Universally Programmable Intelligent Matter

A Systematic Approach to Nanotechnology

Bruce MacLennan

University of Tennessee, Knoxville

Supported by NSF NER grantand UTK Center for Information Technology Research

Introduction & Definitions

• Intelligent matter: individual molecules or molecular clusters function as agents

• Universally programmable intelligent matter: made from a small set of building blocks that are computationally universal

Goals

• Avoid case-by-case nano-engineering of materials

• Design one “universal material” that can be “programmed” for many applications

• Requires a small, fixed set of molecular building blocks (& reactions), which can be arranged for varied purposes

• Suggestive evidence for such sets

K-substitution

((K X) Y) X

K-Substitutionas a Molecular Process

S-Substitution (with Copying)

(((S X) Y) Z) ((X Z) (Y Z))

S-Substitution (with Sharing)

(((S X) Y) Z) ((X Z) (Y Z))

Computational Properties

• Universality: S and K can compute anything that is computable

• Church-Rosser Property: substitutions can be done in any order without affecting result

SK Computation

• Good model of nondeterministic & parallel computing

• Has been studied as model of massively parallel computer architecture

• Functional computer programs can be compiled into SK networks

Example: Computing a Ring

Ring (X,Y) = R

where rec R = Aux (X,Y,R)

Aux (X, nil, R) = R

Aux (x:X, y:Y, R)

= (x,y) : Aux (X,Y,R)

Example: Computing a Tube

Tube (nil, X, Y)

= Ring (X, Y)

Tube (a:N, X, Y)

= Ring [X, Tube(N,X,Y)]

Extensions

• Sensor operations respond to environmental conditions

• Effector operations have physical effects on environment

• Execution of these “imperative” operations must be controlled

Some Static Applications

• Complex physical structures: chains, tubes, spheres, fibers, networks, quasi-crystalline structures

• Membranes with pores or channels

• Very dense analog neural networks

• Sensor & effector organs for microrobots

• Conventional computation

Some Dynamic Applications

• Membrane with controllable channels• Free-floating clusters controlling fluid properties• Semiautonomous agents to recognize and bind

molecules• Sensory transducers, such as artificial retinas &

cochleas• Effectors, such as cilia & artificial muscle fibers• Self-repair

Developing an Application

1) Write & debug program

2) Compile into SK network

3) Simulate on computer

4) Flatten into DNA sequence

5) Replicate DNA

6) Construct molecular network from DNA

7) Supply reactants for computation

8) Optionally, replace by permanent groups

Issues

• Appropriate model of computation• Replication/sharing problem• Appropriate choice of combinators• Blocking computation• Nontraditional effects on computation• Dealing with substitution error• Geometrical issues• Supply of reactants• Identifying/synthesizing appropriate reactions

Current Activities

• Developing mathematical model

• Theoretical analysis

• Developing simulation tool

• Programming sample applications