Scientific Achievements to date.
I have spent the last few years researching on a new-generation graphene-enhanced biosensor built using low-cost, scalable nanotechnology using customized conductive polymers to highly sensitive and a robust biosensor that is versatile to be adapted into applications in biomedicine (noninvasive glucose measurements) and the environment (water-quality monitoring using a mobile sensor platform).
The key value propositions include biosensors that have 100x better sensitivity achieved in lab conditions, enough to pursue saliva-based diabetes measurement, low unit cost: even at lab scale, manufacturing costs 10-100x lower than market price for conventional sensors, and low upfront cost: low capital expenditures for manufacturing, since does not require expensive and maintenance-intensive “clean rooms”.
Furthermore, the biosensors are versatile and adaptable which can be easily adapted to measure other biomarkers including cancer markers, pathogens (salmonella, E. coli, etc) as well as water quality parameters (heavy metals, ions, etc) and reverse-fitted / retrofitted into existing sensors. Currently, we are evaluating the sensor technology potential to improve Covid-19 kits. Robust and sensitive sensor technology is enabled by electrochemical transducer-based of graphene and conductive polymer composites that were characterized to have improved electron transfer kinetics and effective surface area.
These technologies with improved transduction are meant to address real problems in the developing world where monitoring of health conditions such as glucose level in the blood for diabetics or water quality monitoring of rivers by communities can be made more accessible.
Five of My Most Important Publications.
The performance of a sensing device is dependent on its construction material, especially for components that are directly involved in transporting and translating signals across the device. Fabrication of workable sensor devices in developing countries with a lack of cleanroom facilities remains challenging and requires out-of-the-box solutions. We have developed a straightforward process to fabricate sensitive and versatile electrochemical sensors without a cleanroom facility using graphene and conductive polymers.
The published papers below reflected the efforts:
1) Abd-Wahab, F.; Abdul Guthoos, H.F.; Wan Salim, W.W.A. Solid-State rGO-PEDOT:PSS Transducing Material for Cost-Effective Enzymatic Sensing. Biosensors 2019, 9, 36. This paper examines the morphological and electrochemical characteristics of reduced graphene oxide (rGO) interspersed with conductive polymer named poly (3,4-ethylenedioxythiophene) poly (sodium 4-styrenesulfonate) (PEDOT:PSS) used as a transducer material deposited on low-cost screen-printed carbon electrode (SPCE).
Characterizations of electron microscopy shows that conductive polymer is interspersed between rGO layers; Raman and XRD analyses suggest that the graphene crystallinity in rGO-PEDOT:PSS remains intact. Instead, PEDOT:PSS undergoes a change in structure to allow PEDOT to blend into the graphene structure and partake in the π-π interaction with the surface of the rGO layers. Incorporation of PEDOT:PSS also appears to improve the electrochemical the behavior of the composite, leading to a higher peak current of 1.184 mA, as measured by cyclic voltammetry, compared to 0.522 mA when rGO is used alone. The rGO-PEDOT:PSS transducing material blended with glucose oxidase was tested for glucose detection. The sensitivity of glucose detection was shown to be 57.3 µA/(mM·cm2) with a detection limit of 86.8 µM. We hope to apply the transducer to produce other low-cost sensor technologies for the developing world.
2) Benoudjit, A.; Bader, M. M.; Wan Salim, W. W. A. Study of electropolymerized PEDOT:PSS transducers for application as electrochemical sensors in aqueous media. Sensing and Biosensing Research 2018, 17. Poly (3,4-ethylenedioxythiophene) poly (sodium 4-styrenesulfonate) (PEDOT:PSS) electropolymerized and deposited onto screen-printed carbon electrodes (SPCEs) was studied for anodic/cathodic peak current and cycle stability (life cycle). Cyclic voltammetry (CV) shows that the redox ability of SPCEs electropolymerized with PEDOT:PSS (SPCE/PEDOT:PSS) was significantly improved (ΔISPCE = 350 µA). Oxidation and reduction peak current of the CVs showed that the modified electrode could maintain electrode integrity for over 30 days. The results suggest that the electropolymerized PEDOT:PSS had good adhesion to SPCE surfaces. There was an insignificant change in the life cycle curve after 3000 cycles compare to the initial cycle and an insignificant change in the life cycle after 30 days in comparison to the first day.
The results suggest that electrode integrity of SPCE/PEDOT:PSS was maintained after repetitive CV cycles in aqueous media, which could be applied as electrodes in microbial fuel cells and energy storage devices like battery, capacitor, and supercapacitor. The method is scalable and can be used to develop electrodes for sensors and energy storage applications. We are currently using the fabrication technique to develop water-quality sensors and energy storage devices.
3) Park, J.; Salmi, M.L.; Wan Salim, W.W.A.; Rademacher, A.; Wickizer, B.; Schooley, A.; Benton, J.; Cantero, A.; Argote, P.F.; Ren, M.; et al. An autonomous lab on a chip for space flight calibration of gravity-induced transcellular calcium polarization in single-cell fern spores. Lab Chip 2017, 17, 1095–1103. I was entrusted as the Principal Investigator to a NASA Nanosatellite project called SporeSat (www.sporesat.org) where my team developed a lab-on-chip device to be integrated to a 3U satellite. The work describes the lab-on-a-chip device to measure changes in cellular ion gradients that are induced by changes in gravitational (g) forces.
The bioCD presented detects differential calcium ion concentrations outside of individual cells. The device includes enough replicates for statistical analysis of the gradients around multiple single cells and around control wells that are empty or include dead cells. In the data presented, the degree of the cellular response correlates with the magnitude of the g-force applied via rotation of the bioCD. The experiments recorded the longest continuous observation of cellular response to hypergravity made to date, and they demonstrate the potential utility of this device for assaying the threshold of cells’ g-force responses in spaceflight conditions. The work demonstrated capability of the biochip device to provide long-term and continuous monitoring of extracellular calcium ion from a single cell. Such devices are now being adapted for ground applications in my research group for the development of noninvasive biomedical sensors and water-quality monitoring.
4) Salim, A., C. Son; Ziaie, B. Selective nanofiber deposition via electrodynamic focusing. Nanotechnology 2008, 19, 37. Electrospinning is a a technique used to produce nanofibers (diameter ˂ 500 nm). The basic set up requires different components such as syringe and pump, a source of high voltage, and a collector. The integration of different components can be achieved in a laboratory setup and scaled up to an industrial process. A well-characterized nanofiber is used to develop a diversified portfolio of applications including energy devices and storage, oil-water separation, textile industry, and wound healing scaffolds. Selective nanofibers patterning with electrospinning allows the deposition of conductive nanofibers on electrode sensor devices, enhancing device sensitivity, and improving limit of detection.
Furthermore, selective nanofiber deposition enables the creation of smart bandage technology which combines embedded nanofiber matrix with integrated sensors technology. The smart bandage utilized a nanotechnology-based bottom-up approach that can be scaled up; these nanofibers are composed of biocompatible polymer modified with carbon-based nanomaterials. Biochemical sensors integrated with a bandage made of nanofibers can detect changes in pH and oxygen content and deliver medications at a set time interval. We envision a smart bandage prototype of high versatility and customizability, that can be tuned to cater to different wound conditions. The smart bandage technology is important in developing countries where access to clinics can be challenging for those in rural communities.
5) Wu, R.; Wan Salim, W. W. A.; Malhotra, S.; Brovont, A.; Pekarek, S.; Banks, M. K.; Porterfield, D. M. Self-powered Mobile Sensor for in-pipe Potable Water Quality Monitoring. MicroTAS: Proc. of the 17th International Conference on Miniaturized Systems for Chemistry and Life Science 2013, Freiburg, Germany. My team at Purdue University, USA have developed a sensor technology to be used in EPA potable water system out of concern of tampering. The Purdue sensor was self-powered and moved with the water flow with real-time detection of water contamination with high temporal resolution. I am currently adapting the technology to monitor river water quality in Malaysia.
Water-quality monitoring has always been a great challenge for industries and government agencies that are dependent on manual data collection. With recent occurrence of toxic pollution at Sungai Kim Kim in Johor, Malaysia which resulted in nearly 2000 people affected by the fumes so far, as reported in the local news, there is an urgency to establish an early warning system in Malaysia to predict contamination in water quality so that mitigation strategies can be invoked to protect and strengthen resilience to abiotic and biotic stresses in rivers as a result of pollution. Continuous water-quality monitoring is key to establish an early warning system so remedial actions can be taken effectively by the government, industries, and local communities.
Three of My Most Important Scientific Achievements.
1) L’Oréal -UNESCO for Women in Science National Fellowship 2015.
Award description: Founded in 1998, the L’Oréal-UNESCO For Women in Science partnership was created to recognize and promote women in science. Its programs reward established women scientists whose outstanding achievements have contributed to the advancement of scientific knowledge and of its benefits to society and provide support to promising young women who are already making significant contributions in their scientific disciplines (L’Oréal -UNESCO for Women in Science National Fellowship). I was awarded the fellowship through my work on developing water-quality sensors for developing resilient communities
2) Thora W. Halstead Young Investigator Award, American Society for Gravitational and Space Research (International) 2012.
Award description: The award was established in 1994 to honor a young scientist who exemplifies Thora’s drive and enthusiasm for science, and who has made significant contributions to the field of gravitational and space research. The award is dedicated to Dr. Thora Halstead in recognition of the years she spent encouraging young scientists to enter gravitational and space research. https://www.nasa.gov/mission_pages/station/research/news/asgsr_2012.html I spent my postdoctoral training years developing sensors technology for NASA and was involved in two NASA nanosatellite projects, GraviSat and SporeSat, which the latter I was appointed as Principal Investigator.
3) Iclif Leadership Energy Award (Corporate category, 2nd runner up), 2018
Award description: Iclif Leadership Energy Awards (ILEA) reward individuals who’ve harnessed their Personal Leadership Energy to effect a positive, sustainable impact in their organizations or communities. The Leadership Energy Champions are selected via a holistic range of criteria, including vision & strategy, personal conviction, measurable results, commercial or social impact, and sustainability (https://iclif.org/ilea/). I was awarded for my work on sensor technologies for space, biomedicine and the environment, especially focusing on low-cost sensor technology for the developing world.
My Goals for Current Research Programme.
A versatile and scalable sensors technology for the developing world.
The research program aims to build local capacity in affordable sensor technologies for the developing world. The radical approach in fabricating sensor technologies include utilizing nanotechnology to improve sensor sensing performance in terms of sensitivity, lower detection limit and high selectivity without the need for high-end first-world facility. Our goals are:
1) Develop scalable sensor fabrication technologies that do not require a high-end cleanroom by leveraging on local manufacturing capacity which includes roll-to-roll technology, 3D-printing, eletropolymerization, electrospinning, to name a few.
2) Build in-house sensor manufacturing from the ground up which includes novel material synthesis, low-cost and scalable fabrication, and prototype integration.
3) Collaborate closely with industry and global partners for prototype testing and validation, scaling up, and product commercialization.
4) Produce highly trained scientists at a third-world facility that can result in at least one Nobel-prize winning discovery in nanotechnology/nanomaterials.
Breakthrough Nature of My Team’s Research.
With the constraints of local laboratories, our research team has come out with affordable solutions for the developing world and are ready to tackle issues such as clean water supply, new generation medical devices and sensor technology, energy storage, as well as other valuable and in-demand applications. Research areas include simulations to identify new materials for sensor technologies, study and characterization of newly synthesized materials for sensors, scalable sensor fabrication methods, integration of sensors with open source platforms, data analytics, and IoT.
Since these sensors are not fabricated in a cleanroom facility, understanding how the processes in standard laboratories affect sensor performance is crucial. We characterized electrodes deposited with electropolymerized materials in terms of how the material affects sensor sensitivity and detection limit. We studied the stability performance of electrodes electropolymerized with conductive polymers in liquid media and the electrodes were found to have increased lifetime and stability thus are suitable as water-quality sensors.
In addition, owing to the sensitivity of the transduction, we developed noninvasive glucose sensors that can detect glucose in saliva that is 100 times diluted than blood. Furthermore, new materials developed from electrospinning are used for developing smart bandage for wound healing, which can enable the wound to be monitored in real-time. The developed fabrication methods allow for sensors to be developed at scale with affordable cost with a low upfront cost, but with 100x better sensitivity achieved in lab conditions.