The six spines, and why you need one

Here is the structural fact about biomedical engineering that nobody tells freshmen. Medical device companies mostly hire mechanical, electrical, and software engineers, and BME graduates compete against them for the same jobs. A BME degree, on its own, is a little of everything. The students who do well pick a spine, one deep engineering skill that an employer will pay for on its own, and use the biology, the clinical context, and the regulatory fluency as wings that the pure engineers do not have.

In neuroengineering the spines are sharper than in the rest of BME, because the field is so specialized. Pick one by the end of sophomore year. Not before, because you have not tried them yet. Not after, because junior summer is when it gets tested.

The six

Analog and mixed-signal hardware. Microvolt-level amplifiers, low-noise design, electrodeElectrode The conductor that turns ion currents in tissue into electron currents in a wire; its chemistry and contact quality set the noise you live with. Related: Silver/silver-chloride (Ag/AgCl)Silver/silver-chloride (Ag/AgCl) The standard electrode material for biopotentials, because its chemistry produces a stable, low-noise, low-drift interface with salty gel. , Electrode impedanceElectrode impedance How hard it is to push current through the skin-electrode contact, typically 5 to 50 kilohms with gel and megohms dry, higher at low frequencies. , Half-cell potentialHalf-cell potential The DC voltage that appears wherever a metal meets an electrolyte; two electrodes with different half-cell potentials produce an offset that can swamp the signal. . Glossary entry interfaces, stimulation circuits, the firmwareFirmware The program running on the microcontroller, which configures the chip, reads samples on time, and ships them to the computer. Related: SPISPI A simple four-wire bus for talking to chips like the ADS1299 from a microcontroller. . Glossary entry that runs them. The scarcest skill in the field. Every BCIBrain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. Related: DecoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. , Closed loopClosed loop A system in which the output feeds back to influence the input, such as a user adjusting their brain activity while watching the cursor it controls. . Glossary entry company is short of people who can design a front end, and the ones who can are paid accordingly. Phase 2 is a long audition for this spine.

Decoding, signal processing, and machine learning. The algorithms that turn neural data into intent. The most crowded spine and still in huge demand. It is far stronger when you also have real hardware experience, because you will know where the noise comes from instead of treating the data as given. Phase 3 is the audition.

Computational neuroscience. Models of neurons and populations, the theory that says what a decoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. Related: ClassifierClassifier An algorithm that assigns each trial a label, such as left hand or right hand, after being trained on labelled examples. , Kalman filterKalman filter An estimator that blends a prediction from a motion model with a noisy measurement, weighting each by how much it trusts it; the decoder behind most intracortical cursor control. , Brain-computer interface (BCI)Brain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. . Glossary entry should be. Academic-leaning; increasingly hired by BCIBrain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. Related: DecoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. , Closed loopClosed loop A system in which the output feeds back to influence the input, such as a user adjusting their brain activity while watching the cursor it controls. . Glossary entry companies for decoderDecoder The algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. Related: ClassifierClassifier An algorithm that assigns each trial a label, such as left hand or right hand, after being trained on labelled examples. , Kalman filterKalman filter An estimator that blends a prediction from a motion model with a noisy measurement, weighting each by how much it trusts it; the decoder behind most intracortical cursor control. , Brain-computer interface (BCI)Brain-computer interface (BCI) A system that turns measured brain activity into control of something outside the body, from a cursor to a wheelchair to a speech synthesizer. . Glossary entry design. Phase 4.

Electrophysiology and the wet lab. Patch clamp, in-vivo recording, optogenetics, cell culture on electrodesElectrode The conductor that turns ion currents in tissue into electron currents in a wire; its chemistry and contact quality set the noise you live with. Related: Silver/silver-chloride (Ag/AgCl)Silver/silver-chloride (Ag/AgCl) The standard electrode material for biopotentials, because its chemistry produces a stable, low-noise, low-drift interface with salty gel. , Electrode impedanceElectrode impedance How hard it is to push current through the skin-electrode contact, typically 5 to 50 kilohms with gel and megohms dry, higher at low frequencies. , Half-cell potentialHalf-cell potential The DC voltage that appears wherever a metal meets an electrolyte; two electrodes with different half-cell potentials produce an offset that can swamp the signal. . Glossary entry. Needs a lab from the first semester and usually leads to a PhD. The research ladder is the whole path.

Materials and microfabrication. ElectrodeElectrode The conductor that turns ion currents in tissue into electron currents in a wire; its chemistry and contact quality set the noise you live with. Related: Silver/silver-chloride (Ag/AgCl)Silver/silver-chloride (Ag/AgCl) The standard electrode material for biopotentials, because its chemistry produces a stable, low-noise, low-drift interface with salty gel. , Electrode impedanceElectrode impedance How hard it is to push current through the skin-electrode contact, typically 5 to 50 kilohms with gel and megohms dry, higher at low frequencies. , Half-cell potentialHalf-cell potential The DC voltage that appears wherever a metal meets an electrolyte; two electrodes with different half-cell potentials produce an offset that can swamp the signal. . Glossary entry materials, flexible arrays, coatings, hermetic packagingHermetic packaging Sealing implanted electronics against body fluid for decades, one of the hardest unsolved engineering problems in the field. Glossary entry. Underpopulated, deeply valuable, and it needs a cleanroom, which this campus has. Phase 6.

Clinical, regulatory, and human factorsHuman factors Designing so the device fits how people actually behave, especially under stress and fatigue, so that errors are hard to make. Related: IEC 62366IEC 62366 The standard for usability engineering of medical devices, aimed at preventing use errors. , Use errorUse error A mistake made while using a device that the design invited, as opposed to random user carelessness. . Glossary entry. Needs findingBiodesign Stanford's process for medical technology innovation that starts from an observed clinical need rather than a technology looking for a use. Related: Needs findingNeeds finding Observing clinical work to catch the moments that are slow, awkward, or unsafe, before proposing any solution., Need statementNeed statement One sentence, "a way to [do X] for [whom] that [outcome]," with no solution in it.. Glossary entry, design controlsDesign controls FDA's required process for developing a medical device: user needs, requirements, design, verification, validation, and the records of all of it. Related: Design history file (DHF)Design history file (DHF) The complete record of how a device was designed, showing every requirement traced to a test; writing a mock one teaches more than any lecture., RequirementsRequirements Testable statements of what the device must do, such as "input-referred noise below 1 microvolt RMS from 0.5 to 40 Hz.", VerificationVerification Testing that the device meets its requirements; did you build what you specified., ValidationValidation Testing that the device meets the user's need in real use; did you specify the right thing.. Glossary entry, risk analysisFMEA Failure mode and effects analysis: a table of every way the device could fail, how bad and how likely each is, and what you did about it. Related: ISO 14971ISO 14971 The international standard for medical device risk management that every company follows.. Glossary entry, FDA pathwaysFDA device classes Class I is low risk (a tongue depressor), Class II moderate (most EEG amplifiers), Class III highest (implanted BCIs), each with heavier review. Related: 510(k)510(k) The FDA pathway that clears a device by showing it is substantially equivalent to one already on the market, its predicate., Premarket approval (PMA)Premarket approval (PMA) The strictest FDA pathway, requiring clinical evidence of safety and effectiveness; the route for Class III implants., De NovoDe Novo The FDA pathway for a low-to-moderate-risk device that has no predicate.. Glossary entry, usability. Rare, valuable, and almost never chosen by undergraduates, which is exactly why it works. Phase 5. This one pairs with any of the others as a second spine.

How to actually choose

Not by which sounds most impressive. By which one you find yourself doing when nobody assigned it. The student who keeps redrawing the amplifier schematic at midnight has found the hardware spine. The one who cannot stop trying to beat the published accuracy has found decoding. The one who reads FDA recallRecall A correction or removal of a marketed device; FDA's public database of them is a catalogue of how designs fail people. Glossary entry reports for fun has found regulatory. This site is arranged so that you try each spine’s audition project before you decide.