Ultra-sensitive microfibre absorption detection in a microfluidic chip

Abstract

We report a microfibre absorption sensor by using a 900 nm diameter silica microfibre embedded in a 125 μm wide microchannel with a detection length of 2.5 cm. Investigated by measuring the absorbance of methylene blue (MB), the sensor shows a detection limit down to 50 pM with excellent reversibility in a concentration range of 0-5 nM. The sensor has also been applied to bovine serum albumin (BSA) measurement, with a detection limit of 10 fg mL(-1). In addition, the sample volume requirement is merely 500 nL with a probing light power of about 150 nW, which is very promising for safe detection of single or a few molecules of biological specimens.

Microfiber Optical Sensors: A Review

“…By measuring the refractive-index-dependent leakage loss of 1.5 μm wavelength light guided in a 700 nm diameter silica microfiber, they realized an accuracy of refractive-index measurement of 5.3 × 10 −4 . In 2011, by integrating a 900 nm diameter microfiber into a 125 μm wide microfluidic channel, Zhang et al demonstrated a microfiber sensor for chemical and biological applications (Figure 8) [33]. As shown in Figure 8f, using a broadband white light as probing light with power of about 150 nW, the absorbance of bovine serum albumin (BSA) was clearly observed with a detection limit down to 10 fg·mL −1 .…”

“…Microfiber absorption sensor [33]. ( a ) Biconical tapered fiber with a 900 nm diameter waist (microfiber).…”

Optical microfibers and nanofibers

“…In 2007, relying on absorption of molecules adsorbed on the surface of a 500-nm-diameter MNF, Warken et al reported an ultrasensitive molecular sensor that was possible to detect sub-monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules at ambient conditions [27]. In 2011, by integrating a 900-nm-diameter MNF into a 125-μm-wide microfluidic channel, Zhang et al demonstrated a MNF sensor for chemical and biological applications ( Figure 16A-E) [32]. As shown in Figure 16F, using a broadband white light as probing light with power of about 150 nW, the absorbance of bovine serum albumin (BSA) was clearly observed with a detection limit down to 10 fgml -1 .…”

“…(2) Strong evanescent field Strong evanescent field offers strong near-field interaction between the MNF and its surroundings, making the MNF highly favorable for optical sensing [21][22][23][24][25][26][27][28][29][30][31][32] and evanescent coupling between the MNF and other waveguides (e.g., a semiconductor [33,34], metal [35,36] nanowire or planar waveguide [37]) or a substrate [30,35,38,39]. Based on the high-efficiency evanescent coupling, a variety of optical components or devices (e.g., loop and knots resonators [40][41][42][43][44][45][46][47][48][49][50][51], lasers [52][53][54][55][56][57][58], and sensors [21][22][23][24][25][26][27]…”

“…Based on the high-efficiency evanescent coupling, a variety of optical components or devices (e.g., loop and knots resonators [40][41][42][43][44][45][46][47][48][49][50][51], lasers [52][53][54][55][56][57][58], and sensors [21][22][23][24][25][26][27][28][29][30][31][32]) have been demonstrated. Meanwhile, since the high fractional evanescent filed is tightly confined around the MNF, it can produce steep field gradient which provides large optical gradient force for manipulating cold atoms [19,[59][60][61][62][63] or micro-/nano-particles [64,65], as well as large or manageable waveguide dispersion under single mode condition [11].…”