Smart Materials and MEMS (Microelectromechanical Systems are two broad research areas in which scientist with a wide variety of training and expertise are enthusiastically involved all over the world. The UALR Smart Materials and MEMS Laboratory was originally founded by Dr. Abhijit Bhattacharyya in the Departament of Applied Science of the Donaghey Cybercollege at the University of Arkansas at Little Rock in January of 2002. He and his team are involved in research on high temperature shape memory alloys (SMA), and SMA-based MEMS.

The term “Smart Materials” is somewhat subjective and has different connotations for different people. If we were to define “Smart Materials”, we would say that any material which is nonlinear and hysteretic is a “smart material”. Lets explain this simply using an example. It is like completing a round trip journey. During the outbound, a person travels from point A to point B along a certain path and during the return, travels along a different path back to the point A. A similar situation can be thought for a material which goes from a certain material state A to B along one path, but returns to A along a different path. In this sense, the material is “smart” as opposed to other materials which are constrained to travel along a straight line and hence cannot display any “smartness” (traveling along different paths but managing to come back to the starting point).

In any case, there are many materials which come under the broad classification of smart materials: shape memory alloys (SMA), shape memory polymers (SMP), piezoelectric materials, ferroelectric materials, magnetostrictive materials , polymeric gels and so on. Our research deals primarily with SMAs and, to some extent, SMPs.

Shape memory alloys or SMA as these are popularly known are alloys that undergo a phase transformation as they are heated or cooled. Therefore, the microscopic change is one in “crystal structure” whereas the macroscopic change is one in shape and/or length (this occurs in presence of applied forces). There is a phenomenon known as the two-way memory effect where the macroscopic change can be seen in absence of applied forces. A very popular shape memory alloy is Nickel-Titanium (or Nitinol). If you are not familiar with what a SMA can do, click on the DEMO. The change is reversible, although with quite a bit of hysteresis. Shape memory alloys are capable of undergoing significant changes in length against pretty high forces. Research on potential applications are wide ranging – biomedical (catheters and orthodontics), process industries (valves and couplings) and aerospace (actuation of trailing edge flaps of aircraft wings or airfoils).

One of the significant disadvantages is that most SMAs operate at moderate temperatures (about 60 deg C or 140 deg F or thereabouts). Many applications (aircraft sitting out on a tarmac on a hot day) need actuation temperatures of 100 – 150 deg C (or 212 – 302 deg F). Our focus is on high temperature shape memory alloys, and to demonstrate that (i) these can undergo controlled actuation in a high temperature environment, (ii) these can undergo fast actuation in a moderate temperature environment.

What are MEMS ?

MEMS (also refered to by a popular term 'miromachines') are devices that integrate mechanical and electrical components on a chip. These components have typical feature sizes of the order of microns. Such "fine" manufacturing has been made possible by adapting the technilogy that was originally developed to make integrated circuits (IC). MEMS fabrication facilities are now available all over the country and the world.

Our focus is on SMA-based MEMS and bio-MEMS. In the first case, we propose to integrate SMAs on MEMS and do for MEMS what is being done for larger devices, i.e. create significant motion against large forces with the added ingredient of fast actuation. Admittedly, the idea of integrating SMAs with MEMS is not new. Folks have tried to make micropumps for intraveneous drug delivery, micro tweezers for cell manipulation and micro-bubbles to control the dynamics of air flow on a surface. We propose to explore the possibility of using SMAs on the micron scale for relatively high speed actuation, in spite of the fact that SMA actuation relies on thermal fields. In the second case, we are working on modeling of time-dependent fluid flow in microchannels and this has certain relevance for micro pump applications.


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