Professor Freddy Boey (centre, showing the swabs), and (from left) Dr Alfred Chia, professor David Allen,
and professor Yen Ching-Chiuan are a part of two NUS teams that developed three nasopharyngeal
swab designs for COVID-19 testing.
Since the outbreak of COVID-19, there has been a worldwide surge in demand for nasopharyngeal (NP)
swabs, a key element in testing for SARS-CoV-2. Singapore is not any exception. Commercially available
NP swabs utilized in COVID-19 test kits are often out of stock thanks to supply chain disruptions.
To help address the worldwide shortage, and to make sure Singapore features a sustainable supply of
those swabs, two multidisciplinary research teams from NUS have developed a complete of three swab
designs that are like the present ‘gold standard’ swabs.
A team led by Professor John Eu-Li Wong, NUS Senior vice chairman (Health Innovation & Translation),
professor Yen Ching-Chiuan, Co-Director of the Keio-NUS CUTE Center, and Professor Jerry Fuh,
Director of the NUS developed ‘Python’. The team worked with professor David Allen and Professor
Wang De Yun from NUS Yong Loo Lin School of drugs , researchers from the NUS School of Design and
Environment and NUS Faculty of Engineering, also as clinicians from the National University Hospital
(NUH), on the planning , pre-clinical testing and clinical validation.
Additionally, to further increase the assembly of suitable swabs for Singapore and therefore the region,
another NUS team led by Professor Freddy Boey, NUS Deputy President (Innovation & Enterprise),
introduced two new designs, named ‘IM2’ and ‘IM3’, that would be manufactured using injection
Nasopharyngeal swabs and screening accuracy
NP swabs used for COVID-19 testing have a carefully designed tip section that serves to gather and
retain sufficient nasopharyngeal fluids which are channelled into a holder for further testing. These are
critical design factors as they might affect the accuracy of the test result when screening for SARS-CoV-
Python, the 3D-printed swab
To derive a viable alternative, the NUS team led by Prof Wong, Assoc Prof Yen, Assoc Prof Allen, and
Prof Fuh combined their experience to style , test, After considering the clinical requirements of the swab
in reference to its mechanical, material and biological properties, a helix structure was used for the swab
tip, because it had excellent fluid adsorption and caused minimal discomfort to the patient.
The clinical efficacy of the swab, named Python, was compared to an industry standard swab in NUH.
This was administered during a case-controlled study of 40 patients diagnosed with COVID-19, and 10
control patients with acute respiratory disease who had tested negative for SARS-CoV-2.
The Python swab, which was developed in but two months, demonstrated comparable accuracy and
performance, with no significant difference against the quality swab. As such, the Python swab was
deemed safe and acceptable for patient use, and will help mitigate strained resources within the
escalating COVID-19 pandemic
Assoc Prof Yen, one among the lead researchers of the project, said, “We are pleased to contribute our
expertise to deal with the pressing need for nasopharyngeal swabs. As a part of NUS’ contribution
towards the nation’s fight against COVID-19, the planning of the Python swab is free to be used in
A large-scale solution: Injection moulded swabs
To further increase the assembly of NP swabs, another NUS team led by Prof Boey developed an
injection moulding process.
“Injection moulding as a producing process is inherently faster than 3D printing as multiple units of the
swabs are often produced during a given cycle. Several hundred swabs are often produced during a jiffy
using the moulding process,” explained Prof Boey.
His team introduced a replacement design that would be injection moulded, named IM2. it had been
tested for its mechanical strength after sterilisation, and for its efficacy in learning viral loads. The results
showed that its performance was like the present commercially used swabs.
The team also redesigned the Python swab to enable it to be injection moulded by increasing the
circumferential strength, and dealing with the manufacturer to style a mould that permits the moulding of
the central hollow cavity. This design was coined IM3. Similar tests were performed to point out that the
planning was like the present commercially used swabs.