PUNCTURING OF SOFT SOLIDS DUE TO INSERTION NEEDLES

PUNCTURING OF SOFT SOLIDS USING HYPODERMIC NEEDLES

Hari om choudhary (12210014)Under the Guidance of: - Dr. Gaurav

Introduction

Literature Review

Gap

Objective

ReferencesContent: -

1. INTRODUCTION: -

Motivation: - piercing of mammalian skin by a hypodermic needle, remote robotic surgery, drilling and puncturing of holes, fixing and anchoring of attachment devices, suturing of thin sheets, drug delivery and surgical instrumentation etc.Insertion of conventional hypodermic needle into our skin causes an acute sense of pain along with irritation and tissue damage; however, a bite from a mosquito is not normally accompanied by this unpleasant experience.

Piering = Mammalian = Suturing = 3

Painless niddle

Pressure-driven deformation with soft polydimethylsiloxane PDMS.Dental Vibe, chikitsiy khechaab.

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The jagged parts may act asCutting edges ,Decreasing the contact area between the surface of the needle and the dermis of a skin, which is effective for reducing the frictional force. Function to anchor the maxillas to the skin organization and may assist the labiums easy insertion.

mosquitos proboscis: -

Among them 2 maxilaa certainly have jagged shape.There are many hypothesis - the first one is that the jagged parts may act as cutting edges like a saw when the needle vibrates. The second one is that the jagged shape may have a merit of decreasing the contact area between the surface of the needle and the dermis of a skin, which is effective forreducing the frictional force. The third one is that the jagged parts may have the function to anchor the maxillas to the skin organization and may assist the labiums easy insertion by someunknown mechanism.

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Insertion mechanism of the mosquitos proboscis: -

(1)The labium bends itself as the penetration progresses. (2) The tip of the labium supports the bundle of other parts, which are labrum, pharynx, mandibles, and maxillas. (3)The tip of labium opens/closes on the object surface synchronously to bundles vibration, which seems to give tension to the surface for easy Insertion. (4) The bundle is moved forward gradually with vibration at approximately 30 Hz based on a saw-toothwaveform (not a sinusoidalwaveform). These elucidated facts are schematically shown in Fig. 6(c). Probosis =

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Background: -In order to understand the physical mechanism of the cooperative effect between closely spaced objects intruding into a so solid, we will work on embedding a tracer grid drawn on a plane inside the soft solid. We will use conventional single tip syringe needles and also specially prepare multiple tip needles as indenters for puncturing into the gel.

A block of poly(acrylamide) gel with smooth and flat faces was prepared by cross-linking a solution inde-ionized (DI) water of an acrylamide monomer, In order to embed a tracer grid inside these gel blocks, an array of dots of diameter 300 mm with 600 mm inter-dot spacing was printed using a commonly used desktop laser printer (HP laserjet 1020) on an easy release surface.7

Different types of punch: -Flat-Bottomed Punch

Single tip and Multi-tip needle: -

2. LITERATURE REVIEW: -

Shergold and Fleck [1] (2005)A sharp tipped punch penetrates by the formation and wedging open of a mode planar crack, while a flat-bottomed punch penetrates by the growth of a mode ring crack. Pressure for a flat bottomed punch is several times that of a sharp-tipped punch of equivalent diameter.Deep penetration of skin is a more complex phenomenon than that of rubber, due to the fact that skin is a layered, orthotropic solid with a more heterogeneous structure than that of rubber.

Orthotropic = anisotropic materials propertiers change when direction change The planar crack advances with the punch, and friction along the flanks of the punch leads to a rising load versus displacement response. In contrast, the flat bottomed punch penetrates by jerky crack advance and the load on the punch is unsteady. The average penetration pressure on the shank cross section of a flat-bottomed punch exceeds that for a sharp-tipped punch of the same diameter. In addition, the penetration pressure decreases as the diameter of the sharp-tipped punch increases9

Flat-Bottomed Punch

where JIIC is the toughness of the material. sum of the crack work and the strain energy S in the penetrated solid. S = that due to compression of the column, SC, andthat due to expansion of the hole, SH.strain energy stored in the solid SE. Shergold and Fleck equation use ki h .10

Sharp Punch

strain energy stored in the solid SE. WC, is determined by the mode I toughness of the material.11

Aoyagi , Izumi and Fukuda [2] (2007)The stress concentration occurs more severely at the tip area as the tip angle becomes sharp, and the needle becomes thin, which makes the penetration easier.

FEM simulaton : - finite element simulation by 12

PLA microneedle is fabricated.Observation of mosquitos penetrating motion.

Biodegradable polymer polylactic acid (PLA) microneedle.13

Reff.[6]

Das and Ghatak [3] (2010)

A rigid, flat bottom punch and a punch with sharp tip, for these needles, puncturing of the gel does not occur continuously but intermittently with the fracture progressing alternately in the wedge opening and the shear fracture modes.

Needles show that compared to a conventional single tip needle of equivalent diameter, the multi-tip needles penetrate the solid at smaller load with a smaller energy cost for fracture

brittle polyacrylamide gels using hypodermic needles of different diameters.Fig. 1j, k show that the tip of the needle first indents against the surface of the gel; eventually, a threshold load is reached at which the gel surface ruptures and the needle punctures into it (micrograph k).load on the needle (k ! l). The load eventually attains a threshold value, Fmax at which fracture no longer occurs in the opening mode alone, as the secondary crack culminates into shear fracture cylindrical wall of the needle.15

The inter-peak spacing varies with scaled diameter: -

Das, Laha and Ghatak[5] (2014)

They also showed that in addition to a primary crack ahead of the needle-tip, there occurs also a periodically appearing secondary radial crack from its side. Closely spaced multiple indenters the overlapping strain profiles cause compressive stress at the vicinity of the needles, which arrest the side cracks, the diminishing effect of which leads to stress concentration for the primary crack and the resultant decrease in required load for driving the indenters through the solid.Overlapping strain fields arrest the secondary side cracks thus enhancing the stress concentration ahead of the primary crack.

3. GAP: -They did not consider multi-layer soft body for penetration. They did not give the idea about the relative orientation of the sharp tip.They did not tell about the material properties effect on penetration.They did not give idea about the flexible needle. They did not give the idea about effect of length of sharp object in penetration of soft material.

4. OBJECTIVES: -

We are planning to work on: -Puncture of a multi-layer soft body (gel) by a sharp single or multiple tip needle this will help us to study of penetration of skin. Make a flexible multiple tip so they can adjust them self at less stress. Design a multiple sharp tip of different orientation so that we can reduce the pain and stress from a soft body. Design of a vibration sharp tip so we can adjust vibration to minimise stress. Study of soft body material properties and their dependence on puncturing and stress generation.

REFERENCES: -

Oliver A. Shergold Norman A. Fleck1 Experimental Investigation into the Deep Penetration of Soft Solids by Sharp and Blunt Punches 2005.Biodegradable polymer needle with various tip angles and consideration on insertion mechanism of mosquitos proboscisSeiji Aoyagi, Hayato Izumi, Mitsuo Fukuda2007. Susmita Das, Animangsu Ghatak Puncturing of soft gels with multi-tip needles2010. Sami Fakhouri,a Shelby B. Hutchensb and Alfred J. Crosby*Puncture mechanics of soft solids 2015. A co-operative effect of closely spaced intruding objects puncturing into a soft solid Susmita Das, Sukumar Laha and Animangsu Ghatak.https://www.youtube.com/watch?v=6idUWxtJ97g.