Deoxyribonucleic acid (DNA) is the coding material in living organisms. Complementary pairs of nu... more Deoxyribonucleic acid (DNA) is the coding material in living organisms. Complementary pairs of nucleobases contribute to the Watson-Crick helical shape of DNA. The nucleobases are connected through hydrogen bonding. This unique feature not only allows for genetic information to be stored but also the assembly of complex nanostructures. DNA-based nanotechnology utilizes DNA as the engineering materials. DNA nanodevices can be designed to work as a drug carrier with programmable selectivity, sensor and computer. Since DNA is a natural material, the application of DNA nanodevices in a biological environment ranging from the relatively simple cell to a complex living organism is a complex, risky but rewarding task.
Concentration gradient generation in microfluidics is typically constrained by two conflicting ma... more Concentration gradient generation in microfluidics is typically constrained by two conflicting mass transport requirements: short characteristic times (τ) for precise temporal control of concentration gradients but at the expense of high flow rates and hence, high flow shear stresses (σ). To decouple the limitations from these parameters, here we propose the use of stagnation flows to confine concentration gradients within large velocity gradients that surround the stagnation point. We developed a modified cross-slot (MCS) device capable of feeding binary and combinational concentration sources in stagnation flows. We show that across the velocity well, source-sink pairs can form permanent concentration gradients. As source-sink concentration pairs are continuously supplied to the MCS, a permanently stable concentration gradient can be generated. Tuning the flow rates directly controls the velocity gradients, and hence the stagnation point location, allowing the confined concentrati...
This paper reports a method to control the bubble size generated in a microfluidic flow-focusing ... more This paper reports a method to control the bubble size generated in a microfluidic flow-focusing configuration. With an ultrasonic transducer, we induce acoustic streaming using a forward moving, oscillating gas-liquid interface. The induced streaming substantially affects the formation process of gas bubbles. The oscillating interface acts as a pump that increases the gas flow rate significantly and forms a larger bubble. This method is applicable to a wide range of gas pressure from 30 to 90 kPa and flow rate from 380 to 2700 μL h(-1). The bubble size can be tuned repeatedly with the response time on the order of seconds. We believe that this method will enhance the capability of a microfluidic bubble generator to produce a tunable bubble size.
Deoxyribonucleic acid (DNA) is the coding material in living organisms. Complementary pairs of nu... more Deoxyribonucleic acid (DNA) is the coding material in living organisms. Complementary pairs of nucleobases contribute to the Watson-Crick helical shape of DNA. The nucleobases are connected through hydrogen bonding. This unique feature not only allows for genetic information to be stored but also the assembly of complex nanostructures. DNA-based nanotechnology utilizes DNA as the engineering materials. DNA nanodevices can be designed to work as a drug carrier with programmable selectivity, sensor and computer. Since DNA is a natural material, the application of DNA nanodevices in a biological environment ranging from the relatively simple cell to a complex living organism is a complex, risky but rewarding task.
Concentration gradient generation in microfluidics is typically constrained by two conflicting ma... more Concentration gradient generation in microfluidics is typically constrained by two conflicting mass transport requirements: short characteristic times (τ) for precise temporal control of concentration gradients but at the expense of high flow rates and hence, high flow shear stresses (σ). To decouple the limitations from these parameters, here we propose the use of stagnation flows to confine concentration gradients within large velocity gradients that surround the stagnation point. We developed a modified cross-slot (MCS) device capable of feeding binary and combinational concentration sources in stagnation flows. We show that across the velocity well, source-sink pairs can form permanent concentration gradients. As source-sink concentration pairs are continuously supplied to the MCS, a permanently stable concentration gradient can be generated. Tuning the flow rates directly controls the velocity gradients, and hence the stagnation point location, allowing the confined concentrati...
This paper reports a method to control the bubble size generated in a microfluidic flow-focusing ... more This paper reports a method to control the bubble size generated in a microfluidic flow-focusing configuration. With an ultrasonic transducer, we induce acoustic streaming using a forward moving, oscillating gas-liquid interface. The induced streaming substantially affects the formation process of gas bubbles. The oscillating interface acts as a pump that increases the gas flow rate significantly and forms a larger bubble. This method is applicable to a wide range of gas pressure from 30 to 90 kPa and flow rate from 380 to 2700 μL h(-1). The bubble size can be tuned repeatedly with the response time on the order of seconds. We believe that this method will enhance the capability of a microfluidic bubble generator to produce a tunable bubble size.
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