<ion-toolbar>
<ion-title>TODO APP</ion-title>
<button class = "button button-icon">
    <i class="icon ion-compose"></i>
</button>
</ion-toolbar>

<ion-header>
  <ion-navbar primary>
    <ion-buttons start>
      <button menuToggle>
        <ion-icon name="menu"></ion-icon>
      </button>
    </ion-buttons>

    <ion-title>
      My Page
    </ion-title>

    <ion-buttons end>
      <button (click)="myFunction()" ion-button icon-only>
        <ion-icon name="search"></ion-icon>
      </button>
    </ion-buttons>
  </ion-navbar>
</ion-header>

<ion-navbar *navbar>
    <ion-title>
        TODO APP
    </ion-title>
    <ion-buttons end>
        <button ><ion-icon name="home"></ion-icon></button>
    </ion-buttons>
</ion-navbar>

.ion-ios-custom:before {
    background-image: url("image-icon.png");
 }

.ion-ios-custom:before {
   content: "f439"; /* your font code */
 }

.ion-ios-custom:before {
   content: url("image-icon.png") !important;
}

<ion-icon name="custom"></ion-icon>

ion-buttons {
    order: 10
}

<ion-toolbar color='primary'>
    <button ion-button menuToggle>
        <ion-icon name='menu'></ion-icon>
    </button>
    <ion-title>TODO APP</ion-title>
    <ion-buttons start>
        <button (click)='YOUR_FUNCTION_CALL' ion-button icon-only>
            <ion-icon name='YOUR_ICON_NAME'></ion-icon>
        </button>
    </ion-buttons>
</ion-toolbar>

<ion-toolbar>
<ion-title>
  TODO APP
<button  style="float: right;">
   <ion-icon name="home"></ion-icon>
</button>
</ion-title>

</ion-toolbar>

<ion-view title="home" align-title="center">
    <ion-nav-buttons side="right">
        <button ng-click="search()" class="button button-icon icon ion-android-search"></button>
    </ion-nav-buttons>
    <ion-content has-bouncing="0px">
    </ion-content>
</ion-view>