For the need to measure large deformation from the swollen arthritis knees, a strain sensor that can measure large strain has been developed, which uses ionic liquid or liquid metal alloy as the piezoresistive gauge materials encapsulated inside an elastomeric microchannel. Liquid conductor can totally comply with the deformation of the microchannel to measure its resistance increase when stretching the channel for large strain sensing up to 50% or compressing the channel narrower for tactile force sensing.

We have developed strain and tactile sensors that can sense both large axial strain and also transverse force applied across the channel direction. It is ready to be applied on products require measurement of large strain and tactile force with higher repeatability and longer sensor life that other sensors cannot provide. We have found an environmental friendly conductive liquid to replace the mercury that is not environmental friendly or expensive Ga-In alloy for making the strain and tactile sensors. With its flexible, stretchable, and transparent properties, it can be applied to different applications.　 　

- Strain & Tactile Sensing Principles

- Fabricated Strain & Tactile Sensor

Other Technologies - Other research uses carbon powder or carbon nanotube to dope inside the non-conductive elastomer. However, it has the problem of hysterisis and aging from the proceeding of micro-cracks. The hysterisis is from the redistribution of the conductive powder in the elastomer during stretching and compressing. The aging is due to the increased hardness after adding the solid conductive powder with micro-cracks starting from the defects of the doped elastomer during large deformation. Although the ultimate solution is to use an intrinsic conductive elastomer, however, most of the conductive polymer developed today is stiff and brittle, which is not soft enough to apply with large strain. Another solution is to use liquid metal, like mercury, which is not environmental friendly.

Our Technology - We have found an environmental friendly conductive liquid to replace the electrolyte containing heavy metal. Liquid metal alloy has been used to replace the mercury in the thermometer. However, the resistance of the conductive liquid needs to be measured by AC but having a higher resistance to reduce joule heating effect for power saving. DC measurement is used for liquid metal alloy but with lower resistance to cause more joule heating effect. By using these two materials, we have developed strain and tactile sensors that can sense both large axial strain and also transverse force applied across the channel direction. It is ready to be applied on products require measurement of large strain and tactile force with higher repeatability and longer sensor life that other sensors can not provide. 　

• Flat Panel Scale:
  By laying out the conductive fluid microchannel on a thin substrate, it can be used as a scale to weigh stuffs. 　

• Transparent Touch Screen Panel:
  When laying out two layers of the conductive fluid microchannel, it becomes a transparent touch screen panel. 　

• Pressure and Tactile Sensing:
  A single element of the fluidic tactile sensor can measure the pressure applied on an interested spot.　 　

• Industrial Strain Measurement:
  It can also be used to measure the industrial structures when the strain is more than 10%.　 　

In addition to above applications, the large strain and tactile sensing can be applied to the flexible electronics, which can be the next industry after the personal computer and other consumer electronics. 　

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For different drug delivery purposes, micropumps are developed to achieve control of flow rate in the micro to nano liter range. The miniature pump size also makes it possible to implant the whole pump to the human body to constantly deliver the medication to the target organs when required. For the microfluidic systems, the flow rate modulation needs to be down to nano-liter range with higher back pressure to push fluid in the microchannels, where the nano-rate pump can serve this purpose. This can also be applied to concentrated drugs in the nano –liter scale. 　

To achieve a better portability, microfabrication technique is used to reduce the pump thickness to the millimeter range. The valveless micropump provides an easy structure with no valve failure but also lower back pressure. The check-valve micropump can increase the back pressure. By using the piezoelectric material to drive the micropump, it can also prevent the interference to the magnetic resonance imaging (MRI) when pumps driven by the electromagnetic motor can have. The nano-rate pump has achieved a flow rate that cannot be achieved by the mechanical pumps. 　

- A Piezoelectric Valveless Micropump　

- A Piezoelectric Check-Valve Micropump　

- Micropump Driving Electronics 　

- Pump Curves of the Valveless Micropump

- Piston Type Nano-Rate Pump 　

- Barrel Type Nano-Rate Pump　

- Measurement of the Pump Flow Rate in Nano Liters per Second Rate 　

- Asymmetric Nanoporous PES Membrane 　

- Micropump with PES Membrane as
One-Way Valve 　

- Micropump Actuated by Ultrasound 　

- Volume Flow Rate at Sub-Micro Liter Range 　

Other Technologies – Most of the drug pump currently in the market uses electromagnetic motor to drive the syringe needle, which needs a big space to include the motor together with the gears to transfer rotary motion to linear actuation. For applications limited by the size, including transdermal and implantable drug delivery, they require much smaller pumps to fit in the space. Our Technology – We have developed three different micropumps to fulfill this need. They include valveless and check-valve micropumps, nano-rate pumps, and nanoporous membrane micropumps. They all have very small pump body to fit for drug delivery applications that are limited by the space. The pump rate can achieve from micro to nano liter per second range for control of drug delivery rate. 　 　

• Implantable Drug Pump (Courtesy of Medtronic, Inc.) 　 　

• Insulin Pump (Courtesy of The Hughston Foundation, Inc.) 　

• Subdermal Implanted Pump (Courtesy of Healthwise, Inc.)

In addition to above applications, the micropumps can be applied to the fuel cell and liquid cooling of microprocessors, which can be applied to the personal computer and other consumer electronics. 　 　

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Currently people have become more concerned about their health and fitness. The demand of medical and healthcare devices for prevention, detection and control of diseases has increased. Moreover, the growth of ageing population also drives such need. Since health conditions tend to deteriorate with age, an ageing population means increasing demand for health services, as well as related devices and supplies. The blood diagnostic devices will gain acceptance by the general public given they are portable, user-friendly, minimal usage of blood sample and reagents, and with acceptable accuracy. So, with these properties, the diagnostic devices should be appropriate for both home care and ambulatory environment.　

The portable immunoassay device is a miniaturized laboratory that can perform screening test on-site. Conventionally, immunoassay involves various equipment and is designed to run in a well equipped laboratory. These biological processes are tedious and labor intensity. Our developing device incorporates the technologies of microfluidics and nano-technology. Such that, miniaturized fluidic platform is realized by microfluidic technology and most of the biological process can be handled in this portable device. Colorimetric detection and electrical detection of immunoassay are developed for a miniaturized detection technology which does not involve sophisticated optical system. Therefore, the portable immunoassay device can be realized by those technologies.

We are developing a portable immunoassay device for screening application. The device consists of a portable device and a disposable cartridge. The portable device provides fluidic control, detection and result analysis capability. The disposable cartridge has a reaction chamber and several detection sites inside performing biological reactions. In order to prevent cross-contamination in every single diagnosis, cartridge is designed for single use only.

The procedure of one diagnostic test in this device is user-friendly and automated. Fluid sample is first applied to the reaction chamber in the disposable cartridge. Then, the cartridge is inserted to the portable device. The reagents are manipulated to the cartridge automatically. A series of biological reactions will be conducted in the cartridge. Then, the portable device captures the detection signal from the disposable cartridge. After data analysis, the diagnostic results are shown on the display of the portable device. 　

For the existing blood diagnostic test, people must go to hospital or clinical center for blood sampling and the duration of test is around one to two weeks. The process of the test is labor intensive and involves various bulky equipment. Similar to the environmental test, field sample is collected and brought to the laboratory for analysis. The process involves tedious and labor intensive laboratory works and time-consuming. Our device incorporates microfluidics and nano-technology. It has the benefits of portable and automation, therefore, the diagnostic test can be performed on site.　

For the existing blood diagnostic test, people must go to hospital or clinical center for blood sampling and the duration of test is around one to two weeks. The process of the test is labor intensive and involves various bulky equipment. Similar to the environmental test, field sample is collected and brought to the laboratory for analysis. The process involves tedious and labor intensive laboratory works and time-consuming. Our device incorporates microfluidics and nano-technology. It has the benefits of portable and automation, therefore, the diagnostic test can be performed on site.　

The portable immunoassay device is a platform technology which can further develop for various applications, such as:

• Disease screening, e.g., bird flu disease, hepatitis B, HIV, malaria, etc.;
• Environmental screening, e.g., legionnaire’s disease, etc.;
• Food safety screening, e.g., salmonella, E. coli, etc.;
• Health screening, e.g., glucose, cholesterol, etc.;
• Indoor air screening, e.g., bacteria and virus level, etc.

The developing system could facilitate many point-of-care or on-site applications including rapid diagnostics, disease prevention and control, environmental protection, etc.

Collaborators:

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