REAL-SAMPLE HURDLES

What changes outside the buffer

🩸

Complex matrix

Blood, saliva, or food add proteins, salts, and particles

🧂

High salt

Physiological salt shortens the Debye length

🧴

Fouling

Non-specific binding builds up over minutes

Every earlier limit gets harder in a real sample.

SAMPLE PREP

Making the sample easier

Filter Removes cells and particles

Dilute Lowers salt and background proteins together

Desalt Swaps the buffer for a low-salt one before measurement

Concentrate Raises a scarce target's concentration before it reaches the sensor

Prep steps trade convenience for a cleaner signal.

RELIABILITY

Sensors must agree with each other

device-to-device variation

Two nominally identical BioFETs rarely respond identically. Threshold voltages, receptor densities, and noise all vary. Reliable results need calibration per device or per batch, replicates, and reference sensors on the same chip.

Calibrate, replicate, and always run a reference.

POINT OF CARE

What users need

💰

Affordable

A low cost per test

⚡

Rapid and robust

A fast answer that tolerates rough handling

🎛️

User-friendly

Little or no training required

📦

Deliverable

Usable where the patient is, without lab infrastructure

These are four of the seven ASSURED criteria for point-of-care tests.

VALIDATION

A checklist before claiming a result

Calibration curve Known concentrations, fitted, with error bars

Selectivity Blanks and wrong targets give no response

Reproducibility Several devices and batches agree

Real sample The same response in a spiked real matrix, not just in buffer

A result is only as strong as its weakest control.

UNIT 25 STUDY COMPLETE

🔬

Ready for the Fab Challenge?

You've covered what it takes to turn a working prototype into a dependable measurement.