In memory of Abraham Tuwei Kirwa – a trailblazer in science of sensors

By Dr Paul Kamweru (Guest Writer)

We have lost a friend and a respectable colleague. Dr. Abraham Tuwei Kirwa passed on today (9th July 2020) following injuries he sustained on a road accident.

To help me escape the reality of his demise, and the feeling of sadness and sorrow for even the thinnest moment, I choose to take my mind and focus on the good science Dr. Tuwei will forever be remembered for.

For those unfamiliar with his work, allow for a moment to highlight a few of his successes in physics.

Fibre optic sensors

Without doubt, Dr. Tuwei was passionate about physics, and especially the physics of sensors and sensing, utilizing evanescent waves of an optical fibre.

For starters a fibre is a thin cylindrical piece of either glass or plastic, which allows a ray of light to pass through it without loss, due to a principle we call total internal reflection.

What this means, is that the ray of light is not lost, made possible by cladding (coating) a material of a different (lower) refractive index.

Even though the ray is ‘total internally reflected’, there remains a portion of the ray of light (electromagnetic field), that ‘jumps’ into the cladding.


However this ray or wave (a group of rays) normally disappear quickly, that is, it evanescence, such that it is only on a very thin layer of the cladding.

This evanescence wave therefore interacts, and carries with it the information about the cladding (the coating layer). The information about the cladding can therefore be detected.

This is done by analyzing the light signal at other end of the optical fibre, and quantifies any differences in the signal, for different claddings.

This is the principle that Dr. Tuwei utilized to make sensors (i.e. the Evanescent Wave Sensor or EWS) that can detect analyte (chemicals) either in air or in water.

University of Sheffield

For his work that he did at the University of Sheffield, UK, Dr. Tuwei replaced the cladding for a small portion of the fibre with three chemicals i.e. 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO),  1-(2-pyridylazo)-2-naphthol(PAN) and zinc 5-(4-carboxyphenyl),10,15,20-triphenyl porphyrin (Zn(P-CO2H-TPP)) that are sensitive to acetic acid vapors,  Zinc ions and octylamine respectively.

What happens is that when the newly coated cladding is exposed to the analyte to be detected, it changes its optical properties, and hence the evanescent wave in and from it will behave differently, change, and this is detectable.

Journal articles

Dr. Tuwei’s results that are published a journal articles and a thesis of the same University, proves that the EWS with the sensitive chemicals sprayed as the cladding is efficient to detect the analyte in water, more than in air.

What else can EWS sensors be used for?

Their findings could be stretched further, and explored for sensing other parameters such as temperature, pressure and even noise. The ball is in the court of lovers of Science.

Besides the published thesis work, Dr. Tuwei was working in corroboration of others to make sensors for different purposes, such as detecting electrical signals in plants, monitoring human traffic and movements, among others.

What does this mean for application?

These findings means that we now have, courtesy of the late Dr. Tuwei and others working in a similar discipline, an easy to assemble and sensor that could tell of the presence of harmful compounds and elements in drinking water for example.

With the EWS, fish farmers could be able to follow when toxic compounds are accumulating if fish ponds that may lead to fish deaths. When applied to detect airborne analyte the EWS could be used to detect and monitor air pollution from industries, motor vehicles among others.

Even though gone, his work will remain useful to the scientific community and will be utilized to benefit the human race.

Dr. Tuwei was also a husband, a father, a brother and a friend. He will forever be remembered.

Fare thee well, our Colleague, Dr. Abraham Tuwei Kirwa.

About Gatonye Gathura 142 Articles
Science Journalist


  1. Truly,we have lost a legend,a scholar n a great physicist who has made great contributions in modern physics, as you rest in peace with the Angels know that we will walk in your footsteps and make more contributions in physics, #fare thee well Dr. Tuwei

  2. Its unfortunate he has left before we work on dye sensitised cells. The loss is just too much. May you rest peacefuly with angels my colegue n supervisor

  3. He truly was a great scholar, he handled his work with consistent determination and had a special mind few posses. May he rest with the angels.
    Till we meet again.

  4. Words may never be enough to explain the vast impact you made on the lives of young physicists you came across in the lecture halls.Indead,we’ve lost s great scholar. May his soul rest in eternal rest..

  5. Words may never be enough to explain the vast impact you made on the lives of young physicists you came across in the lecture halls.Indead,we’ve lost a great scholar. May his soul rest in eternal peace..

  6. Great loss to the chuka University physics department and university at large indeed we have lost a scholar and a great physicist. You shall be remembered by many for your great contributions to modern physics. Rest in peace Dr. Tuwei

  7. As a physicist I will truely miss not only a friend but also one of my Mentors. Dr. Tuwei had passion in sensors and sensing and he will always be remembered for his great works.
    May his soul rest in peace. Shine on your way Dr.Tuwei

  8. Very sad at such a young age daktari was so close to achieving what has never been thought of in the field of physics.
    May his sole rest in peace.

  9. Life is the greatest gift that God has given us. Death is only a bridge towards eternal life with God. My deepest condolence for the loss of our beloved lecturer.

  10. Dr Tuwei had an unfading smile and very organized. I once told a colleague of mine “this guy behaves as if he received Training Abroad” until i read it today. I remember asking him to pass me an internet cable from his desk to the biochemistry section office and he never got tired to do this. Other times i would sit on his desk when he wasnt in peace daktari.

  11. We have lost a great person, your good physics will forever be remembered, you inspired many,fare thee well Doctor Tuwei, rest in eternal peace

  12. Death is something that needs a research on its own… I lost strength to type RIP to our Dr in physics,,, remembered him in digital electronics a unit that gave me light in electronics,, forever we will miss you Dr. Tuwei… Fare thee well

  13. I lack enough words to describe Dr Tuwei. Indeed he had a call in the field of science. His work will forever remain in our hearts. Fare thee well Daktari…

  14. A great man Dr Tuwei was He taught me physics and I remember his words so encouraging and did his work with passion. It is a great loss to the university and his family too.
    May the lord comfort his family and his friends during this time.
    We will miss u daktari rest in peace

  15. Rest in peace my advisor whenever I had a problem in the institution.I will continue follow ing your advice

  16. Is unfortunate that death has taken my lecturer in physics when just about to start.Rest in peace DR TUWEI

  17. It was a great loss to to chuka fraternity and mostly to the physics department ,,,,he was a hero in physics and a mentor to many ,,,,, farewell dartari

  18. I was Abraham’s PhD supervisor at Sheffield University and I am heartbroken to hear of his untimely passing. We remember him for both his scientific talent, and his kindness. He contributed so much in his short life, it is so sad he didn’t get more time in this world. My thoughts are with his family, their loss is unmeasurable.

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