In Memory of My Mentor, Mark Chignell

The weather in Hong Kong has finally turned cool, but the wind blows fierce tonight, carrying with it a trace of sorrow.

On the morning of November 22nd, in the hazy early light, a message from Michael McGuffin appeared in my WeChat. Michael is a dear friend of mine — a professor at a university in Montreal, Canada. We have kept in touch for over twenty years now. But distance and the busyness of life have kept our exchanges infrequent, the kind where you catch up a few times a year, no more.

The message was short, but every word landed like a stone: "Mark Chignell passed away yesterday. Sachi posted the news on Facebook."

What had happened? Mark was born in 1956. He was only 69…

Just over a year ago, we were together at the ACM CHI conference in Hawaii. Mark arrived with his signature warm smile and his newest PhD student, and sat with me and my students. The atmosphere was so easy, so full of warmth. He talked with everyone — attentive, unhurried, the way he always was. He looked so healthy then, his smile as gentle as ever. I always assumed there would be many more gatherings like that one, that every conference would bring another happy reunion, that time would never really take anything away…

A little over two years ago, in Hamburg, Germany — inside a cozy hotel along the ancient cobblestone streets of that old European city — Mark, I, and a student who had just begun at an Ivy League school in the United States, full of questions and hopes about the future, talked for several hours. The student had many questions. Mark answered every single one, patiently and without reservation. The way he looked as he spoke, and the quiet image of us all rising together afterward to walk home through the evening streets — that image remains vivid in my mind…

Going further back to 2017: I traveled to Toronto with a company delegation, and we paid Mark a visit. He was in the middle of launching a new startup. The lab was full of new faces, buzzing with fresh energy — just the way it had felt when I was a PhD student there, only with a new cast of people…

And back to 2009, the year I finished my doctorate. I had received an interview invitation from Singapore Management University. As it happened, Mark had a long connection with Singapore — he had worked there for several years. He warmly introduced me to his friends there and encouraged me to visit them, among them Professor Chua at NUS. At the time, NUS was quietly looking for a Human-Computer Interaction scholar to join their faculty, though nothing had been announced publicly. I remember clearly: when I wrote to Professor Chua asking if I might come by for a visit, his reply was — "Would you be interested in coming for an interview?" "Oh, my god. Of course yes!" And just like that, through a stroke of serendipity, I joined NUS and stepped into what I can only describe as a dream chapter of my life. Without Mark, none of it would have happened…

Then there were the years in the middle and late 2000s — the years of the PhD itself. Those years were full of hardship and doubt: the frustration of late nights that went nowhere, the dejection of failed experiments, the despair of rejected papers. But no matter what storms I faced outside, Mark's lab was always a warm harbor, a place we could return to whenever we needed to recover. It was an office I called home for five years — a modest room, just big enough for three rows of desks. Standing at the doorway and looking in, the deep-red desk tucked against the cabinets at the far end was where I worked and lived for those five years. The spot nearest the door belonged to my good friend Alvin — a young man who radiated energy and optimism in everything he did. Turning left from the entrance was a common room, filled with memories of every MIE Lab party. That long rectangular table, big enough for a dozen people, would be covered at those times with food from every corner of the world — and the dishes that always outnumbered everything else were the desserts. At the far end of the common room, just past the table, was Mark's office. Looking in from the doorway, you would always find him there, quietly working through his papers. And we could always go to him, any time — that door, in my memory, was almost always open, always welcoming us in. The Bahen Centre, home to the University of Toronto's Department of Computer Science, is a building of industrial lines — clean, direct, and not without a certain seriousness. But the MIE Lab on the eighth floor felt nothing like the rest of the building. Every time you walked through its door, you were met with something warm and familiar. That was the most precious thing Mark had given that place…

Back to the winter of 2004. I had been in the doctoral program at U of T for over a year, but I still had no real home within it. The supervisor who had recruited me had left the university shortly after my arrival, leaving me adrift for more than a year — without a supervisor, like a small boat lost on an open sea. I was searching desperately for a lab to belong to, but the other faculty in the department all had full rosters. It was at this near-desperate moment that I found Mark — a professor in Industrial Engineering, cross-appointed to Computer Science. And he accepted me, quickly and without hesitation…

...

Life is a journey. Along the way, you meet many people. Most come and go in a flash, but a rare few walk alongside you for years — even decades. They are sometimes far away, sometimes close at hand. Most of the time, your paths run parallel, each of you moving forward into your own unknown horizon. But every so often, those lines cross, and in that crossing, they leave warmth and kindness woven into the fabric of your days.

It is with great sadness that on November 21st, 2025, that warm, kind, and wise parallel line — the one that had woven itself through so many of our lives for so many years — came to rest.

But he left what he had nurtured in all of us. Among just our cohort alone: I am at the National University of Singapore and the City University of Hong Kong; Alvin is at the University of Illinois Chicago; Danielle Lotridge is at the University of Auckland — and so many others are scattered across the world, each of us carrying his journey forward in our own way…

We will pass on the gifts Mark gave us. We will let that warmth live on in our students, as it once lived in us. That is the truest memorial we can offer him.

Compared to Singapore, the seasons in Hong Kong are unpredictable — summer arrives with fierce passion, autumn and winter bring a certain bleakness, and every so often, a Typhoon Signal 8 or a Black Rainstorm Warning tears across this city without warning. Tonight, the wind in Hong Kong is still howling.

But I will never stop missing you. This book is dedicated to you, my dear mentor, Mark Chignell.