Mr. Ang Li Profile

Ang Li

Research Assistant

SPIE Involvement:

Author

Publications (2)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 15 February 2012 Paper

Fabrication and testing of hydrogel-based microvalves for flow control in flexible lab-on-a-chip systems

Ang Li, Jonathan Lee, Bonnie Gray, Paul C. H. Li

Proceedings Volume 8251, 82510Z (2012) https://doi.org/10.1117/12.910239

KEYWORDS: Microfluidics, Polymers, Actuators, Control systems, Lab on a chip, Polymeric actuators, Nanocomposites, Tolerancing, Chemical elements, Lithography

Read Abstract +

Due to the ease of fabrication and localized response to stimulus (pH, ionic strength, or heat), many researchers have employed stimuli-responsive hydrogels such as poly(N-isopropylacrylamide) (PNIPAAm) as excellent biocompatible materials for microfluidic actuators. We have previously presented the design and fabrication of a mechanically flexible diaphragm-based actuator by employing a reservoir of thermally responsive hydrogel PNIPAAm and a conductive nanocomposite polymer (C-NCP) heater element. We now present the construction, characterization, and simulation of a hydrogel-based microvalve and its application for flow control with a new inexpensive and efficient flexible heater. In this work, we have fabricated the microvalve using traditional microfabrication and soft lithography processes. We accurately pattern and insert the hydrogel plug structure as a fluidic control component within a microfluidic channel. We demonstrate that swelling and shrinking of the hydrogel plug in the microchannel results in closing and opening of the valve. New simulations of the hydrogel plug design were employed using COMSOL® Multiphysics to show the pressure distribution and hydrogel plug movement as well as fluidic velocity in the simulated channel. We then compare the theoretical computed value with the prediction of the COMSOL simulation result which verifies the functionality of our hydrogel plug microvalve design.

Proceedings Article | 15 February 2011 Paper

Fabrication and testing of thermally responsive hydrogel-based actuators using polymer heater elements for flexible microvalves

Ang Li, Ajit Khosla, Connie Drewbrook, Bonnie Gray

Proceedings Volume 7929, 79290G (2011) https://doi.org/10.1117/12.873197

KEYWORDS: Actuators, Polymers, Microfluidics, Polymeric actuators, Nanocomposites, Microactuators, Tungsten, Nanoparticles, Silicon, Polymerization

Read Abstract +

We present the design, fabrication and characterization of a mechanically flexible diaphragm-based microvalve actuator employing a reservoir of the thermally responsive hydrogel PNIPAAm and a conductive nanocomposite polymer (C-NCP) heater element. The microvalve actuator can be fabricated employing traditional soft lithography processes for fabrication of all components, including the tungsten-based C-NCP heater element, the hydrogel reservoir, and the deflecting polymer membrane. Shrinking of the hydrogel under the application of heat supplied by the flexible heater, or the removal of this thermal energy by turning off the heater, forces the diaphragm to move. The silicone diaphragm actuator is compatible with a normally-closed polymer microvalve design where-by the fluidic channel can be opened and closed via the hydrogel diaphragm actuator, in which the hydrogel is normally swollen and heating opens the valve via membrane deflection. Our prototype hydrogel actuator diaphragms are between 100-200 micrometers in diameter, and experimentally deflect approximately 100 micrometers under heating to 32 degrees ºC or above, which is sufficient to theoretically open a microvalve to allow flow to pass through a 100 micrometer deep channel. We characterize the flexible tungsten C-NCP heaters for voltage versus temperature and show that the flexible heaters can reach the hydrogel transition temperature of 32 degrees °C at approximately 13-15 V. We further characterize the hydrogel response to heat, and diaphragm deflection using both hot plate and flexible C-NCP heater elements. While our results show diaphragm deflection adequate for microvalves at a reasonable voltage, the speed of deflection is currently very slow and would result in slow microvalve response speed (30 seconds to open the valve, and 120 seconds to reclose it).

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years