PhD thesis repository of Carlos David Prado-Socorro at the Institute of Molecular Science (ICMol), Universitat de Valencia.
Read the current thesis draft | Introduction | Proof-of-concept chapter | Comparative chapter | Temporal-computing chapter
This thesis studies solution-processed organic memristive devices whose electrical response is shaped by mobile ions inside a polymer composite. These devices do not merely store a static resistance value: their conductance carries a decaying record of recent electrical activity.
The central idea is to use that fading memory as a computational resource. The current experimental result is strongest for polymer-electrolyte composition: in the replicated PEO/LiOTf grid, composition tunes the switching window, pulse integration, and fading-memory time. Host, anion, and cation chemistry are retained as an illustrative, sample-limited tuning landscape rather than as a powered Li > Na > K law.
The active layer combines a semiconducting conjugated polymer, an oxygen-rich ion-transport host, and a dissolved salt. An applied electric field redistributes the ions. The residual ionic profile changes the device conductance and acts as its internal memory state.
Conventional computers repeatedly move data between memory and processing units. For data-intensive workloads, this transfer can cost more energy and time than the computation itself. Memristive hardware offers two complementary routes around that bottleneck:
- In-memory computing, where programmed conductances perform operations inside a memory array.
- Event-driven temporal computing, where the natural relaxation of a physical device processes time-dependent signals.
This thesis focuses on the second route. A device that gradually forgets is not treated as a failed non-volatile memory. Its relaxation time becomes a useful feature for processing streams, spikes, transients, and other time-resolved signals.
The working physical hypothesis was that memory timescale is linked to ion transport inside the polymer electrolyte. Ether oxygens in the host coordinate alkali-metal cations, so cation identity was expected to change the relaxation dynamics:
Li+: stronger coordination and longer fading-memory timescalesNa+: intermediate behaviourK+: weaker coordination and shorter fading-memory timescales
The current Chapter 3 draft keeps that HSAB argument as qualitative framing, but the archive does not support a robust host- and anion-independent Li > Na > K ordering. The defensible quantitative result is the composition dependence in the PEO/LiOTf grid; chemistry beyond that is explicitly sample-limited.
| Chapter | Focus | Status |
|---|---|---|
| 1. Introduction | Computing bottlenecks, synaptic inspiration, memristors, organic materials, and the polymer-electrolyte strategy | Draft available |
| 2. Proof of concept | A fully characterised SY/Hybrane/LiOTf two-terminal device with analogue switching, short- and long-term retention, EPSC-like response, and STDP |
Draft available |
| 3. Comparative study | How composition (the PEO/LiOTf grid) tunes volatile dynamics — switching, potentiation, and fading memory — and how electrolyte chemistry shifts them further as sample-limited side evidence |
Draft available |
| 4. Temporal computing | Data-driven reservoir simulations from Chapter 3 parameter cards: memory-capacity/NARMA benchmarks, WESAD physiological temporal-context reconstruction, and WESAD affective-computing demonstrations; coincidence detection is cut and filter-bank logic is folded into the reservoir framing | Draft available |
| 5. Conclusions | Contributions, limitations, and future directions | Planned |
The proof-of-concept chapter expands the published work:
Carlos David Prado-Socorro et al., "Polymer-Based Composites for Engineering Organic Memristive Devices", Advanced Electronic Materials 8, 2101192 (2022).
| Path | Contents |
|---|---|
thesis.tex |
Top-level LaTeX entry point |
chapters/ |
Standalone chapter sources and shared thesis formatting |
figures/ |
Figures used throughout the thesis |
bibliography/ |
Shared BibLaTeX database |
exports/ |
Committed PDF snapshots |
handouts/ |
Planning documents, outlines, and working notes |
docs/ |
Reference docs about the experimental archive and analysis pipeline (data and code live in the sibling Nanomem_Devices_Library/) |
The chapter files compile both independently and as part of the complete thesis. A local LaTeX installation with latexmk and biber is required.
make chapter1 # build/chapters/chapter1_introduction.pdf
make chapter2 # build/chapters/chapter2_proof_of_concept.pdf
make thesis # build/thesis.pdf
make all # build chapters and thesis
make exports # refresh committed PDF snapshots
make clean # remove generated LaTeX artefactsRun these commands from the repository root. Generated LaTeX files are written to build/ and excluded from version control.