BME4496 Graduation Project · Efe ATEŞ (22290588)

NFC Potentiostat

A Battery-Free, Ultra-Low-Power Electrochemical Sensing Platform Powered via NFC Energy Harvesting with On-Device Gemma 3 1B AI

Zero Battery (13.56 MHz V_EH)
STM32U545 + ST25DV
Gemma 3 1B AI & Voice
Sensitify Go App
Launch CV Simulator Explore Project Details
~5 mW
Power Draw
14-bit
ADC Resolution
5 Modes
CV / DPV / SWV / CA
98.5%
Linearity Accuracy
Overview

About the Project

The NFC Potentiostat is an ultra-compact, battery-free electrochemical diagnostic platform designed for point-of-care biosensing. Powered entirely through 13.56 MHz Near-Field Communication (NFC) energy harvesting from a smartphone, the system executes precision cyclic voltammetry, differential pulse voltammetry, and chronoamperometry with zero external wires or batteries. It combines custom 4-layer analog circuitry, an ARM Cortex-M33 microcontroller, and on-device Gemma 3 1B AI for instantaneous automated peak interpretation and hands-free voice control.

TÜBİTAK 2209-B (2025) – Approved Research Project
Ankara University · Biomedical Engineering
Interactive Simulation

Live Electrochemical Potentiostat · Real-Time CV Engine

Real-Time Cyclic Voltammogram (I vs E)
SCANNING ACTIVE
Potential ($E$): 0.00 V
Current ($I$): 0.00 μA
Anodic Peak ($I_{pa}$): +142.6 μA
Cathodic Peak ($I_{pc}$): -138.4 μA

Potentiostat Sweep Parameters

Scan Rate ($\nu$) 100 mV/s
Potential Window ($E_{low} \leftrightarrow E_{high}$) ± 0.60 V
Analyte Redox Couple Ferricyanide Fe(CN)₆
Motivation

The Challenge & Our Breakthrough

The Problem

Traditional benchtop potentiostats are bulky, cost thousands of dollars, and require mains power or bulky lithium batteries that degrade. This creates a severe barrier for field diagnostics, decentralized telemedicine, and resource-limited clinics.

The Wireless Solution

A credit-card sized potentiostat operating entirely on energy scavenged from a smartphone's 13.56 MHz RF field. By eliminating all batteries and cables, it achieves 100% maintenance-free electrochemical analysis with a single tap.

AI & Voice Intelligence

Integrated on-device Gemma 3 1B AI analyzes voltammograms in real time, detecting oxidation peaks and calculating analyte concentrations without cloud latency. Hands-free voice commands enable sterile operation in glove-wearing lab conditions.

Complete Ecosystem

Custom 4-layer PCB with STM32U545 + ST25DV dynamic tag, 3D-printed enclosure with magnetic alignment, CNC-milled NFC antennas, and the Sensitify Go Mobile companion app with live real-time graphing.

Architecture

System Overview · Complete Signal Path

Smartphone Sensitify Go App Gemma 3 1B AI Voice Commands Live CV Plotter 13.56 MHz NFC RF FIELD ST25DV-I2C Dynamic NFC Tag 256-B Fast Mailbox V_EH Harvest I²C STM32U545CE ARM Cortex-M33 Dual 12-bit DAC 14-bit ADC (128x OS) CMSIS-NN Core STOP2 Mode · ~5mW DAC ADC Analog AFE AD8606 Dual TIA 10 kΩ Gain Resistor MAX4634 MUX TPS61094 Boost Electrodes WE RE CE NFC Energy Harvesting Power Bus
Hardware

Technical Specifications · Custom 4-Layer PCB

Microcontroller

STM32U545CE

ARM Cortex-M33 ultra-low-power MCU with STOP2 deep-sleep mode, TrustZone security, and CMSIS-NN hardware neural accelerator.

NFC Tag IC

ST25DV04KC

Dynamic ISO 15693 NFC tag with 256-byte Fast Transfer Mailbox, energy harvesting output pin (V_EH), and 1 MHz I²C interface.

ADC Precision

14-bit (128x OS)

Successive approximation ADC with 128x hardware oversampling, yielding an effective resolution >16 bits for nanoampere currents.

Dual DAC Output

12-bit × 2 CH

CH1 generates dynamic sweep ramp potential ($V_{CE}$), while CH2 sets precision virtual ground bias ($V_{ref}$) on the transimpedance amplifier.

Analog Front-End

AD8606 + TIA

Ultra-low noise CMOS dual op-amp. 10 kΩ feedback transimpedance amplifier supporting current dynamic ranges of ±165 μA.

Power Budget

~5 mW Total

100% powered from harvested RF field via TPS61094 buck-boost converter. Zero battery weight, zero hazardous chemical waste.

Communication

NFC Binary Protocol · ST25DV Fast Transfer Mailbox

ST25DV Mailbox Frame Structure

Binary packet serialized into ST25DV 256-byte dual-port static RAM mailbox with strict CRC-8 validation:

[CMD]1 Byte
[LEN_LSB]1 Byte
[LEN_MSB]1 Byte
[PAYLOAD DATA]0 .. 251 Bytes
[CRC8_CCITT]1 Byte

Select NFC Command

RUN_CV (Cyclic Voltammetry) 0x14
RUN_DPV (Differential Pulse) 0x1E
RUN_SWV (Square Wave) 0x12
RUN_CA (Chronoamperometry) 0x28
GET_STATUS (Query State) 0x01
GET_RESULTS (Chunked Read) 0x30
ABORT (Emergency Stop) 0xFF
RUN_CV (0x14)

Cyclic Voltammetry Command

Initiates a full cyclic voltammetry potential sweep with programmable vertices.

Serialized Frame (Hex):
14 08 00 04 00 00 00 20 4E 64 00 8F
Simulated ST25DV Response:
0x00 OK (Sweep Started)
Intelligence

On-Device AI · Gemma 3 1B & Voice Agent

Voice-Controlled Hands-Free Lab

Working in wet biochemical laboratories requires protective nitrile gloves, making touchscreen interaction inconvenient and prone to contamination. Sensitify Go NFC Edition integrates on-device voice recognition and Google’s lightweight Gemma 3 1B model to interpret voltammograms automatically.

Try Sample Voice Prompts:
"Run CV scan from -0.5V to +0.8V at 100 mV/s"
"Calculate anodic oxidation peak current and potential"
"Check NFC energy harvesting voltage status"
Gemma 3 1B Response

"Identified reversible redox couple [Fe(CN)6]³⁻/⁴⁻. Anodic peak at +0.245V (142.6 µA), cathodic peak at +0.186V (-138.4 µA). Peak separation ΔEp = 59 mV indicates ideal Nernstian 1-electron transfer kinetics."

Mechanical CAD

3D Enclosure Explorer · MagSafe Snap Architecture

Drag to Rotate • Scroll to Zoom
Autodesk Fusion 360 · Iteration 5

Zero-Screw Snap-Fit Enclosure

Engineered specifically for point-of-care diagnostics. Incorporates an embedded MagSafe neodymium magnet ring channel for precise NFC antenna concentricity, slide-in guide rails for standard 3-pin Screen-Printed Electrodes (SPE), and integrated PCB clip locks.

MagSafe Concentric 3-Pin SPE Strip Slot Zero Screws Download STL
Methodology

15 Work Areas · 4 Engineering Disciplines

4 Areas

Electronic Design

  • 13.56 MHz Planar Spiral Antenna Design & Tuning
  • Low-Noise Analog Front-End (AD8606 TIA & Control Amp)
  • Precision 4-Layer SMD SMT PCB Assembly & Soldering
  • Embedded Firmware (DMA ADC Oversampling & Dual DAC Ramp)
4 Areas

Mechanical Design

  • CNC FR4 Antenna Isolation Milling
  • Parametric CAD Modeling in Autodesk Fusion 360
  • FDM 3D Printing Prototyping (Initial Iterations)
  • Magnetic MagSafe Snap Enclosure (5th Final Iteration)
3 Areas

Software & AI

  • Mobile App Development (Sensitify Go NFC Edition)
  • Gemma 3 1B Fine-Tuning & Automated Peak Analytics
  • Voice Control & Text-to-Speech Lab Assistant
4 Areas

Testing & Validation

  • 10 kΩ Dummy Resistor Multi-Run Calibration
  • Potassium Ferricyanide $[Fe(CN)_6]^{3-/4-}$ Redox Tests
  • Power Harvesting Efficiency & Voltage Droop Analysis
  • Commercial Benchtop vs. NFC Potentiostat Comparison
Academic Sources

Scientific References

  1. H. S. Lee, R. K. Panesar, L. Gonzalez-Macia, G. Barandun, F. Güder, “NFC-enabled sensing platform for the onsite determination of asparagine in food,” Materials Today Bio, vol. 36, 2025. doi:10.1016/j.mtbio.2025.102675
  2. D. R. Gawade, “Development of a low-power, battery-less near field communication sensor transponder for wireless sensing applications,” MRes Thesis, University College Cork, 2022. CORA UCC Repository
  3. K. Krorakai, S. Klangphukhiew, S. Kulchat, R. Patramanon, “Smartphone-Based NFC Potentiostat for Wireless Electrochemical Sensing,” Applied Sciences, vol. 11, no. 1, 2021. SOAR Repository
  4. STMicroelectronics, “AN2866 – How to design a 13.56 MHz customized antenna for ST25 NFC / RFID tags,” Application Note. ST AN2866
  5. I. Sommerville, Software Engineering, 10th ed. Pearson, 2015.
  6. ISO/IEC 15693, “Identification cards – Contactless integrated circuit cards – Vicinity cards.” ISO 15693 Standard
  7. Google, Material UI 3 Foundations & Customization. Material UI 3
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