biomedical Molecular Bio-Optics

What is fNIRS?

Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive optical neuro-imaging technology that uses safe near-infrared light to measure real-time blood oxygenation and cognitive energy inside the prefrontal cortex.

The Optical Window

Seeing Through Human Tissue

Just like pressing a bright flashlight against your hand makes your skin glow, near-infrared light in the 650nm to 900nm spectrum safely passes through skin, tissue, and frontal skull bone.

Photons travel 1.5 to 2.0 cm deep into the prefrontal cortex—the brain's executive control center for focus, decision-making, and emotional self-regulation.

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Optical Penetration Depth
1.5cm – 2.0cm
Direct Prefrontal Cortex Sampling
Biochemical Foundation

The Science of Hemoglobin Color Shift

Why blood changes color when it binds to oxygen—and how optics measure it.

Deoxyhemoglobin (HHb) Dark Maroon / Purple

When hemoglobin has delivered its oxygen to working brain cells, the central iron ion (Fe2+) sits slightly outside the plane of the heme ring in a high-spin state (S = 2).

Optical Absorption: Strongly absorbs 730 nm near-infrared light while allowing 850 nm light to pass through.
Oxyhemoglobin (O₂Hb) Bright Scarlet Red

When oxygen binds to the iron ion, it pulls the Fe2+ atom directly into the plane of the heme ring (transitioning to a low-spin state S = 0). This electronic shift changes how d-electrons absorb light.

Optical Absorption: Strongly absorbs 850 nm near-infrared light while reflecting bright red photons.
Spectrophotometric Formula

The Modified Beer-Lambert Law (MBLL)

By measuring light attenuation (A) at 730nm and 850nm, NoBrainer mathematically calculates exact concentration changes of oxygenated (Δ[O2Hb]) and deoxygenated (Δ[HHb]) blood in real time:

A(λ) = ε(λ) · c · d · DPF + G

Where ε is the molar extinction coefficient, d is detector distance (28mm), and DPF is the differential pathlength factor.

System Integration

How fNIRS Works in NoBrainer

Dual-Modality EEG + fNIRS engineered into a sleek 15mm headband.

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Dual-Channel Prefrontal Asymmetry

NoBrainer places two independent fNIRS channels across the forehead: Left (FP1) and Right (FP2).

  • Left Forehead (FP1): Measures logical task focus & flow state.
  • Right Forehead (FP2): Measures stress load & emotional strain.
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100% Ambient Light Immunity (TDM)

The Texas Instruments AFE4404 chip pulses LEDs in microsecond slots at 1 kHz (Time-Division Multiplexing).

It measures ambient room light between pulses and subtracts it instantly—delivering clinical accuracy indoors under office lights or outdoors in direct sunlight.

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15-Minute Executive Brain Fog Warning

By tracking continuous prefrontal oxygen saturation (rSO2), NoBrainer warns executives 15 minutes before cognitive exhaustion hits, ensuring peak performance without burnout.

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Automatic iPad Screen Time Lock

Monitors child prefrontal blood oxygen depletion during iPad screen time. When brain fatigue sets in, the app sends an automated signal to lock the tablet screen.