The development of self-power electronics has attracted wide-spread attention owing to their potential applications in internet of things (IoT), nanorobotics, health monitoring, wireless communications, etc. However, the harvested energy resources (solar energy, thermal energy, radio frequency energy, etc.) are normally intermittent and unpredictable, so suitable energy storage devices that can store collected energies and have a stable are in high demand. Supercapacitors typically show a high-power density and an extended cycling life (>10,000 cycles) that perfectly fit the requirement of self-powered electronics. However, their practical applications are limited by the low energy densities and significant self-discharge problem. To enhance the performance of the supercapacitors, we demonstrated the electro-deposition of an open-shell conjugated polymer with reduced graphene oxide achieves electrodes with capacitance up to 186 mF cm−2 (372 F cm−3). The extended delocalization within the synthesized polymer stabilizes the redox states and facilitates a 3 V wide potential window, while the hierarchical composite electrode structure promotes ultrafast kinetics. The micro-supercapacitor shows a high-power density of 227 mW cm−2 with an energy density of 10.5 μWh cm−2 and stability of 84% capacitance retention after 11,000 cycles. These attributes allow operation at 120 Hz for fast charging and alternating current (AC) line filtering applications, which may be suitable to replace bulky electrolytic capacitors or serve as high-endurance energy storage for wireless electronics. Beyond the electrode material development, a novel supercapacitor configuration, structural supercapacitor was also developed to enhance the energy density of the whole device. A novel gradient structural electrolyte was designed for structural supercapacitor to balance its ionic conductivity and mechanical strength. By combining this electrode-electrolyte system, a structural supercapacitor that can replace the metallic chassis of transportation vehicles to provide extra electricity was fabricated. The structural supercapacitor was shaped into the hull of a model boat with a solar energy harvesting system, and it achieved both a high electrochemical and mechanical strength compared to its monofunctional counterparts. The demonstration was a promising prototype to show that structural energy storage can complement energy harvesting system to make electronics more energy-autonomous, requiring less maintenance cost if we have billions of electronics that can have operated on self-recharge. In addition, to enhance the efficiency of the self-powered electronics, an ion-exchange mechanism was also developed to suppress the self-discharge problem of energy storage units of self-powered electronics. This design increases the charging efficiency of the device and prevents the loss of stored energy during standby. It was demonstrated to work with radio frequency energy-harvesting circuits and showed the potential to serve as an energy reservoir for wireless electronic applications.

3D printing has been demonstrated as a mighty tool for fast prototyping in many fields. The fast reconfigurability, high repeatability and low cost enables itself to be accepted by everyone with general knowledge in engineering. That is, when the designs and process parameters are given, anyone would be able to simply perform the manufacturing processes. However, resulting from the immaturity of material tuning, tooling design and process control, when printing functional parts with special electrical or mechanical requirements, the printed workpieces are still not competitive comparing to the traditional works of manufacturing machines. In the desire of realizing printing as a production approach in professional applications, we propose this dissertation with guidelines from the hardware improvement in printers to the specific rules in modeling and printing toolpath designs in the fields of thin-film electronic devices, wearable haptic devices, and soft robotics. In the first work, we deposited silver inks with an inkjet printer for high-frequency inductive and capacitive components, which were combined into a pressure sensor to track liquid pressure with wireless readout. Then we turned our focus to extrusion printing with functional materials. For this exploration, a special hybrid printing system was build combining fused deposition modeling (FDM) and pneumatic extrusion printing, as well as functions in force tracking, shear force control and UV curing. The pneumatic printing apparatus was optimized to process an organic actuator material, liquid crystal elastomer (LCE), in order to control the mesogen alignment. As applications, incorporating with silver extrusion inks, two LCE haptic interfaces were demonstrated—including a tactile number-display surface and a kinesthetic glove. To demonstrate the application in robotics, soft LCE actuators and printed rigid exoskeleton parts were integrated into a self-sustained moving robot, which performs autonomous motion under constant light sources with a high payload-carrying ability. We also studied the actuation range of LCE with respect to the quantitive shear control during printing processes, which proved that printed LCE structures are advantageous in topological surface reconstruction. An example of human face model reconstructed by LCE was displayed, showing higher fidelity than other existing works. Details of all our works in the modifications to the printing setups and design rules of the fabricated devices are given in this dissertation, which provide guidelines not only in the flexible electro-mechanical devices we have been focusing on, but also inspirations to the researches in all the digital manufacturing fields as we wish.

A low-cost and scalable short-wavelength infrared (SWIR: λ = 1–3 μm) photosensor will be widely deployable and transformative for a wide range of spectroscopic systems and optoelectronics that form the foundation for scientific, industrial, medical, and defense applications. Conventional SWIR photosensors are cost-prohibitive due to complex fabrication involving epitaxial growth of inorganic crystals. To make SWIR photodetectors affordable for ubiquitous sensing, this thesis aims to realize low-cost organic SWIR bulk heterojunction (BHJ) photodiodes by using a novel class of modular narrow bandgap conjugated polymers, and to demonstrate the direct solution deposition of organic thin films can replace complex manufacturing processes and produce the comparable performance.

While polymeric semiconducting materials have been widely used and extensively studied in organic photovoltaics, different device behaviors accompany the progressive shrinkage of polymer bandgap to extend spectral absorption out to SWIR region. A better understanding of the fundamental properties of SWIR organic photodiode (OPD) is therefore needed to predict and advance performance. This thesis focuses on understanding different aspects of OPD performance that centers around specific detectivity, which ultimately defines the signal-to-noise ratio.

Firstly, in Chapter 3, the challenges in the dark noise increase associated with the low-bandgap organic system are discussed, followed by an introduction to different noise suppression methods. An emphasis is made on the importance of direct noise measurement to stay out of the pitfall of overestimating detectivity. Two approaches including interface engineering and electrode work function tuning are demonstrated to suppress the noise current in SWIR OPDs. Secondly, in Chapter 4, an improved model to decouple dissociation and collection efficiency is proposed to pinpoint the limiting factor of SWIR OPDs, and exemplary device engineering methods are shown to improve the dissociation bottleneck. Then, in Chapter 5, two recombination mechanisms limiting the device efficiency are shed light upon by connecting the optoelectronic properties to the materials composition. Lastly, in Chapter 6, three applications are demonstrated to show the practicality of solution-processed SWIR OPDs and the potential in realizing the low-cost and large-scale SWIR sensing.

Energy storage systems, including batteries, fuel cells, and supercapacitors, plays an essential role in various applications, from mass energy storage to transient energy buffering to assist power. Among these systems, supercapacitors have attracted widespread attention due to their high-power density and substantial cycle life. However, their practical applications are still limited by their low energy. To address this limitation, hybrid supercapacitors have been introduced. With the development of lithium-ion batteries, hybrid supercapacitor utilizing monovalent metal ions, such as lithium and sodium ions, have emerged. However, the actual anode capacities of lithium and sodium ion capacitors are lower than their theoretical capacities (Li: 3,860 mAh/g / Na: 1,166 mAh/g) due to the avoidance of direct plating/stripping. Additionally, although monovalent metal ions offer higher theoretical capacities, their charge density is lower than that of divalent metal ions, such as zinc and magnesium. Among the divalent metal ions, zinc is preferred due to its reduction potential (-0.76 V vs. SHE). Thus, zinc ion hybrid supercapacitors have been introduced. However, the dendritic zinc growth and low cathode capacity pose significant obstacles to practical applications. Moreover, low thermal stability, resulting from low ion conductivity in cold environments and high self-discharge at high temperatures, significantly degrade device performance. This study investigates strategies to enhance the energy and cycle lifetime of zinc ion hybrid supercapacitors across a wide temperature range. The dissertation is divided into three parts. The first part discusses the suppression of dendritic zinc growth on anode to enhance the cycle life. In this study, we demonstrated the effectiveness of a zinc-copper dual-ion electrolyte in promoting uniform zinc plating by reducing the zinc nuclei radius. The zinc ion capacitor utilizing the zinc-copper dual-ion electrolyte achieved a density of 41 W/kg with a negative-to-positive (n/p) electrode capacity ratio of 3.10. At an n/p ratio of 5.93, the device exhibited a remarkable cycle life of 22,000 full charge-discharge cycles, equivalent to 557 hours of discharge. The cumulative capacity reached ~581 ampere hour per gram, surpassing the benchmarks of lithium and sodium ion capacitors. These results highlight the promise of the dual-ion electrolyte for delivering high- performance, low-maintenance electrochemical energy supplies. The second part of the dissertation focuses on improving cathode capacity with extended cycle life. In this work, we investigated the use of protic additive to mitigate capacity fading and increase the utilization emeraldine salt (ES) polyaniline (PANI) cathode in a non-aqueous electrolyte. The protic additive, propylene glycol, characterized by its hydrogen-bonding capabilities, stabilizes the PS PANI and promotes reversible redox reactions. This facilitates high capacity and an extended cycle lifetime for applications in zinc ion hybrid supercapacitors. The use of this protic non-aqueous electrolyte in a PANI-zinc device resulted in an energy density of 255 Wh/kg at a power density of 1.8 kW/kg and a robust cycle lifetime of 3,850 charge/discharge cycles. At a high current density of 6.5 mA/cm2, the PANI reached a capacity of 257 mAh/g, equivalent to 87% of its theoretical capacity (294 mAh/g). These results showcase the effectiveness of the protic additive in improving both capacity and cycle life in electrochemical supercapacitors. In addition, we developed a gel polymer electrolyte (GPE) consisting of polyacrylonitrile (PAN) mixed with an ion exchange resin filler to broaden the operational temperature range and minimize self-discharge characteristics in supercapacitor. The inclusion of the ion exchange resin filler effectively lowered the self-discharge rate and impurity diffusion coefficients in the supercapacitors, thereby minimizing energy loss in hot environments. In cold settings, the device exhibited an energy density of 94 uWh/cm2 at an output power density of 0.4 mW/cm2 in a -20°C chamber. The combination of our improved GPE increased the stored energy and extended the operational time of a motor driven from a cold start by a supercapacitor. This demonstrates a high-performance design suitable for harsh environments. During the training for high thermal stability supercapacitor research, the research of short-wave infrared (SWIR) organic photodetectors with heterojunction bilayer was conducted. The utilization of a heterojunction bilayer in SWIR organic photodetectors improved the external quantum efficiency and detectivity, enabling the photomultiplication effect due to the electron blocking capability of CuSCN layer. Despite the enhanced external quantum efficiency (560%), the noise current was efficiently reduced by the heterojunction bilayer, resulting in improved detectivity (3.5x10^9 Jones).

Continuous monitoring of the heart rhythm and electrophysiology is a vital biosensing ability that is routinely utilized by hospitals around the world. This process is made available by detecting electrical activity of the heart during the cardiac cycles using electrodes placed on the surface of the skin; hence producing an electrocardiogram (ECG). Due to the urgency of care, specifically in the emergency rooms, rapid and accurate application of such biosensors are crucial. To address this need, an elastic multi-electrode fabric-based band will be prototyped wherein ECG electrodes and their connecting wires are integrated.Chapter 1 focuses on fabrication and characterization of multi-electrode bands using screen-printing for both dry-electrodes and hydrogel-coated electrodes. Then ECG data is collected for the fabricated electrodes and compared to commercial electrodes in terms of signal-to-noise ratio (SNR) and waveform. The results indicated that the fabricated multi-electrode band has a slightly lower SNR in comparison to the commercial electrode, but it can be a suitable candidate for ECG recordings. Although screen-printing of electrodes allows for low-cost and rapid manufacturing of such electrodes, the fabrication process can be more automated using printing. In Chapter 2, printing of a passivation layer will be established for an all-printed supercapacitor, and the technology used for printing of this device can be directly transferred to ECG electrode fabrication. Chapter 3, demonstrates a distributed multi-channel frequency-modulation-based data acquisition system for a capacitive pressure sensing transducer; however, this technology is sensor-type-agnostic and can be applied to other biosensors, such as for ECG recordings.

To study human development and disease, and develop therapies for regenerative medicine, the ability to create scalable, physiologically relevant human tissues is critical. In this regard, engineering cells and tissues from pluripotent stem cells has led to significant advances in our understanding of human-specific biology and holds promise for therapies. However, several challenges remain, including the ability to differentiate diverse lineages and drive disease states, vascularization to build tissues at scale, and monitoring capabilities to assess function. In this dissertation, I present a multi-faceted approach to address these limitations in creating and assaying complex tissue. To rapidly discover methods to differentiate pluripotent stem cells, I developed a screening method leveraging single cell RNA-sequencing to study the effects of gene overexpression. Using this approach, I assayed both fitness and transcriptomic responses of transcription factors, mutant gene libraries and whole gene families on pluripotent stem cells in multiple culture conditions. From these responses I built gene regulatory networks and found ETV2 as a reprogramming factor toward endothelial cells. I further engineered the system in combination with teratoma formation to develop a multiplexed system to assay the potential of genes and variants to drive oncogenic transformation in a tissue-specific manner. I found that c-MYC alone or together with myristoylated AKT1 drives transformation of neural progenitor lineages, while MEK1 (S218D/S222D) drives proliferative advantage in mesenchymal lineages like fibroblasts. I then harnessed these reprogramming approaches to engineer densely vascularized human tissue. I combined reprogramming and chemically directed differentiation by overexpressing lineage-specifying transcription factors in differentiating vascular organoids to introduce neurons and skeletal muscle into the organoids, demonstrating maintenance of molecular and functional characteristics of the parenchymal and vascular lineages. Finally, I developed flexible, printed electrodes to enable the monitoring of electrophysiological signals and electrical perturbation of tissues. I enabled low noise, high spatial resolution measurement of clinically relevant signals using screen-printed, stretchable concentric ring electrodes. I then applied these screen-printed electrodes to study the effects of electrical stimulation on the wound healing response in vivo. Lastly, I demonstrated preliminary data on a novel fabrication method to print microelectrodes to map cellular electrical activity.

Conductive polymer is studied intensively in the last several decades. Due to its eminent properties, such as high electronic and ionic conductivity, flexible, stretchable, easy to process and so on, it is widely employed in the flexible electronics and energy storage devices.The multichannel flexible concentric – ring dry electrodes for electrophysiological recordings is developed. Conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate is utilized as the interface layer to lower the impedance and noise level. The concentric ring geometry enables Laplacian filtering to pinpoint the bioelectric potential source with spatial resolution determined by the ring distance. Build on this flexible electrode, we develope a platform to systematically study the effects of electrical stimulation upon the inflammation phase and the activation of signaling mediators. With the help of flexible electrode, this platform enable studies of in-vivo immune cell response of electrical stimulation in the molecular level. We find that low frequency electrical stimulation increase phosphorylation of Erk proteins in recruited leukocytes, identifying a signaling pathway that is activated during the healing process. Besides the application of conductive polymer in flexible electrode, we demonstrate a new type of faradaic electrode material comprised of a very narrow bandgap donor−acceptor conductive polymer in electrochemical supercapacitor. Due to its charge delocalization in the reduced state, the anode retain 90% of its initial capacitance after 2000 full charge – discharge cycles, which exceeds other n-dopable organic materials and is practical for commercial use. Redox cycling processes are monitored in situ by optoelectronic measurements due to the polymer’s electrochromism to separate chemical versus physical degradation mechanisms. Asymmetric supercapacitors is fabricated using this n-dopable polymer in combination with p-type PEDOT:PSS operate within a 3 V potential window, with a best-in-class energy density of 30.4 Wh/kg at a 1 A/g discharge rate, a power density of 14.4 kW/kg at a 10 A/g discharge rate. During the electrochemical supercapacitor development, we find that self-discharge of supercapacitor is one of the bottleneck for its widely application. To solve this issue, we demonstrate a separator with sulfonate ion-exchange resin which can suppress self-discharge by trapping impurities in the electrolyte. Temperature-dependent characteristics are analyzed to identify that the reduction of impurity concentration and diffusion is key to improve potential retention. It is demonstrated to work with radio-frequency energy harvesting circuits and shows the potential to serve as an energy reservoir for wireless electronic applications.

In marine studies, the current sensors technologies have limitations such as time-consuming batch sample analysis, size-weight-power restrictions, and complex encapsulation, which impedes real-time in-situ measurements. In this thesis, we develop printed integrated ocean sensor designs that address the challenges through novel device configurations and soft materials selection and processing and integration strategies. My novel device configuration of dual-gate organic electrochemical transistors (OECTs) extended the operating potential window over 2 V with remarkable stability, allowing high potential redox reactions to occur. Detailed analysis of the operating principle has been derived by introducing two capacitance ratios to describe the mechanism of modulating the channel conductance. The printed dual-gate OECTs achieves a detection limit of 0.3 ppm dissolved oxygen concentration in seawater, with a sensitivity of 222 µA cm−2 ppm−1 for concentrations below 5 ppm. My second approach to enhance the sensitivity of the printed integrated ocean sensor is through the use of a compact microfluidics design. This design allows for the in-situ detection of target anions that are generally interfered with by the high background of chloride, especially under seawater. The tandem microfluidics structure comprises a flow feeding unit, two desalination electrochemical cells, channel extensions to reduce signals cross talk, and downstream detection through a solid-state ion-selective membrane (ISM) sensor. The integration of these components was achieved through digital cutting, stencil-printing, and lamination. This printed microfluidics platform has demonstrated a detection limit of 0.5 mM nitrate with a sensitivity of 11.3 mV/dec under a continuous seawater flow, with a response time within 8 minutes. The integration of electronic components into printed ocean sensors has been demonstrated, allowing for the simultaneous detection of multiple signals, including dissolved oxygen, salinity, and curvature changes, using customized integrated multiplexer (MUXs) systems. The printed integrated ocean sensor was constructed by patterning conductive carbon paste/graphite foils onto a flexible plastic substrate. The active devices were fabricated through electrodeposition in different configurations, including electrochemical cells and transistor structures. This integrated ocean sensor demonstrated the feasibility of detecting oyster gape down to sub-mm levels, with a measurement range of dissolved oxygen between 0.5-6 ppm and salinity between 4-40 g kg-1. In addition, I also contributed to the development of an organic retinomorphic sensor for infrared spectrum. The sensor achieved a noise-equivalent power of 0.24 nW over 0.09 cm2 detector area. Leveraging the technique of intensity-modulated photovoltage spectroscopy from the photovoltaic community, my study probed the detector operation mechanism and in turn enhanced the sensor detectivity by interfacial modifications. The improved sensor is compatible with the aforementioned ocean sensors and has the potential to serve as a high-performance motion detector in ocean environments.