Robert Kimball

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Senior capstone · in progress

Flexible Micro-Supercapacitors

Problem
Make a micro-scale, mechanically flexible supercapacitor for wearable and implantable devices.
Date
Spring 2026 – Spring 2027
Team
Team 13 "Micro Charge": 6 students; advisor Prof. Yung Joon Jung
My role
Technical lead (team charter): check calculations and verify designs
Status
Research and design done; nothing fabricated yet. Fabrication and testing in Capstone 2
Team Micro Charge logo: a chip outline with negative and positive electrodes, and the words MICRO CHARGEOpen larger image
Team Micro Charge, MEIE senior capstone Team 13 (Northeastern University, 2026–2027).
Top-view schematic of interlocking carbon-nanotube finger electrodes on a flexible orange film, with gold + and − pads and a gel electrolyte areaOpen larger image
Planned device concept: in-plane interdigitated CNT electrodes on Kapton/PET under a PVA-acid gel electrolyte. Redrawn illustrative schematic, not to scale; the lab's existing masks offer 10, 20, 50 and 200 µm finger patterns.
Table comparing activated carbon, carbon nanotubes, graphene and MXene electrodes, aqueous, organic and gel electrolytes, and Kapton/PET substrates, with selected options highlighted greenOpen larger image
Material selection outcome: CNT electrodes, acid-based PVA gel electrolyte, and Kapton or PET substrate. MXene was dropped because it is "easily oxidized, not easy to acquire". Redrawn from the team's Capstone 1 slides and advisor notes; qualitative comparison, not a scored matrix.
Table of typical supercapacitor values: capacitance 1 F – 3,000 F, impedance 0.01–150 mΩ, ~2.5–2.7 V, 5-10 seconds charge/discharge, ~1M cyclesOpen larger image
Quantitative goals: typical supercapacitor benchmarks the flexible MSC should at least match. Targets, not measured results. Redrawn from the Capstone 1 final presentation (slide 5), whose original table was not readable.
Presentation slide showing four steps: flexible substrate roll, photolithography (light, reticle mask, lens, wafer), carbon nanotube deposition equipment, and an electrode-coating gloveboxOpen larger image
Solution approach slide from the team's Capstone 1 final presentation: flexible substrate → photolithography → CNT deposition → electrode coating.
Eight cross-section panels: Kapton on silicon, photoresist spin-coat, UV exposure through a finger mask, development, CNT deposition, lift-off, gel electrolyte with metal terminals, and encapsulationOpen larger image
Planned fabrication sequence for Spring 2027, redrawn from the final-presentation speaker notes. Schematic only; no device has been fabricated yet.
Exploded illustration of a micro-supercapacitor chip between two flexible orange substrate layersOpen larger image
Encapsulation concept from the team's ethics slide: a protective flexible layer keeps the CNTs and electrolyte from escaping, which addresses the chemical-leakage risk I raised in the Ethics memo.
Gantt chart from May 11 to June 17, 2026 with research, presentation, literature review and report tasks; critical path in redOpen larger image
Capstone 1 schedule (Summer 2026, completed). Critical path: memo & Gantt → advisor background presentation → draft literature review → written report. Redrawn from the team's Gantt chart.xlsx.
Gantt chart from January 4 to April 23, 2027 with lab trainings, BOM and ordering, prototyping and characterization cycles, and the final report and presentationOpen larger image
Capstone 2 plan (Spring 2027): trainings → materials → initial prototype → characterization → iterative prototypes → final presentation. Redrawn from the team's Capstone 2 Gantt chart.xlsx.

Problem

  • Supercapacitors charge almost instantly and store far more energy than ordinary capacitors, but they are bulky and rigid. A micro-scale, flexible version could power implantable, wearable and compact devices.
  • Example use case: a smaller, flexible continuous glucose monitor patch. Current monitors are rigid and roughly the size of a walnut.

My role

  • Technical lead, as defined in the team charter: responsible for checking calculations and verifying that designs are valid.
  • As technical lead, I assigned two teammates to cleanroom and dip-coating training so they can fabricate the prototypes. I do not do cleanroom work myself.
  • My research topic: which materials are used in supercapacitors today, and why (activated-carbon pore size, carbon nanotubes, graphene, MXene, and aqueous, organic and gel electrolytes).

Material selection

  • Compared electrode, electrolyte and substrate candidates on surface area, conductivity, flexibility, leakage, cost and ease of getting them, then discussed them with the advisor.
  • Selected design: carbon-nanotube (CNT) electrodes, a PVA gel electrolyte based on phosphoric or sulfuric acid, and a Kapton or PET film as the flexible substrate.
  • MXene was dropped: it is easily oxidized and hard to get. A solid gel electrolyte was chosen so nothing can leak.

Planned process

  • Kapton on a silicon carrier wafer → positive photoresist → UV exposure through the lab's existing interdigitated finger masks (10, 20, 50 and 200 µm) → CNT dip or spray coating → lift-off → gel electrolyte and metal terminals → protective encapsulation.
  • Planned tests: cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy, microscope checks for short circuits, and bending fatigue.

Ethics: chemical leakage

  • I wrote the ethical-issues section of the team's Ethics and Impact memo. I named preventing chemical leakage as the top safety duty for a device worn on or in the body.
  • This supports the solid gel electrolyte and the protective encapsulation layer in the design.

Timeline

  • Capstone 1 (May–Jun 2026, done): problem statement, team charter, literature research, advisor presentation, Ethics and Impact memo, and final presentation.
  • Capstone 2 (Jan–Apr 2027, planned): lab, cleanroom, dip-coating and photolithography training; BOM and material orders; initial prototype; characterization; iterative prototypes; final report and presentation.
  • This page will be updated when there are test results.