Development of a Nereis Model

Presumed Brief of Bioloch To develop a miniature robotic system primarily able to investigate and perform therapeutic procedures on the colon and other lumen of the human being.

G.I. Environment Inputs – Consultation with an endoscopist Review of endoscope / G.I. Literature, Reference to visible human 3D model of ‘real’ human large and small intestines 1. Smooth 2. Slippery 3. Liquid, semi solid 4. Convoluted path of varying profiles, widths and surface textures.

Appropriateness of Nereis Model Inputs – Observations of locomotion of live animal in smooth semi liquid environment ‘similar’ to G.I. Environment including observations made using high speed digital photography. Initial Observations of locomotion of Nereis in semi solid material analogous to remnant semi solid material found in G.I. tract. Literature detailing numerous ‘adhesive’ mechanisms within the morphology of the Nereid worm. Observation of some of this mirco morphology using S.E.M. 1. Able to propel itself on a smooth slippery surface 2. Able to locomote on / through irregular semi solid material

Setae S.E.M. study

Method 1 Inputs- Existing undulatory mechanism Reference to literature on gait of Nereis. Review of existing robotic endoscopes with endoscopist on to determine practical specification. Feedback from first Bioloch meeting 1. Further development of screw based robot. Initial evaluation of benefits and limitations. 2. Development of mechanism appropriate for miniaturization. 3. Development of experimental procedures appropriate to capture micro morphology of the Nereis worm.

Method 2 Design and fabrication of Mk1 screw based Nereid robot. Inputs- Reference to PIC / electronics literature Outputs- Motorised PC controlled model - Attached MPEG

Method 3 Repoduction of model parapodia and setae including details of micro morphology. Inputs- Consultation with vacuum casting specialists. Outputs- Vacuum cast of Nereis in both rigid and elastomeric polyurethane resins. No evaluation of reproduction of micro morphology has yet been undertaken.

Method 4 Design and production of a Mk2 Nereid undulatory mechanism capable of miniaturization using existing commercial technology. Inputs- Use of digital imagery as reference for CAD model. Consultation with photolithographic specialists. Consultation with micro motor specialists (Myonic). Use of scale models to develop photolithographic tooling. Outputs- Scale model of single ‘segment’ Currently production of 1:1 half segment. *NP

Method 4 continued

Method 5 Construction of clear, circular profile, elastomeric colon phantom and angling jig. Inputs – Anatomy texts on the average diameter of the colon.

Method 5 Construction of rotating mandrels to simulate the different profiles of the large colon in clear RTV silicone. Inputs – Anatomy texts on the changing profiles of the lumen, e.g. transverse section of ‘triangular’ profile.

Discussion Current commercial technology permits the design and fabrication of a Nereis model. An evaluation jig comprising clear silicone tubes lined with a ‘phantom’ mucus has been constructed to test the appropriateness of the Nereis worm as model on which to base a robot that can locomote within the G.I. tract of the human body. Several evaluations need to be met before this test can be considered fair and accurate. These include accuracy of gait reproduction, micro morphology reproduction, material property reproduction, and magnitude / distribution of mass within the model. However, it is envisaged that even the first tests within the tube jig will indicate to some extent whether Nereis and particularly the undulatory gait of the Nereis worm is an appropriate subject for analogy to achieve the Bioloch team’s primary objective. Replica mechanisms, CAD schemas will be made available to the group. It is considered that the further therapeutic potential of this type of device might be explored using this as a ‘platform’.