Droplet-based electricity generators are lightweight and nearly metal-free, making them promising for hydraulic power applications. However, two critical challenges hinder their practical application: significant performance degradation, potentially up to 90%, in existing small-scale integrated panels, and low efficiency, often less than 2%, in storing the irregular high-voltage pulsed electricity produced by large-scale arrays. Here, we demonstrate that by tailoring the bottom electrodes so that their area is comparable to the spread area of the impinging water droplets, we double the average output power of individual cells and fabricate large-scale (30-cell) arrays that achieve approximately 2.5 times higher power than state-of-the-art arrays. Furthermore, without using any power management chip, we integrate a large-scale (400-cell) micro-supercapacitor array to store the irregular high-voltage electricity produced by the 30-cell generator array at an efficiency of 21.8%. The integration of large-scale electricity generator arrays and micro-supercapacitor arrays forms a simple, chipless, self-charging power system with an output power of 81.2 μW, which is 27 times higher than current systems based on 30-cell arrays. This work provides important insights towards practical applications of droplet-based electricity generators.

Many emerging industry applications demand electronic systems with reliable operation at temperatures >300 °C. To date, the most promising on‐chip power sources, micro‐supercapacitors (MSCs), can only operate at temperatures up to 250 °C for a short period as limited by the vulnerability of their electrolyte frameworks at high temperatures. Here, a strategy is proposed to use liquids to lock the phase transformations of bassanite microrods for scalable on‐chip printing of interlocking ceramic frameworks with high thermal stability. The robust ceramic frameworks enable simple yet scalable fabrication of MSCs to work at 300 °C with an areal capacitance of up to >60 mF cm −2 and only ≈3% performance degradation after 1000 cycles during a test period of ≈3 h. A large‐scale MSC array, consisting of 20 cells within a footprint area of 4 cm × 8 cm, has been able to supply a power of 7.2 mW at 300 °C. These break through the present limit of 250 °C of almost all high‐temperature energy storage devices and pave the way for on‐chip MSCs for high‐temperature electronics.

The rapid advancement of miniaturized electronics demands compact, high-performance on-chip energy storage with seamless integration. Printed micro-supercapacitors (MSCs) are promising candidates, offering high power density, long cycle life, and inherent compatibility with planar integration. Direct printing techniques like direct ink writing (DIW) and direct laser patterning (DLP) enable flexible design, material versatility, scalability, and high precision on-chip integration. However, realizing miniaturized MSCs that combine high electrochemical performance, scalability, environmental versatility and seamless on-chip fabrication remains challenging. Key obstacles include developments of high-performance material design and well-defined patterning strategies. 

Part I of this thesis enhances MSC performance and printing scalability using DIW. The first work developed a doped PEDOT:PSS electrode ink with optimized rheology and electrochemical properties, enabling fully printed compact 100-cells MSC arrays on paper substrate with high capacitance, ultrahigh-rate capability, and an extended operating voltage window (up to 160 V) for efficient instantaneous electricity storage. The second work significantly improves thermal stability through a DIW-printable bassanite framework combined with ionic liquid electrolytes, enabling the MSC array a long-term cycling at a record temperature of 300 °C. These advances demonstrate ink formulation designs for DIW enabled scalable fabrication of high-rate, robust MSC array capable of operating across diverse application environments.

Part II of this thesis improves on-chip MSC performance and integration based on DLP approach. The third work utilized DLP in hydrogen silsesquioxane (HSQ) to directly fabricate 3D hierarchical inorganic electrodes with self-formed nanogratings. Based on this structure, a compact on-chip MSCs with exceptional rate performance was fabricated with high-rate performance of 1 mF cm-2 at 50 V s-1 and high temperature stability up to 200 °C. The fourth work further using the 3D nanograting printing approach tailored on-chip MSC electrode microstructures to achieve high-frequency line-filtering up to 10 kHz. The precise fabrication of 3D standing nanograting structure provides large open surface area, facilitating fast ion transport, resulting in highly compact on-chip MSC with the highest reported areal capacitance of 0.32 mF cm-2 at 10 kHz, thereby enabling effective filtering applications and further advancing the miniaturization of capacitors in microelectronic systems. These results establish DLP as a powerful approach for the high-precision construction of on-chip 3D structures and pave the way for integration of ultra-compact MSCs into miniaturized electronic systems for high-frequency applications.

Den snabba utvecklingen av miniatyriserad elektronik ställer krav på kompakt, högpresterande energilagring på chip med sömlös integration. Tryckta mikrosuperkondensatorer (MSCs) är lovande kandidater då de erbjuder hög effekttäthet, lång cykellivslängd och inneboende kompatibilitet med plan integration. Direkta trycktekniker såsom direct ink writing (DIW) och direct laser patterning (DLP) möjliggör flexibel design, materialmångfald, skalbarhet och högprecis integrering på chip. Att realisera miniatyriserade MSC:er som kombinerar hög elektrokemisk prestanda, skalbarhet, miljömässig mångsidighet och sömlös integration på chip är dock fortfarande en utmaning. Centrala hinder är utvecklingen av högpresterande materialdesign samt väldefinierade mönstringsstrategier.

Del I av denna avhandling förbättrar MSC-prestanda och tryckbar skalbarhet med hjälp av DIW. Det första arbetet utvecklade ett dopat PEDOT:PSS-elektrodbläck med optimerad reologi och elektrokemiska egenskaper, vilket möjliggjorde fullständigt tryckta, kompakta 100-cells MSC-arrayer på papperssubstrat med hög kapacitans, ultrahög laddnings-/urladdningshastighet samt ett utökat driftspänningsfönster (upp till 160 V) för effektiv omedelbar energilagring av elektricitet. I den andra studien förbättrades den termiska stabiliteten avsevärt genom en DIW-printbar bassanitram kombinerad med jonvätskeelektrolyter, vilket möjliggjorde långtidscykling av MSC-arrayer vid en rekordtemperatur på 300 °C. Dessa framsteg visar på bläckformuleringsdesigner för DIW som möjliggör skalbar tillverkning av högfrekventa, robusta MSC-arrayer kapabla att fungera i varierande applikationsmiljöer.

Del II av denna avhandling förbättrar prestanda och integrering av MSC:er på chip baserat på DLP-metoden. I den tredje studien användes DLP i hydrogen silsesquioxane (HSQ) för att direkt tillverka 3D-hierarkiska oorganiska elektroder med självorganiserade nanogitter. Baserat på denna struktur framställdes kompakta MSC:er på chip med exceptionell frekvensprestanda, uppvisande en arealkapacitans på 1 mF cm⁻² vid 50 V s⁻¹ och hög temperaturstabilitet upp till 200 °C. I den fjärde studien vidareutvecklades 3D-nanogitterstrategin för att skräddarsy MSC-elektroders mikrostrukturer på chip och därigenom uppnå högfrekvent linjefiltrering upp till 10 kHz. Den precisa framställningen av stående 3D-nanogitterstrukturer ger en stor öppen yta, vilket underlättar snabb jontransport och resulterar i en mycket kompakt MSC på chip med den högsta rapporterade arealkapacitansen, 0,32 mF cm⁻² vid 10 kHz. Detta möjliggör effektiva filtreringsapplikationer och driver ytterligare miniatyriseringen av kondensatorer i mikroelektroniska system. Dessa resultat etablerar DLP som en kraftfull metod för högprecisionskonstruktion av 3D-strukturer på chip och för integrering av ultrakompakta MSC:er i miniatyriserade elektroniska system för högfrekventa applikationer.

Hierarchical structures are abundant in nature, such as in the superhydrophobic surfaces of lotus leaves and the structural coloration of butterfly wings. They consist of ordered features across multiple size scales, and their advantageous properties have attracted enormous interest in wide-ranging fields including energy storage, nanofluidics, and nanophotonics. Femtosecond lasers, which are capable of inducing various material modifications, have shown promise for manufacturing tailored hierarchical structures. However, existing methods, such as multiphoton lithography and three-dimensional (3D) printing using nanoparticle-filled inks, typically involve polymers and suffer from high process complexity. Here, we demonstrate the 3D printing of hierarchical structures in inorganic silicon-rich glass featuring self-forming nanogratings. This approach takes advantage of our finding that femtosecond laser pulses can induce simultaneous multiphoton cross-linking and self-formation of nanogratings in hydrogen silsesquioxane. The 3D printing process combines the 3D patterning capability of multiphoton lithography and the efficient generation of periodic structures by the self-formation of nanogratings. We 3D-printed micro-supercapacitors with large surface areas and a high areal capacitance of 1 mF/cm² at an ultrahigh scan rate of 50 V/s, thereby demonstrating the utility of our 3D printing approach for device applications in emerging fields such as energy storage.

Self-charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco-friendly conductive inks based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer-free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of “one ink, multiple functions” enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post-integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while the 6-cell array to 3.0 V. On-paper SCPSs are promising to serve as lightweight, thin, sustainable, and low-cost power supplies. 

The rapid development of emerging electronics requires power sources with the advantages of lightweight, high efficiency, and portability. Considering the use of critical raw materials (such as Li, Co, etc.) and the increasing global concern of battery waste, self-charging power systems (SCPSs) integrating energy harvesting, power management, and energy storage devices have been envisioned as promising solutions to replace traditional batteries to avoid the use of toxic materials and the need of frequent recharging/replacement. Up to date, the reported SCPSs still hold the problem of large form factor, unscalable fabrication, noble materials, and material complexity. In our work, a highly stable and eco-friendly organic conductive ink based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has been developed for monolithic fabrication on-paper SCPSs almost fully through a simple direct ink writing (DIW) process. The ink possesses multiple functions and enables to directly print almost all the key components in the SCPSs, including electrodes for triboelectric nanogenerators (TENGs, mechanical energy harvesters), electrodes for micro-supercapacitors (MSCs, energy storage devices), and interconnects, on the same paper substrate in a monolithic manner without the need for “post-integration”. The monolithic printing process exhibits excellent upscaling capability for manufacturing. In particular, the direct patterning merit of the DIW process offers great flexibility in optimizing the system performance through adjusting the cell number, electrode dimension, and thickness of the MSC arrays. By adjusting the cell numbers, the MSC arrays attain high-rate capability up to 50 V/s to match the pulsing electricity produced from the TENGs. For small-size printed SCPSs (~ 2 cm × 3 cm ×1 mm), after continuous press and release of the TENGs for ~79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while 6-cell array to 3.0 V. For a larger-size printed SCPS with 30 MSC cells (~ 7.5 cm × 5 cm ×0.5 mm), after charging through pressing/releasing for 10 min (nearly 1200 cycles), it can light up a LED (~ 4 W) for 5 s. The demo of successfully powering an LED device exhibited its great potential for powering various electronics. The monolithically fabricated on-paper SCPSs have great potential to serve as lightweight, thin, sustainable, eco-friendly, and low-cost power supplies for emerging electronics.

Harvesting renewable mechanical energy is envisioned as a promising and sustainable way for power generation. Many recent mechanical energy harvesters are able to produce instantaneous (pulsed) electricity with a high peak voltage of over 100 V. However, directly storing such irregular high-voltage pulse electricity remains a great challenge. The use of extra power management components can boost storage efficiency but increase system complexity. Here utilizing the conducting polymer PEDOT:PSS, high-rate metal-free micro-supercapacitor (MSC) arrays are successfully fabricated for direct high-efficiency storage of high-voltage pulse electricity. Within an area of 2.4 × 3.4 cm2 on various paper substrates, large-scale MSC arrays (comprising up to 100 cells) can be printed to deliver a working voltage window of 160 V at an ultrahigh scan rate up to 30 V s−1. The ultrahigh rate capability enables the MSC arrays to quickly capture and efficiently store the high-voltage (≈150 V) pulse electricity produced by a droplet-based electricity generator at a high efficiency of 62%, significantly higher than that (<2%) of the batteries or capacitors demonstrated in the literature. Moreover, the compact and metal-free features make these MSC arrays excellent candidates for sustainable high-performance energy storage in self-charging power systems.

The raised demand for portable electronics in high-temperature environments (>150 °C) stimulates the search for solutions to release the temperature constraints of power supply. All-solid-state microsupercapacitors (MSCs) are envisioned as promising on-chip power supply components, but at present, nearly none of them can work at temperature over 200 °C, mainly restricted by the electrolytes which possess either low thermal stability or incompatible fabrication process with on-chip integration. In this work, we have developed a novel process to fabricate highly thermally stable ionic liquid/ceramic composite electrolytes for on-chip integrated MSCs. Remarkably, the electrolytes enable MSCs with graphene-based electrodes to operate at temperatures as high as 250 °C with a high areal capacitance (~72 mF cm⁻² at 5 mV s⁻¹) and good cycling stability (70 % capacitance retention after 1000 cycles at 1.4 mA cm⁻²).

The demand for miniaturized electronics has created a need for compact, high-performance on-chip power sources. Micro supercapacitors (MSCs) have emerged as promising candidates for on-chip filtering applications due to their high specific capacitance and on-chip integrity. However, most existing MSCs suffer from significant capacitance attenuation at high frequencies, limiting their effectiveness in modern electronic circuits operating above 10 kHz. This study addresses this challenge by developing a printed on-chip MSC with open-through nanograting electrode microstructure using a high-resolution 3D printing technique. The resulting 3D nanograting structure enables on-chip MSC high capacitance while facilitating rapid ion transport, crucial for maintaining high-frequency performance. Consequently, the on-chip MSC demonstrates an ultra-compact footprint of 0.048 mm2, about 260 time smaller than conventional aluminum electrolytic capacitor (AEC), while offering two-order higher areal capacitance of 1.2 mF cm-² at 1 kHz, and retain 0.32 mF cm-² at 10 kHz. This performance is twice as large as the highest value reported among state-of-the-art. The nanograting MSC simultaneously offers both high capacitance and excellent frequency response in a compact form factor, enabling effective line-filtering up to 10 kHz and provides promising potential for miniaturized, high-frequency line-filtering applications in advanced electronic systems.