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Graphene-mediated microfluidic transport and nebulization via high frequency Rayleigh wave substrate excitation

Ang KM, Yeo LY, Hung YM, Tan MK

Lab Chip, 2016 09 21;16(18):3503-14.
PMID: 27502324 DOI: 10.1039/c6lc00780e

The deposition of a thin graphene film atop a chip scale piezoelectric substrate on which surface acoustic waves are excited is observed to enhance its performance for fluid transport and manipulation considerably, which can be exploited to achieve further efficiency gains in these devices. Such gains can then enable complete integration and miniaturization for true portability for a variety of microfluidic applications across drug delivery, biosensing and point-of-care diagnostics, among others, where field-use, point-of-collection or point-of-care functionality is desired. In addition to a first demonstration of vibration-induced molecular transport in graphene films, we show that the coupling of the surface acoustic wave gives rise to antisymmetric Lamb waves in the film which enhance molecular diffusion and hence the flow through the interstitial layers that make up the film. Above a critical input power, the strong substrate vibration displacement can also force the molecules out of the graphene film to form a thin fluid layer, which subsequently destabilizes and breaks up to form a mist of micron dimension aerosol droplets. We provide physical insight into this coupling through a simple numerical model, verified through experiments, and show several-fold improvement in the rate of fluid transport through the film, and up to 55% enhancement in the rate of fluid atomization from the film using this simple method.
Amplitude modulation schemes for enhancing acoustically-driven microcentrifugation and micromixing

Ang KM, Yeo LY, Hung YM, Tan MK

Biomicrofluidics, 2016 Sep;10(5):054106.
PMID: 27703592

The ability to drive microcentrifugation for efficient micromixing and particle concentration and separation on a microfluidic platform is critical for a wide range of lab-on-a-chip applications. In this work, we investigate the use of amplitude modulation to enhance the efficiency of the microcentrifugal recirculation flows in surface acoustic wave microfluidic systems, thus concomitantly reducing the power consumption in these devices for a given performance requirement-a crucial step in the development of miniaturized, integrated circuits for true portable functionality. In particular, we show that it is possible to obtain an increase of up to 60% in the acoustic streaming velocity in a microdroplet with kHz order modulation frequencies due to the intensification in Eckart streaming; the streaming velocity is increasing as the modulation index is increased. Additionally, we show that it is possible to exploit this streaming enhancement to effect improvements in the speed of particle concentration by up to 70% and the efficiency of micromixing by 50%, together with a modest decrease in the droplet temperature.
Acoustially-mediated microfluidic nanofiltration through graphene films

Ang KM, Yeo LY, Hung YM, Tan MK

Nanoscale, 2017 May 18;9(19):6497-6508.
PMID: 28466906 DOI: 10.1039/c7nr01690e

We exploit the possibility of enhancing the molecular transport of liquids through graphene films using amplitude modulated surface acoustic waves (SAWs) to demonstrate effective and efficient nanoparticle filtration. The use of the SAW, which is an extremely efficient means for driving microfluidic transport, overcomes the need for the large mechanical pumps required to circumvent the large pressure drops encountered in conventional membranes for nanoparticle filtration. 100% filtration efficiency was obtained for micron-dimension particulates, decreasing to only 95% for the filtration of particles of tens of nanometers in dimension, which is comparable to that achieved with other methods. To circumvent clogging of the film, which is typical with all membrane filters, a backwash operation to flush the nanoparticles is incorporated simply by reversing the SAW-induced flow such that 98% recovery of the initial filtration rate is recovered. Given these efficiencies, together with the low cost and compact size of the chipscale SAW devices, we envisage the possibility of scaling out the process by operating a large number of devices in parallel to achieve typical industrial-scale throughputs with potential benefits in terms of substantially lower capital, operating and maintenance costs.
Acoustically enhanced heat transport

Ang KM, Yeo LY, Friend JR, Hung YM, Tan MK

Rev Sci Instrum, 2016 Jan;87(1):014902.
PMID: 26827343 DOI: 10.1063/1.4939757

We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10(6) Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ∼ 10(-9) m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξs ∼ 10(-8) m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10(-8) m with 10(6) Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.
Fulltext Exploring patients' experience and perception of being diagnosed with bladder cancer: a mixed-methods approach

Tan WS, Teo CH, Chan D, Ang KM, Heinrich M, Feber A, et al.

BJU Int, 2020 05;125(5):669-678.
PMID: 31975539 DOI: 10.1111/bju.15008

OBJECTIVE: To determine patient experience and perception following a diagnosis of non-muscle-invasive bladder cancer (NMIBC).
PATIENT AND METHODS: Patients were part of a prospective multicentre observational study recruiting patients with NMIBC for a urine biomarker study (DETECT II; ClinicalTrials.gov: NCT02781428). A mixed-methods approach comprising: (i) the Brief Illness Perception Questionnaire (Brief-IPQ) and (ii) semi-structured interviews to explore patients' experience of having haematuria, and initial and subsequent experience with a NMIBC diagnosis. Both assessments were completed at 6 months after NMIBC diagnosis.
RESULTS: A total of 213 patients completed the Brief-IPQ. Patients felt that they had minimal symptoms (median [interquartile range, IQR] score 2 [0-5]) and were not particularly affected emotionally (median [IQR] score 3 [1-6]) with a minimal effect to their daily life (median [IQR] score 2 [0-5]). However, they remained concerned about their cancer diagnosis (median [IQR] score 5 [3-8]) and felt that they had no personal control over the cancer (median [IQR] score 2 [2-5]) and believed that their illness would affect them for some time (median [IQR] score 6 [3-10]). A significant association with a lower personal control of the disease (P 70 years. Many patients were uncertain about the cause of bladder cancer. Qualitative analysis found that at initial presentation of haematuria, most patients were not aware of the risk of bladder cancer. Patients were most anxious and psychologically affected between the interval of cystoscopy diagnosis and transurethral resection of bladder tumour (TURBT). Following TURBT, most patients were positive about their cancer prognosis.
CONCLUSION: Patients with NMIBC have a poor perception of disease control and believe that their disease will continue over a prolonged period of time. This is particularly more pertinent in the elderly. Patients are most psychologically affected during the interval between cancer diagnosis following cystoscopy and TURBT. Health awareness about bladder cancer remained poor with a significant number of patients unaware of the causes of bladder cancer. Psychological support and prompt TURBT following bladder cancer diagnosis would help improve the mental health of patients with NMIBC.
Barriers to implementing a national health screening program for men in Malaysia: An online survey of healthcare providers

Ng CJ, Teo CH, Ang KM, Kok YL, Ashraf K, Leong HL, et al.

Malays Fam Physician, 2020;15(1):6-14.
PMID: 32284799

Introduction: This study aimed to determine the views and practices of healthcare providers and barriers they encountered when implementing the national health screening program for men in a public primary care setting in Malaysia.
Methods: An online survey was conducted among healthcare providers across public health clinics in Malaysia. All family medicine specialists, medical officers, nurses and assistant medical officers involved in the screening program for adult men were invited to answer a 51-item questionnaire via email or WhatsApp. The questionnaire comprised five sections: participants' socio-demographic information, current screening practices, barriers and facilitators to using the screening tool, and views on the content and format of the screening tool.
Results: A total of 231 healthcare providers from 129 health clinics participated in this survey. Among them, 37.44% perceived the implementation of the screening program as a "top-down decision." Although 37.44% found the screening tool for adult men "useful," some felt that it was "time consuming" to fill out (38.2%) and "lengthy" (28.3%). In addition, 'adult men refuse to answer' (24.1%) was cited as the most common patient-related barrier.
Conclusions: This study provided useful insights into the challenges encountered by the public healthcare providers when implementing a national screening program for men. The screening tool for adult men should be revised to make it more user-friendly. Further studies should explore the reasons why men were reluctant to participate in health screenings, thus enhancing the implementation of screening programs in primary care.