocardiográficos, os eléctrodos impressos em papel fotográfico mostraram-me vantajosos quanto à morfologia do traçado, pois o termo de comparação foi similar aos obtidos por eléctrodos convencionais. No estudo de sinais electromiográficos, os eléctrodos impressos em biocelulose e papel fotográfico tiveram taxas de sinal-ruído abaixo das obtidas pelos tradicionais eléctrodos de uso clínico. Ainda assim, os dados dos eléctrodos impressos podem ser utilizados para captação de sinais fisiológicos pois foi possível demonstrar a extração de informações acerca do movimento dos músculos esqueléticos e cardíaco. Contudo, não foi possível a obtenção de sinais fisiológicos utilizando eléctrodos impressos em PDMS. Devido a uma fraca adesão da tinta de prata à superfície do substrato, a tinta era removida do eléctrodo quando havia contacto entre o eléctrodo e a pele. Tarefas intermédias incluíram a impressão de pequenos circuitos eletrónicos, nomeadamente um circuito impresso cuja principal função é a leitura e tratamento (amplificação e filtragem) de sinais electrocardiográficos. Dois outros circuitos, mais simples, foram impressos: um díodo emissor de luz e um sensor de luz. Todas as pistas de condução de ambas as camadas foram impressas com prata em papel fotográfico e os componentes eletrónicos foram colados com cola de prata. A otimização deste processo poderá trazer enormes vantagens pela possibilidade de construção de circuitos eletrónicos flexíveis e finos com eléctrodos incorporados. Por fim, a última tarefa inclui processamento de sinal a qual inclui a implementação de algoritmos em ambiente MatLab para extracção de movimentos dos músculos do antebraço. Com a informação extraída por três movimentos distintos da mão foi provado que os eléctrodos impressos podem ser usados para posterior reconhecimento de padrões. A distinção dos três movimentos foi feita com sucesso, sobretudo para os eléctrodos impressos em biocelulose e para os eléctrodos de baixa resistividade em papel fotográfico. Este trabalho também abriu portas para investigações futuras em que mais substratos e tintas podem ser testadas e mais componentes podem ser integrados aos já aqui desenvolvidos. Desta forma, a tecnologia inkjet pode contribuir com a sua versatilidade para a inovação nos campos electrofisiologia e das interacções homem-máquina.Inkjet technology has advantages as a fabrication method when compared to other conventional procedures. Inkjet technology allows the deposition of several materials directly with non contact with it, mask-less and the possibility of printing over a previous printed pattern. Due its versatility of inks (conductive, polymers and organic) and substrates, direct deposition of materials with high precision (-5 um) using simple methods, this technique shows a high potential as a fabrication method. Despite the wide range of applications of inkjet printing in electronics, a lack of intend for printing devices for collecting biosignals. The subject of the work presented was the first step towards the development of a inkjet device for a close contact with skin for collecting biosignals. One way to apply the functionalities of an inkjet printer, in biomedical engineering, is developing printed electrodes introducing electronic skin concept, i.e., implement electronic devices using features of electronic skin (exibility, extensibility and compatibility). Thus, the major goal of this work was develop, using this technique, electrodes capable of measuring electromyographic signals from the forearm's muscles responsible to move hand and fingers. In order to use the potentials of inkjet technology, these electrodes must obtain congruent measurements and should prove advantageous when compared to the standard electrodes. The versatility of inkjet printing allowed to print electrodes, using a inkjet printer DMP-2831, onto substrates that included photographic paper, biocellulose and PDMS and test the performance of different designs: standard at discs, spiked, filamentary and serpentine array of small electrodes. This thesis presents the development of tasks that includes the design and choice of materials, optimization of printing and sintering procedures, printing electronic circuits and ends with signal processing. During the optimization of the electrodes measurements of resistivity and impedance were performed to understand the behavior and characteristics of them. Finally, a linear discriminant analysis was used to successfully distinguish between three hand movements

Development, fabrication and application of electrochemical devices using 3D-printing

Esta tese tem como foco o uso de recentes inovações em manufatura aditiva (impressao 3D) na confecção de células e sensores eletroquímicos. Como introdução este trabalho faz uma revisão completa sobre o tema, seguida de construção, caracterizações e aplicações de sensores e células impressas em 3D na eletroanalítica. A primeira delas é uma célula eletroanalítica para medidas hidrodinâmicas e estacionárias. A segunda se trata de sensores impressos por 3D baseado em um termoplástico condutivo, dopado com materiais carbonáceos (grafeno ou negro de fumo). A combinação destas células e eletrodos impressos em 3D contendo grafeno, foram aplicados na área forense na amostragem, identificação e quantificação do explosivo 2,4,6-trinitrotolueno, o conhecido TNT. O dispositivo foi proposto para amostragens em locais suspeitos de crimes que envolvam manuseio deste material. Um limite de detecção (LOD) de 0,4 −1 em uma faixa linear de 1 – 870 mol L−1 foram reportados. Na área de bioanalítica, 3 moléculas foram analisadas em metodologias propostas. A primeira utilizando ou amperometria de múltiplos pulsos, para analise simultânea de nitrito e ácido úrico, em saliva e urina atingindo resultados de faixa linear de 0,5–250 mol L−1 para ambos analitos e LODs de 0,02 e 0,03 mol L−1 para ácido úrico e nitrito respectivamente, com precisão calculada de até RSD < 2,1 %. A modificação do sensor com a enzima glicose oxidase (GOx) foi proposta, atingindo LOD de 15 mol L−1, precisão intra-dia de 5% e índices de recuperação entre 90–105 % para glicose em plasma sanguíneo. Todos os dispositivos apresentaram custo inferior a U$0,50/unidade e alta precisão de fabricação (RSD = 4uma caneta 3D pode ser utilizada na construção de sensores com termoplástico condutivo contendo negro de fumo como material condutor. Em uma comparação o eletrodo impresso por impressora 3d! apresentou melhores característica analíticas em comparação ao eletrodo 3 em 1 proposto usando a caneta 3D, porém características promissoras foram observadas como possibilidade de análise em uma gota, baixo consumo de plástico condutivo na construção e resultados voltamétricos comparáveis a eletrodos SPE’s comerciais. Tudo isso com formato portátil e totalmente adaptável.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorFAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas GeraisFAU - Fundação de Apoio UniversitárioIQUFU - Instituto de Química da Universidade Federal de UberlândiaTese (Doutorado)Recent advances in the manufacturing of electroanalytical sensors, cells and devices using 3D-printing is the focus of this work. This thesis introduces this theme/topic with a wide and critical literature review, followed by several proposed applications at electroanalytical prototyping and sensing. The first of those is an electroanalytical cell, for hydrodynamic and stationary measurements, and 3D-printed sensors based on a conductive thermoplastic with carbonaceous materials (graphene or carbon black). The electrodes were applied in the forensic field by quantification, detection and sampling 2,4,6-trinitrotoluene, well known as TNT. The proposed device is a flexible samplersensor for suspect powders in crime scenes and presented proper analytical characteristics reaching a LOD of 0.4 mol L−1 in a linear interval of 1 – 870 molL−1 for TNT. This thesis also shows how a 3D pen can be used to fabricate electrochemical sensors, also proposed for TNT detection,presenting higher LOD, but interesting characteristics such as low volume in a drop of 100 L, low conductive plastic consumption and voltammetric results similar to a commercial SPE. All this in portable shape cylindrical or three in one electrode. In the field of bioanalytics, glucose was a target molecule for 3D-printed electrodes modified with glucose oxidase, using chronoamperometry, reaching LOD of 15 molL−1, inter-day and intra-day precision lower than 5 analysis of blood plasma. A simultaneous method using amperometric detection of nitrite and uric acid within a linear range from 0.5–250 mol L−1 for both analytes, LODs of 0.02 and 0.03 mol L−1 for uric acid and nitrite, respectively, and high precision (RSD < 2.1 biosensors for the analysis of real biological samples with analytical features comparable to conventional modified electrodes.All the 3D-printed devices presented a unit cost lower than U$0.50 and high precision of fabrication (RSD = 4%)

Development and applications of inkjet printed conducting polymer micro-rings

A drying sessile drop moves the solute particles to the periphery where they get deposited in the form of a ring. This phenomenon is prevalent even with micro drops falling at high velocity from a piezo-actuator based inkjet printer. In polymer microelectronic field, this phenomenon is a major challenge for fabricating devices using inkjet printing. We exploited this problem and applied it for various novel applications in the field of polymer microelectronics. Various dispensing techniques and temperature variations for micro-drop printing were used for modifying the micro-drops in such a way that the periphery of the micro-ring holds most of the solute as compared to inner base layer. Reactive ion etching (RIE) was used for removing the inner base layer in order to make the micro-rings completely hollow from the center. These micro-rings were applied in the fabrication of polymer light emitting diode, humidity sensor and vertical channel field effect transistor. High resolution polymer light emitting diode array (\u3e200 pixels/inch) was fabricated by inkjet printing of micro-ring and each micro-ring acts as a single pixel. These micro-rings were applied as a platform for layer-by-layer (LbL) nano-assembly of poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS) for the fabrication of humidity sensor. Enhanced sensitivity of the humidity sensor was obtained when the inkjet printed micro-rings are combined with LbL assembled PEDOT:PSS films. During the fabrication of vertical channel field effect transistors, inkjet printed PEDOT:PSS micro-rings were used as source and the inner spacers between the adjacent micro-rings were used to make channel. These micro-rings can also find other applications in the field of biological sciences. These micro-rings can be used as cell culture plates and as scaffolds for cell and/or tissue growth

An inkjet-printed field-effect transistor for label-free biosensing

A flexible, biological field-effect transistor (BioFET) for use in biosensing is reported. The BioFET is based on an organic thin-film transistor (OTFT) fabricated mainly by inkjet printing and subsequently functionalized with antibodies for protein recognition. The BioFET is assessed for label-free detection of a model protein, human immunoglobulin G (HIgG). It is characterized electrically to evaluate the contribution of each step in the functionalization of the OTFT and to detect the presence of the target protein. The fabrication, structure, materials optimization, electrical characteristics, and functionality of the starting OTFT and final BioFET are also discussed. Different materials are evaluated for the top insulator layer, with the aim of protecting the lower layers from the electrolyte and preserving the BioFET electrical performance