WO2016203329A1 - Household appliance component for a household appliance - Google Patents

Household appliance component for a household appliance Download PDF

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Publication number
WO2016203329A1
WO2016203329A1 PCT/IB2016/053123 IB2016053123W WO2016203329A1 WO 2016203329 A1 WO2016203329 A1 WO 2016203329A1 IB 2016053123 W IB2016053123 W IB 2016053123W WO 2016203329 A1 WO2016203329 A1 WO 2016203329A1
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WO
WIPO (PCT)
Prior art keywords
household appliance
appliance component
microstructured
component
microstructured surface
Prior art date
Application number
PCT/IB2016/053123
Other languages
French (fr)
Inventor
Maria Carmen Artal Lahoz
Marta LAFUENTE ADIEGO
Elena Martinez Solanas
Ismael PELLEJERO ALCÁZAR
Mª Pilar PINA IRITIA
Javier SANZ NAVAL
Original Assignee
BSH Hausgeräte GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BSH Hausgeräte GmbH filed Critical BSH Hausgeräte GmbH
Publication of WO2016203329A1 publication Critical patent/WO2016203329A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
    • A47L15/00—Washing or rinsing machines for crockery or tableware
    • A47L15/42—Details
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F37/00—Details specific to washing machines covered by groups D06F21/00 - D06F25/00
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
    • A47L15/00—Washing or rinsing machines for crockery or tableware
    • A47L15/42—Details
    • A47L15/4246—Details of the tub
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B17/00—Methods preventing fouling
    • B08B17/02—Preventing deposition of fouling or of dust
    • B08B17/06—Preventing deposition of fouling or of dust by giving articles subject to fouling a special shape or arrangement
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F58/00—Domestic laundry dryers
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
    • D06F39/00—Details of washing machines not specific to a single type of machines covered by groups D06F9/00 - D06F27/00 
    • D06F39/12—Casings; Tubs

Definitions

  • the invention relates to a household appliance component for a household appliance.
  • the invention further relates to a method for manufacturing a household appliance component for a household appliance and a household appliance comprising at least one household appliance component.
  • Micro organisms have evolved with unique properties allowing them to survive under difficult conditions and to adhere to solid surfaces in many environments. As soon as pathogenic bacteria are involved, the consequences may be problematic and can range from hygiene problems to infections and even public health problems. Therefore the surface properties of household appliance components such as walls and linings are very important, because these surfaces are in frequent or continuous contact with the environment so that a settlement by micro organisms may take place. This is particularly noticeable in water working household appliances such as dishwashers, dryers, and washing machines. For example, the inside walls of water storage tanks are prone to biofilm formation if a relatively long time passes between dishwashing cycles. In this case biofilms may build up on these inner walls and can sometimes not be completely removed during a following washing cycle.
  • coatings are the most common countermeasure to avoid bacteria adhesion on household appliance components.
  • Such coatings are designed to provide inert chemical groups on the surface to prevent bacteria cells from adhering to the surface and from reacting with functional groups on the surface of the household appliance component.
  • a further approach is to increase the surface roughness to inhibit the adhesion and growth of bacteria cells.
  • the currently known coatings exhibit some disadvantages such as poor adhesion on different common materials for household appliance components and relatively low resistance to detergents. Therefore the antimicrobial properties of such coatings decrease over time and may even be completely lost. This results in an increasing risk of biofilm formation and bacteria proliferation.
  • a further task of the invention consists in providing a method for manufacturing a wall element with enhanced protection against biofilm formation in a household appliance. Still further, it is an object of the current invention to provide a household appliance comprising at least one wall element with enhanced biofilm protection properties.
  • a wall element for a household appliance a method for manufacturing a wall element for a household appliance, and a household appliance according to the independent claims.
  • Advantageous developments of the invention are specified in the respective dependent claims, wherein advantageous developments of the wall element are to be regarded as advantageous developments of the method and the household appliance and vice versa.
  • a first aspect of the invention relates to a household appliance component for a household appliance, wherein the household appliance component at least in portions has a microstructured surface.
  • the present invention is based on the discovery that bacteria adhesion and biofilm formation can be prevented or at least strongly hindered without the need for additional coatings, active or passive bactericides, chemicals or the like by providing a microstructured surface.
  • a microstructured surface allows for precisely adjusting the topography, roughness, wettability, surface charge and functional groups of the household appliance component so that the settlement and adherence of micro organisms can be significantly hindered or completely prevented at low costs.
  • the microstructured surface in contrast for instance to coatings generally does not alter the macroscopic properties of the base material(s) the household appliance component is made of.
  • a microstructure is generally defined as the structure of a surface as revealed by a microscope above 25* magnification.
  • microstructuring within the scope of the present invention means that the surface of the household appliance component is at least in one or more portions or completely modified at scales in the micrometer range or below in order to influence the antimicrobial properties of the surface.
  • Microstructures at scales smaller than can be viewed with optical microscopes and/or below the micrometer range can be referred to as ultrastructures or nanostructures and are also encompassed by the term microstructures.
  • said household appliance component at least partly consist of a plastic, in particular of polypropene.
  • Plastic materials can be used for very different kinds of household appliance components and for very different purposes. Further, plastic materials like polystyrene, polyethene or polypropene can be easily and precisely provided with a microstructured surface at low costs. Still further, plastic materials are very robust and durable in mechanical and chemical respects.
  • said household appliance component at least in the region of its microstructured surface is superhydrophobic and/or has a water contact angle of at least 120 °, in particular of between 130 ° and 160 °.
  • a superhydrophobic surface could be created by using a base material with low surface energy and/or by increasing the roughness of the surface by microstructuring. The water contact angle generally increases by creating microstructures on the material surface, too.
  • microstructures reduce the solid surface in contact with the liquid water.
  • a microstructured surface allows for ameliorating the antimicrobial surface properties without coating or alteration of the chemical composition of the base material of the household appliance component.
  • the water contact angle on the microstructures surface is at least 120 °.
  • the microstructured surface comprises recesses having a width of between 10 ⁇ m and 35 ⁇ m, in particular of between 15 ⁇ m and 30 ⁇ m, and/or a depth of between 2.5 ⁇ m and 20 ⁇ m, in particular of between 2.8 ⁇ m and 18.8 ⁇ m, and/or that the microstructured surface comprises recesses, which are arranged in a grid-type manner at a distance of between 5 ⁇ m and 35 ⁇ m, in particular of between 10 ⁇ m and 30 ⁇ , from each other.
  • a width of between 10 ⁇ m and 35 ⁇ m may comprise widths of 10 ⁇ m, 1 1 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m, 31 ⁇ m, 32 ⁇ m, 33 ⁇ m, 34 ⁇ m, and 35 ⁇ m, as well as respective intermediate values.
  • a depth of between 2.5 ⁇ m and 20 ⁇ m may comprise depths of 2.5 ⁇ m, 2.6 ⁇ m, 2.7 ⁇ m, 2.8 ⁇ m, 2.9 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 1 1 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 1 ⁇ m, 18 ⁇ m, 19 ⁇ m, and 20 ⁇ m, as well as respective intermediate values like 17.0 ⁇ m, 17.1 ⁇ m, 17.2 ⁇ m, 17.3 ⁇ m, 17.4 ⁇ , 17.5 ⁇ m, 17.6 ⁇ m, 17.7 ⁇ , 17.8 ⁇ m, 17.9 ⁇ m and so on.
  • Recesses which are arranged in a grid-type manner at a distance of between 5 ⁇ m and 35 ⁇ m from each other may be arranged at a distance of 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m, 31 ⁇ m, 32 ⁇ m, 33 ⁇ m,
  • the microstructured surface comprises cylindrical bodies, which have a maximum width of between 14 ⁇ m and
  • the microstructured surface comprises cylindrical bodies, which are arranged in a grid-type manner at a distance of between 5 ⁇ m and 30 ⁇ m, in particular of between 6 ⁇ m and 28 ⁇ m, from each other.
  • the cylindrical bodies generally may have any basic geometric shape, wherein rectangular or at least nearly rectangular shapes like squares and rectangulars are preferred.
  • a maximum width of between 14 ⁇ m and 35 ⁇ m may comprise widths of 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m , 30 ⁇ m, 31 ⁇ m, 32 ⁇ m, 33 ⁇ m, 34 ⁇ m, and 35 ⁇ m, as well as respective intermediate values.
  • a height of between 3.5 ⁇ m and 21 ⁇ m may comprise heights of 3.5 ⁇ m, 3.6 ⁇ m, 3.7 ⁇ m, 3.8 ⁇ m, 3.9 ⁇ m, 4.0 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 1 1 ⁇ m, 12 ⁇ m, 13 ⁇ m, as well as respective
  • the cylindrical bodies which are arranged in a grid-type manner, may have a mutual distance of between ⁇ m ⁇ m wherein respective intermediate
  • the household appliance component is configured as a lining or wall element of a household appliance, in particular as a lining or wall element of a water working household appliance. This allows for avoidance of biofilm formation to such inner and/or outer walls of household appliances surfaces.
  • water working household appliances like dishwashers, washing machines and dryers benefit from the antimicrobial surface features of the household appliance component and its detergent and chemical resistance.
  • a second aspect of the invention relates to a method for manufacturing a household appliance component for a household appliance, in which a surface of the household appliance component is microstructured at least in portions.
  • the present invention is based on the discovery that bacteria adhesion and biofilm formation can be prevented or at least strongly hindered without the need for additional coatings, active or passive bactericides, chemicals or the like by providing a microstructured surface.
  • a microstructured surface allows for precisely adjusting the topography, roughness, wettability, surface charge and functional groups of the household appliance component so that the settlement and adherence of micro organisms can be significantly hindered or completely prevented at low costs.
  • the microstructured surface in contrast for instance to coatings generally does not alter the macroscopic properties of the base material(s) the household appliance component is made of.
  • the household appliance component according to the invention can be used under the influence of chemically aggressive environments, extreme temperatures, frequent washing, hard water and the like without losing its advantageous surface properties. Because of its endurance there is also no need to check the antimicrobial function of the household appliance component on a regular or frequent basis.
  • a microstructure is generally defined as the structure of a surface as revealed by a microscope above 25* magnification.
  • microstructuring within the scope of the present invention means that the surface of the household appliance component is at least in one or more portions or completely modified at scales in the micrometer range or below in order to influence the antimicrobial properties of the surface.
  • Microstructures at scales smaller than can be viewed with optical microscopes and/or below the micrometer range can be referred to as ultrastructures or nanostructures and are also encompassed by the term microstructures.
  • the microstructuring comprises at least one manufacturing step from the group of photolithography, plasma etching, injection molding, in particular with micro-inserts, photoengraving, laser engraving, thermal nanoimprint lithography, hot embossing, UV nanoimprint lithography, and roll-to-roll processing.
  • various household appliance components can be optimally manufactured.
  • the microstructuring comprises the steps of at least partial metallization of the surface and photolithography of the metallized surface using a predetermined photolithography mask to create the microstructures.
  • photolithography allows for a fast and easy determination of an optimum pattern to microstructure the surface with. Once this pattern or microstructure is determined, conventional injection molding with appropriate micro-inserts in the mold may be used for large scale production of the microstructured household appliance component.
  • a third aspect of the invention relates to a household appliance comprising at least one household appliance component according to the first aspect of the invention and/or at least one household appliance component, which is at least in portions microstructured by a method according to the second aspect of the invention.
  • the household appliance is thus equipped with an antimicrobial household appliance component, wherein the antimicrobial activity is long- lasting, resistant against detergents and other aggressive chemicals, temperature resistant, easy and cheap to manufacture, and does not need further steps or components like coatings, biocidal chemicals, and safety checks.
  • Fig. 1 a scanning electron microscope (SEM) image of a household appliance component during the manufacturing of a microstructured surface
  • Fig. 2 a scanning electron microscope (SEM) image of the household appliance component after the manufacturing of the microstructured surface
  • Fig. 3 a schematic sectional view of the household appliance component having a microstructured surface comprising cylindrical bodies;
  • Fig. 4 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention
  • Fig. 5 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention
  • Fig. 6 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention; and a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention.
  • SEM scanning electron microscope
  • different methods to manufacture household appliance components 1 with microstructured, superhydrophobic surfaces 2 as a low-cost strategy to reduce the risk of biofilm formation in an associated household appliance, for example a dishwasher, a dryer, or a washing machine are disclosed.
  • the household appliance components 1 shown in Figs. 1 to 7 are all made from polypropylene. Different methods and surface modifications can be applied to control the resulting antimicrobial surfaces properties in order to avoid cell adhesion of micro organisms.
  • Suitable methods for microstructuring the surface 2 of household appliance components 1 are for example UV irradiation, plasma modifications, printing using lithography techniques or laser modifications. Other suitable techniques are based on topographic patterning of the surfaces 2 by lithographic etching or hot embossing in order to avoid cell adhesion.
  • surface structuring on polypropylene is disclosed to define the optimum parameters in terms of superhydrophobic properties and low biofilm formation. For such purposes, photolithography and plasma etching techniques are used. Once the optimum pattern has been identified, conventional injection molding with appropriate micro-inserts on the mold can be employed for large-scale production of the microstructured household appliance components 1 .
  • the polypropylene superhydrophobic surfaces 2 are created by microstructures.
  • the manufacturing methods that have been used to test different patterns in order to optimally reduce the bacteria growth comprise lithography and reactive ion etching though other methods as laser or injection moulding would be possible. The steps are briefly described in the following:
  • Providing a household appliance component 1 which is entirely made from polypropene (PP);
  • Photolithography on the aluminum film a. Apply positive photoresist (e. g. Tl 35ES, Microchemicals GmbH) with a thickness of 2.7 ⁇ m; b. Create photolithography mask: patterns with a depth (a) of 10-55 ⁇ m, a width (b) of 5-22 ⁇ m and a spacing (c) between structures of 7-30 ⁇ m; c. Wet Chemical etching of the aluminum film using a suitable etchant solution (e. g.
  • Fig.1 shows a scanning electron microscope (SEM) picture of the household appliance component 1 during the manufacturing of the microstructured surface 2 after step 3.d.
  • the already microstructured surface 2 comprises recesses 3, which are arranged in a grid-type manner at a distance of approximately 35 ⁇ m, having a width of approximately 35 ⁇ m.
  • Fig. 2 shows a scanning electron microscope (SEM) image of the household appliance component 1 after the manufacturing of the microstructured surface 2, i.e. after Step 3.e.
  • SEM scanning electron microscope
  • Fig. 3 shows a schematic sectional view of the household appliance component 1 having a microstructured surface 2 comprising such cylindrical bodies 4.
  • the depth (a) of the bodies 4 may vary e.g. between 10-55 ⁇ m
  • the width (b) may vary e.g. between 5-22 ⁇ m
  • the spacing (c) between the bodies 4 may vary between 7-30 ⁇ m.
  • the microstructured surface 2 had a water contact angle of between 130° and 160°: 1. Grooves having a width varying from 15 to 30 ⁇ m, and a height varying from 2,8 to 18,8 ⁇ m distributed in a regular array with spacing factors from 10 to 30 ⁇ m;
  • the following table 1 contains a list of several embodiments of the invention, wherein the samples PP1 to PP21 are microstructured household appliance components 1 made from polypropene.
  • Figs 4 to 7 show scanning electron microscope (SEM) images of the household appliance components 1 according to sample PP2 (Fig. 4), PP9 (Fig 5), PP10 (Fig. 6), and PP20 (Fig. 7).
  • SEM scanning electron microscope
  • AVG C. A indicates the average water contact angle
  • “AVG Reduction” indicates the average reduction of bacteria colonisation compared to a corresponding household appliance component without a microstructured surface.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)
  • Apparatus For Disinfection Or Sterilisation (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

The invention relates a household appliance component (1) for a household appliance, wherein said household appliance component (1) at least in portions has a microstructured surface (2). The invention further relates to a method for manufacturing a household appliance component (1) for a household appliance, in which a surface (2) of the household appliance component (1) is microstructured at least in portions.

Description

Household appliance component for a household appliance
The invention relates to a household appliance component for a household appliance. The invention further relates to a method for manufacturing a household appliance component for a household appliance and a household appliance comprising at least one household appliance component.
Micro organisms have evolved with unique properties allowing them to survive under difficult conditions and to adhere to solid surfaces in many environments. As soon as pathogenic bacteria are involved, the consequences may be problematic and can range from hygiene problems to infections and even public health problems. Therefore the surface properties of household appliance components such as walls and linings are very important, because these surfaces are in frequent or continuous contact with the environment so that a settlement by micro organisms may take place. This is particularly noticeable in water working household appliances such as dishwashers, dryers, and washing machines. For example, the inside walls of water storage tanks are prone to biofilm formation if a relatively long time passes between dishwashing cycles. In this case biofilms may build up on these inner walls and can sometimes not be completely removed during a following washing cycle. The same problems can be observed in the detergent box of a washing machine and the like. Therefore it is of great interest to develop household appliance components for household appliances with special surface properties to avoid adherence of micro organisms and biofilm formation so that a bacterial contamination of the household appliance and related problems can be avoided.
At the moment, coatings are the most common countermeasure to avoid bacteria adhesion on household appliance components. Such coatings are designed to provide inert chemical groups on the surface to prevent bacteria cells from adhering to the surface and from reacting with functional groups on the surface of the household appliance component. A further approach is to increase the surface roughness to inhibit the adhesion and growth of bacteria cells.
However, the currently known coatings exhibit some disadvantages such as poor adhesion on different common materials for household appliance components and relatively low resistance to detergents. Therefore the antimicrobial properties of such coatings decrease over time and may even be completely lost. This results in an increasing risk of biofilm formation and bacteria proliferation.
It is the task of the present invention to provide a wall element for a household appliance with enhanced protection against biofilm formation. A further task of the invention consists in providing a method for manufacturing a wall element with enhanced protection against biofilm formation in a household appliance. Still further, it is an object of the current invention to provide a household appliance comprising at least one wall element with enhanced biofilm protection properties.
These tasks are solved by a wall element for a household appliance, a method for manufacturing a wall element for a household appliance, and a household appliance according to the independent claims. Advantageous developments of the invention are specified in the respective dependent claims, wherein advantageous developments of the wall element are to be regarded as advantageous developments of the method and the household appliance and vice versa.
A first aspect of the invention relates to a household appliance component for a household appliance, wherein the household appliance component at least in portions has a microstructured surface. The present invention is based on the discovery that bacteria adhesion and biofilm formation can be prevented or at least strongly hindered without the need for additional coatings, active or passive bactericides, chemicals or the like by providing a microstructured surface. A microstructured surface allows for precisely adjusting the topography, roughness, wettability, surface charge and functional groups of the household appliance component so that the settlement and adherence of micro organisms can be significantly hindered or completely prevented at low costs. Further, the microstructured surface in contrast for instance to coatings generally does not alter the macroscopic properties of the base material(s) the household appliance component is made of. Thus the household appliance component according to the invention can be used under the influence of chemically aggressive environments, extreme temperatures, frequent washing, hard water and the like without losing its advantageous surface properties. Because of its endurance there is also no need to check the antimicrobial function of the household appliance component on a regular or frequent basis. A microstructure is generally defined as the structure of a surface as revealed by a microscope above 25* magnification. Thus, microstructuring within the scope of the present invention means that the surface of the household appliance component is at least in one or more portions or completely modified at scales in the micrometer range or below in order to influence the antimicrobial properties of the surface. Microstructures at scales smaller than can be viewed with optical microscopes and/or below the micrometer range can be referred to as ultrastructures or nanostructures and are also encompassed by the term microstructures.
In an advantageous development of the invention it is provided that said household appliance component at least partly consist of a plastic, in particular of polypropene. Plastic materials can be used for very different kinds of household appliance components and for very different purposes. Further, plastic materials like polystyrene, polyethene or polypropene can be easily and precisely provided with a microstructured surface at low costs. Still further, plastic materials are very robust and durable in mechanical and chemical respects. In a further advantageous development of the invention it is provided that said household appliance component at least in the region of its microstructured surface is superhydrophobic and/or has a water contact angle of at least 120 °, in particular of between 130 ° and 160 °. A superhydrophobic surface could be created by using a base material with low surface energy and/or by increasing the roughness of the surface by microstructuring. The water contact angle generally increases by creating microstructures on the material surface, too. Such
microstructures reduce the solid surface in contact with the liquid water. Thus, a microstructured surface allows for ameliorating the antimicrobial surface properties without coating or alteration of the chemical composition of the base material of the household appliance component.
Preferably, the water contact angle on the microstructures surface is at least 120 °. This includes for example water contact angles of 120 °, 121 °, 122 °, 123 °, 124 °, 125 °, 126 °, 127 °, 128 °, 129 °, 130 °, 131 °, 132 °, 133 °, 134 °, 135 °, 136 °, 137 °, 138 °, 139 °, 140 °, 141 °, 142 °, 143 °, 144 °, 145 °, 146 °, 147 °, 148 °, 149 °, 150 °, 151 °, 152 °, 153 °, 154 °, 155 °, 156 °, 157 °, 158 °, 159 °, 160 °, 161 °, 162 °, 163 °, 164 °, 165 °, 166 °, 167 °, 168 °, 169 °, 170 0 or more.
In a further advantageous development of the invention it is provided that the microstructured surface comprises recesses having a width of between 10 μm and 35 μm, in particular of between 15 μm and 30 μm, and/or a depth of between 2.5 μm and 20 μm, in particular of between 2.8 μm and 18.8 μm, and/or that the microstructured surface comprises recesses, which are arranged in a grid-type manner at a distance of between 5 μm and 35 μm, in particular of between 10 μm and 30 μιη, from each other. These geometric features allow for a reduction in bacteria adhesion and growth of at least between log 0.2 to log 2. A width of between 10 μm and 35 μm may comprise widths of 10 μm, 1 1 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, and 35 μm, as well as respective intermediate values. A depth of between 2.5 μm and 20 μm may comprise depths of 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 1 1 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 1 μm, 18 μm, 19 μm, and 20 μm, as well as respective intermediate values like 17.0 μm, 17.1 μm, 17.2 μm, 17.3 μm, 17.4 μιτΐ, 17.5 μm, 17.6 μm, 17.7 μιη, 17.8 μm, 17.9 μm and so on. Recesses, which are arranged in a grid-type manner at a distance of between 5 μm and 35 μm from each other may be arranged at a distance of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm,
34 μm, and 35 μm, wherein respective intermediate values are to be regarded as being comprised and disclosed by the invention, too.
In a further advantageous development of the invention it is provided that the microstructured surface comprises cylindrical bodies, which have a maximum width of between 14 μm and
35 μm , in particular of between 16 μm and 31 μm, and/or a height of between 3.5 μm and 21μm , in particular of between 3.9 μm and 19.9 μm, and/or that the microstructured surface comprises cylindrical bodies, which are arranged in a grid-type manner at a distance of between 5 μm and 30 μm, in particular of between 6 μm and 28 μm, from each other. These geometric features allow for a reduction in bacteria adhesion and growth of at least between log 0.2 to log 2 as well. The cylindrical bodies generally may have any basic geometric shape, wherein rectangular or at least nearly rectangular shapes like squares and rectangulars are preferred. A maximum width of between 14 μm and 35 μm may comprise widths of 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29μm , 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, and 35 μm, as well as respective intermediate values. A height of between 3.5 μm and 21 μm may comprise heights of 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 1 1 μm, 12 μm, 13 μm,
Figure imgf000006_0001
as well as respective
intermediate values. The cylindrical bodies, which are arranged in a grid-type manner, may have a mutual distance of between
Figure imgf000006_0004
μm
Figure imgf000006_0002
μm wherein respective intermediate
Figure imgf000006_0003
values are to be regarded as being comprised and disclosed by the invention, too.
In a further advantageous development of the invention it is provided that the household appliance component is configured as a lining or wall element of a household appliance, in particular as a lining or wall element of a water working household appliance. This allows for avoidance of biofilm formation to such inner and/or outer walls of household appliances surfaces. In particular water working household appliances like dishwashers, washing machines and dryers benefit from the antimicrobial surface features of the household appliance component and its detergent and chemical resistance.
A second aspect of the invention relates to a method for manufacturing a household appliance component for a household appliance, in which a surface of the household appliance component is microstructured at least in portions. The present invention is based on the discovery that bacteria adhesion and biofilm formation can be prevented or at least strongly hindered without the need for additional coatings, active or passive bactericides, chemicals or the like by providing a microstructured surface. A microstructured surface allows for precisely adjusting the topography, roughness, wettability, surface charge and functional groups of the household appliance component so that the settlement and adherence of micro organisms can be significantly hindered or completely prevented at low costs. Further, the microstructured surface in contrast for instance to coatings generally does not alter the macroscopic properties of the base material(s) the household appliance component is made of. Thus the household appliance component according to the invention can be used under the influence of chemically aggressive environments, extreme temperatures, frequent washing, hard water and the like without losing its advantageous surface properties. Because of its endurance there is also no need to check the antimicrobial function of the household appliance component on a regular or frequent basis.
A microstructure is generally defined as the structure of a surface as revealed by a microscope above 25* magnification. Thus, microstructuring within the scope of the present invention means that the surface of the household appliance component is at least in one or more portions or completely modified at scales in the micrometer range or below in order to influence the antimicrobial properties of the surface. Microstructures at scales smaller than can be viewed with optical microscopes and/or below the micrometer range can be referred to as ultrastructures or nanostructures and are also encompassed by the term microstructures.
In a further advantageous development of the invention it is provided that the microstructuring comprises at least one manufacturing step from the group of photolithography, plasma etching, injection molding, in particular with micro-inserts, photoengraving, laser engraving, thermal nanoimprint lithography, hot embossing, UV nanoimprint lithography, and roll-to-roll processing. In this way, various household appliance components can be optimally manufactured.
In a further advantageous development of the invention it is provided that the microstructuring comprises the steps of at least partial metallization of the surface and photolithography of the metallized surface using a predetermined photolithography mask to create the microstructures. The use of photolithography allows for a fast and easy determination of an optimum pattern to microstructure the surface with. Once this pattern or microstructure is determined, conventional injection molding with appropriate micro-inserts in the mold may be used for large scale production of the microstructured household appliance component. A third aspect of the invention relates to a household appliance comprising at least one household appliance component according to the first aspect of the invention and/or at least one household appliance component, which is at least in portions microstructured by a method according to the second aspect of the invention. The household appliance is thus equipped with an antimicrobial household appliance component, wherein the antimicrobial activity is long- lasting, resistant against detergents and other aggressive chemicals, temperature resistant, easy and cheap to manufacture, and does not need further steps or components like coatings, biocidal chemicals, and safety checks. Further features and their advantages can be gathered from the description of the first and second aspect of the invention. Also, further features of the invention derive from the claims and the embodiments. The features and feature combinations previously named in the description as well as the features and feature combinations mentioned in the following in the embodiments and/or shown in the figures alone cannot only be employed in the respective indicated combination but also in other combinations or taken alone without leaving the scope of the invention. Accordingly, also embodiments that are not explicitly shown and explained in the embodiments but may be gathered and generated from the explained embodiments by separated feature combinations are to be regarded as being comprised and disclosed by the invention. Thus, also embodiments and feature combinations are to be regarded as being disclosed, which do not exhibit all features of an originally formulated independent claim. In the following, embodiments of the invention are shown in more detail in the figures. These show in:
Fig. 1 a scanning electron microscope (SEM) image of a household appliance component during the manufacturing of a microstructured surface;
Fig. 2 a scanning electron microscope (SEM) image of the household appliance component after the manufacturing of the microstructured surface; Fig. 3 a schematic sectional view of the household appliance component having a microstructured surface comprising cylindrical bodies;
Fig. 4 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention;
Fig. 5 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention;
Fig. 6 a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention; and a scanning electron microscope (SEM) image of the household appliance component with a microstructured surface according to a further embodiment of the invention. In the following embodiments, different methods to manufacture household appliance components 1 with microstructured, superhydrophobic surfaces 2 as a low-cost strategy to reduce the risk of biofilm formation in an associated household appliance, for example a dishwasher, a dryer, or a washing machine, are disclosed. The household appliance components 1 shown in Figs. 1 to 7 are all made from polypropylene. Different methods and surface modifications can be applied to control the resulting antimicrobial surfaces properties in order to avoid cell adhesion of micro organisms. Suitable methods for microstructuring the surface 2 of household appliance components 1 are for example UV irradiation, plasma modifications, printing using lithography techniques or laser modifications. Other suitable techniques are based on topographic patterning of the surfaces 2 by lithographic etching or hot embossing in order to avoid cell adhesion. In Figs. 1 and 2, surface structuring on polypropylene is disclosed to define the optimum parameters in terms of superhydrophobic properties and low biofilm formation. For such purposes, photolithography and plasma etching techniques are used. Once the optimum pattern has been identified, conventional injection molding with appropriate micro-inserts on the mold can be employed for large-scale production of the microstructured household appliance components 1 . In all figures, the polypropylene superhydrophobic surfaces 2 are created by microstructures.
The manufacturing methods that have been used to test different patterns in order to optimally reduce the bacteria growth comprise lithography and reactive ion etching though other methods as laser or injection moulding would be possible. The steps are briefly described in the following:
1 . Providing a household appliance component 1 , which is entirely made from polypropene (PP);
2. Metallization of the surface 2 with aluminum (film thickness 200 nm) in order to coat the whole uneven surface 2 (the initial roughness Ra of PP without microstructuring is usually approx. 100 nm)
3. Photolithography on the aluminum film: a. Apply positive photoresist (e. g. Tl 35ES, Microchemicals GmbH) with a thickness of 2.7 μm; b. Create photolithography mask: patterns with a depth (a) of 10-55 μm, a width (b) of 5-22 μm and a spacing (c) between structures of 7-30 μm; c. Wet Chemical etching of the aluminum film using a suitable etchant solution (e. g.
Aluminum etchant from Technic Inc or Transene Electronic Chemicals); d. Reactive Ion Etching on the polypropylene surface 2 (oxygen plasma; radio frequency 300 W; P=0.19 mbar; Flow 02: 20 seem); and e. Removing the aluminum thin film by suitable etchant solution.
Fig.1 shows a scanning electron microscope (SEM) picture of the household appliance component 1 during the manufacturing of the microstructured surface 2 after step 3.d. The already microstructured surface 2 comprises recesses 3, which are arranged in a grid-type manner at a distance of approximately 35 μm, having a width of approximately 35 μm.
Fig. 2 shows a scanning electron microscope (SEM) image of the household appliance component 1 after the manufacturing of the microstructured surface 2, i.e. after Step 3.e. One can see cylindrical bodies 4, which are arranged in a grid-type manner and have a rectangular geometry.
Fig. 3 shows a schematic sectional view of the household appliance component 1 having a microstructured surface 2 comprising such cylindrical bodies 4. Generally, the depth (a) of the bodies 4 may vary e.g. between 10-55 μm, the width (b) may vary e.g. between 5-22 μm, and the spacing (c) between the bodies 4 may vary between 7-30 μm.
Of course, also other fabrication methods could be used to create the microstructured surface, such as laser or thermal nanoimprint lithography, hot embossing, UV nanoimprint lithography or roll to roll processes to obtain such patterns. It could be proved that patterns with the following parameters are able to reduce the bacteria growth between log 0.2 to log 2 reduction. In all cases, the microstructured surface 2 had a water contact angle of between 130° and 160°: 1. Grooves having a width varying from 15 to 30 μm, and a height varying from 2,8 to 18,8 μm distributed in a regular array with spacing factors from 10 to 30 μm;
2. Square shape pillars with a width varying from 16 to 31 μm and a height varying from 3,9 to 19,9 μm distributed in a regular array with spacing factors from 6 to 28 μm.
The following table 1 contains a list of several embodiments of the invention, wherein the samples PP1 to PP21 are microstructured household appliance components 1 made from polypropene. Figs 4 to 7 show scanning electron microscope (SEM) images of the household appliance components 1 according to sample PP2 (Fig. 4), PP9 (Fig 5), PP10 (Fig. 6), and PP20 (Fig. 7). In table 1 , "AVG C. A", indicates the average water contact angle, while "AVG Reduction" indicates the average reduction of bacteria colonisation compared to a corresponding household appliance component without a microstructured surface. Table 1
Figure imgf000011_0001
Main advantages of the surface microstructuring are: long-term endurance
- detergent and chemical resistance temperature resistance
process simplicity
No need to apply coatings or chemicals and check safety of the coatings/chemicals. The parameter values mentioned in the documents for the definition of process and measuring conditions for the characterization of specific properties of the subject matter of the invention are to be regarded as being comprised by the scope of the invention also in the course of deviations - for instance due to measuring errors, system errors, errors in the weighed amount, DIN tolerances, and the like.
List of references 1 household appliance component
2 microstructured surface
3 recess
cylindrical body
4

Claims

CLAIMS 1. A household appliance component (1 ) for a household appliance,
characterized in that
said household appliance component (1 ) at least in portions has a microstructured
surface (2).
2. The household appliance component (1 ) according to claim 1 ,
characterized in that
said household appliance component (1) at least partly consist of a plastic, in particular of polypropene.
3. The household appliance component (1 ) according to claim 1 or 2,
characterized in that
said household appliance component (1) at least in the region of its microstructured
surface (2) is superhydrophobic and/or has a water contact angle of at least 120 °, in
particular of between 130 ° and 160 °.
The household appliance component (1 ) according to any one of claims 1 to 3,
4.
characterized in that
the microstructured surface (2) comprises recesses (3) having a width of between 10 μm and 35 μm, in particular of between 15 anμdm 30 , andμ/omr a depth of between 2.5 μm and 20 μm, in particular of between 2.8 μm and 18.8 μm, and/or that the microstructured
surface (2) comprises recesses (3), which are arranged in a grid-type manner at a
distance of between 5 μm and 35 μm, in particular of between 10 μm and 30 μm, from
each other.
The household appliance component (1 ) according to any one of claims 1 to 4,
5.
characterized in that
the microstructured surface (2) comprises cylindrical bodies (4), which have a maximum
width of between 14 μm and 35 μm in particular of between 16 μm and 31 μm, and/or a
height of between 3.5 μm and 21 μm, in particular of between 3.9 μm and 19.9 μm,
and/or that the microstructured surface (2) comprises cylindrical bodies (4), which are arranged in a grid-type manner at a distance of between 5 and 3μ0m , in partiμcmular of between 6 μm and 28 μιτι, from each other.
6. The household appliance component (1 ) according to any one of claims 1 to 5,
characterized in that
at least the microstructured surface (2) has a mean roughness of between 1 .10 μm and 3.4 μm, in particular of between 1 .13 μm and 3.36 μm.
7. The household appliance component (1 ) according to any one of claims 1 to 6,
which is configured as a lining or wall element of a household appliance, in particular as a lining or wall element of a water working household appliance.
8. A method for manufacturing a household appliance component (1) for a household
appliance, in which a surface (2) of the household appliance component (1) is microstructured at least in portions.
9. The method according to claim 8,
characterized in that
the microstructuring comprises at least one manufacturing step from the group of photolithography, plasma etching, injection molding, in particular with micro-inserts, photoengraving, laser engraving, thermal nanoimprint lithography, hot embossing, UV nanoimprint lithography, and roll-to-roll processing.
10. The method according to claim 9,
characterized in that
the microstructuring comprises the steps
at least partial metallization of the surface; and
photolithography of the metallized surface using a predetermined photolithography mask to create the microstructures.
11. A household appliance comprising at least one household appliance component (1 ) according to any one of claims 1 to 7 and/or at least one household appliance component (1 ), which is at least in portions microstructured by a method according to any one of claims 8 to 10.
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