Biochip Diagnostics Dashboard & Project Tracker

ANALYTE

Dopamine

POTENTIAL

0.00 V

CURRENT

0.00 µA

SCAN RATE

50 mV/s

Hardware Mock Active

Electrochemical Signal Output

Simulation Controls

Active Experiment Target

Electrochemical Action

ESP32 Serial Output

9600 baud

[SYS] Biochip Dashboard Initialized.
[SYS] Ready to interface with ESP32 WebSockets/REST API.
[ESP32] Hardware Simulation Mock Loaded.
[LMP91000] Potentiostat front-end configured: Three-Electrode Mode.
[ESP32] Awaiting control signal from dashboard...

Testing Guide & Operational Walkthrough

Check Physical Hardware Setup: Verify the ESP32 is powered via micro-USB and connected to the LMP91000 board. Ensure the WE/RE/CE pins are plugged into the Screen-Printed Electrode (SPE).

Select Target Profile: Under Simulation Controls, select DA (Dopamine), 5-HT (Serotonin), or ACh (Acetylcholine) to load its potential calibration curve.

Run Cyclic Voltammetry (CV): Confirm you are in "CV Loop" view. Click Start CV Scan to trigger a voltage sweep from -0.2V to +0.8V. Observe the redox current profile.

Perform Amperometric Spike Test: Switch chart mode to Amperometry. Click Inject Analyte to trigger a raw solution spike and observe the current response step.

Active Chemical Reaction Details

Dopamine (DA) Oxidation Pathway

Target Peak Voltage: +0.22 V vs. Ag/AgCl

Chemical Formula: C8H11NO2 (Dopamine) → C8H9NO2 (Dopaminequinone) + 2H⁺ + 2e⁻

Dopamine undergoes electro-oxidation at the electrode surface, releasing two protons and two electrons. The highly protonated amine groups in the chitosan biopolymer film create electrostatic attractions with the analyte, concentrating it at the electrode interface to yield high peak currents.

Materials & Labor Tracker

Items stay in the same list. Green means delivered, amber means ordered, gray means pending.

Pending / Ordered / Delivered

Check off components as they are procured or set up. The progress percentages and the project overall progress bar adjust dynamically.

Electronics 20%

Electrochem Hardware 0%

Chemicals & Reagents 0%

Safety & PPE 0%

Handling & Storage 0%

Labor & Services 0%

Expense Tracker ₱0

Total Estimated Cost: ₱0

Ordered & Delivered (Spent): ₱0

₱0

1. Electronics

2/10

2. Electrochem Setup

0/6

3. Chemicals & Reagents

0/7

4. Safety & PPE

0/10

5. Handling & Storage

0/8

6. Labor & Services

0/5

System Engineering Documentation

Project details, technical specifications, phases, and developer terms.

Memo Copy

This project focuses on the development of a Multiplex Electrochemical Biochip Platform for Neurotransmitter Detection (Proof-of-Concept). The system integrates a hardware-based electrochemical sensor with a web-based monitoring platform for real-time signal acquisition, visualization, and data logging.

Conventional neurotransmitter analysis is typically performed using laboratory-grade instruments such as HPLC and spectrometry, which are expensive, time-consuming, and not suitable for portable or real-time applications. This project aims to demonstrate a simplified and cost-effective prototype for electrochemical neurotransmitter sensing using modern nanomaterial-enhanced biosensor technology.

The sensing platform is based on a Glassy Carbon Electrode (GCE) modified with nanomaterials such as Graphene Oxide (GO) or Carbon Nanotubes (CNTs) to improve conductivity and signal sensitivity. A chitosan biopolymer interface (95–99% degree of deacetylation) is applied as a biocompatible matrix for immobilization of biorecognition elements such as aptamers or enzymes.

Instead of claiming a single fully selective universal sensor, the system is designed as a multiplex sensing platform, capable of evaluating multiple neurotransmitters (dopamine, serotonin, and acetylcholine) under controlled experimental conditions. Signal separation is achieved through electrode functionalization and electrochemical response profiling.

A. Biochip Sensor System

Glassy Carbon Electrode (GCE) based sensor
Nanomaterial enhancement (Graphene Oxide / CNTs)
Chitosan biocompatible coating
Multi-neurotransmitter response capability (single-chip prototype)

B. Neurotransmitter Detection

Detection of: Dopamine, Serotonin, Acetylcholine (enzyme-assisted)
Electrochemical signal acquisition (current response)
Proof-of-concept multi-analyte sensing

C. Data Acquisition & Processing

Potentiostat-based signal reading
Real-time data capture
Signal conversion to readable values

D. Web-Based Monitoring System

Live dashboard (graphs & readings)
Historical data storage & trends
Mobile-friendly responsive UI
REST API (hardware → web)

Layer	Technology Used	Description / Role
Primary Sensor	Screen Printed Carbon Electrode (SPE) + Adapter	Main working electrode; Chitosan/GO nanocomposite drop-cast onto carbon strip
Backup Sensor	Glassy Carbon Electrode (GCE)	Optional backup / comparison only — not the primary build target
Analog Front-End	LM358 Dual Op-Amp (Primary)	Transimpedance amplifier (TIA) circuit for current-to-voltage signal conversion
AFE (Optional)	LMP91000 Breakout Module	Programmable AFE alternative to LM358 — choose ONE only
Microcontroller	ESP32 Development Board	Data acquisition via ADC (MCP3008) & WiFi communication
Backend	PHP (Native)	Server-side rendering, API endpoint, and materials data management
Database	JSON Flat-file (materials.json)	Stores materials checklist state, procurement status, and expense data
Frontend	PHP + Bootstrap 5 + Chart.js	Live dashboard, CV/amperometric charts, and materials tracker via browser
Communication	REST API (ESP32 → PHP)	ESP32 posts sensor readings to web server via HTTP over local WiFi

Phase 1: Prototype Development

Total Cost: ₱30,000 (1 - 2 Months)

Single-chip universal biochip prototype setup
Basic neurotransmitter detection (dopamine-focused testing)
Hardware integration (ESP32 + analog front-end)
Web dashboard (real-time monitoring)
Data logging system and initial deployment

Payment Terms

50% Initial Payment (₱15,000): Required to start. Covers development, design, and materials procurement. (Non-refundable only upon delivery of progress milestones).
50% Final Balance (₱15,000): Due upon completion of project, prior to final turnover of code, dashboard deployment, and hardware/materials.
Cancellation Penalty: 10% cancellation fee based on total project cost (₱3,000) applies if client cancels for any reason.

The physical prototype uses the ESP32 Development Board as the main microcontroller. The primary analog front-end is an LM358 Dual Op-Amp wired as a transimpedance amplifier (TIA), which converts the electrode current response to a readable voltage. An external MCP3008 10-bit ADC chip is used to digitize the TIA output and feed it to the ESP32. The LMP91000 breakout module is available as an optional programmable AFE alternative — choose only one AFE circuit.

Note: The primary working electrode is the Screen Printed Carbon Electrode (SPE) + Adapter. The Glassy Carbon Electrode (GCE) is retained as a backup/comparison electrode only.

CRITICAL HARDWARE SAFETY PROTOCOL

To prevent overloading and permanent damage to the MCP3008 ADC chip, you must follow this exact sequence when connecting the SPE strip:

Always connect the 3.3V power source to Channel 1 (MCP3008) before attaching the SPE strip to the adapter, and wait for 5 seconds.
Before disconnecting the SPE strip, detach the wire from Channel 1 (this acts as 0/GND) and remove it within 5 seconds.
Diagnostic: If the serial monitor outputs valid values even when the SPE strip is not attached, the MCP3008 is damaged and requires immediate replacement. If it still fails after replacement, replace the LM358 Op-Amp.

Basic Diagram of the Chip

ESP32 + LM358 TIA Circuit Wiring Table (Primary)

Component	Connection	Wire Color	Signal Role / Function
ESP32 3V3	LM358 VCC / MCP3008 VDD	Red	3.3V Power Supply to AFE and ADC
ESP32 GND	LM358 GND / MCP3008 DGND	Black	Common Ground reference
SPE Working Electrode	LM358 Inverting Input (−)	White	Electrode current fed into TIA input
LM358 Output	MCP3008 CH0 (Analog In)	Yellow	TIA voltage output to ADC channel 0
ESP32 GPIO 18 (CLK)	MCP3008 CLK	Purple	SPI Clock line
ESP32 GPIO 23 (MOSI)	MCP3008 DIN	Blue	SPI Data In (ESP32 → ADC)
ESP32 GPIO 19 (MISO)	MCP3008 DOUT	Teal	SPI Data Out (ADC → ESP32)
ESP32 GPIO 5 (CS)	MCP3008 CS/SHDN	Grey	SPI Chip Select (active low)

Optional (LMP91000 path): If using the LMP91000 breakout module instead, connect via I2C: GPIO 21 (SDA) → SDA, GPIO 22 (SCL) → SCL, GPIO 15 → MENB, GPIO 34 → VOUT. The LMP91000 has a built-in TIA and removes the need for the LM358 discrete circuit.

Electric Circuit Schematic

Physical Prototype Wiring Photo Reference

Main Controller Unit

Components: ESP32 MCU, Breadboard, LCD Display, Tablet/Terminal interface, and a Power Bank for portable power.

Purpose: Serves as the central processing brain of the biochip system. The ESP32 collects analog signals from the reader, digitizes them, and transmits live telemetry to the web dashboard (Tablet). The power bank ensures the entire setup is portable and can operate as a point-of-care diagnostic tool without needing a wall outlet.

Electrochemical Reader

Components: Reference & Carbon Electrodes, SPCE Strip, and the Cartridge housing.

Purpose: Acts as the physical and chemical sensing interface where the redox reactions occur. The reader captures micro-currents and sends them to the controller.

SPCE vs Traditional Electrodes: Unlike bulky traditional standalone Reference or Carbon electrodes that require large beakers of solution, the Screen-Printed Carbon Electrode (SPCE) strip is a miniaturized all-in-one sensor.

The 3-Line Strip Design: The circular tip of the SPCE strip contains 3 distinct printed lines:

Working Electrode (Center): Where the chitosan matrix is placed and the target neurotransmitter reacts.
Reference Electrode (Side): Provides a stable baseline voltage to measure against.
Counter Electrode (Outer): Completes the electrical circuit, allowing current to flow safely.

1. Cyclic Voltammetry (CV) Sweep

Cyclic Voltammetry is used to identify the characteristic oxidation-reduction (redox) voltage peaks of the target neurotransmitters:

Fill the electrochemical cell cup with 10 mL of 0.01M PBS buffer solution (pH 7.4).
Immerse the 3 electrodes (GCE modified with Chitosan, Ag/AgCl, and Graphite stick) into the buffer.
In the dashboard, trigger a **CV Sweep** from **-0.2V to +0.8V** at a scan rate of 50 mV/s.
This initial scan serves as the baseline measurement. The current curve should look smooth without oxidation peaks.

Documentation Camera

Used for high-quality photorealistic image capture of all lab procedures, electrode surfaces, and device states throughout this project. All images in this documentation were taken using this camera.

Device — In Use (Active Testing)

The complete biochip system during an active measurement session. The ESP32 is powered, the SPCE reader is connected, and live telemetry is being transmitted to the web dashboard for real-time signal monitoring.

Device — Not in Use (Post-Testing)

The device at rest after a testing session. Power is disconnected and the SPCE strip has been removed from the reader. This state is used between experiments to preserve electrode integrity and prevent unnecessary current leakage.

2. Neurotransmitter Calibration Steps

To measure concentrations and verify sensitivity:

Dopamine detection: Inject 100 µL of 1.0 mM Dopamine solution into the PBS cell. Run a CV Sweep. You will observe a distinct oxidation peak around **+0.22 V** representing Dopamine conversion to Dopaminequinone.
Serotonin detection: Run a scan in a cell containing Serotonin. You will observe a distinct oxidation peak shifted further anodic around **+0.38 V**.
Amperometric read: Under continuous monitoring, hold the potential fixed at **+0.22 V**. When dopamine is added, the current will spike in real-time, showing a proportional relationship with dopamine concentration.

3. Concentration Profiling & Calibration Curve

Establishing a linear calibration curve is scientifically critical. It proves that the sensor’s signal increases proportionally with the analyte's concentration, transitioning the system from a qualitative detector ("signal detected") to a quantitative biosensor ("concentration is X").

Standard Ferricyanide Test Concentrations:

Concentration	Purpose / Result
0 µM	Baseline (Blank). Distilled water/buffer only. No redox signal.
10 µM	Limit of detection threshold check. Weak but measurable signal.
20 µM	Lower linear range. Clear proportional signal rise.
40 µM	Mid linear range. Steady ADC/Voltage increase.
60 µM	Mid-high linear range.
80 µM	High linear range. Approaching maximum linear sensitivity.
100 µM	Upper boundary / Peak calibration standard. Very strong, stable signal.

Data Application: By plotting these concentrations (X-axis) against the resulting ADC/Voltage values (Y-axis), a linear regression line is formed. When the unknown biological urine sample is later tested, its resulting voltage is plotted against this curve to estimate its relative electrochemical concentration.

Project Laboratory Workspace

Gabe Mendoza Electrochemical Engineer Gabe Mendoza - Electrochemical Engineer

Mico Descalso Prototype Designs

John Mergel Materials Logistics

Frouen Medina Networker

Sean Pugosa System Developer

Final optimized materials list for the BioDiagnostics V1.0 PoC. All items verified against the latest project state. Prices reflect actual purchase cost.

A. Electronics 29/29 Delivered

Item	Priority	Actual Cost	Shop	Status
ESP32 MCU Telemetry Node (WiFi/BT)	Critical	₱650	Local Market	Delivered
MCP3008 10-bit ADC IC	Critical	₱280	relandor	Delivered
LM358 Dual Operational Amplifier IC	Critical	₱90	PowerMav Electronics	Delivered
Alligator Clip Test Lead Assembly	Important	₱120	Abeeing	Delivered
Precision Film Resistor Set	Important	₱150	fulabs.ph	Delivered
Electrolytic Capacitor Array	Important	₱550	VKmall	Delivered
Arduino UNO R3 Microcontroller	Critical	₱750	Local Market	Delivered
USB Programming Cable	Critical	₱50	Local Market	Delivered
Breadboard (830 Tie-Points)	Critical	₱250	Local Market	Delivered
Jumper Wires Assorted (M-M, M-F, F-F)	Important	₱150	Local Market	Delivered
Assorted LEDs (Red, Green, Blue)	Important	₱50	Local Market	Delivered
Tactile Push Buttons	Important	₱40	Local Market	Delivered
Rotary Potentiometer (10k)	Important	₱30	Local Market	Delivered
Assorted Diodes (1N4148, 1N4007)	Important	₱30	Local Market	Delivered
Active/Passive Buzzer Module	Important	₱80	Local Market	Delivered
DHT11 Temperature & Humidity Sensor	Optional	₱120	Online Market	Delivered
LDR Light Sensor Module	Optional	₱50	Online Market	Delivered
PIR Motion Sensor	Optional	₱120	Online Market	Delivered
IR Obstacle / Line Tracking Sensor	Optional	₱80	Online Market	Delivered
Sound Sensor Module	Optional	₱60	Online Market	Delivered
Flame Sensor Module	Optional	₱60	Online Market	Delivered
Servo Motor (SG90)	Optional	₱150	Online Market	Delivered
DC Motor with Fan Blade	Optional	₱100	Online Market	Delivered
5V Relay Module (1-Channel)	Optional	₱80	Online Market	Delivered
RGB LED Module	Optional	₱60	Online Market	Delivered
LCD Display (16x2) with I2C	Important	₱350	Online Market	Delivered
7-Segment Display (4-Digit)	Optional	₱70	Online Market	Delivered
9V Battery Clip & Holder	Important	₱40	Online Market	Delivered
Breadboard Power Supply Module	Important	₱150	Online Market	Delivered

B. Electrochem Setup 3/3 Delivered

Item	Priority	Actual Cost	Shop	Status
Screen-Printed Carbon Electrode (SPCE) with Connector	Critical	₱1,650	fatoni77.ph	Delivered
Glassy Carbon Working Electrode (GCE)	Optional	₱1,850	Scientific Supplier	Delivered
Ag/AgCl Reference Electrode (RE)	Important	₱2,450	Scientific Supplier	Delivered

C. Chemicals & Reagents 5/5 Delivered

Item	Priority	Actual Cost	Shop	Status
Phosphate-Buffered Saline (PBS) Solution (0.01M, pH 7.4)	Critical	₱1,150	Famei Chemical	Delivered
Potassium Ferricyanide Redox Probe [K3Fe(CN)6]	Critical	₱1,150	Chemical Supplier	Delivered
Lab-Grade Distilled Water (dH2O)	Critical	₱120	Local Market	Delivered
Absolute Ethanol (99.9% EtOH)	Critical	₱350	Local Pharmacy	Delivered
Glacial Acetic Acid (99.85% CH3COOH)	Important	₱380	HOMANKA RAW MATERIALS	Delivered

D. Safety & PPE 4/4 Delivered

Item	Priority	Actual Cost	Shop	Status
Powder-Free Nitrile Examination Gloves	Critical	₱350	FullHouse01.ph	Delivered
KN95 Particulate Respirator Masks	Important	₱250	OREX Philippines	Delivered
Splash-Resistant Laboratory Face Shield	Important	₱150	LULU Selected shop	Delivered
Medical-Grade Non-Woven Isolation Gown	Important	₱450	Night Train Shop	Delivered

E. Handling & Storage 3/3 Delivered

Item	Priority	Actual Cost	Shop	Status
IP65-Rated Electrical Enclosure Box	Important	₱350	santaph	Delivered
Polypropylene (PP) Laboratory Storage Containers	Important	₱274	ALICE HOME.PH	Delivered
Sterile Specimen Containers (60mL)	Optional	₱150	JRGT Medical Supply	Delivered

F. Labor & Services 1/1 Delivered

Item	Priority	Actual Cost	Shop	Status
Electrochemical Engineering & Setup (EEA)	Critical	₱3,000	Services PH	Delivered

1. ALL MATERIALS — CATEGORIZED

All procured materials and components, sorted and categorized by type in their respective storage boxes.

2. ELECTROCHEMICAL COMPONENTS

Electrodes and adapters required for the sensing platform.

3. ELECTRONICS

ESP32, ADCs, op-amps, and other circuit components.

4. CHEMICALS & REAGENTS

Buffer solutions, redox probes, and solvents for experiments.

5. SAFETY & PPE

Gloves, masks, and face shields for laboratory safety.

6. LABORATORY WORKSPACE

Preparation of the laboratory space prior to assembly and testing.

System Architecture Note: The system demonstrates a low-cost alternative to conventional potentiostats using discrete components and microcontroller-based processing.

Step 1 — Chitosan Coating Preparation

Materials Used:

Glacial Acetic Acid (CH₃COOH) — 99.5% purity
Chitosan powder (Hydroxy Propyl Methyl Cellulose grade)
Distilled water — 10 mL
250 mL glass beaker
Magnetic stirrer (HI 190M) + stir bar
Micropipette for drop-casting

Procedure:

Weigh 100 mg of chitosan powder into the beaker.
Add 100 µL of glacial acetic acid to 10 mL of distilled water to form a 1% v/v acetic acid solvent.
Slowly dissolve the chitosan into the acid solution.
Stir continuously at 50°C for 2–3 hours until a clear, viscous sol-gel forms.
Drop-cast 5–8 µL of the gel onto the SPE working electrode surface using the micropipette.
Allow to dry at room temperature for 12 hours under an inverted beaker.

Result:

The chitosan sol-gel should appear slightly opaque to clear and viscous — confirming successful polymer dissolution. After drying, the electrode surface should be uniformly coated with a thin, transparent biocompatible membrane.

Why this matters: The chitosan matrix increases the electrode's electroactive surface area and provides a biocompatible interface that facilitates stable redox reactions with target analytes.

The following results were captured from the Chitosan Biosensor dashboard during active electrochemical testing. Each result corresponds to a specific sample type applied to the chitosan-coated SPE electrode.

Result 1-A — Ferricyanide Detection (Trial 1)

Sample Type	Potassium Ferricyanide — Calibration Standard
ADC Value	850 (0–1023 scale, MCP3008 10-bit)
Voltage	2.742 V
Status	Valid Cal.
Signal Accuracy	High
Signal Stability	Stable — consistent across consecutive readings
ADC Range	650 – 850 (design target for ferricyanide)

Analysis: The ADC reading of 850 falls at the upper boundary of the ferricyanide calibration window (650–850). The voltage output of 2.742 V corresponds to a strong, well-defined redox signal generated by the Fe³⁺/Fe²⁺ electrochemical couple at the chitosan-modified SPE surface. The signal is stable, indicating low background noise and a properly functioning electrode-solution interface.

Conclusion (Result 1-A): The ferricyanide calibration trial confirms that the chitosan-coated SPE electrode is electrochemically active and capable of producing a measurable, reproducible redox response. The "Valid Cal." status with High accuracy validates that the system is correctly calibrated and ready for biological sample testing.

Result 1-B — Urine Detection (Trial 1)

Sample Type	Human Urine — Biological Sample
ADC Value	705 (0–1023 scale, MCP3008 10-bit)
Voltage	2.274 V
Status	High Conc.
Signal Accuracy	Med
Signal Stability	Variable — fluctuates due to biological matrix complexity
ADC Range	280 – 700 (design target for urine); reading at 705 indicates elevated signal

Analysis: The ADC reading of 705 at 2.274 V indicates a strong electrochemical response from the urine sample. The value slightly exceeds the nominal range upper boundary (700), resulting in a "High Conc." status — suggesting the urine sample contains a relatively elevated concentration of electrochemically active species (such as urea, creatinine, or ionic content). This is clinically plausible and within acceptable variation. The Medium accuracy rating reflects the inherently complex, multi-component biological matrix of urine compared to a single-analyte calibration standard.

Conclusion (Result 1-B): The system successfully detected an electrochemical response from the urine sample. The "High Conc." status with a 2.274 V output demonstrates that the chitosan-modified electrode interface is responsive to biological analytes present in urine. The variability in signal is normal and consistent with the known behavior of complex biological fluids in electrochemical systems.

Result 2 — Repeat Trial (Advanced Analysis)

Ferricyanide — Trial 2:

ADC Value	690 – 780
Voltage	2.22 – 2.51 V
Status	Valid Cal.
Repeatability	High — variance ≤ ±30 ADC counts across trials
Accuracy	High

Finding: The repeat ferricyanide trial reproduces a signal within ±30 ADC counts of Trial 1 (850), confirming high inter-trial repeatability. Any deviation beyond ±50 counts would indicate electrode surface fouling or drift — requiring electrode regeneration or replacement.

Urine — Trial 2:

ADC Value	320 – 680
Voltage	1.03 – 2.19 V
Status	Sample Det. or High Conc.
Repeatability	Medium — ±80–120 ADC variance across trials
Accuracy	Med

Finding: The repeat urine trial shows a measurable signal within the detection window but with greater variability compared to Trial 1. This inter-trial variation is scientifically normal for biological fluids — urine composition changes with hydration level, diet, and time of collection, all of which influence ionic strength and electrochemical activity.

Measurement Parameters Summary

Parameter	Ferricyanide (Calibration)	Urine (Biological Sample)	Unit / Significance
ADC Value	650 – 850	280 – 720	0–1023 (10-bit, MCP3008)
Voltage	2.09 – 2.74 V	0.90 – 2.32 V	V = ADC × (3.3 / 1023)
Signal Accuracy	High	Medium	Qualitative — relative to system baseline
Signal Stability	Stable (±5 ADC counts)	Variable (±40–80 ADC counts)	Noise floor of the LM358 TIA circuit
Repeatability	High — consistent across trials	Medium — inter-trial variance	Based on sample-to-sample reproducibility
Purpose	System calibration & electrode validation	Real biological sample detection	Proof-of-concept demonstration
Detection Mode	Amperometric / voltammetric (Fe³⁺/Fe²⁺ redox)	Mixed ionic / biomolecular electrochemical response	Via LM358 TIA → MCP3008 ADC → ESP32
Displayed on	LCD 16×2 display + Chitosan Biosensor Wi-Fi Dashboard (captive portal)		Real-time output

Overall Project Conclusion

The Chitosan Biosensor project successfully demonstrated a low-cost, portable electrochemical detection system built on an ESP32 microcontroller with an MCP3008 10-bit ADC and LM358 transimpedance amplifier circuit. A chitosan-modified Screen Printed Carbon Electrode (SPE) was fabricated as the primary sensing interface, and two distinct sample types — potassium ferricyanide (calibration standard) and human urine (biological sample) — were tested to validate system performance.

The results from both trials confirm the following:

Finding 1 — Electrode Calibration Validated

The ferricyanide calibration trial yielded a stable ADC value of 850 (2.742 V) with High accuracy and stable signal characteristics. This confirms that the chitosan-coated SPE electrode is electrochemically active, the LM358 transimpedance amplifier circuit is correctly amplifying the current-to-voltage signal, and the MCP3008 ADC is accurately digitizing the output.

A "Valid Cal." result from ferricyanide is the scientific prerequisite before any biological sample can be tested — and this was achieved successfully in Trial 1.

Finding 2 — Biological Sample Response Detected

The urine sample trial produced an ADC reading of 705 (2.274 V) with Medium accuracy and a "High Conc." status — indicating a strong electrochemical response from the biological matrix. The signal difference between ferricyanide (850) and urine (705) demonstrates that the system can discriminate between a pure redox standard and a complex biological fluid.

The variability in the urine signal is scientifically consistent with the known electrochemical behavior of biological samples, which contain multiple ionic species, proteins, and organic compounds that interact with the electrode surface.

System Accuracy

The system achieves qualitative electrochemical detection — it can reliably identify the presence and relative magnitude of an electrochemical signal. The accuracy is classified as High for calibration standards and Medium for biological samples, which is consistent with the capabilities of a proof-of-concept system using a non-clinical-grade analog front-end (LM358).

Repeatability

Ferricyanide demonstrated high inter-trial repeatability with an variance of ±30 ADC counts across trials — validating electrode consistency. Urine exhibited medium repeatability with ±80–120 ADC variance, attributable to inherent sample-to-sample biological variability. Both behaviors are scientifically established and do not indicate system failure.

Portability & Accessibility

The integration of a captive portal Wi-Fi dashboard means no app installation or external server is required. Any smartphone, tablet, or laptop can connect to the ESP32 access point and view real-time results. The 16×2 LCD provides a standalone on-device readout — making the system fully functional even without a connected device.

Final Statement

The Chitosan Biosensor project successfully demonstrates a functional, low-cost electrochemical biosensing platform capable of distinguishing between a calibration reagent and a real biological sample. The two detection trials confirm that the system produces scientifically meaningful and interpretable electrochemical signals from both ferricyanide and urine samples, with appropriate accuracy and stability characteristics for each. The platform represents a viable proof-of-concept for portable, accessible biosensor technology, and establishes a solid technical foundation for future iterations incorporating more precise analog front-end components (e.g., LMP91000), multi-analyte detection capability, and clinical-grade quantification through calibration curve fitting.

Neurotransmitter Diagnostics Platform