The Laser Physicist Unlocking Navigation Technology

Lia Li is an award-winning founder of start-up Zero Point Motion, bringing optomechanical sensors to consumers. She talks to Laura Hiscott about the switch from academia to business, and using LIGO-style technology to help us navigate where global navigation satellite systems can’t

Lia Li

(Courtesy: Joe Burgess)

When exploring an unfamiliar place, many of us default to a modern method of navigation: watching a blue dot move around a map, on a screen, and course-correcting to keep it on the right track. We owe this convenient technology to global navigation satellite systems (GNSSs)—such as the Global Positioning System (GPS), Galileo and BeiDou—which regularly broadcast radio waves from their orbits around the Earth. Our devices use the time difference between receiving signals from different satellites to calculate our location on the Earth’s surface to an impressive degree of accuracy.

But GNSSs have their pitfalls; as soon as you venture underground or into, say, a forest or a building (like an airport or train station), your blue dot might start jumping around erratically, leaving you lost. This is because obstructions between you and the satellites can weaken the signals or reflect them so that they bounce around before reaching your device, causing a time delay that leads to errors in the calculations.

A form of location tracking that we could count on while hiking through the woods or traversing a labyrinthine subway station would be a welcome improvement. This is a reality that physicist Lia Li is seeking to create with her start-up Zero Point Motion (, a company developing sensors that track your position independently of a GNSS.

As it happens, our devices do already have so-called “inertial sensors” designed to do exactly this. The problem is they are not very reliable. These chips consist of tiny silicon structures that move slightly in response to acceleration or rotation of the device, thereby altering the capacitance of the component, which in turn changes its electrical signal. The device is programmed to register that change as an acceleration and double integrate it over time to calculate the displacement of the object from its starting point. But these capacitive signals are easily overwhelmed by electrical noise in the device’s circuitry, Li explains. “This is why, if you’re on your phone or in your car and you switch off the GPS, your pin might hop to a random nearby street and you think ‘I’m definitely not there.’”


Follow the dot When underground, in a forest or a building, global navigation satellite systems struggle as the radio waves bounce off your surroundings. (Courtesy: iStock/svetikd)

Beyond mere convenience, Li points out that better GNSS-independent motion tracking is essential for safety in some applications. Autonomous vehicles, for example, will need extremely reliable and live information about their trajectory relative to their surroundings to ensure that they don’t swerve or change speed in a dangerous way. 

As it happens, Li’s scientific background has set her up well to tackle this problem. She was immersed in an academic environment as a child, with both her parents doing Ph.D.s in mechanical engineering at the University of Bristol, UK. The family lived in student dorms for several years and Li often spent time in the university labs, surrounded by huge pieces of equipment testing the strength of metals. She knew from a young age that she liked the freedom that research allows for, as well as being at the cutting edge of a field and having access to state-of-the-art equipment.

Best of Both Worlds

Li went on to study physics at Imperial College London, but it wasn’t until her senior-year project, which involved building a laser from scratch, that she discovered her love of photonics. She enjoyed the work so much that she did a summer internship with the same research group following her final exams and even considered doing a Ph.D. with them. However, Li already had a job lined up at BAE Systems’ photonics department for after graduation. Although she questioned whether this was the right decision for her, she decided to give industry a try after her father pointed out that she’d only known the education system so far. It proved a very valuable experience. “I learned so much from these fantastic scientists who had worked there for 20-plus years,” she says. “It was a different way of gaining knowledge, and I loved the focus on application and needing something tangible to come out of it.”

After a while, BAE Systems was keen to promote Li to project management, but she wanted to stay in the labs doing hands-on work. So in 2012, after a year and a half in the job, she left to do a Ph.D. in quantum physics at University College London (UCL).

That time in industry has continued to inform her work, however, as it gave her a glimpse into the huge potential of inertial sensors. Many people have the impression that these kinds of sensors are not worth spending time on, largely because of their low quality in everyday devices like phones. But during her spell in the defense industry, Li became aware of $300,000 inertial sensors that can track your position accurately for hours without a GNSS. “I know there’s technology out there that gives you exactly what you require to enhance safety in cars or to do indoor navigation for long periods,” she says, “so I felt that there was a definitive need to bring some of that high performance to consumers.”

The key to developing this technology is to change the sensing mechanism from the noisy capacitive sensor currently found in our devices to one that uses cavity optomechanics—the interactions between light and the motion of physical objects. Instead of placing the tiny movable silicon structure so that it influences the capacitance, you put it next to a chip-scale optical cavity, which traps laser light by reflecting it internally. Li uses ones with curved boundaries, like rings, spheres and donut shapes.

Lia Li prototype

Sensor revolution Lia Li’s prototype optomechanical sensor from her UCL research, which uses the same mechanism as LIGO but on a much smaller scale. The company is now developing chip-scale versions that could revolutionize inertial sensor chips in phones. (Courtesy: Lia Li)

Depending on the cavity’s exact parameters, it will have an optical resonance at certain frequencies of light where the reflections combine to form standing waves. But if the sensor is accelerated, the silicon structure will move closer or further away from the cavity in response, temporarily changing the effective refractive index experienced by the cavity, and therefore causing a slight shift in its resonant frequencies. This shift can be used to calculate the acceleration, which can be double integrated over time, as with the capacitive sensors, to find the displacement.

Unlike capacitive sensors, this mechanism is not affected much by noise. “Because there’s a resonance condition, you get this extra boost in signal-to-noise that makes it super sensitive,” Li explains. “So a tiny amount of motion results in a huge amount of measurable shifting.”

Indeed, a similar mechanism is at the heart of the Laser Interferometer Gravitational-Wave Observatory (LIGO), which has detected some of the subtlest vibrations scientists have ever looked for. By measuring the shift in resonant frequencies between mirrors placed far apart, LIGO is able to sense gravitational waves as they squeeze and stretch space–time.

LIGO’s historic success in detecting gravitational waves—which won three of its scientists the 2017 Nobel Prize for Physics—strengthened Li’s faith in the revolutionary power of the technology. “LIGO is a giant version of a cavity optomechanics experiment,” she says. “So to me it was really obvious that if it can transform fundamental physics, it would absolutely do the same for normal sensing devices. Lots of academic groups have demonstrated similar effects, but no one had done it at a commercial product level yet. With the power of photonic integrated circuits, which can mass produce these cavities the same way computer chips are made, it feels like the market is ready.”

Finding Your Feet

Li made her first foray into entrepreneurship straight after finishing her Ph.D. in 2016, when she participated in the Nature/Entrepreneur First Innovation Forum. This was a three-month Shark Tank-type program where participants were trained in assessing business concepts and pitched their own ideas to a panel of academics and industry experts. She enjoyed being around other entrepreneurs as well as veteran businesspeople who were looking to mentor new founders. “I thought ‘Wow, I really want to be a CEO,’” she says.

Another reason Li wanted to start a company was that she found it difficult to support herself in academia, let alone give others opportunities—a cycle of trying to stay afloat but not having the resources to seek help or grow a team. Her motivation was often dampened by experiencing or witnessing gender and racial inequity in science, but her desire to help younger scientists remained alive due to the support she’s received from strong women in the field.

While in academia, Li was involved with the UCL Women in Physics group, which she led for three years, as well as Tigers in STEMM, a UK-wide grassroots group promoting diversity and inclusion. As part of her work in this area, Li wrote a paper on race equity in science funding with Erinma Ochu of Manchester Metropolitan University, and Hope Bretscher and Rachel Oliver from the University of Cambridge for the journal of the Parliamentary and Scientific Committee of the British Houses of Parliament ( By analyzing science funding data, the team showed that, on average, ethnic minority scientists write grants for six months longer than white scientists before grant success but then receive nearly £200,000 ($235,000) less.

This can have a particularly negative impact in the already harsh academic environment of short-term contracts and job insecurity. Li experienced the difficult system of constant grant applications when she returned to academia as a postdoctoral researcher at UCL, after finishing the Nature/Entrepreneur First Innovation Forum. She continued to think about commercializing her research, but encountered various dead ends, often because she would burn out trying to do that and her academic work simultaneously.

Lia Li certificate

Success in lockdown While away from her academic position in 2020 because of the UK’s COVID lockdown, Lia Li used the time to write the business plan for Zero Point Motion. (Courtesy: Lia Li)

Then, in 2019, Li won an innovation grant of £50,000 ($59,000) from the UCL Quantum Science and Technology Institute. The award had no strings attached; the only condition was that she had to officially set up a business and have a business bank account. Li found that going through that formal process felt surprisingly significant, and made the idea of Zero Point Motion seem much more real.

When COVID hit the following year, she was put on a government-funded absence rom her academic work, but this gave her the time and freedom she needed to focus on the company. “I wrote the entire business plan during that furlough period,” she recalls. “I actually ended up inventing the two foundation patents for the company during that time.”

The final piece of the puzzle fell into place when Gordon Aspin, a scientist and engineer who has developed four companies relating to smartphone chips in the past, joined as executive chairman. “As a physicist, I have no connection to mass-producing smartphone chips, which he has,” says Li, “so he’s the exact kind of mentor that I needed.”

In 2021, Li won the UK Institute of Physics (IOP) Clifford Paterson Medal and Prize, which recognizes “exceptional early-career contributions to the application of physics in an industrial or commercial context.” The IOP cited her pioneering research into commercializing optomechanical sensors, as well as her drive to build a better and more supportive research community. In February 2022, she was able to become full-time chief executive of Zero Point Motion.

Silicon Vision

Although Li is looking at enhanced navigation as the primary application of her optomechanical sensors, they have potential for many other uses too. The technology is sensitive enough to pick up someone’s heartbeat from underneath a mattress, so it could be used for health monitoring. Since structures like bridges also vibrate in specific ways that change with wear and tear, the sensors could be used to monitor these changes over time and implement predictive maintenance too.

After raising a £2.58m ($3.03m) seed round from Foresight Williams Technology, Verve Ventures and u-blox, the next steps for Li are to expand the team and work through early prototype iterations. The aim is to have prototypes that can be tested and demonstrated next year, and to receive feedback from potential end users. “I think I’m slowly learning to be more ambitious,” she says. “It’s hard when you come from a really competitive research area where you feel that you don’t want to dream too big. But in business, you can’t afford to do that because so much of it is how you inspire employees and bring people to the company; hiring is what we’re focused on right now. So if any readers want to work on this technology and own part of the company, come to Bristol and join us!”

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