Research
We are creatures of sensation, with hundreds of millions of photoreceptors, millions more for touch, smell, and taste. Yet, in each ear, only 16000 sensory hair cells allow us to hear from a whisper to a thunderclap, operating at frequencies that make vision seem slow. How do hair cells achieve this? They must be doing something different—and different by orders of magnitude.
🎻 From violins to the ear
I began my career studying physics at the University of Turin, Italy, where, unlike my peers drawn to particle physics, I chose to explore the physics of the violin. Though a mediocre violinist, I had learned violin-making as a hobby since high school under the guidance of master luthier Gianfranco Dindo, who had retired in my hometown. My persistence in persuading him to take me on as a student led to the founding of a non-profit violin-making school, the Associazione Arte Liutaria, which still exists today. Read about it here.
One of the challenges I faced in violin-making was constructing the violin bridge, a wooden structure that transfers string vibrations to the violin body. In physics terms, the bridge matches the impedance between the strings and the body, effectively transferring vibrations. Traditionally, violin makers craft multiple bridges for each instrument, selecting the best one through trial and error, often with the feedback of a violinist.
By measuring the mechanical impedance of the strings, the violin body, and the bridge during its construction, I developed a new method to guide the creation of the optimal violin bridge. This resulted in my Bachelor thesis: The Physics of the Violin: a method for the guided construction of a violin bridge, Gianoli F., supervisor Prof. Roberto Tateo in 2012 and an accessible science book Violin-making from Art to Science, Dindo G., Gianoli F., Ribella D., Saggistica, 2012.
I became interested in the physics of hearing because of the similarity between the violin bridge and the middle-ear ossicles—both optimizing power transfer, one to the violin body, the other from the eardrum to the cochlea. Intriguingly, and likely a coincidence, the violin bridge even shares the shape of the stapes.
Sensory mechanotransduction
At the very start of our sense of hearing are the hair cells. They take their name from the hair bundle, a crown of tiny, flexible projections (stereocilia) that pivot when sound vibrates the inner ear. That minute bend tightens protein linkages called tip links and opens mechanosensitive ion channels, letting electrical current flow. In an instant, a mechanical ripple becomes an electrical signal the brain can interpret. This conversion isn’t passive: the ear supplies energy of its own, sharpening both sensitivity and speed so that roughly sixteen thousand hair cells per ear can span intensities from a whisper to a thunderclap and frequencies into the tens of kilohertz. For perspective, hearing follows vibrations from ~20 to 20,000 times per second, whereas vision fuses flicker into steady light once flashes exceed ~60 per second. In other words, hearing tracks events hundreds of times faster than sight.
That speed is possible because force opens the channels directly. A nanometer-scale deflection of the hair bundle raises tension in the tip links, which tug on the channels at stereociliary tips and flip them open in well under a millisecond. There is no slow chemical cascade required. Rapid adaptation systems then reset the tension so the bundle is immediately ready for the next vibration. Direct mechanical gating plus swift adaptation explains how hair cells keep up with the fastest audible stimuli.
Zoom in and a cooperative molecular machine emerges. Strong evidence points to TMC1/2 as core components of the transduction channel, with partners such as TMIE, LHFPL5, and CIB proteins stabilizing the complex and coupling it to the tip link. Mutations in these parts frequently cause hereditary deafness. Yet key details remain to be clarified. Experiments show that an elastic element converts bundle motion into channel opening; we call it the gating spring. Is the tip link itself the spring, or do additional proteins and the membrane share that load? Mapping this force path at molecular resolution is an active frontier. Why this matters is practical as well as profound. Over a billion people live with some degree of hearing loss, often tied to damage or mutations in the very molecules that make mechanotransduction possible. Pinpointing each component’s role is improving genetic diagnoses, guiding experimental gene therapies (for example, in TMC1-related deafness), and informing strategies to protect the ear from noise and drug toxicity.
Equally important, the cell’s membrane is not a passive wrapper around the channel. It’s a thin, flexible skin whose tension and makeup can subtly help or hinder the channel’s gate and how quickly the system “resets” after each sound. When the membrane tightens or its mix of fats shifts, channels may open a bit more easily or close a bit faster—fine-tuning sensitivity and adaptation so the ear doesn’t get overwhelmed by steady noise yet stays ready for the next whisper. This matters because the membrane’s properties change with age, health, noise exposure, and some medicines. If we learn how this soft layer steers the gate, we may be able to protect hearing under stress or nudge damaged ears back toward normal function.
Cochlear mechanics
Coming soon.
🎤 Conferences and Workshops
Throughout my career, I have been honoured with several travel grants to attend international conferences, where I presented my research in various formats including posters and invited talks:
- Association for Research in Otolaryngology (ARO) – February 2025, Orlando, Florida, USA
- Mechanics of Hearing Workshop 2024 – Ann Arbor, Michigan, USA
- Naito Conference 2024 – Sapporo, Japan
- Association for Research in Otolaryngology (ARO) – 2024, Anaheim, California, USA
- Biophysical Society Meeting 2023 – Dublin, Ireland
- Mechanics of Hearing Workshop 2022 – Copenhagen, Denmark
- Association for Research in Otolaryngology (ARO) – 2022, San Jose, California, USA
- Institut de l’Audition Opening Meeting 2020 – Paris, France
- Biophysical Society Meeting 2020 – San Diego, California, USA
- The Royal Society 2019 – London, UK